Jasmonic acid (JA) is an important and widely distributed plant hormone. However, the molecular and physiological mechanism of JA in improving drought tolerance in response to sodium selenite is limited. This work was performed to investigate the effects of exogenous sodium selenite application in promoting drought tolerance of cucumber. The drought tolerance of cucumber seedlings is enhanced under the application of selenite, positively influencing shoot fresh weight and chlorophyll relative content and altering the chloroplast ultrastructure. The contents of JA and JA-isoleucine (JA-ILE) increased significantly in response to selenite application under drought conditions. Furthermore, the expression of JA biosynthesis and regulatory genes, namely, LOX (Lipoxygenase), AOC (alleneoxide cyclase), AOS (alleneoxide synthase), and MYC2 (the basic helix-loop-helix (bHLH) protein) was upregulated to greater levels when selenite was added in combination with drought treatment. This study provides methods to mitigate drought stress and valuable theoretical support for further understanding the plant response to drought signals.

In this study, gibberellic acid 3 (GA3) and uniconazole were applied as the means of improving of cadmium (Cd) polluted site phytoremediation using maize (Zea mays L.). The results showed that GA3 (40 mg/L), and uniconazole (800 mg/L) could increase the biomass, plant height, stem diameter, leaf area, and root parameters of maize plants under Cd stress (0.4 mg/L) by foliar spraying. GA3 (40 mg/L) could increase the SPAD value of maize leaves by 23.45% and the net photosynthetic rate by 645.93%. Both plant regulators could alleviate the oxidative damage of maize and increase the activity of SOD and POD up to 11.44~58.41% and 35.00~99.55%, respectively. The content of MDA and H2O2 could be reduced by GA3 to 31.91% and 24.77%, respectively. GA3 at 40 mg/L could significantly increase the accumulation of Cd ions in the shoots, roots and whole plants of maize by 222.01%, 603.13% and 341.70%, respectively, showing the best effect among tested treatments. It was found that the application of plant growth regulators (PGRs) could increase the biomass and Cd concentration in maize organs, ultimately achieving the purpose of improving the remediation efficiency of Cd by increasing the absolute content of Cd in maize biomass.