Comprehensive journey from past to present to future about seed priming with hydrogen peroxide and hydrogen sulfide concerning drought, temperature, UV and ozone stresses- a review

Background and aims: Abiotic stresses lead to drastic changes in functional and physiological anatomy in plants such as generation of reactive oxygen species, loss of photosynthetic efficiency, membrane damage etc resulting in a slower expansion and causing a significant harvest penalty. Methodologies like conventional breeding or the use of transgenics are in trend to abate stress impacts on plants, however, alternatively, the use of simple and cost-effective solutions to this problem are also popular. This review focuses on the amelioration of four chief abiotic stressors in plants with reference to priming by H2O2 and H2S. In light of this, the mechanism of resilience to abiotic stress is thoroughly elucidated from past to current scientific efforts in addition to elaborating the critical knowledge gaps and bridging those as well. There are reviews on the use of these two molecules in agronomic systems for drought, and, heat stresses, however, the present review differs in reviewing their impacts on very less addressed UV and ozone stress, including their parallel view of action in terms of similarities and dissimilarities elaborating the interconnection with other signaling molecules. Conclusion: Recently, pre-treatment with hydrogen peroxide (H2O2) and hydrogen sulfide (H2S) has emerged as an economic, feasible, and efficient approach to abate the various abiotic stresses. H2O2 and H2S are multitasking cell signaling molecules in plants. Chemical priming with H2O2 and H2S helps in acclimation of seedlings by hardening and activating antioxidant machinery and thus, in stress tolerance to deal with numerous abiotic stress exposures like drought, temperature, UV, and ozone stress.