Environmental stresses negatively affect the growth and development of plants. Several previous studies have elucidated the response mechanisms of plants to drought and heat applied separately; however, these two abiotic stresses often coincide in environmental conditions. The global climate change pattern has projected that combined drought and heat stresses will tend to increase in the near future. In this study, we down-regulated the expression of a cytokinin receptor gene SlHK2 using RNAi and investigated the role of this gene in regulating plant responses to individual drought, heat, and combined stresses (drought + heat) in tomato. Compared to the wild-type (WT), SlHK2 RNAi plants exhibited fewer stress symptoms in response to individual and combined stress treatments. The enhanced abiotic stress tolerance of SlHK2 RNAi plants can be associated with increased membrane stability, osmoprotectant accumulation, and antioxidant enzyme activities. Furthermore, photosynthesis machinery was also protected in SlHK2 RNAi plants. Collectively, our results show that down-regulation of the cytokinin receptor gene SlHK2, and consequently cytokinin signaling, can improve plant tolerance to drought, heat, and combined stress.

Pea is an important legume crop because of its higher bioactive compounds, and its seeds are famous as functional foods. However, the yield of pea is still limited because of multiple biotic and abiotic stresses which prevailed during the growth period. Saline conditions significantly hamper pea growth, yield, and quality among abiotic stresses. Salicylic acid is effective for the activation of oxidative, non-oxidative, osmolytes, and metabolites. Hence, the present study was conducted at exogenous application of salicylic acid (control, 1 µM, 2 µM, and 3 µM) to mitigate the adverse effects of salt stress (control, 25 mM, 50 mM, and 100 mM NaCl) in pea plants grown in the year 2019–2020. The aim of the present study was to evaluate pea performance under saline conditions by salicylic acid sprays. Pea growth and yield were significantly decreased at 100 mM NaCl compared with the control and other salinity levels. Moreover, the growth and yield of pea were improved under exogenous application of salicylic acid treatment at 3 µM than others. Quality traits, i.e., carotenoids, ascorbic acid, and phenolic content, were decreased at 100 mM NaCl, and these quality traits were significantly improved under salicylic acid treatment of 3 µM. Chlorophyll a, chlorophyll b, total chlorophyll, photosynthesis, and stomatal conductance were reduced at 100 mM NaCl. In contrast, photosynthetic pigments, photosynthesis, and stomatal conductance were enhanced at 3 µM salicylic acid. The increases in SOD, CAT, POD, and APX were observed at 100 mM NaCl and 3 µM salicylic acid. The current study proved that exogenous application of salicylic acid concentrations had the potential to mitigate the salinity’s adverse effects by maintaining the physiological and metabolic activities of pea plants.

Morus alba L. is a multipurpose and fast-growing tree species. However, its growth and productivity are susceptible to water stress. Therefore, a study was conducted to check the effectiveness of foliar application of salicylic acid (SA) in improving the water stress tolerance of M. alba. A pot experiment was conducted and the morphological, physiological and biochemical attributes of young M. alba saplings were assessed under control (CK, 90% of field capacity (FC)), moderate (MS, 60% of FC) and high soil water deficits (HS, 30% of FC), along with MS and HS + foliar application of SA 0.5 and 1.0 mM (MS + 0.5; HS + 0.5; MS + 1.0, and HS+1.0, respectively). Results demonstrated that the highest decrease in plant growth, leaf, stems and roots’ dry biomass, chlorophyll a, b, carotenoid contents and leaf gas exchange parameters was observed under HS, whereas the lowest decrease was evidenced for HS + 1.0 mM SA. Electrolyte leakage, malondialdehyde contents, hydrogen peroxide and superoxide radicals significantly increased under HS, while the lowest increase was evidenced for HS + 1.0 mM SA. The highest increase in proline content, total soluble sugar, total phenolic content, soluble protein and superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase was also found under HS + 1.0 mM SA. Based on the results, it can be concluded that foliar application of SA can help improve the water deficit tolerance of Morus alba saplings, especially under high soil water deficit.

Auxin/indole-3-acetic acid (Aux/IAA) is a transcriptional repressor in the auxin signaling pathway that plays a role in several plant growth and development as well as fruit and embryo development. However, it is unclear what role they play in Japanese apricot (Prunus mume) fruit development and maturity. To investigate the role of Aux/IAA genes in fruit texture, development, and maturity, we comprehensively identified and expressed 19 PmIAA genes, and demonstrated their conserved domains and homology across species. The majority of PmIAA genes are highly responsive and expressed in different hormone treatments. PmIAA2, PmIAA5, PmIAA7, PmIAA10, PmIAA13, PmIAA18, and PmIAA19 showed a substantial increase in expression, suggesting that these genes are involved in fruit growth and maturity. During fruit maturation, alteration in the expression of PmIAA genes in response to 1-Methylcyclopropene (1-MCP) treatment revealed an interaction between auxin and ethylene. The current study investigated the response of Aux/IAA development regulators to auxin during fruit ripening, with the goal of better understanding their potential application in functional genomics.