Agriculture is directly linked to human life, providing food for survival and health. It is threatened by a number of challenges, such as climate change, resource depletion, and abiotic stresses, including heavy metals (HMs), salinity, drought, etc. Various strategies have been employed to palliate the phytotoxic effects of these stressors from the soil–plant system. Nanotechnological approaches have emerged as a promising tool for increasing crop productivity and promoting sustainable agriculture. Interestingly, the seed nano-priming approach has shown potential against all of the above-mentioned abiotic stress factors and has improved crop productivity. The application of nanoparticles (NPs) via seed priming is an innovative and cost-effective approach that improves seed germination and subsequent plant growth by activating plant physiological processes and providing tolerance against various stresses. The seed priming with NPs induces electron exchange and increases surface reaction capabilities related to plant cell and tissue components. This review aims to provide an overview of recent advances and research findings on seed nano-priming and the possible mechanism of plant stress-tolerance augmentation against various stresses. Furthermore, we also shed light on gaps in studies conducted in previous years, which will open new avenues for future research.

In recent decades, global climate change and heavy metal stress have severely affected plant growth and biomass, which has led to a serious threat to food safety and human health. Anthropogenic activities, the rapid pace of urbanization, and the use of modern agricultural technologies have further aggravated environmental conditions, resulting in limited crop growth and productivity. This review highlights the various adaptive transcriptomic responses of plants to tolerate detrimental environmental conditions, such as drought, salinity, and heavy metal contamination. These stresses hinder plant growth and development by disrupting their physiological and biochemical processes by inducing oxidative stress, nutritional imbalance, and osmotic disturbance, and by deteriorating their photosynthetic machinery. Plants have developed different strategies to safeguard themselves against the toxic effects of these environmental stresses. They stimulate their secondary messenger to activate cell signaling, and they trigger other numerous transcriptomic responses associated with plant defense mechanisms. Therefore, the recent advances in biological sciences, such as transcriptomics, metabolomics, and proteomics, have assisted our understanding of the stress-tolerant strategies adopted by plants, which could be further utilized to breed tolerant species. This review summarizes the stress-tolerant strategies of crops by covering the role of transcriptional factors in plants.

Nanoparticle contamination has been associated with adverse impacts on crop productivity. Thus, effective approaches are necessary to ameliorate NP-induced phytotoxicity. The present study aimed to investigate the efficacy of brassinosteroids and ethylene in regulating CuO NPs toxicity in rice seedlings. Therefore, we comprehensively evaluated the crosstalk of 24-Epibrassinolide and ethylene in regulating CuO NP-induced phytotoxicity at the physiological, cellular ultrastructural, and biochemical levels. The results of the study illustrated that exposure to CuO NPs at 450 mg/L displayed a significant decline in growth attributes and induced toxic effects in rice seedlings. Furthermore, the exogenous application of ethylene biosynthesis precursor 1-aminocyclopropane-1-carboxylic acid (ACC) at 20 µM with 450 mg/L of CuO NPs significantly enhanced the reactive oxygen species (ROS) accumulation that led to the stimulation of ultrastructural and stomatal damage and reduced antioxidant enzyme activities (CAT and APX) in rice tissues. On the contrary, it was noticed that 24-Epibrassinolide (BR) at 0.01 µM improved plant biomass and growth, restored cellular ultrastructure, and enhanced antioxidant enzyme activities (CAT and APX) under exposure to 450 mg/L of CuO NPs. In addition, brassinosteroids reduced ROS accumulation and the toxic effects of 450 mg/L of CuO NPs on guard cells and the stomatal aperture of rice seedlings. Interestingly, when 0.01 µM of brassinosteroids, 20 µM of ACC, and 450 mg/L of CuO NPs were applied together, BRs and ethylene showed antagonistic crosstalk under CuO NP stress via partially reducing the ethylene-induced CuO NP toxicity on plant growth, cellular ultrastructure, stomatal aperture, and guard cell and antioxidant enzyme activities (CAT and APX) in rice seedlings. BR supplementation with ACC and CuO NPs notably diminished ACC-induced CuO NPs’ toxic effects on all of the mentioned attributes in rice seedlings. This study uncovered the interesting crosstalk of two main phytohormones under CuO NPs stress, providing basic knowledge to improve crop yield and productivity in CuO NPs-contaminated areas.