Calcium Affects Growth and Physiological Indices of Panax quinquefolium L.

in HortScience
Authors:
Zhenghai ZhangInstitute of Special Animal and Plant Sciences of the Chinese Academy of Agricultural Sciences, Changchun, Jilin, 130112, China; and Jilin Provincial Key Laboratory of Traditional Chinese Medicinal Materials Cultivation and Propagation, Jilin, 130112, China

Search for other papers by Zhenghai Zhang in
ASHS
Google Scholar
PubMed
Close
,
Hai SunInstitute of Special Animal and Plant Sciences of the Chinese Academy of Agricultural Sciences, Changchun, Jilin, 130112, China; and Jilin Provincial Key Laboratory of Traditional Chinese Medicinal Materials Cultivation and Propagation, Jilin, 130112, China

Search for other papers by Hai Sun in
ASHS
Google Scholar
PubMed
Close
,
Cai ShaoInstitute of Special Animal and Plant Sciences of the Chinese Academy of Agricultural Sciences, Changchun, Jilin, 130112, China; and Jilin Provincial Key Laboratory of Traditional Chinese Medicinal Materials Cultivation and Propagation, Jilin, 130112, China

Search for other papers by Cai Shao in
ASHS
Google Scholar
PubMed
Close
,
Huixia LeiInstitute of Special Animal and Plant Sciences of the Chinese Academy of Agricultural Sciences, Changchun, Jilin, 130112, China

Search for other papers by Huixia Lei in
ASHS
Google Scholar
PubMed
Close
,
Jiaqi QianInstitute of Special Animal and Plant Sciences of the Chinese Academy of Agricultural Sciences, Changchun, Jilin, 130112, China

Search for other papers by Jiaqi Qian in
ASHS
Google Scholar
PubMed
Close
,
Yinyin RuanInstitute of Special Animal and Plant Sciences of the Chinese Academy of Agricultural Sciences, Changchun, Jilin, 130112, China

Search for other papers by Yinyin Ruan in
ASHS
Google Scholar
PubMed
Close
, and
Yayu ZhangInstitute of Special Animal and Plant Sciences of the Chinese Academy of Agricultural Sciences, Changchun, Jilin, 130112, China; and Jilin Provincial Key Laboratory of Traditional Chinese Medicinal Materials Cultivation and Propagation, Jilin, 130112, China

Search for other papers by Yayu Zhang in
ASHS
Google Scholar
PubMed
Close

Calcium (Ca) is necessary for plant growth and stress resistance, which are essential for the successful cultivation of Panax quinquefolium L. (American ginseng). However, information about the physiology of Ca nutrition in this species is limited. Therefore, the objective of this study was to determine the effect of Ca on the growth and physiological performance of American ginseng. Two-year-old American ginseng plants were supplemented with the following Ca concentrations [Ca2+] in a hydroponic system: 0, 160.17, 320.34, 640.68, and 961.02 mg⋅L−1. Measurements included growth biomass accumulation, chlorophyll (Chl) content and fluorescence, photosynthetic parameters, antioxidant enzyme activity, root activity, and malondialdehyde content. Biomass, stem height, leaf area, maximum photochemical efficiency, and superoxide dismutase activity peaked at [Ca2+] of 640.68 mg⋅L−1. Actual photochemical efficiency, minimum saturating irradiance, photosynthetic rate, catalase and peroxidase activities, and root activity reached their maximum at [Ca2+] of 320.34 mg⋅L−1. Stem diameter and regulated thermal energy dissipation increased with [Ca2+]. The sum of nonregulated heat dissipation and fluorescence emission and malondialdehyde content decreased to a minimum at [Ca2+] of 320.34 mg⋅L−1. The Chl content reached a maximum at [Ca2+] of 160.17 mg⋅L−1, but the Chl a/b ratio increased with [Ca2+]; the actual photochemical efficiency and photosynthetic rate reached their maximum level at Chl a/b ratios of 2.04 and [Ca2+] of 320.34 mg⋅L−1. Therefore, the optimal [Ca2+] for American ginseng growth was 320.34 mg⋅L−1. Furthermore, an appropriate increase [Ca2+] in the growth medium may improve biomass accumulation, light energy utilization efficiency, and stress resistance in American ginseng.

Abstract

Calcium (Ca) is necessary for plant growth and stress resistance, which are essential for the successful cultivation of Panax quinquefolium L. (American ginseng). However, information about the physiology of Ca nutrition in this species is limited. Therefore, the objective of this study was to determine the effect of Ca on the growth and physiological performance of American ginseng. Two-year-old American ginseng plants were supplemented with the following Ca concentrations [Ca2+] in a hydroponic system: 0, 160.17, 320.34, 640.68, and 961.02 mg⋅L−1. Measurements included growth biomass accumulation, chlorophyll (Chl) content and fluorescence, photosynthetic parameters, antioxidant enzyme activity, root activity, and malondialdehyde content. Biomass, stem height, leaf area, maximum photochemical efficiency, and superoxide dismutase activity peaked at [Ca2+] of 640.68 mg⋅L−1. Actual photochemical efficiency, minimum saturating irradiance, photosynthetic rate, catalase and peroxidase activities, and root activity reached their maximum at [Ca2+] of 320.34 mg⋅L−1. Stem diameter and regulated thermal energy dissipation increased with [Ca2+]. The sum of nonregulated heat dissipation and fluorescence emission and malondialdehyde content decreased to a minimum at [Ca2+] of 320.34 mg⋅L−1. The Chl content reached a maximum at [Ca2+] of 160.17 mg⋅L−1, but the Chl a/b ratio increased with [Ca2+]; the actual photochemical efficiency and photosynthetic rate reached their maximum level at Chl a/b ratios of 2.04 and [Ca2+] of 320.34 mg⋅L−1. Therefore, the optimal [Ca2+] for American ginseng growth was 320.34 mg⋅L−1. Furthermore, an appropriate increase [Ca2+] in the growth medium may improve biomass accumulation, light energy utilization efficiency, and stress resistance in American ginseng.

Panax quinquefolium L. (American ginseng) is an herb native to North America that is now cultivated in East Asia as well. Its active compounds, ginsenosides, have been documented to exert a wide range of biological activities resulting in hypoglycemic, anti-inflammatory, cardioprotective, and antitumor effects, and the plant has been postulated to have therapeutic applications for chronic obstructive pulmonary and menopause symptoms, among others (Szczuka et al., 2019). Currently, the American ginseng supply relies mainly on intensive field cultivation under artificial shade structures (Nadeau et al., 2003). However, this system commonly causes various diseases because of high planting density. Therefore, enhancing the health of American ginseng has become the focus of research.

Ca is the third most abundant element in plants, is necessary for plant growth, and has a role in resistance to abiotic and biotic stresses (Pathak et al., 2020). Ca in American ginseng cultivation has received attention since the 1980s. The absence of Ca was more restrictive to root growth and resulted in earlier foliar deficiency symptoms than withholding nitrogen, phosphorus, or magnesium from the nutrient solution in sand culture (Stoltz, 1982). Ca deficiency also led to a lower root/shoot ratio and relative root growth rate than iron or boron deficiency in the nutrient solution of hydroponic plants (Clippard et al., 2020). An analysis of soil samples (0–20 cm depth, within 15 cm adjacent to the root) collected from 54 wild and wild-simulated ginseng sites showed that American ginseng grows in a wide range of soil pH (4.2–7.1), but especially in Ca-rich soils with an average soil Ca content of 3500 kg⋅ha−1 [using the Mehlich 3 (ICP) method] (Burkhart, 2013). During research trials simulating wild habitat conditions, the survival and growth of American ginseng were improved with liming (Slak, 2005). Therefore, for example, dolomitic lime increased the germination, leaf area, and height and root weights of American ginseng in field cultivation (Konsler and Shelton, 1990; Thyroff, 2015). However, the soil pH and Ca concentration ([Ca2+]) depend on the type of Ca applied, which has different influences on American ginseng (Peever, 2004). For instance, excess gypsum (>2 Mt⋅ha−1) application decreased shoot and root growth and reduced the contents of total ginsenosides (Lee and Mudge, 2013). Therefore, maintaining a certain soil Ca content is one of the key elements for the successful cultivation of American ginseng.

However, information about the suitable [Ca2+] range and Ca nutrition physiology of American ginseng remains limited. Therefore, the objective of this study was to determine the adequate [Ca2+] for optimum American ginseng growth and physiological indices, namely, biomass, size, Chl content, Chl fluorescence, photosynthetic parameters, antioxidant enzyme activity, root activity, and malondialdehyde (MDA) content. Moreover, using the observed physiological function of Ca in American ginseng, we discussed why Ca promotes growth and enhances stress resistance of American ginseng.

Materials and Methods

Plant materials and treatments.

One-year-old American ginseng roots were selected as test materials in Nov. 2020; the average root weight was 1.62 ± 0.09 g. After the roots were carefully washed, the buds were immersed in a gibberellic acid solution (250 mg⋅L−1) for 2 h. Then, the roots were cultured in an artificial climate chamber at 26.5 °C with 58.9% relative humidity, 44.38 μmol⋅m−2⋅s−1 photosynthetically active radiation, and a 16-h/8-h light/dark regime.

The first year’s dormant buds began to germinate after 2 d (similar to the germination after natural dormancy, they were considered 2-year-old American ginseng). On day 7, when the bending stem began to straighten and the curly leaves began to unfold, plantlets were transplanted to hydroponic tanks containing Hoagland’s nutrient solution with the following five different [Ca2+] obtained by the addition of Ca(NO3)2: 0, 160.17, 320.34, 640.68, and 961.02 mg⋅L−1. Each [Ca2+] treatment was applied to 45 plantlets divided into three replicates of 15 plantlets each; all culture media were changed every 3 d and circulated by a pump. On day 20, when leaves appeared in different colors among the treatments, samples were collected and the growth parameters and physiological indices were measured.

Measurement of growth parameters.

Stem height was measured from the top of the rhizome to the base of the petiole. Stem diameter was measured at 1.5 cm below the base of the petiole. In addition, root, stem, and leaf weights were measured. The middle leaflet of one prong from each plant was selected as the sample, and the leaf area was calculated using ImageJ 1.52v (National Institutes of Health, Bethesda, MA) after scanning the leaves at 300 dpi. For all measured parameters, the average value for 15 plants was regarded as a replicate.

Measurement of Chl fluorescence.

The maximum photochemical efficiency of photosystem II (PS II; Fv/Fm), actual photochemical efficiency of PS II [Y(II)], regulated thermal energy dissipation [Y(NPQ)], and the sum of nonregulated heat dissipation and fluorescence emission [Y(NO)] (Ralph and Gademann, 2005) were measured with IMAG-MIN/B (Heinz Walz GmbH, Effeltrich, Germany). The actinic light source was a blue (450 nm) light-emitting diode with a saturation pulse light of 22 μmol⋅m−2⋅s−1 at 20-s intervals. The measure light was 0.05 μmol⋅m−2⋅s−1, with the basic fluorescence intensity kept between 0.03 and 0.1. The relative electron transfer rate for PS II was measured with a set of light pulses (0, 40, 80, 225, 325, 405, 495, and 625 μmol⋅m−2⋅s−1) at 20-s intervals. The rapid light curve and initial slope were fitted and calculated using Origin Pro 9.7 (OriginLab, Northampton, MA). Minimum saturating irradiance (Ek) was calculated according to a previously described method (Klughammer and Schreiber, 2008). Measurements were performed in a dark artificial climate chamber with a 20-min dark adaptation time.

Measurement of photosynthetic parameters.

The transpiration rate E, vapor pressure deficit (VPD), stomatal conductance (GH2O), photosynthetic rate (Pn), and intercellular CO2 concentration (Ci) were measured with a GFS-3000 portable photosynthesis measurement system (Heinz Walz GmbH). The gas flow rate was 750 μmol⋅m−2⋅s−1, the fan speed of the gas mixer comprised seven stages, and the leaf chamber area was 3 cm2. The measurements were performed in an artificial climate chamber, and the light was 44.38 μmol⋅m−2⋅s−1.

Determination of enzyme activity, root activity, Chl, and MDA content.

The activity of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) and the contents of dehydrogenase (DHA), Chl, and MDA were determined using the corresponding assay kits (Cominbio, Suzhou, China) according to the instructions provided by the manufacturer. For each [Ca2+] treatment, leaves or lateral roots (used for extracting DHA) of 15 plants were mixed as a replicate (0.1 g per sample). Leaf samples were stored at −80 °C until use. An equal weight of CaCO3 powder was added to each leaf sample for Chl extraction before grinding under liquid nitrogen, and the ground samples were extracted by adding 1 mL precooled sodium phosphate buffer (pH 7.0). The homogenates were extracted in an ice bath, followed by centrifugation at 8000 gn for 10 min at 4 °C; the supernatants were used for spectrophotometric determination. All spectrophotometric analyses were conducted using a SpectraMax iD3 microplate spectrophotometer (Molecular Devices, Sunnyvale, CA).

Statistical analysis.

Each [Ca2+] treatment was analyzed in three replicates, and the data shown are the mean ± sd of the three replicates. An analysis of variance was used to estimate significant effects, followed by Fisher’s least significant difference test (P = 0.05) to separate the means. All analyses were conducted using SAS 8.0 (SAS Institute Inc., Cary, NC).

Results

Growth parameters of American ginseng.

Root weight of American ginseng decreased during sprouting, but root, stem, and leaf weights all increased after the leaves were fully unfolded. Ca had a significant effect on the total biomass of American ginseng, which increased and peaked at [Ca2+] of 640.68 mg⋅L−1; then, it decreased with further increases in [Ca2+] (Fig. 1A). Compared with the Ca deficiency treatment (0 mg⋅L−1 control), the maximum root weight and maximum sum of stem and leaf weights increased significantly by 45.56% and 58.82%, respectively (Table 1).

Fig. 1.
Fig. 1.

Effects of calcium concentrations ([Ca2+]) on the growth state, leaf area, and color of American ginseng.

Citation: HortScience 57, 1; 10.21273/HORTSCI16129-21

Table 1.

Effects of calcium concentrations ([Ca2+]) on the growth parameters of American ginseng.

Table 1.

Additionally, Ca had a significant effect on stem height, leaf area, and stem diameter. Stem height and leaf area first increased and then decreased with [Ca2+], reaching their maxima at [Ca2+] of 640.68 mg⋅L−1 and then decreasing with further [Ca2+] increases, whereas stem diameter increased continuously over the tested [Ca2+] range. Compared with Ca deficiency, the maximum stem height and leaf area increased significantly by 30.19% and 62.55%, respectively (Table 1).

Chl content and Chl a/b ratio of American ginseng.

Leaves deficient in Ca were light green in color, but at [Ca2+] >640.68 mg⋅L−1, yellow patches with an irregular shape appeared among the leaf veins and increased with increasing [Ca2+] (Fig. 1B). Moreover, [Ca2+] had a significant effect on the Chl content and Chl a/b ratio. Chl (a + b) and Chl a content increased and then decreased with increasing [Ca2+]; in contrast, Chl b decreased with increasing [Ca2+]. The Chl (a + b) content peaked at [Ca2+] of 160.17 mg⋅L−1, whereas Chl a peaked at [Ca2+] of 320.34 mg⋅L−1. The Chl a/b ratio increased from 1.81 to 2.22 (Table 2).

Table 2.

Effects of calcium concentrations ([Ca2+]) on the chlorophyll (Chl) content and Chl a/b ratio of American ginseng.

Table 2.

Chl fluorescence of American ginseng.

Ca had a significant concentration-dependent effect on the Chl fluorescence parameters of American ginseng (Fig. 2). Specifically, Fv/Fm and Y(II) first increased and then decreased with [Ca2+]; Fv/Fm reached a maximum value at [Ca2+] of 640.68 mg⋅L−1 (Fig. 2 A); however, Y(II) decreased before the Fv/Fm reached its peak and reached its maximum value at [Ca2+] of 320.34 mg⋅L−1 (Fig. 2B).

Fig. 2.
Fig. 2.

Effects of calcium concentrations ([Ca2+]) on the chlorophyll fluorescence parameters of American ginseng. Fv/Fm, maximum photochemical efficiency of photosystem II (PS II); Y(II), actual photochemical efficiency of PS II; Y(NPQ), regulated thermal energy dissipation; Y(NO), the sum of nonregulated heat dissipation and fluorescence emission; Ek, minimum saturating irradiance. Different lowercase letters indicate significant difference at P ≤ 0.05 according to Fisher’s least significant difference test.

Citation: HortScience 57, 1; 10.21273/HORTSCI16129-21

The values for Y(NPQ) increased with [Ca2+] (Fig. 2C); however, the Y(NO) value first decreased to a minimum at [Ca2+] of 320.34 and 640.68 mg⋅L−1; then, it increased at [Ca2+] of 961.02 mg⋅L−1 (Fig. 2D). With the Y(NPQ) increase and Y(NO) decrease, the Y(II) reached a peak at [Ca2+] of 320.34 mg⋅L−1 (Fig. 2 B). The Ek increased with [Ca2+] and reached the saturation state (73.60 μmol⋅m−2⋅s−1) at [Ca2+] of 320.34 mg⋅L−1 (Fig. 2E).

Photosynthetic parameters of American ginseng.

The Ca treatment had significant effects on E, GH2O, and Pn, all of which showed an increasing pattern, followed by a decrease with [Ca2+] (Table 3). Pn was similar at [Ca2+] of 160.17 and 320.34 mg⋅L−1, but it was significantly higher than Pn with other [Ca2+] treatments. The Ca concentrations of <160.17 mg⋅L−1 or >640.68 mg⋅L−1 significantly reduced E, GH2O, and Pn. However, the Ci increased with increasing [Ca2+] and could be divided into three different stages. At [Ca2+] <160.17 mg⋅L−1, Ca deficiency decreased the GH2O, thus limiting CO2 availability and ultimately reducing Pn. At [Ca2+] ranging from 160.17 to 640.68 mg⋅L−1, the stomata maintained an open state, and there was enough CO2 available for photosynthesis. However, when [Ca2+] was >640.68 mg⋅L−1, the GH2O and Pn decreased while the respiration increased, thus leading to Ci accumulation.

Table 3.

Effects of calcium concentrations ([Ca2+]) on the photosynthetic parameters of American ginseng.

Table 3.

Antioxidant enzyme activity, root activity, and MDA content of American ginseng.

The Ca treatment had a significant effect on the antioxidant enzyme activity and MDA content of American ginseng (Fig. 3). As expected, SOD, POD, and CAT activities increased and then decreased with [Ca2+]. The activity of SOD, which is the most important antioxidant enzyme, intensified as [Ca2+] increased to 640.68 mg⋅L−1 (Fig. 3A). The POD and CAT activities were more sensitive to increasing [Ca2+] (Fig. 3B and C), reaching a maximum level at [Ca2+] of 320.34 mg⋅L−1 and then decreasing before the inflection point for SOD activity.

Fig. 3.
Fig. 3.

Effects of calcium concentrations ([Ca2+]) on the antioxidant enzyme activity, root activity, and malondialdehyde (MDA) content of American ginseng. SOD, superoxide dismutase; CAT, catalase; POD, peroxidase; DHA, dehydrogenase. Different lowercase letters indicate significant difference at P ≤ 0.05 according to Fisher’s least significant difference test.

Citation: HortScience 57, 1; 10.21273/HORTSCI16129-21

Root activity influences water and mineral absorption; therefore, we chose DHA activity as an index of root activity to estimate the growth condition and vigor of the root system. Our data showed that DHA activity followed a similar change pattern with [Ca2+] as POD and CAT activities, suggesting that 320.34 mg⋅L−1 was the suitable [Ca2+] for root growth of American ginseng (Fig. 3D).

MDA is most commonly used to indicate the extent of damage caused by stress in plants; MDA first decreased and then increased with [Ca2+] (Fig. 3E). Furthermore, the MDA content did not differ between [Ca2+] of 160.17 and 320.34 mg⋅L−1 treatments and was significantly lower at these than at other [Ca2+] treatments tested herein, thus implying that both Ca deficiency and its excess cause severe damage to plant tissues.

Discussion

During the experiments summarized here, the Chl (a + b) and Chl a content increased and then decreased with [Ca2+], whereas that of Chl b decreased. Similar results were observed for passion fruit, except for the Chl a/b ratio (Bizarre et al., 2019), which has been associated with plant species and growth environment (Liang et al., 2009). For American ginseng, when [Ca2+] was 320.34 mg⋅L−1, the Chl a/b ratio was 2.04, at which point Pn, Y(II), and Ek reached maximum values.

The excitation energy absorbed in PS II is distributed among Y(II), Y(NPQ), and Y(NO). Under a given environmental condition, successful regulation of such partitioning is aimed at maximal values of Y(II), with a maximal ratio of Y(NPQ)/Y(NO). High values of Y(NPQ) are indicative of a high photoprotective capacity, whereas high values of Y(NO), mainly caused by closed PS II reaction centers, reflect the inability of a plant to protect itself against damage by excess illumination (Bizarre et al., 2019; Klughammer and Schreiber, 2008). Y(NPQ) is linked to the xanthophyll cycle, which involves nonphotochemical quenching of excess light energy in PS II (Jahns and Holzwarth, 2012). Exogenous Ca2+ can facilitate the xanthophyll cycle through the Ca2+/CaM-mediated expression of the violaxanthin de-epoxidase gene and increase in the antheraxanthin and zeaxanthin ratio (Yang et al., 2013). D1 protein constitutes the binding site of the oxygen-evolving complex and Mn4Ca cluster; it is highly susceptible to excitation energy and reactive oxygen species. As the primary site of photoinhibitory damage, the D1 protein has a high turnover rate when repairing the light-induced inactivation and functional closure of reaction centers (Townsend et al., 2018). The turnover of D1 protein consists of four processes: de novo synthesis, phosphorylation, dephosphorylation, and degradation (Li et al., 2017). The transcription and translation of the psbA gene (encoding D1 protein) are specifically inactivated by hydrogen peroxide and singlet oxygen (Kojima et al., 2007). However, exogenous Ca upregulates the antioxidant gene transcript levels and the expression of the psbA gene, resulting in an increase of antioxidant enzyme activity and upregulation of the D1 protein (Erinle et al., 2016). At [Ca2+] between 0 and 320.34 mg⋅L−1, the value of Y(NPQ) and SOD, CAT, and POD activities of American ginseng increased, whereas the value of Y(NO) decreased, and Y(NPQ)/Y(NO) reached a maximum value at [Ca2+] of 320.34 mg⋅L−1, at which point the Y(II) peaked.

The value for Ek, which reflects the adaptation of plants to light intensity, is determined by finding the maximum photosynthetic rate in the light-limited regions of rapid light curves (Ralph and Gademann, 2005; Sakshaug et al., 1997). Ek is related to quenching such that photochemical fluorescence quenching is dominant below and nonphotochemical quenching is dominant above the Ek value (Henley, 1993). The Ek value of American ginseng increased with [Ca2+] and reached the saturation state at [Ca2+] of 320 mg⋅L−1, indicating that the application of an appropriate amount of Ca improves American ginseng tolerance to high light intensity stress.

Furthermore, plant stomata are the main channel for gas exchange during photosynthesis and are coregulated by a signal network that includes the Ca2+ signal transduction pathway, the plant hormone pathway, and the reactive oxygen species signaling pathway (Wang et al., 2019). Reactive oxygen species comprise a key signal for stomatal regulation (Song et al., 2014). SOD catalyzes the dismutation of O2− to H2O2 and O2, whereas CAT mediates H2O2 cleavage to produce H2O and O2, and POD reduces H2O2 to H2O and prevents H2O2-mediated inhibition of amylase activity (Sparta et al., 2006). Additionally, amylase can regulate the water content of guard cells through starch degradation into soluble sugars, thus regulating stomatal movement (Leshem and Levine, 2013). At [Ca2+] between 160.17 and 320.34 mg⋅L−1, SOD, CAT, and POD activities increased, thereby reducing H2O2 content and relieving the inhibitory effect of H2O2 on amylase activity. Finally, Ca upregulated the water content of guard cells and kept the stoma open, thus enhancing gas exchange in American ginseng plants.

The Ca ion is a cofactor in the formation of activation sites on PS II (Popelkova et al., 2011), and it maintains the stability of the PS II reaction center components through the Ca/calmodulinsignal transduction pathway (Yang et al., 2015) and regulates the activities of sedoheptulose-1,7-bisphosphatase, fructose-l,6-bisphosphatase, and transketolase. However, high concentrations of exogenous Ca2+ inhibit carbon assimilation (Hochmal et al., 2015). Therefore, Ca can influence the stability of PS II and carbon assimilation-related enzyme activities, thus influencing the photosynthetic rate. The photosynthetic rate of American ginseng reached the maximum at [Ca2+] ranging from 160.17 to 320.34 mg⋅L−1. Therefore, this range is suitable for American ginseng to maximize CO2 assimilation.

Exogenous Ca2+ treatment not only affects membrane structure but is also involved in oxidative signal transduction (Agarwal et al., 2005), concomitant with the upregulation of antioxidant enzyme activity aimed at reducing stress-induced MDA accumulation (Gong et al., 1997). Our results show that the antioxidant enzyme activity of American ginseng increased and then decreased with [Ca2+], with the MDA content decreasing to its lowest levels at [Ca2+] of 160.17 mg⋅L−1 and 320.34 mg⋅L−1, which means that an appropriate amount of Ca applied effectively enhances membrane integrity. Moreover, root activity reached the maximum rate at [Ca2+] of 320.34 mg⋅L−1, further confirming that Ca improved the tolerance of American ginseng to waterlogging and hypoxia stress.

Nonetheless, excess Ca2+ released into the cytosol and sustained high cytosolic Ca2+ concentrations might be cytotoxic (White and Martin, 2003). Therefore, when [Ca2+] exceeded 320.34 mg⋅L−1, the Chl content, Y(II), Pn, and activities of CAT, POD, and root activity decreased significantly in American ginseng. Intriguingly, at [Ca2+] of 320.34 mg⋅L−1, the physiological parameters were most favorable for the growth of American ginseng, although the biomass did not reach its maximum; instead, biomass accumulation peaked at [Ca2+] of 640.68 mg⋅L−1, despite the leaves showing obvious stress symptoms, specifically, yellow patches.

Conclusion

The results of this study clearly showed that increasing [Ca2+] from 0 to 320.34 mg⋅L−1 effectively promoted a robust, healthy growth of American ginseng plants and increased plant resistance to high light intensity stress and hypoxia stress. However, [Ca2+] exceeding 320.34 mg⋅L−1 was toxic to American ginseng, and the toxicity increased with increasing [Ca2+]. Therefore, suitable [Ca2+] for growth promotion in American ginseng was 320.34 mg⋅L−1. Finally, although these results were obtained from American ginseng plantlets that were only 2 years old and grown in a hydroponic system, which might differ greatly from common [Ca2+] conditions in soil environments, our findings clearly indicated that growth and stress resistance of American ginseng might be effectively promoted by regulating the Ca supply.

Literature Cited

  • Agarwal, S., Sairam, R.K., Srivastava, G.C., Tyagi, A. & Meena, R.C. 2005 Role of ABA, salicylic acid, calcium and hydrogen peroxide on antioxidant enzymes induction in wheat seedlings Plant Sci. 169 559 570 https://doi.org/10.1016/j.plantsci.2005.05.004

    • Search Google Scholar
    • Export Citation
  • Bizarre, M.A.F., Cavalcante, L.F., Bezerra, F.T.C., Silva, A.R., Oliveira, F.F. & Medeiros, S.A.S. 2019 Saline water, pit coating and calcium fertilization on chlorophyll, fluorescence, gas exchange and production in passion fruit J. Agr. Sci. 11 319 329 https://doi.org/10.5539/jas.v11n2p319

    • Search Google Scholar
    • Export Citation
  • Burkhart, E.P 2013 American ginseng (Panax quinquefolius L.) floristic associations in Pennsylvania: Guidance for identifying calcium-rich forest farming sites Agrofor. Syst. 87 1157 1172 https://doi.org/10.1007/s10457-013-9627-8

    • Search Google Scholar
    • Export Citation
  • Clippard, E., Wright, D., McMahon, M., Phillips, N. & Gao, Y. 2020 Developmental responses of American ginseng (Panax quinquefolius) seedlings grown in nutrient solutions absent of either iron, calcium, boron, or manganese In 2020 ASHS Annual Conference. ASHS. https://ashs.confex.com/ashs/2020/meetingapp.cgi/Paper/33845

    • Search Google Scholar
    • Export Citation
  • Erinle, K.O., Jiang, Z., Ma, B., Li, J., Chen, Y., Ur-Rehman, K., Shahla, A. & Zhang, Y. 2016 Exogenous calcium induces tolerance to atrazine stress in Pennisetum seedlings and promotes photosynthetic activity, antioxidant enzymes and psbA gene transcripts Ecotoxicol. Environ. Saf. 132 403 412 https://doi.org/10.1016/j.ecoenv.2016.06.035

    • Search Google Scholar
    • Export Citation
  • Gong, M., Chen, S., Song, Y. & Li, Z. 1997 Effect of calcium and calmodulin on intrinsic heat tolerance in relation to antioxidant systems in maize seedlings Funct. Plant Biol. 24 371 379 https://doi.org/10.1071/PP96118

    • Search Google Scholar
    • Export Citation
  • Henley, W.J 1993 Measurement and interpretation of photosynthetic light-response curves in algae in the context of photoinhibition and diel changes J. Phycol. 29 729 739 https://doi.org/10.1111/j.0022-3646.1993.00729.x

    • Search Google Scholar
    • Export Citation
  • Hochmal, A.K., Schulze, S., Trompelt, K. & Hippler, M. 2015 Calcium-dependent regulation of photosynthesis Biochim. Biophys. Acta 1847 993 1003 https://doi.org/10.1016/j.bbabio.2015.02.010

    • Search Google Scholar
    • Export Citation
  • Jahns, P. & Holzwarth, A.R. 2012 The role of the xanthophyll cycle and of lutein in photoprotection of photosystem II Biochim. Biophys. Acta 1817 182 193 https://doi.org/10.1016/j.bbabio.2011.04.012

    • Search Google Scholar
    • Export Citation
  • Klughammer, C. & Schreiber, U. 2008 Complementary PS II quantum yields calculated from simple fluorescence parameters measured by PAM fluorometry and the Saturation Pulse method PAM Appl. Notes 1 27 35

    • Search Google Scholar
    • Export Citation
  • Kojima, K., Oshita, M., Nanjo, Y., Kasai, K., Tozawa, Y., Hayashi, H. & Nishiyama, Y. 2007 Oxidation of elongation factor G inhibits the synthesis of the D1 protein of photosystem II Mol. Microbiol. 65 936 947 https://doi.org/10.1111/j.1365-2958.2007.05836.x

    • Search Google Scholar
    • Export Citation
  • Konsler, T.R. & Shelton, J.E. 1990 Lime and phosphorus effects on American ginseng: I. Growth, soil fertility, and root tissue nutrient status response J. Amer. Soc. Hort. Sci. 115 570 574 https://doi.org/10.21273/JASHS.115.4.570

    • Search Google Scholar
    • Export Citation
  • Lee, J. & Mudge, K.W. 2013 Gypsum effects on plant growth, nutrients, ginsenosides, and their relationship in American ginseng Hortic. Environ. Biotechnol. 54 228 235 https://doi.org/10.1007/s13580-013-0029-7

    • Search Google Scholar
    • Export Citation
  • Leshem, Y. & Levine, A. 2013 Zooming into sub-organellar localization of reactive oxygen species in guard cell chloroplasts during abscisic acid and methyl jasmonate treatments Plant Signal. Behav. 8 e25689 https://doi.org/10.4161/psb.25689

    • Search Google Scholar
    • Export Citation
  • Li, H., Xu, H., Zhang, P., Gao, M., Wang, D. & Zhao, H. 2017 High temperature effects on D1 protein turnover in three wheat varieties with different heat susceptibility Plant Growth Regulat. 81 1 9 https://doi.org/10.1007/s10725-016-0179-6

    • Search Google Scholar
    • Export Citation
  • Liang, W., Wang, M. & Ai, X. 2009 The role of calcium in regulating photosynthesis and related physiological indexes of cucumber seedlings under low light intensity and suboptimal temperature stress Scientia Hort. 123 34 38 https://doi.org/10.1016/j.scienta.2009.07.015

    • Search Google Scholar
    • Export Citation
  • Nadeau, I., Simard, R.R. & Olivier, A. 2003 The impact of lime and organic fertilization on the growth of wild-simulated American ginseng Can. J. Plant Sci. 83 603 609 https://doi.org/10.4141/P02-044

    • Search Google Scholar
    • Export Citation
  • Pathak, J., Ahmed, H., Kumari, N., Pandey, A. & Sinha, R.P. 2020 Role of calcium and potassium in amelioration of environmental stress in plants 535 562 Roychoudhury, A. & Kumar Tripathi, D. Protective chemical agents in the amelioration of plant abiotic stress https://doi.org/10.1002/9781119552154.ch27

    • Search Google Scholar
    • Export Citation
  • Peever, M.J 2004 The effect of manganese, sodium, calcium, acidity and tree competition on the growth and nutritional status of American ginseng (Doctoral dissertation, University of Guelph, Canada). https://hdl.handle.net/10214/23082

    • Search Google Scholar
    • Export Citation
  • Popelkova, H., Boswell, N. & Yocum, C. 2011 Probing the topography of the photosystem II oxygen evolving complex: PsbO is required for efficient calcium protection of the manganese cluster against dark-inhibition by an artificial reductant Photosynth. Res. 110 111 121 https://doi.org/10.1007/s11120-011-9703-8

    • Search Google Scholar
    • Export Citation
  • Ralph, P.J. & Gademann, R. 2005 Rapid light curves: A powerful tool to assess photosynthetic activity Aquat. Bot. 82 222 237 https://doi.org/10.1016/j.aquabot.2005.02.006

    • Search Google Scholar
    • Export Citation
  • Sakshaug, E., Bricaud, A., Dandonneau, Y., Falkowski, P.G., Kiefer, D.A., Legendre, L., Morel, A., Parslow, J. & Takahashi, M. 1997 Parameters of photosynthesis: Definitions, theory and interpretation of results J. Plankton Res. 19 1637 1670 https://doi.org/10.1093/plankt/19.11.1637

    • Search Google Scholar
    • Export Citation
  • Slak, D.L 2005 The establishment and persistence of American ginseng (Panax quinquefolius L.) in Maryland forests Univ. Maryland College Park PhD Diss

    • Search Google Scholar
    • Export Citation
  • Song, Y., Miao, Y. & Song, C.P. 2014 Behind the scenes: The roles of reactive oxygen species in guard cells New Phytol. 201 1121 1140 https://doi.org/10.1111/nph.12565

    • Search Google Scholar
    • Export Citation
  • Sparta, F., Costa, A., Lo Schiavo, F., Pupillo, P. & Trost, P. 2006 Redox regulation of a novel plastid-targeted β-amylase of Arabidopsis Plant Physiol. 141 840 850 https://doi.org/10.1104/pp.106.079186

    • Search Google Scholar
    • Export Citation
  • Stoltz, L.P 1982 Leaf symptoms, yield, and composition of mineral-deficient American ginseng Hort. Sci. 17 740 741

  • Szczuka, D., Nowak, A., Zakłos-Szyda, M., Kochan, E., Szymańska, G., Motyl, I. & Blasiak, J. 2019 American ginseng (Panax quinquefolium L.) as a source of bioactive phytochemicals with pro-Health properties Nutrients 11 1041 https://doi.org/10.3390/nu11051041

    • Search Google Scholar
    • Export Citation
  • Thyroff, E 2015 Experimental greenhouse and field trials on American Ginseng, Panax quinquefolium: Implications for restoration in Appalachia Senior Honors Projects, 2010-current. 16, https://commons.lib.jmu.edu/honors201019/16

    • Search Google Scholar
    • Export Citation
  • Townsend, A.J., Ware, M.A. & Ruban, A.V. 2018 Dynamic interplay between photodamage and photoprotection in photosystem II Plant Cell Environ. 41 1098 1112 https://doi.org/10.1111/pce.13107

    • Search Google Scholar
    • Export Citation
  • Wang, Q., Yang, S., Wan, S. & Li, X. 2019 The significance of calcium in photosynthesis Int. J. Mol. Sci. 20 1353 https://doi.org/10.3390/ijms20061353

    • Search Google Scholar
    • Export Citation
  • White, P.J. & Martin, R.B. 2003 Calcium in plants Ann. Bot. 92 487 511 https://doi.org/10.1093/aob/mcg164

  • Yang, S., Wang, F., Guo, F., Meng, J.J., Li, X.G., Dong, S.T. & Wan, S.B. 2013 Exogenous calcium alleviates photoinhibition of PS II by improving the xanthophyll cycle in peanut (Arachis hypogaea) leaves during heat stress under high irradiance PLoS One 8 e71214 https://doi.org/10.1371/journal.pone.0071214

    • Search Google Scholar
    • Export Citation
  • Yang, S., Wang, F., Guo, F., Meng, J.J., Li, X.G. & Wan, S.B. 2015 Calcium contributes to photoprotection and repair of photosystem II in peanut leaves during heat and high irradiance J. Integr. Plant Biol. 57 486 495 https://doi.org/10.1111/jipb.12249

    • Search Google Scholar
    • Export Citation

Contributor Notes

This work was funded by the Agricultural Science and Technology Innovation Program of the Chinese Academy of Agricultural Sciences (grant no. CAAS-XTCX20190025-6) and the Central Public-interest Scientific Institution Basal Research Fund (no. CAAS-ASTIP-ISAPS-2021-017). The authors have no conflict of interest to declare.

Y.Z. is the corresponding author. E-mail: zyy1966999@sina.com.

  • Collapse
  • Expand
  • View in gallery
    Fig. 1.

    Effects of calcium concentrations ([Ca2+]) on the growth state, leaf area, and color of American ginseng.

  • View in gallery
    Fig. 2.

    Effects of calcium concentrations ([Ca2+]) on the chlorophyll fluorescence parameters of American ginseng. Fv/Fm, maximum photochemical efficiency of photosystem II (PS II); Y(II), actual photochemical efficiency of PS II; Y(NPQ), regulated thermal energy dissipation; Y(NO), the sum of nonregulated heat dissipation and fluorescence emission; Ek, minimum saturating irradiance. Different lowercase letters indicate significant difference at P ≤ 0.05 according to Fisher’s least significant difference test.

  • View in gallery
    Fig. 3.

    Effects of calcium concentrations ([Ca2+]) on the antioxidant enzyme activity, root activity, and malondialdehyde (MDA) content of American ginseng. SOD, superoxide dismutase; CAT, catalase; POD, peroxidase; DHA, dehydrogenase. Different lowercase letters indicate significant difference at P ≤ 0.05 according to Fisher’s least significant difference test.

  • Agarwal, S., Sairam, R.K., Srivastava, G.C., Tyagi, A. & Meena, R.C. 2005 Role of ABA, salicylic acid, calcium and hydrogen peroxide on antioxidant enzymes induction in wheat seedlings Plant Sci. 169 559 570 https://doi.org/10.1016/j.plantsci.2005.05.004

    • Search Google Scholar
    • Export Citation
  • Bizarre, M.A.F., Cavalcante, L.F., Bezerra, F.T.C., Silva, A.R., Oliveira, F.F. & Medeiros, S.A.S. 2019 Saline water, pit coating and calcium fertilization on chlorophyll, fluorescence, gas exchange and production in passion fruit J. Agr. Sci. 11 319 329 https://doi.org/10.5539/jas.v11n2p319

    • Search Google Scholar
    • Export Citation
  • Burkhart, E.P 2013 American ginseng (Panax quinquefolius L.) floristic associations in Pennsylvania: Guidance for identifying calcium-rich forest farming sites Agrofor. Syst. 87 1157 1172 https://doi.org/10.1007/s10457-013-9627-8

    • Search Google Scholar
    • Export Citation
  • Clippard, E., Wright, D., McMahon, M., Phillips, N. & Gao, Y. 2020 Developmental responses of American ginseng (Panax quinquefolius) seedlings grown in nutrient solutions absent of either iron, calcium, boron, or manganese In 2020 ASHS Annual Conference. ASHS. https://ashs.confex.com/ashs/2020/meetingapp.cgi/Paper/33845

    • Search Google Scholar
    • Export Citation
  • Erinle, K.O., Jiang, Z., Ma, B., Li, J., Chen, Y., Ur-Rehman, K., Shahla, A. & Zhang, Y. 2016 Exogenous calcium induces tolerance to atrazine stress in Pennisetum seedlings and promotes photosynthetic activity, antioxidant enzymes and psbA gene transcripts Ecotoxicol. Environ. Saf. 132 403 412 https://doi.org/10.1016/j.ecoenv.2016.06.035

    • Search Google Scholar
    • Export Citation
  • Gong, M., Chen, S., Song, Y. & Li, Z. 1997 Effect of calcium and calmodulin on intrinsic heat tolerance in relation to antioxidant systems in maize seedlings Funct. Plant Biol. 24 371 379 https://doi.org/10.1071/PP96118

    • Search Google Scholar
    • Export Citation
  • Henley, W.J 1993 Measurement and interpretation of photosynthetic light-response curves in algae in the context of photoinhibition and diel changes J. Phycol. 29 729 739 https://doi.org/10.1111/j.0022-3646.1993.00729.x

    • Search Google Scholar
    • Export Citation
  • Hochmal, A.K., Schulze, S., Trompelt, K. & Hippler, M. 2015 Calcium-dependent regulation of photosynthesis Biochim. Biophys. Acta 1847 993 1003 https://doi.org/10.1016/j.bbabio.2015.02.010

    • Search Google Scholar
    • Export Citation
  • Jahns, P. & Holzwarth, A.R. 2012 The role of the xanthophyll cycle and of lutein in photoprotection of photosystem II Biochim. Biophys. Acta 1817 182 193 https://doi.org/10.1016/j.bbabio.2011.04.012

    • Search Google Scholar
    • Export Citation
  • Klughammer, C. & Schreiber, U. 2008 Complementary PS II quantum yields calculated from simple fluorescence parameters measured by PAM fluorometry and the Saturation Pulse method PAM Appl. Notes 1 27 35

    • Search Google Scholar
    • Export Citation
  • Kojima, K., Oshita, M., Nanjo, Y., Kasai, K., Tozawa, Y., Hayashi, H. & Nishiyama, Y. 2007 Oxidation of elongation factor G inhibits the synthesis of the D1 protein of photosystem II Mol. Microbiol. 65 936 947 https://doi.org/10.1111/j.1365-2958.2007.05836.x

    • Search Google Scholar
    • Export Citation
  • Konsler, T.R. & Shelton, J.E. 1990 Lime and phosphorus effects on American ginseng: I. Growth, soil fertility, and root tissue nutrient status response J. Amer. Soc. Hort. Sci. 115 570 574 https://doi.org/10.21273/JASHS.115.4.570

    • Search Google Scholar
    • Export Citation
  • Lee, J. & Mudge, K.W. 2013 Gypsum effects on plant growth, nutrients, ginsenosides, and their relationship in American ginseng Hortic. Environ. Biotechnol. 54 228 235 https://doi.org/10.1007/s13580-013-0029-7

    • Search Google Scholar
    • Export Citation
  • Leshem, Y. & Levine, A. 2013 Zooming into sub-organellar localization of reactive oxygen species in guard cell chloroplasts during abscisic acid and methyl jasmonate treatments Plant Signal. Behav. 8 e25689 https://doi.org/10.4161/psb.25689

    • Search Google Scholar
    • Export Citation
  • Li, H., Xu, H., Zhang, P., Gao, M., Wang, D. & Zhao, H. 2017 High temperature effects on D1 protein turnover in three wheat varieties with different heat susceptibility Plant Growth Regulat. 81 1 9 https://doi.org/10.1007/s10725-016-0179-6

    • Search Google Scholar
    • Export Citation
  • Liang, W., Wang, M. & Ai, X. 2009 The role of calcium in regulating photosynthesis and related physiological indexes of cucumber seedlings under low light intensity and suboptimal temperature stress Scientia Hort. 123 34 38 https://doi.org/10.1016/j.scienta.2009.07.015

    • Search Google Scholar
    • Export Citation
  • Nadeau, I., Simard, R.R. & Olivier, A. 2003 The impact of lime and organic fertilization on the growth of wild-simulated American ginseng Can. J. Plant Sci. 83 603 609 https://doi.org/10.4141/P02-044

    • Search Google Scholar
    • Export Citation
  • Pathak, J., Ahmed, H., Kumari, N., Pandey, A. & Sinha, R.P. 2020 Role of calcium and potassium in amelioration of environmental stress in plants 535 562 Roychoudhury, A. & Kumar Tripathi, D. Protective chemical agents in the amelioration of plant abiotic stress https://doi.org/10.1002/9781119552154.ch27

    • Search Google Scholar
    • Export Citation
  • Peever, M.J 2004 The effect of manganese, sodium, calcium, acidity and tree competition on the growth and nutritional status of American ginseng (Doctoral dissertation, University of Guelph, Canada). https://hdl.handle.net/10214/23082

    • Search Google Scholar
    • Export Citation
  • Popelkova, H., Boswell, N. & Yocum, C. 2011 Probing the topography of the photosystem II oxygen evolving complex: PsbO is required for efficient calcium protection of the manganese cluster against dark-inhibition by an artificial reductant Photosynth. Res. 110 111 121 https://doi.org/10.1007/s11120-011-9703-8

    • Search Google Scholar
    • Export Citation
  • Ralph, P.J. & Gademann, R. 2005 Rapid light curves: A powerful tool to assess photosynthetic activity Aquat. Bot. 82 222 237 https://doi.org/10.1016/j.aquabot.2005.02.006

    • Search Google Scholar
    • Export Citation
  • Sakshaug, E., Bricaud, A., Dandonneau, Y., Falkowski, P.G., Kiefer, D.A., Legendre, L., Morel, A., Parslow, J. & Takahashi, M. 1997 Parameters of photosynthesis: Definitions, theory and interpretation of results J. Plankton Res. 19 1637 1670 https://doi.org/10.1093/plankt/19.11.1637

    • Search Google Scholar
    • Export Citation
  • Slak, D.L 2005 The establishment and persistence of American ginseng (Panax quinquefolius L.) in Maryland forests Univ. Maryland College Park PhD Diss

    • Search Google Scholar
    • Export Citation
  • Song, Y., Miao, Y. & Song, C.P. 2014 Behind the scenes: The roles of reactive oxygen species in guard cells New Phytol. 201 1121 1140 https://doi.org/10.1111/nph.12565

    • Search Google Scholar
    • Export Citation
  • Sparta, F., Costa, A., Lo Schiavo, F., Pupillo, P. & Trost, P. 2006 Redox regulation of a novel plastid-targeted β-amylase of Arabidopsis Plant Physiol. 141 840 850 https://doi.org/10.1104/pp.106.079186

    • Search Google Scholar
    • Export Citation
  • Stoltz, L.P 1982 Leaf symptoms, yield, and composition of mineral-deficient American ginseng Hort. Sci. 17 740 741

  • Szczuka, D., Nowak, A., Zakłos-Szyda, M., Kochan, E., Szymańska, G., Motyl, I. & Blasiak, J. 2019 American ginseng (Panax quinquefolium L.) as a source of bioactive phytochemicals with pro-Health properties Nutrients 11 1041 https://doi.org/10.3390/nu11051041

    • Search Google Scholar
    • Export Citation
  • Thyroff, E 2015 Experimental greenhouse and field trials on American Ginseng, Panax quinquefolium: Implications for restoration in Appalachia Senior Honors Projects, 2010-current. 16, https://commons.lib.jmu.edu/honors201019/16

    • Search Google Scholar
    • Export Citation
  • Townsend, A.J., Ware, M.A. & Ruban, A.V. 2018 Dynamic interplay between photodamage and photoprotection in photosystem II Plant Cell Environ. 41 1098 1112 https://doi.org/10.1111/pce.13107

    • Search Google Scholar
    • Export Citation
  • Wang, Q., Yang, S., Wan, S. & Li, X. 2019 The significance of calcium in photosynthesis Int. J. Mol. Sci. 20 1353 https://doi.org/10.3390/ijms20061353

    • Search Google Scholar
    • Export Citation
  • White, P.J. & Martin, R.B. 2003 Calcium in plants Ann. Bot. 92 487 511 https://doi.org/10.1093/aob/mcg164

  • Yang, S., Wang, F., Guo, F., Meng, J.J., Li, X.G., Dong, S.T. & Wan, S.B. 2013 Exogenous calcium alleviates photoinhibition of PS II by improving the xanthophyll cycle in peanut (Arachis hypogaea) leaves during heat stress under high irradiance PLoS One 8 e71214 https://doi.org/10.1371/journal.pone.0071214

    • Search Google Scholar
    • Export Citation
  • Yang, S., Wang, F., Guo, F., Meng, J.J., Li, X.G. & Wan, S.B. 2015 Calcium contributes to photoprotection and repair of photosystem II in peanut leaves during heat and high irradiance J. Integr. Plant Biol. 57 486 495 https://doi.org/10.1111/jipb.12249

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 299 299 12
PDF Downloads 130 130 12