Plant Growth Regulators Melatonin and Salicylic Acid Protect Muskmelon (Cucumis melo) Plants from Arsenic-Induced Damage by Regulating Photosynthetic Function and Antioxidant Defense Mechanism
摘要
Heavy metal contamination like Arsenic (As) poses serious threat to muskmelon crop production and fruit quality in addition to being a major risk to human health. Thus, reducing As toxicity is essential from the standpoint of crop productivity and human health. In this study, we investigated the role of two important growth regulators melatonin (Me) and salicylic acid (SA) for the alleviation of As effects in muskmelon plants. It is well documented that these dual plant growth regulators are known to alleviate the negative effects of stressors in plants by modulating their physiological, biochemical and molecular adaptive responses. Firstly, muskmelon plants treated with As showed enhanced As uptake, elevated oxidative damages, photosynthesis inhibition, and overall plant growth reduction. However, muskmelon plants supplemented with Me and SA balanced water and ionic ratio, have better photosynthesis potential, lower oxidative stress, all of which help in maintaining and enhancing plant growth. From the findings, it is evident that As treatments result in enhanced oxidative damage, accumulation of hydrogen peroxide, malondialdehyde, and proline, contents with respective rise of 144%, 46%, and 133%, while Me and SA treatments reduce As severity significantly, their concentration with respective percentage increased compared to the control by 55% (13.8 µmol gm−1 to 21.45 µmol gm−1), 23% (1.19 µmol gm−1 to 1.46 µmol gm−1), 73% (28.15 µgm gm−1 to 48.70 µgm gm−1), 43% (13.8 µmol gm−1 to 19.8 µmol gm−1), 17% (1.19 µmol gm−1 to 1.39 µmol gm−1), and 54% (28.15 µgm gm−1 to 43.50 µgm gm−1). In addition to this, Me and SA treatment increased antioxidant enzyme activity and the expression level of defensive genes, supporting their role under As stress. These observations showed that Me and SA supplementation effectively alleviates As toxicity in muskmelon plants, by not only increasing stress resilience but also enhancing growth which can potentially be applied to other industrially important crops.