Osmo-priming of one-year-old chickpea seeds with KNO
3, MgSO
4, Ca(NO
3)
2 at 0.2 % solution and tap water for 06 hours separately significantly enhanced the germination (%), seedling length, seedling dry weight, and vigour index I&II in both the varieties evaluated under normal as well as under water deficit conditions over their respective control (Table 1A-E). Maximum germination followed by seedling length, seedling dry weight and finally vigour index I and II was recorded with KNO3 priming in both the varieties under normal as well as drought conditions. Amongst, the priming agents used, KNO
3 performed better than MgSO
4, Ca(NO
3)
2 and tap water in respect of most of the seed quality parameters. Per cent improvement due to osmo-priming over their respective control was higher in water deficit condition than normal moisture in all the seed quality parameters in general and reflected finally in vigour Index-I and Vigour Index-II (Fig 1 and 2) indicating thereby the role of osmo-priming under limiting environment. Similar findings have also been reported by
Sathyamoorthy and Nakaumura (1995) in potato,
Afzal et al., (2002) in maize,
Yoganada et al., (2004) in bell papper,
Satishkumar (2005) in brinjal, Poonam
Singh et al., (2006) in sunflower,
Tiwari et al. (2013) in mung bean,
Tiwari et al., (2014) in pigeon pea,
Tiwari et al., (2015) in rice,
Tiwari et al., (2015) in mung bean and
Tiwari et al., (2016) in wheat and Tiwari
et al. (2018,
2019 and
2020) in pigeon pea have explained that osmo- priming with various chemicals to seeds eventually enhances rate of seed germination and encourages fast emergence of seedling in the field and this might have led to an improvement in subsequent phases of plant growth and ultimately to higher yield of crop. This is well known that during soaking of seed in KNO
3, Mg SO
4 or Ca(NO
3)
2 solution the cations Ca
++, Mg
++ or K,
+ and anions SO
4-, or NO
3-in fluxed in the seeds and showed their carry over effect during vegetative growth period. Both the varieties responded priming treatments under both normal and water deficit conditions. Seed priming with different in- organic salts and plant growth regulator GA
3 in pigeon pea crop have also been reported to improve the seed germination and seedling growth due to their nutritive role in the germination process by
Tiwari et al. (2019) and
Tiwari and Agarwal (2021). Significant effects of osmo priming with PEG-6000 were also noted on germination and crop performance of sun flower by
Bourioug et al., (2020). Our finding with respect to response of seed priming with in- organic salts are very similar with findings of other workers in the field.
Seed priming with in- organic salts showed a slight improvement in plant height and leaf area over their respective unprimed control (Table 2A and B) under both normal and water deficit condition but statistically the improvements were insignificant though improvement in growth characters including leaf area index have been reported in late sown wheat by
Jatana et al., (2020) using salicylic acid as priming agent. In the present study piming with tap water, KNO, Mg SO
4 and Ca (NO)
2 in 0.2% solution did not improve the plant height and leaf area in varieties Ujjwal and JG-14 both under normal as well as drought condition. The moisture level also did not affect the plant height and leaf area in both the varieties evaluated. Interactions of V×T, V×M, T×M and V×T×M were not significant. Osmo-priming treatments showed the significant and positive response in improvement of biochemical parameters including nitrogen balance index(NBI). Chlorophyll and flavonol over unprimed control and tap water priming in both the varieties evaluated under both normal and water deficit conditions (Table 3 A, B and C). Highest values of nitrogen balance index and chlorophyll were noted with Mg SO
4 followed by KNO
3 and Ca (NO
3)
2 because of their nutritive role in the respective metabolic synthesis but flavonols were higher with KNO
3 followed by MgSO
4 and were relatively higher under drought condition might be due to more synthesis in the moisture stress condition. Chlorophylls are vital pigments that absorb a considerable amount of light energy and perform photosynthesis reactions in plant. Chlorophyll is very sensitive to various environmental stress, thus caused a significant reduction in chlorophyll contents and biosynthesis, thus effects plant growth (
Demir and Mavi, 2004;
Khan et al., 2009; Shah et al., 2012). In the present study seed priming significantly increased chlorophyll contents in chickpea seedlings. The results are in agreement with previous studies, who have reported that priming significantly enhanced chlorophyll contents in wheat leaves
(Jiajin et al., 2010; Rahimi, 2013;
Siri et al., 2013; Sharma et al., 2014). Chlorophyll contents is an important parameter often used as an indicator for developments of chloroplast and photosynthetic capacity
(Xia et al., 2009; Anwar
et al., (2020).
Meena et al., 2016), thus considered as a base for plant growth and developmental process. These results suggested that seed priming enhanced chlorophyll contents thus leads to improve seedlings growth. Leaf nitrogen balance and chlorophyll have strong correlation and affects the photosynthetic capacity
(Castro et al., 2014), which is a key molecule for photosynthesis. In the present study, we have reported that seed priming enhanced nitrogen balance and chlorophyll accumulation in chickpea leaves but their utilization by the plant was affected with moisture stress and resulted in relative decrease in photosynthetic efficiency under drought conditions.
Osmo-priming treatments with different in-organic salts and tap water also showed the positive response in improvement of Stomatal conductance, photosynthetic rate and transpiration rate in both the varieties evaluated under normal as well as water deficit condition (Table 4 A, B and C). Amongst the in- organic salts used, KNO
3 and Ca (NO
3) were found more effective for enhancing the above parameters over the rest of the priming treatments and un primed control. Variety JG-14 showed higher values in the most of the parameters studied. In this study, Photosynthetic activities including photosynthetic rate, stomatal conductance and transpiration rate were significantly improved by seed priming in chickpea seedlings, as compared to un primed control (Fig 3). Chlorophylls accumulation are important parameter frequently used as an indicator of photosynthetic capacity, in the present study we reported that seed priming enhanced chlorophyll accumulation resulted a significant increment in photosynthetic capacity. These results are similar to those of earlier studies, which reported that seed priming with Salicylic acid and PEG enhanced photosynthesis in rice seedlings (
Li and Zhang, 2010;
Shaheen et al., 2016), and
Zhang et al., (2012), who had reported that photosynthesis capacity in cucumber plant were increased by seed priming and also increased photochemical efficiency of PS II. Seed priming enhanced significantly nutrients uptake and balancing of membrane potential and regulating of osmotic pressure cells (
Chérel, 2004), thus it might be reasoning that seed priming regulate nitrogen balance, chlorophylls accumulation and there by photosynthetic efficiency and leads significant enhancement in chickpea seedlings growth.