Abstract
Parsley seeds are known for nonuniform and long germination; consequently, vegetable nurseries commonly use priming techniques to improve the production of parsley seedlings. The objectives of this study were 1) to characterize the imbibition curve of parsley seeds, 2) to evaluate the effect of different priming agents on parsley seedling production, and ultimately 3) to compare priming techniques for emergence and vigor of parsley’s seedlings, thus providing an optimal priming strategy for parsley seedling production. Using three priming agents—water (seeds imbibed for 24, 48, 72, and 96 hours), polyethylene glycol 6000 (PEG6000) (seeds imbibed at –0.5, –1.0, –1.5, and –2.0 MPa for 29, 58, 87, and 116 hours), and gibberellic acid (GA) (seeds imbibed at 0.5, 1.0, 1.5, and 2.0 g·L−1 a.i. of solution for 15, 30, 45, and 60 minutes), and two parsley cultivars (Krausa and Titan), three experiments evaluated parsley seedling parameters, including emergence speed index (ESI) and total emergence (TE) in a complete randomized block design (n = 4) each. In Expt. 1 (hydropriming), increasing water imbibition time (IT) reduced ESI on both parsley cultivars. In addition, the TE quadratically reduced with the increase of water IT. In Expt. 2 (osmopriming), there was no significant main effect or interaction of treatments on ESI. Regardless of PEG6000 concentration, the TE had a linear increase with the increase of IT for cultivar Krausa but not for cultivar Titan. In Expt. 3 (hormonal priming), there was a significant increase in ESI and TE with the increase in GA rate. Ultimately, strategies for analysis of best priming were water at 24 hours of IT, PEG6000 at –2.0 MPa for 116 hours of IT, and GA at 2.0 g·L−1 a.i. of solution for 15 minutes of IT. Once compared with an untreated seeds treatment, priming strategies of water imbibition for 24 hours and PEG6000 at –2.0 MPa for 116 hours had the highest ESI and TE.
Among the numerous seedlings of vegetable crops grown in commercial nurseries, seeds of parsley (Petroselinum crispum), an herb grown worldwide, are challenging to growers (Hassell and Kretchman, 1997). In the southeastern United States, growers have reported difficulty in growing parsley under both greenhouse and field conditions due to poor germination and nonuniformity of seedling emergence (J. Patrick, Patrick Family Farms, personal communication).
In general, parsley germination is reported in 28 d (International Seed Testing Association, 1985) and can be considered long compared with carrot (Daucus carota) (18 d) (Bolton and Simon, 2019), pepper (Capsicum chinense) (14 d) (Diel et al., 2019), cabbage (Brassica oleracea) (14 d) (Ziaf et al., 2017), zucchini (Cucurbita pepo) (8 d) (Tavares, 2018), and tomato (Solanum lycopersicum) (14 d) (Florido et al., 2018). Slow germination and nonuniform emergence of parsley seeds are due to an inhibitory substance called coumarin (Chaturvedi and Muralia, 1975; Hassell and Kretchman, 1997), but enhanced by a physical dormancy caused by an immature embryo and hard seedcoat (Baskin and Baskin, 2014; Kamau and Maina, 2017). The use of priming techniques, such as hydropriming, osmopriming, and hormonal priming, which consist of the imbibition of seeds in different substances, also called priming agents, consequently has become common in the production of parsley seedlings and other vegetables and herbs (Paparella et al., 2015; Sharma et al., 2015).
Compared with untreated seeds, priming seeds allows for accelerated water imbibition and initiation of the gene expression necessary for germination to occur. In short, priming agents allow for a rapid seed hydration level, phase I of germination, and accelerate the digestion of reserve substances, which is phase II of germination (Chen et al., 2010). For example, hydropriming allows seeds to increase hydration levels quickly by breaking physical barriers with a constant supply of oxygen (Podlaski et al., 2003), osmopriming permits the rapid hydration of seeds due to the difference in potential between seeds and solution (Dursun and Ekinci, 2010); finally, hormonal priming allows hormones, such as GA, salicylic acid, ascorbic acid, and cytokinin, to induce seed hydration by breaking seed dormancy if physiological dormancy is present (Hassell and Kretchman, 1997). In response to all techniques, primed seeds have a higher chance to reestablish structural integrity and synthesize new compounds compared with untreated seeds (Pill, 1986).
Regardless of priming agent, primed parsley seeds were reported to increase germination rate and provide higher total emergency (uniformity) compared with untreated seeds (Dawidowicz-Grzegorzewska and Maguire, 1993; Gray et al., 1990). Primed seeds of parsley have also been reported to increase hypocotyl length and allow for high-quality seedlings (Pill and Kilian, 2000). In particular, parsley seeds treated with water (hydropriming) and PEG (osmopriming) increased germination rate and quality of seedling (Kamau and Maina, 2017; Pill and Kilian, 2000), whereas parsley seeds treated with GA using Progibb Plus 2X (Abbott Laboratories, Chicago, IL) as a priming agent (hormonal priming) increased the hypocotyl length and shoot dry weight compared with untreated seeds (Pill and Kilian, 2000). Overall, several studies have reported the effect of priming agents on germination and seedling production of parsley seeds; however, a comparison among different priming agents and a recommendation strategy have not been reported.
The present study hypothesizes that different priming techniques will induce different parsley seed responses—and consequently, improved uniformity of seed emergence and seedling quality. Thus, the objectives of this study were 1) to characterize the imbibition curve of parsley seeds, 2) to evaluate the effect of different priming agents on parsley seedling production, and ultimately 3) to compare priming techniques for emergence and vigor of parsley’s seedlings, providing an optimal priming strategy for parsley seedling production.
Material and methods
Imbibition curve of parsley seeds.
The first step of this study was to conduct a seed imbibition curve approach to evaluate the water uptake of parsley seeds. The imbibition curve was determined using 50 seeds of parsley cultivar Titan replicated four times. Seeds were placed in petri dishes with blotter papers (Whatman Filter Paper; GE Healthcare Life Sciences, Maidstone, UK) of 90-mm diameter and 6-µm pore size, water moistened with 2.5 times the blotter paper dry weight and kept at a constant temperature of 24 °C until germination. Seed total weight was measured at 1, 4, 7, 11, 15, 21, 27, 33, 45, 57, 69, 93, 117, 141, and 165 h after imbibition. Phase I of the germination process was determined when imbibed seeds reached constant weight, phase II was determined from the end of phase I until 50% of parsley seeds had the radicular protrusion, and phase III was determined from the end of phase II until 100% of seeds had radicular protrusion (Bewley and Black, 1994).
Priming techniques.
According to the imbibition curve and using the required time of parsley seeds to reach Phase I and II of the germination process, which is the maximum length or time required by parsley seeds to uptake water and initiate metabolic activities (Bewley and Black, 1994), treatments of three priming agents (i.e., hydropriming, osmopriming, and hormonal priming) were evaluated throughout three simultaneous greenhouse experiments.
Expt. 1 evaluated the hydropriming technique and consisted of a two factorial experimental design of two parsley cultivars and four seed ITs. Parsley cultivars were Krausa and Titan, and IT treatments were 24, 48, 72, and 96 h. Parsley seeds received the hydropriming (distilled water) treatments using petri dishes with blotter papers (Whatman Filter Paper; GE Healthcare Life Sciences) of 90-mm diameter and 6-µm pore size, moistened with 2.5 times the blotter paper dry weight.
Expt. 2 evaluated the osmopriming technique and consisted of a three factorial experimental design of two parsley cultivars, four priming agent rates, and four seed IT. Parsley cultivars were Krausa and Titan. The priming agent used in experiment two was PEG6000 (Polyethylene glycol 6000; Sigma-Aldrich, Merck, St. Louis, MO) at an osmotic potential of –0.5, –1.0, –1.5, and –2.0 MPa. PEG6000 concentrations for each osmotic potential was determined according to Michel and Kaufmann (1973). Seed IT treatments were 29, 58, 87, and 116 h.
Expt. 3 evaluated the hormonal priming technique and consisted of a three factorial experimental design of two parsley cultivars, four priming agent rates, and four seed IT. Once again, parsley cultivars were Krausa and Titan. The priming agent used was the GA (Progibb LV Plus Growth Regulator Solution, 5.7% a.i.; Valent BioSciences Corporation, Libertyville, IL), in which parsley seeds were imbibed at rates of 0.5, 1.0, 1.5, and 2.0 g·L−1 a.i. Seed IT treatments were 15, 30, 45, and 60 min.
Priming agents of experiments two and three were applied using 50-mL bottles with 200 seeds per bottle. During treatment application, seeds treated with PEG6000 and GA were stirred at 120 RPM using an Orbital Shake (ThermoFisher Scientific, Laboratory-Line, Waltham, MA). All priming treatments were applied in the laboratory at a constant temperature of 24 °C. After being treated, parsley seeds of all experiments were washed to removal of priming agents excess and dried with absorbent paper for 24 h.
In the greenhouse, all experiments were individually randomized in a complete block design with four replications. Treated seeds were planted in 338-cell trays filled with soilless media (Pro-Mix BX; Premier Tech, Riviere-du-Loup, Quebec, Canada). The smallest experimental unit (plots) consisted of 24 seedlings of parsley. In addition, a control treatment was added in each experiment, in which parsley seeds received no treatment. Seedlings were greenhouse-grown at an average temperature of 28 °C, and irrigation water was applied two times a day as needed.
Seedling emergence and characterization.
Parsley seeds were considered at full emergence when seed cotyledon was fully exposed and TE of each plot was estimated after 32 d considering plants fully emerged. At 38 d after planting, the leaf number (LN), seedling height (SH), root length (RL), aboveground dry biomass accumulated (AGB), and root dry biomass accumulated (RB) were measured from five representative seedlings of each plot. The LN was determined by counting the fully opened parsley leaves, SH was measured as the distance from the plant base to the shoot tip, RL was measured as the distance from the plant base to the end of roots, and AGB and RB were measured after drying the seedling fresh material at 65 °C until constant weight.
Statistical analysis.
Data of each experiment was individually analyzed using linear mixed techniques as implemented in SAS PROC GLIMMIX (SAS/STAT 14.2; SAS Institute Inc., Cary, NC). For Expt. 1 (hydropriming), the ESI, TE, LN, SH, RL, AGB, and RB were analyzed with parsley seeds cultivar (i.e., Krausa and Titan), water IT (i.e., 24, 48, 72, and 96 h), and their interaction as fixed effects. For Expts. 2 (osmopriming) and 3 (hormonal priming), the ESI, TE, LN, SH, RL, AGB, and RB were analyzed with parsley seeds cultivar (i.e., Krausa and Titan), priming agent rate (i.e., –0.5, –1.0, –1.5, and –2.0 MPa for osmopriming and 0.5, 1.0, 1.5, and 2.0 g·L−1 a.i. for hormonal priming), IT (i.e., 29, 58, 87, and 116 h for osmopriming and 15, 30, 45, and 60 min for hormonal priming), and their interaction as fixed effects. In all analyses, block was considered a random effect, and regression analysis or least-square means comparisons using the Tukey adjust were performed at a P value of 0.05; means were portioned as required using the slice command in SAS.
The best strategy of priming for parsley was also determined using linear mixed techniques as implemented in SAS PROC GLIMMIX (SAS/STAT 14.2; SAS Institute Inc., Cary, NC). The ESI and TE were analyzed with the best strategy of priming from each experiment plus an untread control treatment as a fixed effect, regardless of parsley cultivar. Block was considered a random effect and the least square means comparisons were performed using the Tukey adjust at a P value of 0.05, means were portioned using the slice command in SAS.
Results
Water imbibition curve.
Parsley seeds had a rapid weight gain in the first 15 h of water imbibition, which characterized phase I of germination. After establishing the hydration level, parsley seeds entered phase II of germination and maintained an average weight of 0.106 g per 50 seeds for the next 102 h. Seed weight started to increase again at 117 h after imbibition, which was due to the beginning of the radicular protrusion, phase III of germination. After 165 h of imbibition, all seeds were germinated (Fig. 1).
Water imbibition curve and phases of the germination process for parsley seeds.
Citation: HortScience 57, 9; 10.21273/HORTSCI16675-22
Water imbibition curve and phases of the germination process for parsley seeds.
Citation: HortScience 57, 9; 10.21273/HORTSCI16675-22
Water imbibition curve and phases of the germination process for parsley seeds.
Citation: HortScience 57, 9; 10.21273/HORTSCI16675-22
Effect of parsley cultivar, water imbibition timing, and their interaction on seeds emergence speed index (ESI), total emergence (TE), seedling height (SH), root length (RL), leaf number (LN), aboveground dry biomass (AGB), and root dry biomass (RB) from the hydropriming experiment.
Hydropriming.
Significant interactions between cultivar and IT were measured for the ESI of parsley seeds. However, there was no significant main effect or interaction of cultivar and IT for TE, SH, RL, LN, AGB, and RB (Table 1).
For the interaction between cultivar and IT (Table 2), the ESI had a significant linear reduction with the increase in IT for cultivar Krausa (ESIKrausa = –0.0598 * IT + 8.0625, R2 = 97.7) and Titan (ESITitan = –0.0217 * IT + 5.975, R2 = 66.6). The effect of cultivar within IT was significant only for the 24 h of water imbibition, in which ESI was higher for ‘Krausa’ (6.9) compared with ‘Titan’ (5.4). The TE had a significant quadratic reduction with the increase in IT (TE = –0.0089 * IT2 + 0.7365 * IT + 66.125, R2 = 92.3). In contrast to ESI, the TE of parsley seeds had no significant difference among cultivar within IT.
Effects of the water interaction imbibition timing and parsley cultivar interaction on seeds emergence speed index.
Osmopriming.
Significant differences were measured in the interaction cultivar and IT for TE, and the main effect of cultivar for SH (Table 3). There were no significant main effects or interactions for ESI, RL, LN, AGB, and RB.
Effect of parsley cultivar, polyethylene glycol 6000 (PEG6000) rate, imbibition timing (IT), and their interaction on seeds emergence speed index (ESI), total emergence (TE), seedling height (SH), root length (RL), leaf number (LN), aboveground dry biomass (AGB), and root dry biomass (RB) from the osmopriming experiment.
For the interaction cultivar and IT (Table 4), there was a linear increase in TE with the increase of IT for cultivar Krausa (TEKrausa = 0.075862 * IT + 67.375, R2 = 79.8); however, there was no significant difference among IT treatments for TE within cultivar Titan. The effect of cultivar within IT was only significant for the 87 h of imbibition, in which TE was higher for ‘Krausa’ (75.5%) compared with ‘Titan’ (62.8%). Cultivar had no significant difference for TE on any other IT treatment.
Effects of the interaction between imbibition timing of polyethylene glycol 6000 (PEG6000) and cultivar on total emergence (TE) of parsley seeds.
For the main effect of cultivar in SH (Table 3), cultivar Titan (4.4 cm) had higher SH compared with Krausa (3.9 cm).
Hormonal priming.
There were no significant interactions among cultivar, priming agent rate, and IT treatments for ESI, TE, SH, LN, and AGB. However, the main effect of cultivar was significant for ESI and RL, and the main effect of priming agent rate was significant for ESI and TE (Table 5).
Effect of parsley cultivar, gibberellic acid (GA) rate, imbibition timing (IT), and their interaction on seeds emergence speed index (ESI), total emergence (TE), seedling height (SH), root length (RL), leaf number (LN), aboveground dry biomass (AGB), and root dry biomass (RB) from the hormonal priming experiment.
For the main effect of cultivar, the ESI was significantly higher for ‘Krausa’ (5.2) compared with ‘Titan’ (4.8). Similarly, the RL was significantly higher for ‘Krausa’ (7.6 cm) compared with ‘Titan’ (7.1 cm).
For the main effect of GA rate, the increasing of GA rate linearly increased both ESI (ESI = 0.3925 * [GA] + 4.5141, R2 = 28.1) and TE (TE = 4.175 * [GA] + 66.625, R2 = 22.6).
Best priming strategy.
The ESI and TE of parsley seeds were used for selecting treatments considered the best priming strategy from each experiment (i.e., hydropriming, osmopriming, and hormonal priming). In the case of no significant difference among treatments within each experiment for ESI and TE, the treatment with lowest priming rate and imbibition timing was selected as best treatment. Therefore, selected treatments were the 24 h of water imbibition in the hydropriming experiment, PEG6000 at –2.0 MPa for 116 h of imbibition in the osmopriming experiment, and GA at 2.0 g·L−1 a.i. for 15 min of imbibition in the hormonal priming experiment.
Figure 2 shows the comparison among best treatments from each experiment and the untreated control for the ESI and TE of parsley. Seeds imbibed in water for 24 h and PEG6000 at –2.0 MPa for 116 h had the highest ESI, whereas untreated seeds (control) had the lowest ESI (Fig. 2A). Particularly, the ESI of parsley seeds increased by 35% and 30% under 24 h of water imbibition and PEG6000 at –2.0 MPa for 116 h of imbibition compared with untreated parsley seeds, respectively. The hormonal priming treatment of applying GA at 2.0 g·L−1 a.i. with seeds imbibed for 15 min had no significant difference from the untreated control neither from the hydropriming and osmopriming treatment for ESI. Regarding the parsley seeds TE (Fig. 2B), seeds imbibed in water for 24 had the highest TE, whereas there was no significant difference among PEG6000 at –2.0 MPa for 116 h, GA at 2.0 g·L−1 a.i. for 15 min, and the untreated control for TE.
Effect of parsley seeds imbibition on water for 24 h, gibberellic acid (GA) at 2.0% g·L−1 a.i. for 15 min, polyethylene glycol 6000 (PEG6000) at –2.0 MPa for 116 h, and the untreated control treatment for emergence speed index (A) and total emergence (B). Treatment means followed by the same letter within indicates no significant differences (P ≤ 0.05) according to Tukey test. Error bars indicate the means standard error.
Citation: HortScience 57, 9; 10.21273/HORTSCI16675-22
Effect of parsley seeds imbibition on water for 24 h, gibberellic acid (GA) at 2.0% g·L−1 a.i. for 15 min, polyethylene glycol 6000 (PEG6000) at –2.0 MPa for 116 h, and the untreated control treatment for emergence speed index (A) and total emergence (B). Treatment means followed by the same letter within indicates no significant differences (P ≤ 0.05) according to Tukey test. Error bars indicate the means standard error.
Citation: HortScience 57, 9; 10.21273/HORTSCI16675-22
Effect of parsley seeds imbibition on water for 24 h, gibberellic acid (GA) at 2.0% g·L−1 a.i. for 15 min, polyethylene glycol 6000 (PEG6000) at –2.0 MPa for 116 h, and the untreated control treatment for emergence speed index (A) and total emergence (B). Treatment means followed by the same letter within indicates no significant differences (P ≤ 0.05) according to Tukey test. Error bars indicate the means standard error.
Citation: HortScience 57, 9; 10.21273/HORTSCI16675-22
Discussion
Characterizing the parsley seeds imbibition curve.
As important as it is to understand the stages of crop development for growers, it is equally important to understand the phases of the germination process for greenhouse and nursery managers. In parsley, the seeds of which are known for a long germination process caused by morphological and morpho-physiological dormancy (Baskin and Baskin, 2014), seeds dormancy can delay germination by up to 28 d (International Seed Testing Association, 1985). However, priming agents can accelerate germination when dormancy is broken (Thomas, 1981). In our study, phase I of the germination process took 15 h, and parsley seeds had a weight increase of 90%. This is considered long compared with rape (Brassica napus), which takes 9 and 12 h for phases I and II, respectively (Schopfer and Plachy, 1984). Parsley seeds required 117 h to show radicular protrusion, which extended until 165 h. This characterized phase III of germination and results corroborated with Sorgatto and Silva (2018), measuring from 100 to 156 h for radicular protrusion on parsley. Particularly, Angelica keiskei (Zhanga et al., 2019) and Eryngium maritimum seeds (Necajeva and Ievinsh, 2013), also Apiaceae crops, demanded between 1 to 3 months to have at least 70% germination.
Use of priming agents on parsley seeds.
Hydropriming is an easy and low-cost priming technique used in vegetable nurseries and benefits of hydropriming were previously reported in onion (Caseiro et al., 2004), carrot (Eisvand et al., 2011), pepper (Sanchez et al., 2001), cucumber (Sanchez et al., 2001), and even parsley (Khan et al., 2017). Nevertheless, long periods of contact between water and parsley seeds induce negative effects on the germination process (Hassell and Kretchman, 1997). This is due to the coumarin, a toxic substance, released by parsley seeds when there is a rupture of the integument caused in the imbibition process (Chaturvedi and Muralia, 1975; Hassell and Kretchman, 1997; Kato et al., 1978). In the present study, when imbibed for 96 h in water, parsley seeds of cultivar Krausa and Titan had an ESI reduction of 66% and 35% compared with 24 h of water imbibition, respectively. The TE of parsley seeds was also reduced by 44% for cultivar Krausa and 20% for cultivar Titan when seeds were imbibed for 96 h compared with 24 h. Results corroborate with previous studies using hydropriming on parsley (Dursun and Ekinci, 2010; Kamau and Maina, 2017). Particularly, the imbibition of parsley seeds in water for 24 h was reported to increase ESI compared with untreated seeds (Khan et al., 2017), indicating that finds of the present study highlighted that 24 h of water imbibition is enough to increase both ESI and TE of parsley without damage seed development.
The goal of the osmopriming technique is to extend the phase II of germination, when seeds are digesting reserve substances and mobilizing protein to germination (Khan et al., 2017). Consequently, seeds treated with osmopriming agents tend to provide increased emergence due to increased cell size, cell number, and volume of the seed embryo (Chen et al., 2010; Dawidowicz-Grzegorzewska and Maguire, 1993; Gray et al., 1990). In the present study, the ESI of parsley seeds was unaffected by PEG6000 rates; however, the TE was directly affected by the IT of parsley seeds on PEG6000 and increased from 70.3% from the 29 h of imbibition to 75.5% from the 116 h of imbibition for cultivar Krausa, regardless of PEG6000 rate. Similarly, parsley seeds treated with PEG600, a product concentrated 10 times less than that used in the present study, for 48 h had higher germination and seedling uniformity compared with 24 h of imbibition (Kamau and Maina, 2017). In general, PEG is reported to reduce the seed water uptake and allows for the embryo to start germination before radicular protrusion, which explains the higher TE of seeds treated with PEG6000 (Taylor et al., 1998). The ESI of parsley seeds had no impact from PEG6000 rate and IT treatments, still, low rates of PEG6000 combined with long IT was the best strategy to reduce cost and increase TE. Similar results were previously reported by Sanchez et al. (2001), in which parsley seeds treated with PEG8000 at –0.5 MPa had a higher percentage and rate of germination with longer imbibition timings (4 and 7 d) than untreated seeds.
GA is a common hormonal priming agent used for seed treatment due to this hormone’s capacity to break seed dormancy, induce germination, and regulate metabolic activities that induce cotyledon development (Khan, 1968; Khan and Downing, 1968). High emergence rate and uniformity of emergence for parsley seeds treated with GA were previously reported in the literature (Gonai et al., 2004; Kucera et al., 2005). In the present study, the ESI and TE of parsley seeds increased by 6% for the application of GA at 2.0 g·L−1 a.i. compared with 0.5 g·L−1 a.i., regardless of IT. Consequently, the best strategy for treating parsley seeds was GA at 2.0 g·L−1 a.i. for 15 min of imbibition. Benefits of GA are minimal but allowed for the metabolic pathways to repair and start germination processes before the radicular protrusion (Bray, 1995; Srinivasan et al., 1999).
Best strategies of seed priming for parsley.
Using priming techniques allow growers to increase the number and quality of seedlings (Chen et al., 2010). As mentioned earlier, the benefits of priming techniques were previously reported in several other crops, but priming techniques evaluated in the present study had minimal to no impact on parsley seeds. This is mostly due to the fast germination of kale seeds and the coumarin toxin released after the rupture of the integument (Khan et al., 2017). Among the evaluated priming techniques, hydropriming (seed water imbibition for 24 h) and osmopriming (seed imbibition in PEG6000 at –2.0 MPa for 116 h) were the techniques that significantly increase ESI, whereas hydropriming (seed water imbibition for 24 h) increased TE. Osmopriming (PEG8000 at –0.5 MPa) (Sanchez et al., 2001) and seed water imbibition for 24 h (Dursun and Ekinci, 2010; Khan et al., 2017) were previously reported to increase the percentage and rate of seed germination compared with untreated seeds in parsley. Particularly, parsley seeds treated with water for 48 h and PEG600 for 24 and 48 h improve germination and number of normal seedlings compared with untreated seeds (Kamau and Maina, 2017). In contrast, the GA, a hormone commonly associated with breaking seed dormancy due to an early inhibition of amylase synthesis, had no effect on ESI and TE of parsley seeds in the present study. Results corroborate the literature, in which GA has no impact on lettuce germination (Khan and Downing, 1968), and GA has no influence on cilantro height but decreased biomass and leaf area (Jamshidian and Talat, 2017).
Conclusion
The present study evaluated the effect of different priming agents on parsley seedling production, with the goal to identify priming strategies that improve emergence and vigor of parsley seedlings under greenhouse conditions. Three simultaneous experiments were conducted to evaluate parsley cultivars, priming agent rate, and imbibition timing for the hydropriming, osmopriming, and hormonal priming techniques. Results indicated that the ESI and TE of parsley seeds were higher under 24 h of water imbibition in the hydropriming experiment, 116 h of PEG6000 imbibition at –2.0 MPa in the osmopriming experiment, and 15 min of GA imbibition at 2.0 g·L−1 a.i. in the hormonal priming experiment. Compared with untreated parsley seeds, 24 h of water imbibition and 116 h of PEG6000 imbibition at –2.0 MPa had a highest ESI, whereas 24 h of water imbibition had the highest parsley TE. For the 15 min of GA imbibition at 2.0 g·L−1 a.i. from the hormonal priming experiment, both ESI and TE had no significant difference from untreated control. In conclusion, the best priming strategies for treating parsley seeds were hydropriming under 24 h of water imbibition, followed by the osmopriming under 116 h of PEG6000 imbibition at –2.0 MPa.
Literature Cited
Baskin, C.C. & Baskin, J.M. 2014 Seeds: Ecology, biogeography, and evolution of dormancy and germination 2nd ed. Elsevier San Diego, CA
Bewley, J.D. & Black, M. 1994 Seeds—Physiology of development and germination 2nd ed. Springer Science New York, N.Y.
Bolton, A. & Simon, P. 2019 Variation for salinity tolerance during seed germination in diverse carrot [Daucus carota (L.)] germplasm HortScience 54 38 44 https://doi.org/10.21273/HORTSCI13333-18
Bray, C.M 1995 Biochemical processes during the osmopriming of seeds 767 789 Kigel, J. & Galili, G. Seed development and germination. Marcel Dekker New York, NY
Caseiro, R., Bennett, M.A. & Marcos-Filho, J. 2004 Comparison of three priming techniques for onion seed lots differing in initial seed quality Seed Sci. Technol. 32 365 375 https://doi.org/10.15258/sst.2004.32.2.09
Chaturvedi, S.M. & Muralia, R.N. 1975 Germination inhibitors in some Umbelliferae seeds Ann. Bot. 39 1125 1129 https://doi.org/10.1093/oxfordjournals.aob.a085034
Chen, K., Arora, R. & Arora, U. 2010 Osmopriming of spinach (Spinacia oleracea L. cv. Bloomsdale) seeds and germination performance under temperature and water stress Seed Sci. Technol. 38 36 48 https://doi.org/10.15258/sst.2010.38.1.04
Dawidowicz-Grzegorzewska, A. & Maguire, J.D. 1993 The effects of SMP on the ultrastructure of carrot seeds Proc. Intl. Wkshp. on Seeds. 3 1039 1044
Diel, M.I., Valera, O.V.S., Pinheiros, M.V.M., Thiesen, L.A., Meira, D., de Melo, P.J., Junges, D.L., Caron, B.O. & Schmidt, D. 2019 Temperature and light quality influence seed germination of two biquinho pepper cultivars Bulg. J. Agric. Sci. 25 1007 1014
Dursun, A. & Ekinci, M. 2010 Effects of different priming treatments and priming durations on germination percentage of parsley (Petroselium crispium L.) seeds Agro Sci. 1 17 23 https://doi.org/10.4236/as.2010.11003
Eisvand, H.R., Shahrosvand, S., Zahedi, B., Heidari, S. & Afrougheh, S. 2011 Effects of hydro-priming and hormonal priming by gibberellin and salicylic acid on seed and seedling quality of carrot (Daucus carota var. sativus) Iran J. Plant. Physiol. 1 233 239
Florido, M., Bao, L., Lara, R.M., Castro, Y., Acosta, R. & Alvarez, M. 2018 Effect of water stress simulated with peg 6000 on tomato seed germination (Solanum section Lycopersicon) Cult. Trop. 39 87 92
Gonai, T., Kawahara, S., Tougou, M., Satoh, S., Hashiba, T., Hirai, N., Kawaide, H., Kamiya, Y. & Yoshioka, T. 2004 Abscisic acid in the thermoinhibition of lettuce seed germination and enhancement of its catabolism by gibberellin J. Expt. Bot. 55 111 118 https://doi.org/10.1093/jxb/erh023
Gray, D., Steckel, J.R.A. & Hands, L.J. 1990 Response of vegetable seeds to controlled hydration Ann. Bot. 66 227 235 https://doi.org/10.1093/oxfordjournals.aob.a088107
Hassell, R.L. & Kretchman, D.W. 1997 The effects of umbel order, soaking, and scarification on germination inhibiting substances in Petroselinum crispum L. and other Apiaceae seeds HortScience 32 1227 1230 https://doi.org/10.21273/HORTSCI.32.7.1227
International Seed Testing Association 1985 International rules for seed testing Seed Sci. Technol. 13 299 355
Jamshidian, Z. & Talat, F. 2017 Effects of seed priming on morphological and phonological characteristics of the coriander (Coriandrum sativum L.) Adv. Plants Agric. Res. 7 1 5 https://doi.org/10.15406/apar.2017.07.00275
Kamau, K.S. & Maina, F.N.W. 2017 Percentage germination and seedling evaluation parameters of parsley (Petroselinum crispum) seeds as affected by different priming treatments and durations J. Agr. Ecol. Res. Intl. 13 1 5
Kato, T., Kobayashi, M., Sasaki, N., Kitahara, Y. & Takahashi, N. 1978 The coumarin hereclenol as a growth inhibitor in parsley seeds Phytochemistry 17 158 159 https://doi.org/10.1016/S0031-9422(00)89706-X
Khan, A.A 1968 Inhibition of gibberellic acid induced germination by abscisic acid and reversal by cytokinins Plant Physiol. 43 1463 1465 https://doi.org/10.1104/pp.43.9.1463
Khan, A.A. & Downing, R.D. 1968 Cytokinin reversal of abscisic acid inhibition of growth and amylase synthesis in barley seed Physiol. Plant. 21 1301 1307 https://doi.org/10.1111/j.1399-3054.1968.tb07362.x
Khan, F.A., Narayan, S., Bhat, S.A., Murtuza, I. & Hussain, K. 2017 Hydropriming a useful technique for seed invigoration in okra (Abelmoschus esculentus) and parsley (Petroselinum crispum) J. Appl. Nat. Sci. 9 1792 1795 https://doi.org/10.31018/jans.v9i3.1440
Kucera, B., Cohn, M.A. & Leubner-Metzger, G. 2005 Plant hormone interactions during seed dormancy release and germination Seed Sci. Res. 15 281 307 https://doi.org/10.1079/SSR2005218
Maguire, J.D 1962 Speed of germination aid in selection and evaluation for seedling emergence and vigor Crop Sci. 2 176 177
Michel, B.E. & Kaufmann, M.R. 1973 The osmotic potential of polyethylene glycol 6000 Plant Physiol. 51 914 916 https://doi.org/10.1104/pp.51.5.914
Necajeva, J. & Ievinsh, G. 2013 Seed dormancy and germination of an endangered coastal plant Eryngium maritimum (Apiaceae) Estonian J. Ecol. 62 150 161 https://doi.org/10.3176/eco.2013.2
Paparella, S., Araújo, S.S., Rossi, G., Wijayasinghe, M., Carbonera, D. & Balestrazzi, A. 2015 Seed priming: State of the art and new perspectives Plant Cell Rep. 34 1281 1293 https://doi.org/10.1007/s00299-015-1784-y
Pill, W.G 1986 Parsley emergence and seedling growth from raw, osmoconditioned and pregerminated seeds HortScience 21 1134 1136
Pill, W.G. & Kilian, E.A. 2000 Germination and emergence of parsley in response to osmotic or matric seed priming and treatment with gibberellin HortScience 35 907 909 https://doi.org/10.21273/HORTSCI.35.5.907
Podlaski, S., Chrobak, Z. & Wyszkowska, Z. 2003 The effect of parsley seed hydration treatment and pelleting on seed vigor Plant Soil Environ. 49 114 118
Sanchez, J.A., Munoz, B.C. & Fresneda, J. 2001 Combined effects of hardening hydration dehydration and heat shock treatments on the germination of tomato, pepper, and cucumber Seed Sci. Technol. 29 691 697
Schopfer, P. & Plachy, C. 1984 Control of seed germination by abscisic acid II. Effect on embryo water uptake in Brassica napus L Plant Physiol. 76 155 160 https://doi.org/10.1104/pp.76.1.155
Sharma, K.K., Singh, U.S., Sharma, P., Kumar, A. & Sharma, L. 2015 Seed treatments for sustainable agriculture—A review J. Appl. Nat. Sci. 7 521 539 https://doi.org/10.31018/jans.v7i1.641
Sorgatto, K.P. & Silva, V.N. 2018 Parsley seeds imbibition with Ascophyllum nodosum: Effects on germination and growth of seedlings under thermal stress Acta Biol. Catarinense. 5 98 106
Srinivasan, K., Saxena, S. & Singh, B.B. 1999 Osmo and hydropriming of mustard seeds to improve vigor and some biochemical activities Seed Sci. Technol. 27 785 793
Taylor, A.G., Allen, P.S., Bennet, M.A., Bradford, K.J., Burris, J.S. & Misra, M.K. 1998 Seed enhancements Seed Sci. Res. 8 245 256 https://doi.org/10.1017/S0960258500004141
Tavares, A.E.B 2018 Management of nitrogen fertilization in the production and quality of fruit and seeds of zucchini, Chapter 2 São Paulo State Univ. Botucatu PhD Diss
Thomas, T.H 1981 Seed treatments and techniques to improve germination Scientia Hort. 32 47 59
Zhanga, K., Zhanga, Y., Walckb, J.L. & Taoa, J. 2019 Non-deep simple morphophysiological dormancy in seeds of Angelica keiskei (Apiaceae) Scientia Hort. 255 202 208 https://doi.org/10.1016/j.scienta.2019.05.039
Ziaf, K., Mahmoodur-Rehman, M., Amjad, M., Ahmad, R., Batool, A., Muhammad, A., Latif, J. & Zaman, Q. 2017 Influence of hydro- and halo-priming on germination and seedling growth of cabbage under saline conditions Pure Appl. Biol. 6 97 107 https:/doi.org/dx.doi.org/10.19045/bspab.2017.60002
