Seed Priming with Phytohormones: An Effective Approach for the Mitigation of Abiotic Stress

Plants are often exposed to abiotic stresses such as drought, salinity, heat, cold, and heavy metals that induce complex responses, which result in reduced growth as well as crop yield. Phytohormones are well known for their regulatory role in plant growth and development, and they serve as important chemical messengers, allowing plants to function during exposure to various stresses. Seed priming is a physiological technique involving seed hydration and drying to improve metabolic processes prior to germination, thereby increasing the percentage and rate of germination and improving seedling growth and crop yield under normal and various biotic and abiotic stresses. Seed priming allows plants to obtain an enhanced capacity for rapidly and effectively combating different stresses. Thus, seed priming with phytohormones has emerged as an important tool for mitigating the effects of abiotic stress. Therefore, this review discusses the potential role of priming with phytohormones to mitigate the harmful effects of abiotic stresses, possible mechanisms for how mitigation is accomplished, and roles of priming on the enhancement of crop production

SEED PRIMING AND EXOGENOUS APPLICATION OF SALICYLIC ACID ENHANCE GROWTH AND PRODUCTIVITY OF OKRA (Abelmoschus esculentus L.) BY REGULATING PHOTOSYNTHETIC ATTRIBUTES

Low and uneven germination is a serious problem for the successful production of okra seedlings. Priming of seeds as well as supplementation of different plant growth regulators exhibited better response in successful seedling production which eventually results in higher yield. Therefore, the present study was conducted to evaluate the effects of seed priming and exogenous application of salicylic acid (SA) on okra seed germination and plant development. The okra seeds were primed by 1 mM and 2 mM of SA for 60 minutes whereas the seeds were washed several times with distilled water for the control treatment. Similar doses of SA have been exogenously sprayed to the 12 days okra seedlings for 4 days. The results of the study revealed that seed priming with SA enhanced germination percentage (GP), increased coleoptile length and weight, shoot and root length, and seed vigor index (SVI). Similarly, exogenous application of 1 mM SA increased relative water content (RWC), contents of chlorophyll a, chlorophyll b, total chlorophyll while a higher dose of SA (2 mM) degraded the leaf pigments. Supplementation of SA altered photosynthetic attributes, net photosynthetic (Pn) and transpiration rate (Tr), stomatal conductance (Gs), and water use efficiency (WUE). Moreover, SA treatment reduced the time duration of flower bud initiation and days to first flowering and enhanced the yield per plant. The results of this study indicated that seed priming and exogenous application of SA enhanced germination and okra productivity by regulating RWC and photosynthetic attributes where 1 mM SA is more effective compared to 2 mM SA

Alleviation of Salt-Inhibited Germination and Seedling Growth of Kidney Bean by Seed Priming and Exogenous Application of Salicylic Acid (SA) and Hydrogen Peroxide (H2O2)

Salinity is a dominant obstacle to the proper germination of seeds, growth of seedlings, and, consequently, the production of crops. The priming of seeds with different treating agents can efficiently impart salinity tolerance. Kidney bean is a nutritious and popular vegetable crop in the world. Literature shows that salt stress negatively disturbs the germination and growth of kidney beans. In the present research, we investigated the potentiality of salicylic acid (SA) and hydrogen peroxide (H2O2) as priming and exogenous agents to alleviate the salinity-inhibited germination and growth of kidney beans. The seeds were pretreated with SA (1 mM and 2 mM) and H2O2 (0.1 mM and 0.15 mM) and soaked in normal tap water (hydro-priming) for 60 min. In addition, for the control experiment, untreated seeds were used. Finally, primed seeds were subjected to salt stress (150 mM NaCl). Our results exhibited that salt stress considerably lowered the percentage of germination (GP), germination index (GI), seed vigor index (SVI), shoot length (SL), root length (RL), shoot–root fresh and dry biomass, and plant growth. The results also exhibited that salt stress significantly decreased the relative water content (RWC) and photosynthetic pigments such as chlorophyll, carotenoids, lycopene, and beta-carotene contents. The SA- and H2O2- and hydro-priming stimulated the GP, GI, SL, RL, SVI, and seedling growth. Data also revealed that the supplementation of SA and H2O2 enhanced RWC and photosynthetic pigments. When compared to other treatments, pretreatment with 1 mM SA was determined to be comparatively more effective at imparting the salt tolerance of kidney beans. Overall, these results, via a heatmap and principal component analysis, uncovered that priming and exogenous applications of SA and H2O2 can improve salt tolerance and enhance germination and seedling characteristics of kidney beans

Proline and glycine betaine: A dynamic duo for enhancing salt stress resilience in maize by regulating growth, Stomatal size, and Oxidative stress responses

Osmolytes proline (Pro) and glycine betaine (GB) have been reported to impart tolerance against salinity stress in many plants. However, there is no report available on the combined application of Pro and GB to mitigate salinity-induced growth inhibition in maize. Consequently, the goal of the current study is to assess Pro's and GB's potential as priming and exogenous agents in maize under salt stress. Therefore, the present study was conducted using a petri dish and hydroponic pot experiment to evaluate the morpho-physiological and biochemical characteristics of maize plants subjected to salt stress, with the addition of Pro and GB. The seeds of maize were germinated under 20 mM of each Pro or GB, with or without 120 mM salinity stress. The findings demonstrated that salt stress lessened the final germination percentage (FGP) (52.9 %), photosynthetic pigments (40.0 %), relative water content (RWC) (20.2 %), stomatal size (59.3 %), and leaf and root K+/Na+ ratios of maize seedlings compared to control. In addition, compared to the control, higher levels of malondialdehyde (MDA) (24.2 %) and hydrogen peroxide (H2O2) (25.7 %) were observed, whereas lower levels of catalase (CAT) (43.8 %) and peroxidase (POX) (30.4 %) were noted. The priming with Pro, GB, Pro+GB significantly increased FGP, germination index (GI), shoot-root biomass, seed vigor index (SVI), and reduced mean germination time (MGT) under salt stress. Foliar application of Pro, GB, or Pro+GB resulted in a significant increment in chlorophyll contents, RWC, K+ absorption, and stomatal size under salt stress. Furthermore, supplementing with Pro, GB, or Pro+GB reduced the accumulation of H2O2 (24.0, 23.3, and 31.1 %, respectively) and MDA (22.8, 17.2, and 32.1 %, respectively) caused by salt and augmented the levels of CAT (33.3, 22.8, and 45.2 %, respectively) and POX (36.4, 23.5, and 47.2 %, respectively) in the leaves. Taken together, the current study's findings indicate that combining Pro and GB is one of the most effective techniques for improving the salinity-tolerant seed germination and seedling traits of maize plants. Consequently, this study recommends that Pro and GB can be used as seed priming and exogenous agents to help maize grow faster in salt-stress situations