Exogenous Application of Melatonin Improves Drought Tolerance in Coffee by Regulating Photosynthetic Efficiency and Oxidative Damage

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  • 1 CAS Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Wuhan, Hubei 430074, China; Centre of Economic Botany, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan, Hubei 430074, China; and University of Chinese Academy of Sciences, 19A Yuquanlu, Beijing 100049, China
  • 2 CAS Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Wuhan, Hubei 430074, China; and University of Chinese Academy of Sciences, 19A Yuquanlu, Beijing 100049, China
  • 3 CAS Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Wuhan, Hubei 430074, China; Centre of Economic Botany, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan, Hubei 430074, China; and Sino-African Joint Research Centre, Chinese Academy of Sciences, Wuhan, Hubei 430074, China

The protective role of melatonin in plants under abiotic stress has been reported, but little information is available on its mitigation effect on coffee (Coffea arabica) plants. The objective of this study was to determine the effect of exogenous application of 100 µM melatonin in coffee leaves under 3 months of drought stress treatment. Melatonin was found to alleviate the drought-induced damage in coffee through reducing the rate of chlorophyll degradation, electrolyte leakage, malonaldehyde content, and activating various antioxidant enzymes, such as catalase, guaiacol peroxidase, and superoxide dismutase. Melatonin application suppressed the expression of chlorophyll degradation gene PAO encoding pheophorbide a oxygenase, and upregulated the expression of photosynthetic gene RBCS2 encoding ribulose-1,5-bisphosphate oxygenase (Rubisco) protein, and a drought-related gene AREB encoding abscisic acid-responsive element binding protein. The photosynthetic efficiency of photosystem II under dark adaptation was also improved upon melatonin application in drought-stressed plants. Our results showed that both foliar spray and direct soil application of melatonin could improve drought tolerance by regulating photosynthetic efficiency and oxidative damage in C. arabica seedlings. This study provides insights in application of melatonin as a protective agent against drought stress in improvement of crop yields.

Abstract

The protective role of melatonin in plants under abiotic stress has been reported, but little information is available on its mitigation effect on coffee (Coffea arabica) plants. The objective of this study was to determine the effect of exogenous application of 100 µM melatonin in coffee leaves under 3 months of drought stress treatment. Melatonin was found to alleviate the drought-induced damage in coffee through reducing the rate of chlorophyll degradation, electrolyte leakage, malonaldehyde content, and activating various antioxidant enzymes, such as catalase, guaiacol peroxidase, and superoxide dismutase. Melatonin application suppressed the expression of chlorophyll degradation gene PAO encoding pheophorbide a oxygenase, and upregulated the expression of photosynthetic gene RBCS2 encoding ribulose-1,5-bisphosphate oxygenase (Rubisco) protein, and a drought-related gene AREB encoding abscisic acid-responsive element binding protein. The photosynthetic efficiency of photosystem II under dark adaptation was also improved upon melatonin application in drought-stressed plants. Our results showed that both foliar spray and direct soil application of melatonin could improve drought tolerance by regulating photosynthetic efficiency and oxidative damage in C. arabica seedlings. This study provides insights in application of melatonin as a protective agent against drought stress in improvement of crop yields.

Drought is an environmental factor that causes stress in plants and restricts plant growth and development which has a great impact on crop production. It has been documented that drought stress reduces plant growth and productivity by impairing physiological and biochemical processes, such as photosynthesis, respiration, translocation, and growth promoters. Plants control water loss during drought stress by adjusting stomatal opening to reduce transpiration flux and to limit CO2 absorption, resulting in reduction of net photosynthesis (DaMatta and Ramalho, 2006; Farooq et al., 2009; Jaleel et al., 2009; Liang et al., 2020). Drought stress can rapidly increase generation of toxic reactive oxygen species (ROS), such as superoxide anion (O2), hydroxyl radical (•OH), and hydrogen peroxide (H2O2), which can lead to severe toxicity by initiating an imbalance between the production of ROS and antioxidant defense. This damages cellular membranes and components, resulting to oxidative stress and eventual cell death (Farooq et al., 2009; Foyer and Fletcher, 2001; Talaat et al., 2015). In addition, over accumulation of ROS can impair cells’ normal functions and cause lipid peroxidation, protein denaturation, photoinhibition, stomatal closure, and alteration of enzymes’ activities (Farooq et al., 2009; Li et al., 2011). Plants have developed different enzymatic and nonenzymatic scavenging mechanisms to regulate ROS under environmental stresses. For example, under drought stress, elevated contents of malondialdehyde (MDA) and electrolyte leakage (EL) are often used as indicators of oxidative damage to plant cell membranes (Li et al., 2011; Lima et al., 2002). To increase drought tolerance, plants enhance the activities of scavenging enzymes such as superoxide dismutase (SOD), catalase (CAT), and guaiacol peroxidase (POD) (Mittler, 2006). Similarly, plants adopt nonenzymatic mechanisms including decreased canopy size and closed stomata to minimize water loss (Wang et al., 2019).

Coffee is a widely consumed beverage and the second most-traded global commodity. It belongs to the genus Coffea, subgenus Coffea in the Rubiaceae family with ≈124 species. The main species cultivated are the tetraploid (2n = 4x = 44), C. arabica, which accounts for about 65% of global production; and the two diploid (2n = 2x = 22) species, C. canephora and C. liberica, which account for about 30% of global production (Bita and Preda, 2005; DaMatta, 2004; Ribas et al., 2006). Drought is a major environmental constraint that has led to ≈80% decrease in global coffee production (DaMatta, 2004; DaMatta and Ramalho, 2006; Pinheiro et al., 2005). Therefore, developing strategies to enhance drought resistance and improve productivity in coffee is warranted.

Exogenous application of phytohormones and plant growth regulators, such as melatonin, salicylic acid, jasmonic acid, ethylene, and abscisic acid (ABA), has been shown to enhance drought-stress tolerance in plants (Arnao and Hernandez-Ruiz, 2018; Li et al., 2013). Melatonin (N-acetyl-5-methoxytryptamine) is a low molecular weight tryptophan-derived hormone with an indole ring structure. It is produced by the vertebrate pineal gland and was initially identified as an animal hormone that regulates the circadian rhythms and sleep (Calvo et al., 2013; Korkmaz et al., 2009; Reiter, 1997; Tan et al., 2000, 2012). In plants, melatonin was first detected using high-performance liquid chromatography (HPLC) and radioimmunoassay (Hattori et al., 1995), and many studies have been carried out to elucidate its functions in regulating growth. Melatonin has been associated with plant protection against biotic and abiotic stress as an antioxidant (Afreen et al., 2006). For example, melatonin lessens oxidative damage during drought stress by directly scavenging ROS, and by enhancing antioxidant enzymes activities, thus maintaining plant membrane integrity (Allegra et al., 2003; Tan et al., 2000).

Recently, its role as a signaling hormone was reported, suggesting that plants tend to accumulate higher levels of melatonin under drought stress (Arnao and Hernandez-Ruiz, 2014). In addition, studies have demonstrated that melatonin can alleviate effects of extreme environmental stress such as cold (Kang et al., 2010; Lei et al., 2004), salinity (Jiang et al., 2016; Li et al., 2012), heavy metals (Nabi et al., 2019; Posmyk et al., 2008; Tan et al., 2007), leaf senescence (Ma et al., 2018; Wang et al., 2013), and ultraviolent radiation (ultraviolet) (Afreen et al., 2006) in various plants. Melatonin can maintain plant membrane integrity by directly scavenging ROS. Despite numerous studies on the antioxidative properties of melatonin that have been conducted in plants such as apple (Malus ×domestica), soybean (Glycine max), cucumber (Cucumis sativus), and maize (Zea mays) (Huang et al., 2019; Liang et al., 2018; Wei et al., 2015; Zhang et al., 2013), little is known about its role in improving the tolerance of coffee plants to biotic and abiotic stresses. We explored the effects of melatonin on the dynamics of antioxidant enzymatic activity, lipid peroxidation, photosynthetic efficiency, and EL in C. arabica seedlings under drought stress. Exogenous melatonin application not only showed an effect on the activities of various antioxidant enzymes such as CAT, POD, and SOD, but could also reduce MDA and EL, which are important indicators of cellular membrane integrity. Melatonin could also alleviate chlorophyll degradation in plants exposed to drought stress. Our results provide an insight into the mechanism underlying the regulatory role of melatonin in improving tolerance of coffee to drought stress.

Materials and Methods

Plant materials.

All coffee seedlings used in this study were maintained and cultivated in the greenhouse at the Institute of Wuhan Botanical Garden, Chinese Academy of Sciences, China. One-year-old C. arabica seedlings were cultivated in a growth chamber with a temperature regime of 25/20 °C (day/night), photosynthetically active radiation (PAR) levels of 300 µmol·m−2·s−1, 70% relative humidity, and a photoperiod of 14/10 h (light/dark) (Carr, 2001; Fahl et al., 1994; Fanjul et al., 2008). Plants were grown in plastic pots (10 × 17 cm) filled with forest top soil/sand (5 soil:1 sand, v/v) with 5 g/pot 10N–6.1P–6.8K fertilizer added (52 kg·ha−1 N). The pots were covered with impervious clear paper to prevent excessive water loss. Before the onset of the experiment, all plants were well-watered daily and fertilized with half-strength Hoagland’s solution (pH 6.0) twice per week (Hoagland and Arnon, 1950). After 3 months of growth, plants were selected for treatments. Three treatment groups were arranged in a randomized complete block design with five replicates each: well-watered (WW), drought-stressed (D), drought-stressed along with melatonin treatment (DM). For the well-watered treatment, plants were irrigated with water for the rest of the treatment. For the melatonin treatment, C. arabica plants were treated with melatonin (Sigma-Aldrich, St. Louis, MO) three times per week using both foliar spraying and application into the soil at the same concentration of 100 µM as previously reported (Kabiri et al., 2018; Zhang et al., 2013). About 20 mL of melatonin was sprayed on each plant and 30 mL applied directly to the soil. Three pots without plants for each drought treatment group were used for monitoring evaporative water loss throughout the experimental period. Water loss was evaluated by weighing the pots weekly to maintain the soil water content at 40% field capacity and calculating changes in weight that occurred as a result of evaporative water loss between watering regimes. The amount of water lost was then added back to the DM and D plants in alternate days to maintain similar moisture content. Leaf samples were collected after every month from each treatment, immediately frozen in liquid nitrogen, and then stored at −80 °C for subsequent analysis of physiological traits and gene expression.

Measurement of chlorophyll content and fluorescence.

Chlorophyll (Chl) content was determined according to a previously reported method (Li et al., 2018; Liang et al., 2017; Lichtenthaler, 1987) with slight modifications. Briefly, 0.1 g fresh C. arabica leaf samples were extracted with 95% alcohol. The tubes were wrapped with aluminium foil and incubated for 48 h in darkness at room temperature. The absorbance was assayed with a spectrophotometer (ultraviolet-1100; Macy Instruments, Shanghai, China) at 665 and 649 nm wavelength. Chlorophyll concentration was calculated using the following formulae: Chl a [milligrams per gram fresh weight (FW)] = (13.95 × A665 − 6.88 × A649) × 0.005 ÷ W; Chl b (milligrams per gram FW) = (24.96 × A649 − 7.32 × A665) × 0.005 ÷ W; total Chl (milligrams per gram FW) = Chl a + Chl b = (18.08 × A649 + 6.63 × A665) × 0.005 ÷ W, where A and W are the absorbance of chlorophyll extract and the leaf FW (grams), respectively.

The chlorophyll fluorescence parameters of coffee leaves were determined with a portable photosynthesis system (PAM-2500; Heinz Walz, Eichenring, Germany). Fully expanded third leaves were used for chlorophyll fluorescence analysis. Briefly, leaves were pre-adapted in the dark for 30 min before measurement. All measurements were taken using a saturating light intensity of 2000 µmol·m−2·s−1. For each treatment group, five measurements were taken for each month with a high time resolution of 10 µs and 300 ms. Typical polyphasic OJIP curve, where O is the initial fluorescence, J and I sites are intermediate transients, and P is the peak fluorescence, was analyzed using the JIP-test (Yusuf et al., 2010). Basic fluorescence parameters, specific energy fluxes, quantum yield efficiency, and performance index were extracted and analyzed (Table 1).

Table 1.

Changes in modulated chlorophyll fluorescence parameters during drought stress in leaves of Coffea arabica seedlings.

Table 1.

Measurement of MDA content and EL.

The amount of MDA was determined according to a previously reported protocol (Fan et al., 2015; Heath and Packer, 1968; Hu et al., 2018). About 1 mL crude enzyme extract was added to 2 mL reaction solution containing 20% (v/v) trichloroacetic acid (TCA) and 0.5% (v/v) thiobarbituric acid (TBA). The mixture was heated for 30 min at 95 °C, cooled on ice, and centrifuged at 14,000 gn for 10 min at 20 °C. The supernatant was collected for absorbance measurement with an ultraviolet-visible spectrophotometer (ultraviolet-1100) at 532 and 600 nm. The absorbance at 600 nm was deducted for correction of nonspecific turbidity. MDA content was calculated as MDA (nanomoles per gram FW) = [(A532−A600) × V × 1000/ε] × W, where ε is the specific extinction coefficient of 155 mm·cm−1, while V and W represent the volume of extraction solution (milliliters) and the FW of the leaf sample (grams), respectively. EL was assayed as previously described in Shi et al. (2015). About 0.5 g of fresh samples was transferred into a 50-mL tube filled with deionized water. The tubes were incubated at room temperature for 12 h on a conical shaker, and primary conductivity (EL1) was determined using a conductance meter (3137; Jenco Instruments, San Diego, CA). To release all electrolytes, the leaf samples were autoclaved at 121 °C for 30 min. After cooling them at room temperature, we determined the secondary conductivity (EL2) using the same method as for EL1. The relative electrolyte leakage was calculated as relative EL (%) = (EL1/EL2) × 100.

Crude enzyme extraction.

For crude enzyme extraction, ≈0.5 g of fresh coffee leaf samples frozen in liquid nitrogen were ground into powder using a prechilled mortar and pestle (4 °C) in liquid nitrogen. Then, 6 mL of a 150-mm sodium phosphate buffer (PBS), pH 7.0, was added to the powder. The homogenate was then centrifuged at 4 °C for 20 min at 15,000 gn, and the supernatant was collected and subjected to antioxidant enzyme activity assay and MDA content determination according to a previously reported protocol (Willekens et al., 1997).

Antioxidant enzyme activity assay.

The enzyme activities of POD (EC 1.11.1.7) and SOD (EC 1.15.1.1) were assayed using the reagent kit (Jiancheng Bioengineering Institute, Nanjing, China) according to the manufacturer’s instruction. CAT (EC 1.11.1.6) activity was measured using the previously reported method (Aebi, 1984) with slight modifications. The reaction mixture contained 0.1 mL crude enzyme extract, 1.90 mL of 50-mmol·L−1 PBS (pH 7.0). CAT activity was measured by monitoring the decrease in absorbance once every minute within the first 3 minutes caused by the decomposition of H2O2.

RNA extraction and real-time PCR (qRT-PCR) analysis.

Extraction of total RNA for each sample was performed using an RNAprep Plant Kit (Tiangen, Beijing, China) according to the manufacturer’s instructions. Synthesis of cDNA was carried out using a PrimeScript RT reagent Kit with gDNA Eraser (Takara, Dalian, China) following the manufacturer’s instructions. We performed qRT-PCR in a 20-μL reaction volume containing 10 μL TB Green Premix Ex Taq II (Takara), 6 μL ddH2O, 0.8 μL forward primer (10 µM), 0.8 μL reverse primer (10 µM), 0.4 μL ROX reference dye (50 X), and 2 μL template cDNA. PCR amplification was performed on an Applied Biosystems Step One Plus Real-Time PCR System (Thermo Fisher Scientific, Waltham, MA) using the following program: initial denaturation 95 °C for 30 s, 40 cycles at 95 °C for 5 s, and 60 °C for 30 s. Gene transcript abundance was calculated using the 2−∆∆CT comparative threshold cycle (CT) method as previously described by Livak and Schmittgen (2001). Each treatment was conducted with three biological replicates. The primer sequences used in this study are listed in Supplemental Table 1.

Statistical analysis.

Statistical analysis was performed using one-way analysis of variance combined with Tukey’s test using SPSS software (version 22.0; IBM Corp., Armonk, NY) at a significance level of P < 0.05. Data were presented as mean ± se (n = 5). All figures were created by Origin 9.0 (Origin Laboratory, Hampton, MA).

Results

Effect of melatonin on chlorophyll content and fluorescence parameters in leaves of coffee plants under drought stress.

The contents of Chl a, Chl b, and total Chl were all significantly lower in plants with either drought-stressed (D) or drought-stressed along with melatonin treatment (DM) than in plants well-watered (WW), after treatment for 1 month (Fig. 1A). Significant difference in the content of Chl a, Chl b, and total Chl was observed between D and DM treatments at the second and third month, although there was no significant difference for the first month of treatment. The contents of Chl a, Chl b, and total Chl were 0.45, 0.34, and 0.80 mg·g−1 FW, respectively, in D plants at the third month of treatment, but with corresponding values of 0.61, 0.49, and 1.13 mg·g−1 FW in DM plants. Water deficit adversely affected chlorophyll fluorescence transient curve in D plants, causing the curve to significantly decline (Fig. 1B). In contrast, melatonin ameliorated the drought effect, resulting in an increase in the OJIP curve. Greater variation in the course of transient curve was observed at the O-J and I-P phase, with higher transient course in D and DM plants respective to WW plants. After 3 months of treatment, leaf senescence occurred in D plants, but this was not obvious in WW and DM plants (Fig. 1C).

Fig. 1.
Fig. 1.

Effects of exogenous application of melatonin on chlorophyll content and photosynthetic fluorescence parameters in leaves of Coffea arabica seedlings under 3 months of drought stress treatment. (A) The content of chlorophyll, Chl a, Chl b, and total Chl in leaves of seedlings under different treatments. Data represent means ± se (n = 5). Columns marked with different letters indicate significant differences between the treatments for each month based on Tukey’s test (P < 0.05). (B) Photosynthetic efficiency of chlorophyll fluorescence intensity (V) relative to time for leaves of seedlings under different treatments. (C) Coffee seedlings after treatment for 3 months with different stresses. WW, D, and DM represent well-watered control, drought-stressed, drought-stressed along with melatonin treatment, respectively.

Citation: Journal of the American Society for Horticultural Science J. Amer. Soc. Hort. Sci. 146, 1; 10.21273/JASHS04964-20

Basic photosynthetic parameters were measured, and the results are shown in Table 1. Highest minimal fluorescence (F0) yield values were detected in D plants, whereas the values were significantly decreased in DM plants. Prolonged stress resulted in a consistent decrease in maximal fluorescence intensity (FM) and maximum quantum efficiency at the photosystem II (PSII) photochemistry (FV/FM), in D plants relative to WW plants. However, the FM and FV/FM increased significantly in the DM plants with melatonin treatment compared with D plants. Additionally, a significant increase in specific energy fluxes was detected in D plants relative to WW plants, including trapped excitation flux (TP0), per PSII reaction center (RC), electron transport flux (ET0), per RC, electron flux reducing end electron acceptors at the PSII acceptor side (RE0), per RC, and absorption photon flux (ABS), per RC. A significant decrease in the fluxes was observed in DM plants respective to D plants. Similarly, melatonin treatment significantly increased quantum yield efficiency components, maximum quantum yield (φpo), quantum yield of the electron transport flux (φEo) and primary quinone electron acceptor of PS II, reducing RCs per PSII antenna (RC/ABS), and performance indexes (PITOTAL and PIABS), in DM plants respective to D plants. Altogether, these results suggested that melatonin application improved PSII function under drought stress.

Effect of melatonin on MDA content and EL in plants under drought stress.

Seedlings of C. arabica under drought stress exhibited increased levels of MDA and EL, which suggested lipid membrane peroxidation and cell membrane damage (Fig. 2A). Under drought stress, MDA content increased rapidly in D plants, with 2.22, 3.38, and 3.67 nmol·g−1 FW, at the first, second, and third month, respectively. In contrast, MDA content showed a relatively slow increase in DM plants, with 1.99, 2.79, and 2.56 nmol·g−1 FW in the first, second, and third month, respectively. Similarly, EL values were 8.4%, 18.9%, and 20.5% in D plants at the first, second, and third month, respectively, but with decreased values of 6.9%, 16.8%, and 15.7% in DM plants (Fig. 2B). These results indicated that exogenous application of melatonin inhibited the increase of both MDA content and EL of coffee plants under drought stress, leading to a reduction in lipid membrane peroxidation and alleviation of damage of cell membrane integrity and stability.

Fig. 2.
Fig. 2.

Effects of melatonin treatment on (A) malondialdehyde (MDA) content and (B) electrolyte leakage (EL) in leaves of Coffea arabica seedlings under 3 months of drought stress treatment. Data represent means ± se (n = 5). Columns marked with different letters indicate significant differences between the treatments for each month based on Tukey’s test (P < 0.05). WW, D, and DM represent well-watered control, drought-stressed, and drought-stressed along with melatonin treatment, respectively.

Citation: Journal of the American Society for Horticultural Science J. Amer. Soc. Hort. Sci. 146, 1; 10.21273/JASHS04964-20

Melatonin enhanced enzymatic antioxidant activity in coffee plants.

Activities of 0.8, 0.9, and 1.0 U/mg FW for SOD; 1.9, 2.9, and 3.3 U/mg protein for POD; and 1.9, 2.7, and 3.4 U/g FW for CAT were detected in D plants at the first, second, and third month, respectively (Fig. 3). In contrast, enhanced enzyme activities of 1.0, 1.2, and 1.2 U/mg FW for SOD; 2.8, 3.6, and 3.8 U/mg protein for POD; and 2.8, 3.6, and 3.8 U/g FW for CAT were observed in DM plants at the first, second, and third month, respectively. This suggested that oxidative stress induced antioxidant enzyme activities of SOD, POD, and CAT in coffee plants under drought stress, and this induction could be enhanced by exogenous application of melatonin.

Fig. 3.
Fig. 3.

Melatonin application enhances enzymatic antioxidant activity in leaves of Coffea arabica seedlings under 3 months of drought stress treatment. Catalase (CAT), guaiacol peroxidase (POD), and superoxide dismutase (SOD). Data represent means ± se (n = 5). Columns marked with different letters indicate significant differences between the treatments for each month based on Tukey’s test (P < 0.05). WW, D, and DM represent well-watered control, drought-stressed, and drought-stressed along with melatonin treatment, respectively.

Citation: Journal of the American Society for Horticultural Science J. Amer. Soc. Hort. Sci. 146, 1; 10.21273/JASHS04964-20

Effect of melatonin on relative expression of PAO, RBSC2, and AREB genes.

Relative expression of a chlorophyll degradation gene PAO encoding pheophorbide-a-oxygenase, a photosynthetic gene RBCS2 encoding photosynthetic ribulose-1,5-bisphosphate oxygenase (Rubisco) protein, and a drought-related gene AREB encoding abscisic acid-responsive binding protein were investigated, and the results are shown in Fig. 4. The expression of PAO and AREB was significantly increased by 1.3- and 2.3-fold, respectively, in D plants respective to WW plants. However, their expression was significantly down-regulated in DM plants with melatonin application respective to D plants. In addition, the expression of RBSC2 was down-regulated in D plants relative to WW plants, but it showed a significant increase by 1.9-fold in DM plants. In summary, down-regulation of PAO, AREB genes and up-regulation of RBSC2 in DM plants respectively to D plants suggested that melatonin reduced photosynthesis degradation and enhanced ABA signaling, leading to an improved drought tolerance.

Fig. 4.
Fig. 4.

Effects of melatonin application on relative expression of pheophorbide a oxygenase (PAO), ribulose-1,5-bisphosphate oxygenase (Rubisco) protein (RBSC2), abscisic acid-responsive element binding protein (AREB) in leaves of Coffea arabica seedlings under 3 months of drought stress treatment. Data represent means ± se (n = 5). Columns marked with different letters indicate significant differences between the treatments for each month based on Tukey’s test (P < 0.05). WW, D, and DM represent well-watered control, drought-stressed, and drought-stressed along with melatonin treatment, respectively.

Citation: Journal of the American Society for Horticultural Science J. Amer. Soc. Hort. Sci. 146, 1; 10.21273/JASHS04964-20

Discussion

Melatonin is a plant growth regulator and a free radical scavenger (Huang et al., 2019; Liang et al., 2018; Wei et al., 2015; Zhang et al., 2013) that enhances antioxidant enzymes activities during stress (Afreen et al., 2006; Allegra et al., 2003; Campos et al., 2003; Ding et al., 2018; Tan et al., 2000). In this study, application of melatonin enhanced drought tolerance and delayed leaf senescence in coffee seedlings. Previously, melatonin has been associated with delayed chlorophyll degradation by increasing the overall chlorophyll content under abiotic stress (Chen et al., 2009; Huang et al., 2019; Wang et al., 2013). Similarly, our results indicated that exogenous melatonin application increased the levels of Chl a, Chl b, and total Chl under drought stress, thus increasing capacity for light harvesting in coffee seedlings.

A significant increase in the chlorophyll fluorescence OJIP transient curve suggests that melatonin ameliorates the adverse effects of drought, especially at the O-J and I-P phase, where the greatest impact of drought stress is—probably due to oxidation of electron transport chains, resulting from the reduction in the electron donor of PSII reaction centers (Calatayud et al., 2006; Yusuf et al., 2010). The analysis of chlorophyll fluorescence parameters response to melatonin treatment revealed higher F0 values in coffee plants under drought stress relative to drought-stressed plants with exogenous melatonin application. Under water deficit, increased F0 alters photosynthetic metabolism through delayed electron transfer in the PSII sites, causing chloroplast damage, thus reducing plant photosynthetic activity (Calatayud et al., 2006; Maxwell and Johnson, 2000; Murchie and Lawson, 2013). Decreased F0 in coffee seedlings treated with melatonin demonstrates the hormone’s role in establishing consistent electron flow at the donor and acceptor sites of PSII, which improves photosynthetic capacity (Murchie and Lawson, 2013). The F0 values were also observed to decrease with increasing chlorophyll content in leaves. In addition, melatonin showed a positive effect on chlorophyll florescence in drought-stressed coffee plants as evidenced by a markedly high FV/FM ratio, which indicates a reduction in energy loss and PSII maximum efficiency (Liu et al., 2016). Enhanced levels of specific energy flux parameters (such as TP0/RC, ET0/RC, RE0/RC, and ABS/RC) in drought-stressed coffee plants indicates inactivation of light absorption and trapping reaction centers due to abiotic stress causing a reduction of energy-trapping efficiency from PSII (Liu et al., 2016; Strasser et al., 2000). However, melatonin treatment significantly decreases specific energy flux parameters and promotes photosynthetic capacity and plant vitality, thus demonstrating its ability to induce light absorption in coffee plants under stress (Chen et al., 2013; Murchie and Lawson, 2013; Strasser et al., 2000). Quantum yield efficiency components φpo, φEo, and RC/ABS as well as PIABS and PITOTAL significantly increased in drought-stressed plants treated with melatonin than in drought-stressed plants, which indicates the positive role of melatonin in activating flow of electrons between PSII complexes, thus maintaining photosynthetic activity of coffee plants under drought stress (Chen et al., 2013; Liu et al., 2016). It is however worth noting that plant water status is a key physiological parameter in evaluating drought-stress studies in plants and should be evaluated in future studies.

Lipid peroxidation and EL are indicators of plant cell membrane damage, ion leakage, and impaired function (Farooq et al., 2009). A significant increase in MDA and EL was observed in drought-stressed coffee seedlings, suggesting oxidative damage, decreased membrane fluidity, and altered ion homeostasis due to rapid accumulation of ROS (Li et al., 2011). In contrast, melatonin application significantly decreased the levels of MDA and EL, thus alleviating ROS burst and decreasing oxidative injury of cell membranes. A consistent increase in both MDA and EL observed throughout the whole treatment demonstrates that the extent of cell membrane damage is affected by the duration of stress, which is consistent with previous reports in maize, soybean, and cucumber (Huang et al., 2019; Kabiri et al., 2018; Wei et al., 2015; Zhang et al., 2013). Oxidative stress due to over-accumulation of ROS can induce antioxidant enzyme activities in plants (Posmyk et al., 2008; Shi et al., 2015). In this study, oxidative stress dramatically activated SOD, POD, and CAT during drought stress, while their activities were enhanced upon melatonin application on coffee seedlings. This suggests that melatonin can act as an ROS scavenger through activation of antioxidant enzymes ROS detoxification to maintain equilibrium of the cellular ROS at a low level (Reiter et al., 2000; Shi et al., 2015; Xia et al., 2020). In addition, a high expression of chlorophyll degradation PAO gene in drought-stressed plants was down-regulated by melatonin application. The drought response AREB gene (which activates stress related genes in plants tissues) was up-regulated in drought-stressed coffee seedlings, but down-regulated upon melatonin application. Moreover, the expression of the photosynthetic RBCS2 gene was down-regulated in drought-stressed plants, which could be attributed to chloroplast damage (Bartholomew et al., 1991; Fujita et al., 2005; Kang et al., 2002; Lu et al., 2009; Mofatto et al., 2016; Orellana et al., 2010; Rizhsky et al., 2002), but up-regulated upon melatonin application. Altogether, these results provide strong evidence of the antagonistic role of melatonin during drought stress in reducing damage of chlorophyll and photosynthetic activity in coffee seedlings.

In conclusion, our study demonstrates the mitigating effects of exogenous application of melatonin on coffee seedlings under drought stress. Melatonin could improve photosynthetic efficiency, delay leaf senescence, and enhance antioxidant enzymes activities, thus eliminating ROS to improve drought tolerance in C. arabica plants. To our knowledge, our study provides for the first time an evidence of the protective role of exogenous application of melatonin in coffee seedlings, which can be crucial for plant survival and improved yields in dry environments.

Literature Cited

  • Aebi, H. 1984 Catalase in vitro Methods Enzymol. 105 121 126 doi: 10.1016/S0076-6879(84)05016-3

  • Afreen, F., Zobayed, S.M. & Kozai, T. 2006 Melatonin in Glycyrrhiza uralensis: Response of plant roots to spectral quality of light and UV-B radiation J. Pineal Res. 41 108 115 doi: 10.1111/j.1600-079X.2006.00337.x

    • Search Google Scholar
    • Export Citation
  • Allegra, M., Reiter, R.J., Tan, D.X., Gentile, C., Tesoriere, L. & Livrea, M.A. 2003 The chemistry of melatonin’s interaction with reactive species J. Pineal Res. 34 1 10 doi: 10.1034/j.1600-079x.2003.02112.x

    • Search Google Scholar
    • Export Citation
  • Arnao, M.B. & Hernandez-Ruiz, J. 2014 Melatonin: Plant growth regulator and/or biostimulator during stress? Trends Plant Sci. 19 789 797 doi: 10.1016/j.tplants.2014.07.006

    • Search Google Scholar
    • Export Citation
  • Arnao, M.B. & Hernandez-Ruiz, J. 2018 Melatonin and its relationship to plant hormones Ann. Bot. 121 195 207 doi: 10.1093/aob/mcx114

  • Bartholomew, D.M., Bartley, G.E. & Scolnik, P.A. 1991 Abscisic acid control of rbcS and cab transcription in tomato leaves J. Plant Physiol. 96 291 296 doi: 10.1104/pp.96.1.291

    • Search Google Scholar
    • Export Citation
  • Bita, M.G. & Preda, M. 2005 The effect of temperature and roasting degree on the total phenolic content of coffee brews Sci. Study Res. VI 239 242

  • Calatayud, A., Roca, D. & Martinez, P.F. 2006 Spatial-temporal variations in rose leaves under water stress conditions studied by chlorophyll fluorescence imaging Plant Physiol. Biochem. 44 564 573 doi: 10.1016/j.plaphy.2006.09.015

    • Search Google Scholar
    • Export Citation
  • Calvo, J.R., Gonzalez-Yanes, C. & Maldonado, M.D. 2013 The role of melatonin in the cells of the innate immunity: A review J. Pineal Res. 55 103 120 doi: 10.1111/jpi.12075

    • Search Google Scholar
    • Export Citation
  • Campos, P.S., Quartin, V., Ramalho, J.C. & Nunes, M.A. 2003 Electrolyte leakage and lipid degradation account for cold sensitivity in leaves of Coffea sp. plants J. Plant Physiol. 160 283 292 doi: 10.1078/0176-1617-00833

    • Search Google Scholar
    • Export Citation
  • Carr, M.K.V. 2001 The water relations and irrigation requirements of coffee Exp. Agr. 37 1 36 doi: 10.1017/S0014479701001090

  • Chen, K., Chen, L., Fan, J. & Fu, J. 2013 Alleviation of heat damage to photosystem II by nitric oxide in tall fescue Photosynth. Res. 116 21 31 doi: 10.1007/s11120-013-9883-5

    • Search Google Scholar
    • Export Citation
  • Chen, Q., Qi, W.B., Reiter, R.J., Wei, W. & Wang, B.M. 2009 Exogenously applied melatonin stimulates root growth and raises endogenous indoleacetic acid in roots of etiolated seedlings of Brassica juncea J. Plant Physiol. 166 324 328 doi: 10.1016/j.jplph.2008.06.002

    • Search Google Scholar
    • Export Citation
  • DaMatta, F.M. 2004 Exploring drought tolerance in coffee: A physiological approach with some insights for plant breeding Braz. J. Plant Physiol. 16 1 6 doi: 10.1590/s1677-04202004000100001

    • Search Google Scholar
    • Export Citation
  • DaMatta, F.M. & Ramalho, J.D.C. 2006 Impacts of drought and temperature stress on coffee physiology and production: A review Braz. J. Plant Physiol. 18 55 81 doi: 10.1590/s1677-04202006000100006

    • Search Google Scholar
    • Export Citation
  • Ding, F., Wang, G., Wang, M. & Zhang, S. 2018 Exogenous melatonin improves tolerance to water deficit by promoting cuticle formation in tomato plants Molecules 23 doi: 10.3390/molecules23071605

    • Search Google Scholar
    • Export Citation
  • Fahl, J.I., Carelli, M.L.C., Vega, J. & Magalhães, A.C. 1994 Nitrogen and irradiance levels affecting net photosynthesis and growth of young coffee plants (Coffea arabica L.) Intl. J. Hort. Sci. 69 161 169 doi: 10.1080/14620316.1994.11515262

    • Search Google Scholar
    • Export Citation
  • Fan, J., Hu, Z., Xie, Y., Chan, Z., Chen, K., Amombo, E., Chen, L. & Fu, J. 2015 Alleviation of cold damage to photosystem II and metabolisms by melatonin in bermudagrass Front. Plant Sci. 6 925 doi: 10.3389/fpls.2015.00925

    • Search Google Scholar
    • Export Citation
  • Fanjul, L., Arreola-Rodriguez, R. & Mendez-Castrejon, M.P. 2008 Stomatal responses to environmental variables in shade and sun grown coffee plants in Mexico Exp. Agr. 21 249 258 doi: 10.1017/S0014479700012606

    • Search Google Scholar
    • Export Citation
  • Farooq, M., Wahid, A., Kobayashi, N., Fujita, D. & Basra, S.M.A. 2009 Plant drought stress: Effects, mechanisms and management Agron. Sustain. Dev. 29 185 212 doi: 10.1051/agro:2008021

    • Search Google Scholar
    • Export Citation
  • Foyer, C.H. & Fletcher, J.M. 2001 Plant antioxidants: Colour me healthy Biologist (London) 48 115 120

  • Fujita, Y., Fujita, M., Satoh, R., Maruyama, K., Parvez, M.M., Seki, M., Hiratsu, K., Ohme-Takagi, M., Shinozaki, K. & Yamaguchi-Shinozaki, K. 2005 AREB1 is a transcription activator of novel ABRE-dependent ABA signalling that enhances drought stress tolerance in Arabidopsis Plant Cell 17 3470 3488 doi: 10.1105/tpc.105.035659

    • Search Google Scholar
    • Export Citation
  • Hattori, A., Migitaka, H., Iigo, M., Itoh, M., Yamamoto, K., Ohtani-Kaneko, R., Hara, M., Suzuki, T. & Reiter, R.J. 1995 Identification of melatonin in plants and its effects on plasma melatonin levels and binding to melatonin receptors in vertebrates Biochem. Mol. Biol. Intl. 35 627 634

    • Search Google Scholar
    • Export Citation
  • Heath, R.L. & Packer, L. 1968 Photoperoxidation in isolated chloroplasts Arch. Biochem. Biophys. 125 189 198 doi: 10.1016/0003-9861(68)90654-1

  • Hoagland, D.R. & Arnon, D.I. 1950 The water-culture method for growing plants without soil. California Agr. Expt. Sta. Circ. 347

  • Hu, L., Bi, A., Hu, Z., Amombo, E., Li, H. & Fu, J. 2018 Antioxidant metabolism, photosystem II, and fatty acid composition of two tall fescue genotypes with different heat tolerance under high temperature stress Front. Plant Sci. 9 1242 doi: 10.3389/fpls.2018.01242

    • Search Google Scholar
    • Export Citation
  • Huang, B., Chen, Y.E., Zhao, Y.Q., Ding, C.B., Liao, J.Q., Hu, C., Zhou, L.J., Zhang, Z.W., Yuan, S. & Yuan, M. 2019 Exogenous melatonin alleviates oxidative damages and protects photosystem II in maize seedlings under drought stress Front. Plant Sci. 10 677 doi: 10.3389/fpls.2019.00677

    • Search Google Scholar
    • Export Citation
  • Jaleel, C.A., Manivannan, P., Wahid, A., Farooq, M., Al-Juburi, H.J., Somasundaram, R. & Panneerselvam, R. 2009 Drought stress in plants: A review on morphological characteristics and pigments composition Intl. J. Agr. Biol. 11 100 105

    • Search Google Scholar
    • Export Citation
  • Jiang, C., Cui, Q., Feng, K., Xu, D., Li, C. & Zheng, Q. 2016 Melatonin improves antioxidant capacity and ion homeostasis and enhances salt tolerance in maize seedlings Acta Physiol. Plant. 38 82 doi: 10.1007/s11738-016-2101-2

    • Search Google Scholar
    • Export Citation
  • Kabiri, R., Hatami, A., Oloumi, H., Naghizadeh, M., Nasibi, F. & Tahmasebi, Z. 2018 Foliar application of melatonin induces tolerance to drought stress in Moldavian balm plants (Dracocephalum moldavica) through regulating the antioxidant system Folia Hort. 30 155 167 doi: 10.2478/fhort-2018-0016

    • Search Google Scholar
    • Export Citation
  • Kang, J.Y., Choi, H.I., Im, M.Y. & Kim, S.Y. 2002 Arabidopsis basic leucine zipper proteins that mediate stress-responsive abscisic acid signaling Plant Cell 14 343 357 doi: 10.1105/tpc.010362

    • Search Google Scholar
    • Export Citation
  • Kang, K., Lee, K., Park, S., Kim, Y.S. & Back, K. 2010 Enhanced production of melatonin by ectopic overexpression of human serotonin N-acetyltransferase plays a role in cold resistance in transgenic rice seedlings J. Pineal Res. 49 176 182 doi: 10.1111/j.1600-079X.2010.00783.x

    • Search Google Scholar
    • Export Citation
  • Korkmaz, A., Sanchez-Barcelo, E.J., Tan, D.X. & Reiter, R.J. 2009 Role of melatonin in the epigenetic regulation of breast cancer Breast Cancer Res. Treat. 115 13 27 doi: 10.1007/s10549-008-0103-5

    • Search Google Scholar
    • Export Citation
  • Lei, X.Y., Zhu, R.Y., Zhang, G.Y. & Dai, Y.R. 2004 Attenuation of cold-induced apoptosis by exogenous melatonin in carrot suspension cells: The possible involvement of polyamines J. Pineal Res. 36 126 131 doi: 10.1046/j.1600-079x.2003.00106.x

    • Search Google Scholar
    • Export Citation
  • Li, B., Sang, T., He, L.Z., Sun, J., Li, J. & Guo, S.R. 2013 Exogenous spermidine inhibits ethylene production in leaves of cucumber seedlings under NaCl stress J. Amer. Soc. Hort. Sci. 138 108 113 doi: 10.21273/Jashs.138.2.108

    • Search Google Scholar
    • Export Citation
  • Li, C., Wang, P., Wei, Z., Liang, D., Liu, C., Yin, L., Jia, D., Fu, M. & Ma, F. 2012 The mitigation effects of exogenous melatonin on salinity-induced stress in Malus hupehensis J. Pineal Res. 53 298 306 doi: 10.1111/j.1600-079X.2012.00999.x

    • Search Google Scholar
    • Export Citation
  • Li, Y., Zhao, H.X., Duan, B.L., Korpelainen, H. & Li, C.Y. 2011 Effect of drought and ABA on growth, photosynthesis and antioxidant system of Cotinus coggygria seedlings under two different light conditions Environ. Exp. Bot. 71 107 113 doi: 10.1016/j.envexpbot.2010.11.005

    • Search Google Scholar
    • Export Citation
  • Li, Y., He, N., Hou, J., Xu, L., Liu, C., Zhang, J., Wang, Q., Zhang, X. & Wu, X. 2018 Factors influencing leaf chlorophyll content in natural forests at the biome scale. Front. Ecol. Evol., doi: 10.3389/fevo.2018.00064

  • Liang, B., Ma, C., Zhang, Z., Wei, Z., Gao, T., Zhao, Q., Ma, F. & Li, C. 2018 Long-term exogenous application of melatonin improves nutrient uptake fluxes in apple plants under moderate drought stress Environ. Exp. Bot. 155 650 661 doi: 10.1016/j.envexpbot.2018.08.016

    • Search Google Scholar
    • Export Citation
  • Liang, G., Liu, J., Zhang, J. & Guo, J. 2020 Effects of drought stress on photosynthetic and physiological parameters of tomato J. Amer. Soc. Hort. Sci. 145 12 17 doi: 10.21273/jashs04725-19

    • Search Google Scholar
    • Export Citation
  • Liang, Y., Urano, D., Liao, K.L., Hedrick, T.L., Gao, Y. & Jones, A.M. 2017 A nondestructive method to estimate the chlorophyll content of Arabidopsis seedlings Plant Methods 13 26 doi: 10.1186/s13007-017-0174-6

    • Search Google Scholar
    • Export Citation
  • Lichtenthaler, H.K. 1987 Chlorophylls and carotenoids—Pigments of photosynthetic biomembranes Methods Enzymol. 148 350 382 doi: 10.1016/0076-6879(87)48036-1

    • Search Google Scholar
    • Export Citation
  • Lima, A.L.S., DaMatta, F.M., Pinheiro, H.A., Totola, M.R. & Loureiro, M.E. 2002 Photochemical responses and oxidative stress in two clones of Coffea canephora under water deficit conditions Environ. Exp. Bot. 47 239 247 doi: 10.1016/s0098-8472(01)00130-7

    • Search Google Scholar
    • Export Citation
  • Liu, A., Hu, Z., Bi, A., Fan, J., Gitau, M.M., Amombo, E., Chen, L. & Fu, J. 2016 Photosynthesis, antioxidant system and gene expression of bermudagrass in response to low temperature and salt stress Ecotoxicology 25 1445 1457 doi: 10.1007/s10646-016-1696-9

    • Search Google Scholar
    • Export Citation
  • Livak, K.J. & Schmittgen, T.D. 2001 Analysis of relative gene expression data using real-time quantitative PCR and the 2−ΔΔC T Method Methods 25 402 408 doi: 10.1006/meth.2001.1262

    • Search Google Scholar
    • Export Citation
  • Lu, G., Gao, C., Zheng, X. & Han, B. 2009 Identification of OsbZIP72 as a positive regulator of ABA response and drought tolerance in rice Planta 229 605 615 doi: 10.1007/s00425-008-0857-3

    • Search Google Scholar
    • Export Citation
  • Ma, X., Zhang, J., Burgess, P., Rossi, S. & Huang, B. 2018 Interactive effects of melatonin and cytokinin on alleviating drought-induced leaf senescence in creeping bentgrass (Agrostis stolonifera) Environ. Exp. Bot. 145 1 11 doi: 10.1016/j.envexpbot.2017.10.010

    • Search Google Scholar
    • Export Citation
  • Maxwell, K. & Johnson, G.N. 2000 Chlorophyll fluorescence—A practical guide J. Expt. Bot. 51 659 668 doi: 10.1093/jxb/51.345.659

  • Mittler, R. 2006 Abiotic stress, the field environment and stress combination Trends Plant Sci. 11 15 19 doi: 10.1016/j.tplants.2005.11.002

  • Mofatto, L.S., Carneiro Fde, A., Vieira, N.G., Duarte, K.E., Vidal, R.O., Alekcevetch, J.C., Cotta, M.G., Verdeil, J.L., Lapeyre-Montes, F., Lartaud, M., Leroy, T., De Bellis, F., Pot, D., Rodrigues, G.C., Carazzolle, M.F., Pereira, G.A., Andrade, A.C. & Marraccini, P. 2016 Identification of candidate genes for drought tolerance in coffee by high-throughput sequencing in the shoot apex of different apple cultivars BMC Plant Biol. 16 94 doi: 10.1186/s12870-016-0777-5

    • Search Google Scholar
    • Export Citation
  • Murchie, E.H. & Lawson, T. 2013 Chlorophyll fluorescence analysis: A guide to good practice and understanding some new applications J. Expt. Bot. 64 3983 3998 doi: 10.1093/jxb/ert208

    • Search Google Scholar
    • Export Citation
  • Nabi, R.B.S., Tayade, R., Hussain, A., Kulkarni, K.P., Imran, Q.M., Mun, B.-G. & Yun, B.-W. 2019 Nitric oxide regulates plant responses to drought, salinity, and heavy metal stress Environ. Exp. Bot. 161 120 133 doi: 10.1016/j.envexpbot.2019.02.003

    • Search Google Scholar
    • Export Citation
  • Orellana, S., Yanez, M., Espinoza, A., Verdugo, I., Gonzalez, E., Ruiz-Lara, S. & Casaretto, J.A. 2010 The transcription factor SlAREB1 confers drought, salt stress tolerance and regulates biotic and abiotic stress-related genes in tomato Plant Cell Environ. 33 2191 2208 doi: 10.1111/j.1365-3040.2010.02220.x

    • Search Google Scholar
    • Export Citation
  • Pinheiro, H.A., Damatta, F.M., Chaves, A.R., Loureiro, M.E. & Ducatti, C. 2005 Drought tolerance is associated with rooting depth and stomatal control of water use in clones of Coffea canephora Ann. Bot. 96 101 108 doi: 10.1093/aob/mci154

    • Search Google Scholar
    • Export Citation
  • Posmyk, M.M., Kuran, H., Marciniak, K. & Janas, K.M. 2008 Presowing seed treatment with melatonin protects red cabbage seedlings against toxic copper ion concentrations J. Pineal Res. 45 24 31 doi: 10.1111/j.1600-079X.2007.00552.x

    • Search Google Scholar
    • Export Citation
  • Reiter, R.J. 1997 Aging and oxygen toxicity: Relation to changes in melatonin Age (Omaha) 20 201 213 doi: 10.1007/s11357-997-0020-2

  • Reiter, R.J., Tan, D.X., Osuna, C. & Gitto, E. 2000 Actions of melatonin in the reduction of oxidative stress. A review J. Biomed. Sci. 7 444 458 doi: 10.1007/bf02253360

    • Search Google Scholar
    • Export Citation
  • Ribas, A.F., Pereira, L.F.P. & Vieira, L.G.E. 2006 Genetic transformation of coffee Braz. J. Plant Physiol. 18 83 94 doi: 10.1590/s1677-04202006000100007

    • Search Google Scholar
    • Export Citation
  • Rizhsky, L., Liang, H. & Mittler, R. 2002 The combined effect of drought stress and heat shock on gene expression in tobacco J. Plant Physiol. 130 1143 1151 doi: 10.1104/pp.006858

    • Search Google Scholar
    • Export Citation
  • Shi, H., Jiang, C., Ye, T., Tan, D.X., Reiter, R.J., Zhang, H., Liu, R. & Chan, Z. 2015 Comparative physiological, metabolomic, and transcriptomic analyses reveal mechanisms of improved abiotic stress resistance in bermudagrass [Cynodon dactylon (L). Pers.] by exogenous melatonin J. Expt. Bot. 66 681 694 doi: 10.1093/jxb/eru373

    • Search Google Scholar
    • Export Citation
  • Strasser, R.J., Srivastava, A. & Tsimilli-Michael, M. 2000 The fluorescence transient as a tool to characterize and screen photosynthetic samples, p. 443–480. In: M. Yunus, U. Pathre, and P. Mohanty (eds.). Probing photosynthesis: Mechanism, regulation & adaptation. Taylor and Francis, London, UK

  • Talaat, N.B., Shawky, B.T. & Ibrahim, A.S. 2015 Alleviation of drought-induced oxidative stress in maize (Zea mays L.) plants by dual application of 24-epibrassinolide and spermine Environ. Exp. Bot. 113 47 58 doi: 10.1016/j.envexpbot.2015.01.006

    • Search Google Scholar
    • Export Citation
  • Tan, D.X., Hardeland, R., Manchester, L.C., Korkmaz, A., Ma, S., Rosales-Corral, S. & Reiter, R.J. 2012 Functional roles of melatonin in plants, and perspectives in nutritional and agricultural science J. Expt. Bot. 63 577 597 doi: 10.1093/jxb/err256

    • Search Google Scholar
    • Export Citation
  • Tan, D.X., Manchester, L.C., Helton, P. & Reiter, R.J. 2007 Phytoremediative capacity of plants enriched with melatonin Plant Signal. Behav. 2 514 516 doi: 10.4161/psb.2.6.4639

    • Search Google Scholar
    • Export Citation
  • Tan, D.X., Manchester, L.C., Reiter, R.J., Plummer, B.F., Limson, J., Weintraub, S.T. & Qi, W. 2000 Melatonin directly scavenges hydrogen peroxide: A potentially new metabolic pathway of melatonin biotransformation Free Radic. Biol. Med. 29 1177 1185 doi: 10.1016/s0891-5849(00)00435-4

    • Search Google Scholar
    • Export Citation
  • Wang, C., He, J., Zhao, T.H., Cao, Y., Wang, G., Sun, B., Yan, X., Guo, W. & Li, M.H. 2019 The smaller the leaf is, the faster the leaf water loses in a temperate forest Front. Plant Sci. 10 58 doi: 10.3389/fpls.2019.00058

    • Search Google Scholar
    • Export Citation
  • Wang, P., Sun, X., Li, C., Wei, Z., Liang, D. & Ma, F. 2013 Long-term exogenous application of melatonin delays drought-induced leaf senescence in apple J. Pineal Res. 54 292 302 doi: 10.1111/jpi.12017

    • Search Google Scholar
    • Export Citation
  • Wei, W., Li, Q.T., Chu, Y.N., Reiter, R.J., Yu, X.M., Zhu, D.H., Zhang, W.K., Ma, B., Lin, Q., Zhang, J.S. & Chen, S.Y. 2015 Melatonin enhances plant growth and abiotic stress tolerance in soybean plants J. Expt. Bot. 66 695 707 doi: 10.1093/jxb/eru392

    • Search Google Scholar
    • Export Citation
  • Willekens, H., Chamnongpol, S., Davey, M., Schraudner, M., Langebartels, C., Van Montagu, M., Inze, D. & Van Camp, W. 1997 Catalase is a sink for H2O2 and is indispensable for stress defence in C3 plants EMBO J. 16 4806 4816 doi: 10.1093/emboj/16.16.4806

    • Search Google Scholar
    • Export Citation
  • Xia, H., Ni, Z., Hu, R., Lin, L., Deng, H., Wang, J., Tang, Y., Sun, G., Wang, X., Li, H., Liao, M., Lv, X. & Liang, D. 2020 Melatonin alleviates drought stress by a non-enzymatic and enzymatic antioxidative system in kiwifruit seedlings Intl. J. Mol. Sci. 21 doi: 10.3390/ijms21030852

    • Search Google Scholar
    • Export Citation
  • Yusuf, M.A., Kumar, D., Rajwanshi, R., Strasser, R.J., Tsimilli-Michael, M., Govindjee, & Sarin, N.B. 2010 Overexpression of gamma-tocopherol methyl transferase gene in transgenic Brassica juncea plants alleviates abiotic stress: Physiological and chlorophyll a fluorescence measurements Biochim. Biophys. Acta 1797 1428 1438 doi: 10.1016/j.bbabio.2010.02.002

    • Search Google Scholar
    • Export Citation
  • Zhang, N., Zhao, B., Zhang, H.J., Weeda, S., Yang, C., Yang, Z.C., Ren, S. & Guo, Y.D. 2013 Melatonin promotes water-stress tolerance, lateral root formation, and seed germination in cucumber (Cucumis sativus L.) J. Pineal Res. 54 15 23 doi: 10.1111/j.1600-079X.2012.01015.x

    • Search Google Scholar
    • Export Citation
Supplemental Table 1.

Primer sequences used in the study of relative expression of photosynthetic genes under drought stress tolerance in Coffea arabica seedlings after exogenous melatonin application.

Supplemental Table 1.

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Contributor Notes

This project was supported by funds received from the Overseas Construction Plan for Science and Education Base, China–Africa Center for Research and Education, Chinese Academy of Sciences (Grant SAJC201327).

S.C. and C.O. conducted the experiments and prepared the manuscript. C.N., M.W., and M.D.M. helped with the experiments and manuscript revision. M.A.B. helped with data analysis. Y.H. was overall project leader and revised the manuscript.

C.O. and Y.H. are the corresponding authors. E-mail: collins@wbgcas.cn or yphan@wbgcas.cn.

  • View in gallery

    Effects of exogenous application of melatonin on chlorophyll content and photosynthetic fluorescence parameters in leaves of Coffea arabica seedlings under 3 months of drought stress treatment. (A) The content of chlorophyll, Chl a, Chl b, and total Chl in leaves of seedlings under different treatments. Data represent means ± se (n = 5). Columns marked with different letters indicate significant differences between the treatments for each month based on Tukey’s test (P < 0.05). (B) Photosynthetic efficiency of chlorophyll fluorescence intensity (V) relative to time for leaves of seedlings under different treatments. (C) Coffee seedlings after treatment for 3 months with different stresses. WW, D, and DM represent well-watered control, drought-stressed, drought-stressed along with melatonin treatment, respectively.

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    Effects of melatonin treatment on (A) malondialdehyde (MDA) content and (B) electrolyte leakage (EL) in leaves of Coffea arabica seedlings under 3 months of drought stress treatment. Data represent means ± se (n = 5). Columns marked with different letters indicate significant differences between the treatments for each month based on Tukey’s test (P < 0.05). WW, D, and DM represent well-watered control, drought-stressed, and drought-stressed along with melatonin treatment, respectively.

  • View in gallery

    Melatonin application enhances enzymatic antioxidant activity in leaves of Coffea arabica seedlings under 3 months of drought stress treatment. Catalase (CAT), guaiacol peroxidase (POD), and superoxide dismutase (SOD). Data represent means ± se (n = 5). Columns marked with different letters indicate significant differences between the treatments for each month based on Tukey’s test (P < 0.05). WW, D, and DM represent well-watered control, drought-stressed, and drought-stressed along with melatonin treatment, respectively.

  • View in gallery

    Effects of melatonin application on relative expression of pheophorbide a oxygenase (PAO), ribulose-1,5-bisphosphate oxygenase (Rubisco) protein (RBSC2), abscisic acid-responsive element binding protein (AREB) in leaves of Coffea arabica seedlings under 3 months of drought stress treatment. Data represent means ± se (n = 5). Columns marked with different letters indicate significant differences between the treatments for each month based on Tukey’s test (P < 0.05). WW, D, and DM represent well-watered control, drought-stressed, and drought-stressed along with melatonin treatment, respectively.

  • Aebi, H. 1984 Catalase in vitro Methods Enzymol. 105 121 126 doi: 10.1016/S0076-6879(84)05016-3

  • Afreen, F., Zobayed, S.M. & Kozai, T. 2006 Melatonin in Glycyrrhiza uralensis: Response of plant roots to spectral quality of light and UV-B radiation J. Pineal Res. 41 108 115 doi: 10.1111/j.1600-079X.2006.00337.x

    • Search Google Scholar
    • Export Citation
  • Allegra, M., Reiter, R.J., Tan, D.X., Gentile, C., Tesoriere, L. & Livrea, M.A. 2003 The chemistry of melatonin’s interaction with reactive species J. Pineal Res. 34 1 10 doi: 10.1034/j.1600-079x.2003.02112.x

    • Search Google Scholar
    • Export Citation
  • Arnao, M.B. & Hernandez-Ruiz, J. 2014 Melatonin: Plant growth regulator and/or biostimulator during stress? Trends Plant Sci. 19 789 797 doi: 10.1016/j.tplants.2014.07.006

    • Search Google Scholar
    • Export Citation
  • Arnao, M.B. & Hernandez-Ruiz, J. 2018 Melatonin and its relationship to plant hormones Ann. Bot. 121 195 207 doi: 10.1093/aob/mcx114

  • Bartholomew, D.M., Bartley, G.E. & Scolnik, P.A. 1991 Abscisic acid control of rbcS and cab transcription in tomato leaves J. Plant Physiol. 96 291 296 doi: 10.1104/pp.96.1.291

    • Search Google Scholar
    • Export Citation
  • Bita, M.G. & Preda, M. 2005 The effect of temperature and roasting degree on the total phenolic content of coffee brews Sci. Study Res. VI 239 242

  • Calatayud, A., Roca, D. & Martinez, P.F. 2006 Spatial-temporal variations in rose leaves under water stress conditions studied by chlorophyll fluorescence imaging Plant Physiol. Biochem. 44 564 573 doi: 10.1016/j.plaphy.2006.09.015

    • Search Google Scholar
    • Export Citation
  • Calvo, J.R., Gonzalez-Yanes, C. & Maldonado, M.D. 2013 The role of melatonin in the cells of the innate immunity: A review J. Pineal Res. 55 103 120 doi: 10.1111/jpi.12075

    • Search Google Scholar
    • Export Citation
  • Campos, P.S., Quartin, V., Ramalho, J.C. & Nunes, M.A. 2003 Electrolyte leakage and lipid degradation account for cold sensitivity in leaves of Coffea sp. plants J. Plant Physiol. 160 283 292 doi: 10.1078/0176-1617-00833

    • Search Google Scholar
    • Export Citation
  • Carr, M.K.V. 2001 The water relations and irrigation requirements of coffee Exp. Agr. 37 1 36 doi: 10.1017/S0014479701001090

  • Chen, K., Chen, L., Fan, J. & Fu, J. 2013 Alleviation of heat damage to photosystem II by nitric oxide in tall fescue Photosynth. Res. 116 21 31 doi: 10.1007/s11120-013-9883-5

    • Search Google Scholar
    • Export Citation
  • Chen, Q., Qi, W.B., Reiter, R.J., Wei, W. & Wang, B.M. 2009 Exogenously applied melatonin stimulates root growth and raises endogenous indoleacetic acid in roots of etiolated seedlings of Brassica juncea J. Plant Physiol. 166 324 328 doi: 10.1016/j.jplph.2008.06.002

    • Search Google Scholar
    • Export Citation
  • DaMatta, F.M. 2004 Exploring drought tolerance in coffee: A physiological approach with some insights for plant breeding Braz. J. Plant Physiol. 16 1 6 doi: 10.1590/s1677-04202004000100001

    • Search Google Scholar
    • Export Citation
  • DaMatta, F.M. & Ramalho, J.D.C. 2006 Impacts of drought and temperature stress on coffee physiology and production: A review Braz. J. Plant Physiol. 18 55 81 doi: 10.1590/s1677-04202006000100006

    • Search Google Scholar
    • Export Citation
  • Ding, F., Wang, G., Wang, M. & Zhang, S. 2018 Exogenous melatonin improves tolerance to water deficit by promoting cuticle formation in tomato plants Molecules 23 doi: 10.3390/molecules23071605

    • Search Google Scholar
    • Export Citation
  • Fahl, J.I., Carelli, M.L.C., Vega, J. & Magalhães, A.C. 1994 Nitrogen and irradiance levels affecting net photosynthesis and growth of young coffee plants (Coffea arabica L.) Intl. J. Hort. Sci. 69 161 169 doi: 10.1080/14620316.1994.11515262

    • Search Google Scholar
    • Export Citation
  • Fan, J., Hu, Z., Xie, Y., Chan, Z., Chen, K., Amombo, E., Chen, L. & Fu, J. 2015 Alleviation of cold damage to photosystem II and metabolisms by melatonin in bermudagrass Front. Plant Sci. 6 925 doi: 10.3389/fpls.2015.00925

    • Search Google Scholar
    • Export Citation
  • Fanjul, L., Arreola-Rodriguez, R. & Mendez-Castrejon, M.P. 2008 Stomatal responses to environmental variables in shade and sun grown coffee plants in Mexico Exp. Agr. 21 249 258 doi: 10.1017/S0014479700012606

    • Search Google Scholar
    • Export Citation
  • Farooq, M., Wahid, A., Kobayashi, N., Fujita, D. & Basra, S.M.A. 2009 Plant drought stress: Effects, mechanisms and management Agron. Sustain. Dev. 29 185 212 doi: 10.1051/agro:2008021

    • Search Google Scholar
    • Export Citation
  • Foyer, C.H. & Fletcher, J.M. 2001 Plant antioxidants: Colour me healthy Biologist (London) 48 115 120

  • Fujita, Y., Fujita, M., Satoh, R., Maruyama, K., Parvez, M.M., Seki, M., Hiratsu, K., Ohme-Takagi, M., Shinozaki, K. & Yamaguchi-Shinozaki, K. 2005 AREB1 is a transcription activator of novel ABRE-dependent ABA signalling that enhances drought stress tolerance in Arabidopsis Plant Cell 17 3470 3488 doi: 10.1105/tpc.105.035659

    • Search Google Scholar
    • Export Citation
  • Hattori, A., Migitaka, H., Iigo, M., Itoh, M., Yamamoto, K., Ohtani-Kaneko, R., Hara, M., Suzuki, T. & Reiter, R.J. 1995 Identification of melatonin in plants and its effects on plasma melatonin levels and binding to melatonin receptors in vertebrates Biochem. Mol. Biol. Intl. 35 627 634

    • Search Google Scholar
    • Export Citation
  • Heath, R.L. & Packer, L. 1968 Photoperoxidation in isolated chloroplasts Arch. Biochem. Biophys. 125 189 198 doi: 10.1016/0003-9861(68)90654-1

  • Hoagland, D.R. & Arnon, D.I. 1950 The water-culture method for growing plants without soil. California Agr. Expt. Sta. Circ. 347

  • Hu, L., Bi, A., Hu, Z., Amombo, E., Li, H. & Fu, J. 2018 Antioxidant metabolism, photosystem II, and fatty acid composition of two tall fescue genotypes with different heat tolerance under high temperature stress Front. Plant Sci. 9 1242 doi: 10.3389/fpls.2018.01242

    • Search Google Scholar
    • Export Citation
  • Huang, B., Chen, Y.E., Zhao, Y.Q., Ding, C.B., Liao, J.Q., Hu, C., Zhou, L.J., Zhang, Z.W., Yuan, S. & Yuan, M. 2019 Exogenous melatonin alleviates oxidative damages and protects photosystem II in maize seedlings under drought stress Front. Plant Sci. 10 677 doi: 10.3389/fpls.2019.00677

    • Search Google Scholar
    • Export Citation
  • Jaleel, C.A., Manivannan, P., Wahid, A., Farooq, M., Al-Juburi, H.J., Somasundaram, R. & Panneerselvam, R. 2009 Drought stress in plants: A review on morphological characteristics and pigments composition Intl. J. Agr. Biol. 11 100 105

    • Search Google Scholar
    • Export Citation
  • Jiang, C., Cui, Q., Feng, K., Xu, D., Li, C. & Zheng, Q. 2016 Melatonin improves antioxidant capacity and ion homeostasis and enhances salt tolerance in maize seedlings Acta Physiol. Plant. 38 82 doi: 10.1007/s11738-016-2101-2

    • Search Google Scholar
    • Export Citation
  • Kabiri, R., Hatami, A., Oloumi, H., Naghizadeh, M., Nasibi, F. & Tahmasebi, Z. 2018 Foliar application of melatonin induces tolerance to drought stress in Moldavian balm plants (Dracocephalum moldavica) through regulating the antioxidant system Folia Hort. 30 155 167 doi: 10.2478/fhort-2018-0016

    • Search Google Scholar
    • Export Citation
  • Kang, J.Y., Choi, H.I., Im, M.Y. & Kim, S.Y. 2002 Arabidopsis basic leucine zipper proteins that mediate stress-responsive abscisic acid signaling Plant Cell 14 343 357 doi: 10.1105/tpc.010362

    • Search Google Scholar
    • Export Citation
  • Kang, K., Lee, K., Park, S., Kim, Y.S. & Back, K. 2010 Enhanced production of melatonin by ectopic overexpression of human serotonin N-acetyltransferase plays a role in cold resistance in transgenic rice seedlings J. Pineal Res. 49 176 182 doi: 10.1111/j.1600-079X.2010.00783.x

    • Search Google Scholar
    • Export Citation
  • Korkmaz, A., Sanchez-Barcelo, E.J., Tan, D.X. & Reiter, R.J. 2009 Role of melatonin in the epigenetic regulation of breast cancer Breast Cancer Res. Treat. 115 13 27 doi: 10.1007/s10549-008-0103-5

    • Search Google Scholar
    • Export Citation
  • Lei, X.Y., Zhu, R.Y., Zhang, G.Y. & Dai, Y.R. 2004 Attenuation of cold-induced apoptosis by exogenous melatonin in carrot suspension cells: The possible involvement of polyamines J. Pineal Res. 36 126 131 doi: 10.1046/j.1600-079x.2003.00106.x

    • Search Google Scholar
    • Export Citation
  • Li, B., Sang, T., He, L.Z., Sun, J., Li, J. & Guo, S.R. 2013 Exogenous spermidine inhibits ethylene production in leaves of cucumber seedlings under NaCl stress J. Amer. Soc. Hort. Sci. 138 108 113 doi: 10.21273/Jashs.138.2.108

    • Search Google Scholar
    • Export Citation
  • Li, C., Wang, P., Wei, Z., Liang, D., Liu, C., Yin, L., Jia, D., Fu, M. & Ma, F. 2012 The mitigation effects of exogenous melatonin on salinity-induced stress in Malus hupehensis J. Pineal Res. 53 298 306 doi: 10.1111/j.1600-079X.2012.00999.x

    • Search Google Scholar
    • Export Citation
  • Li, Y., Zhao, H.X., Duan, B.L., Korpelainen, H. & Li, C.Y. 2011 Effect of drought and ABA on growth, photosynthesis and antioxidant system of Cotinus coggygria seedlings under two different light conditions Environ. Exp. Bot. 71 107 113 doi: 10.1016/j.envexpbot.2010.11.005

    • Search Google Scholar
    • Export Citation
  • Li, Y., He, N., Hou, J., Xu, L., Liu, C., Zhang, J., Wang, Q., Zhang, X. & Wu, X. 2018 Factors influencing leaf chlorophyll content in natural forests at the biome scale. Front. Ecol. Evol., doi: 10.3389/fevo.2018.00064

  • Liang, B., Ma, C., Zhang, Z., Wei, Z., Gao, T., Zhao, Q., Ma, F. & Li, C. 2018 Long-term exogenous application of melatonin improves nutrient uptake fluxes in apple plants under moderate drought stress Environ. Exp. Bot. 155 650 661 doi: 10.1016/j.envexpbot.2018.08.016

    • Search Google Scholar
    • Export Citation
  • Liang, G., Liu, J., Zhang, J. & Guo, J. 2020 Effects of drought stress on photosynthetic and physiological parameters of tomato J. Amer. Soc. Hort. Sci. 145 12 17 doi: 10.21273/jashs04725-19

    • Search Google Scholar
    • Export Citation
  • Liang, Y., Urano, D., Liao, K.L., Hedrick, T.L., Gao, Y. & Jones, A.M. 2017 A nondestructive method to estimate the chlorophyll content of Arabidopsis seedlings Plant Methods 13 26 doi: 10.1186/s13007-017-0174-6

    • Search Google Scholar
    • Export Citation
  • Lichtenthaler, H.K. 1987 Chlorophylls and carotenoids—Pigments of photosynthetic biomembranes Methods Enzymol. 148 350 382 doi: 10.1016/0076-6879(87)48036-1

    • Search Google Scholar
    • Export Citation
  • Lima, A.L.S., DaMatta, F.M., Pinheiro, H.A., Totola, M.R. & Loureiro, M.E. 2002 Photochemical responses and oxidative stress in two clones of Coffea canephora under water deficit conditions Environ. Exp. Bot. 47 239 247 doi: 10.1016/s0098-8472(01)00130-7

    • Search Google Scholar
    • Export Citation
  • Liu, A., Hu, Z., Bi, A., Fan, J., Gitau, M.M., Amombo, E., Chen, L. & Fu, J. 2016 Photosynthesis, antioxidant system and gene expression of bermudagrass in response to low temperature and salt stress Ecotoxicology 25 1445 1457 doi: 10.1007/s10646-016-1696-9

    • Search Google Scholar
    • Export Citation
  • Livak, K.J. & Schmittgen, T.D. 2001 Analysis of relative gene expression data using real-time quantitative PCR and the 2−ΔΔC T Method Methods 25 402 408 doi: 10.1006/meth.2001.1262

    • Search Google Scholar
    • Export Citation
  • Lu, G., Gao, C., Zheng, X. & Han, B. 2009 Identification of OsbZIP72 as a positive regulator of ABA response and drought tolerance in rice Planta 229 605 615 doi: 10.1007/s00425-008-0857-3

    • Search Google Scholar
    • Export Citation
  • Ma, X., Zhang, J., Burgess, P., Rossi, S. & Huang, B. 2018 Interactive effects of melatonin and cytokinin on alleviating drought-induced leaf senescence in creeping bentgrass (Agrostis stolonifera) Environ. Exp. Bot. 145 1 11 doi: 10.1016/j.envexpbot.2017.10.010

    • Search Google Scholar
    • Export Citation
  • Maxwell, K. & Johnson, G.N. 2000 Chlorophyll fluorescence—A practical guide J. Expt. Bot. 51 659 668 doi: 10.1093/jxb/51.345.659

  • Mittler, R. 2006 Abiotic stress, the field environment and stress combination Trends Plant Sci. 11 15 19 doi: 10.1016/j.tplants.2005.11.002

  • Mofatto, L.S., Carneiro Fde, A., Vieira, N.G., Duarte, K.E., Vidal, R.O., Alekcevetch, J.C., Cotta, M.G., Verdeil, J.L., Lapeyre-Montes, F., Lartaud, M., Leroy, T., De Bellis, F., Pot, D., Rodrigues, G.C., Carazzolle, M.F., Pereira, G.A., Andrade, A.C. & Marraccini, P. 2016 Identification of candidate genes for drought tolerance in coffee by high-throughput sequencing in the shoot apex of different apple cultivars BMC Plant Biol. 16 94 doi: 10.1186/s12870-016-0777-5

    • Search Google Scholar
    • Export Citation
  • Murchie, E.H. & Lawson, T. 2013 Chlorophyll fluorescence analysis: A guide to good practice and understanding some new applications J. Expt. Bot. 64 3983 3998 doi: 10.1093/jxb/ert208

    • Search Google Scholar
    • Export Citation
  • Nabi, R.B.S., Tayade, R., Hussain, A., Kulkarni, K.P., Imran, Q.M., Mun, B.-G. & Yun, B.-W. 2019 Nitric oxide regulates plant responses to drought, salinity, and heavy metal stress Environ. Exp. Bot. 161 120 133 doi: 10.1016/j.envexpbot.2019.02.003

    • Search Google Scholar
    • Export Citation
  • Orellana, S., Yanez, M., Espinoza, A., Verdugo, I., Gonzalez, E., Ruiz-Lara, S. & Casaretto, J.A. 2010 The transcription factor SlAREB1 confers drought, salt stress tolerance and regulates biotic and abiotic stress-related genes in tomato Plant Cell Environ. 33 2191 2208 doi: 10.1111/j.1365-3040.2010.02220.x

    • Search Google Scholar
    • Export Citation
  • Pinheiro, H.A., Damatta, F.M., Chaves, A.R., Loureiro, M.E. & Ducatti, C. 2005 Drought tolerance is associated with rooting depth and stomatal control of water use in clones of Coffea canephora Ann. Bot. 96 101 108 doi: 10.1093/aob/mci154

    • Search Google Scholar
    • Export Citation
  • Posmyk, M.M., Kuran, H., Marciniak, K. & Janas, K.M. 2008 Presowing seed treatment with melatonin protects red cabbage seedlings against toxic copper ion concentrations J. Pineal Res. 45 24 31 doi: 10.1111/j.1600-079X.2007.00552.x

    • Search Google Scholar
    • Export Citation
  • Reiter, R.J. 1997 Aging and oxygen toxicity: Relation to changes in melatonin Age (Omaha) 20 201 213 doi: 10.1007/s11357-997-0020-2

  • Reiter, R.J., Tan, D.X., Osuna, C. & Gitto, E. 2000 Actions of melatonin in the reduction of oxidative stress. A review J. Biomed. Sci. 7 444 458 doi: 10.1007/bf02253360

    • Search Google Scholar
    • Export Citation
  • Ribas, A.F., Pereira, L.F.P. & Vieira, L.G.E. 2006 Genetic transformation of coffee Braz. J. Plant Physiol. 18 83 94 doi: 10.1590/s1677-04202006000100007

    • Search Google Scholar
    • Export Citation
  • Rizhsky, L., Liang, H. & Mittler, R. 2002 The combined effect of drought stress and heat shock on gene expression in tobacco J. Plant Physiol. 130 1143 1151 doi: 10.1104/pp.006858

    • Search Google Scholar
    • Export Citation
  • Shi, H., Jiang, C., Ye, T., Tan, D.X., Reiter, R.J., Zhang, H., Liu, R. & Chan, Z. 2015 Comparative physiological, metabolomic, and transcriptomic analyses reveal mechanisms of improved abiotic stress resistance in bermudagrass [Cynodon dactylon (L). Pers.] by exogenous melatonin J. Expt. Bot. 66 681 694 doi: 10.1093/jxb/eru373

    • Search Google Scholar
    • Export Citation
  • Strasser, R.J., Srivastava, A. & Tsimilli-Michael, M. 2000 The fluorescence transient as a tool to characterize and screen photosynthetic samples, p. 443–480. In: M. Yunus, U. Pathre, and P. Mohanty (eds.). Probing photosynthesis: Mechanism, regulation & adaptation. Taylor and Francis, London, UK

  • Talaat, N.B., Shawky, B.T. & Ibrahim, A.S. 2015 Alleviation of drought-induced oxidative stress in maize (Zea mays L.) plants by dual application of 24-epibrassinolide and spermine Environ. Exp. Bot. 113 47 58 doi: 10.1016/j.envexpbot.2015.01.006

    • Search Google Scholar
    • Export Citation
  • Tan, D.X., Hardeland, R., Manchester, L.C., Korkmaz, A., Ma, S., Rosales-Corral, S. & Reiter, R.J. 2012 Functional roles of melatonin in plants, and perspectives in nutritional and agricultural science J. Expt. Bot. 63 577 597 doi: 10.1093/jxb/err256

    • Search Google Scholar
    • Export Citation
  • Tan, D.X., Manchester, L.C., Helton, P. & Reiter, R.J. 2007 Phytoremediative capacity of plants enriched with melatonin Plant Signal. Behav. 2 514 516 doi: 10.4161/psb.2.6.4639

    • Search Google Scholar
    • Export Citation
  • Tan, D.X., Manchester, L.C., Reiter, R.J., Plummer, B.F., Limson, J., Weintraub, S.T. & Qi, W. 2000 Melatonin directly scavenges hydrogen peroxide: A potentially new metabolic pathway of melatonin biotransformation Free Radic. Biol. Med. 29 1177 1185 doi: 10.1016/s0891-5849(00)00435-4

    • Search Google Scholar
    • Export Citation
  • Wang, C., He, J., Zhao, T.H., Cao, Y., Wang, G., Sun, B., Yan, X., Guo, W. & Li, M.H. 2019 The smaller the leaf is, the faster the leaf water loses in a temperate forest Front. Plant Sci. 10 58 doi: 10.3389/fpls.2019.00058

    • Search Google Scholar
    • Export Citation
  • Wang, P., Sun, X., Li, C., Wei, Z., Liang, D. & Ma, F. 2013 Long-term exogenous application of melatonin delays drought-induced leaf senescence in apple J. Pineal Res. 54 292 302 doi: 10.1111/jpi.12017

    • Search Google Scholar
    • Export Citation
  • Wei, W., Li, Q.T., Chu, Y.N., Reiter, R.J., Yu, X.M., Zhu, D.H., Zhang, W.K., Ma, B., Lin, Q., Zhang, J.S. & Chen, S.Y. 2015 Melatonin enhances plant growth and abiotic stress tolerance in soybean plants J. Expt. Bot. 66 695 707 doi: 10.1093/jxb/eru392

    • Search Google Scholar
    • Export Citation
  • Willekens, H., Chamnongpol, S., Davey, M., Schraudner, M., Langebartels, C., Van Montagu, M., Inze, D. & Van Camp, W. 1997 Catalase is a sink for H2O2 and is indispensable for stress defence in C3 plants EMBO J. 16 4806 4816 doi: 10.1093/emboj/16.16.4806

    • Search Google Scholar
    • Export Citation
  • Xia, H., Ni, Z., Hu, R., Lin, L., Deng, H., Wang, J., Tang, Y., Sun, G., Wang, X., Li, H., Liao, M., Lv, X. & Liang, D. 2020 Melatonin alleviates drought stress by a non-enzymatic and enzymatic antioxidative system in kiwifruit seedlings Intl. J. Mol. Sci. 21 doi: 10.3390/ijms21030852

    • Search Google Scholar
    • Export Citation
  • Yusuf, M.A., Kumar, D., Rajwanshi, R., Strasser, R.J., Tsimilli-Michael, M., Govindjee, & Sarin, N.B. 2010 Overexpression of gamma-tocopherol methyl transferase gene in transgenic Brassica juncea plants alleviates abiotic stress: Physiological and chlorophyll a fluorescence measurements Biochim. Biophys. Acta 1797 1428 1438 doi: 10.1016/j.bbabio.2010.02.002

    • Search Google Scholar
    • Export Citation
  • Zhang, N., Zhao, B., Zhang, H.J., Weeda, S., Yang, C., Yang, Z.C., Ren, S. & Guo, Y.D. 2013 Melatonin promotes water-stress tolerance, lateral root formation, and seed germination in cucumber (Cucumis sativus L.) J. Pineal Res. 54 15 23 doi: 10.1111/j.1600-079X.2012.01015.x

    • Search Google Scholar
    • Export Citation
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