Enhancing gene expression and metabolites accumulation for better plant growth in under drought stress using hydrogen peroxide.

Growth improvement of the medicinal plant, (Mas Cotek) under drought conditions is a vital issue in Malaysia since it is a slow-growing plant and disposed to leaf damage under the stresses of drought. Therefore, investigation was done to examine the outcomes of hydrogen peroxide (HO) application on gene expression and metabolites accumulation of stressed plants, and thereby to record the changes in leaf histology, photosynthesis, biochemical properties, and the growth of the plant. HO at the rates of 0, 5, 10, 15, and 20 mM were foliar sprayed biweekly on the drought stressed plants using a hand sprayer. The application of 20 mM HO amplified leaf number, tallness, stomatal conductance, and photosynthetic yield by 143, 24, 88, and 18%, respectively, over the control plant. A reduced transpiration rate and improved chlorophyll fluorescence were also noted in HO-treated plants. The treatment produced a greater amount of chlorophyll , total phenols, total flavonoids, sugar content, and antioxidant activities by 1.61-, 1.30-, 1.98-, 1.92-, and 1.53-fold, respectively. Application of 15 mM HO enhanced net photosynthetic rate and internal CO concentrations by 1.05- and 1.25-fold, respectively. Additionally, HO treatments promoted stomatal closure, increased stomata size, the number of stomata, improved vein structure, and reduced the damage of the leaf margin and mesophyll cells of drought stressed plants. The application of HO also accumulated significantly higher contents of sodium (Na), calcium (Ca), potassium (K), magnesium (Mg), and iron (Fe) in stressed plants. Although the amount of Arsenic (As) and Antimony (Sb) increased to some extent, the increases were not at a toxic level. The use of HO enhanced the gene expression to a greater level and the ratio of expression increased up to 16-fold. Finally, thirteen (13) identified and five (5) unmatched volatile compounds with a quality score above 70% were identified by gas chromatography-mass spectrometry (GCMS). The GCMS analysis showed that the foliar application of HO accumulates a higher percentage of volatile components in plants which helps to mitigate the negative effects of drought stress. It is concluded that under drought stressed conditions the plants should be treated with 10-15 mM of HO twice a week to improve leaf histology, photosynthesis, the level of gene expression and volatile compounds accumulation, and plant growth and development.