Exogenous Melatonin Mitigates Acid Rain Stress to Tomato Plants through Modulation of Leaf Ultrastructure, Photosynthesis and Antioxidant Potential

Abstract

Acid rain (AR) is a serious global environmental issue causing physio-morphological changes in plants. Melatonin, as an indoleamine molecule, has been known to mediate many physiological processes in plants under different kinds of environmental stress. However, the role of melatonin in acid rain stress tolerance remains inexpressible. This study investigated the possible role of melatonin on different physiological responses involving reactive oxygen species (ROS) metabolism in tomato plants under simulated acid rain (SAR) stress. SAR stress caused the inhibition of growth, damaged the grana lamella of the chloroplast, photosynthesis, and increased accumulation of ROS and lipid peroxidation in tomato plants. To cope the detrimental effect of SAR stress, plants under SAR condition had increased both enzymatic and nonenzymatic antioxidant substances compared with control plants. But such an increase in the antioxidant activities were incapable of inhibiting the destructive effect of SAR stress. Meanwhile, melatonin treatment increased SAR-stress tolerance by repairing the grana lamella of the chloroplast, improving photosynthesis and antioxidant activities compared with those in SAR-stressed plants. However, these possible effects of melatonin are dependent on concentration. Moreover, our study suggests that 100-μM melatonin treatment improved the SAR-stress tolerance by increasing photosynthesis and ROS scavenging antioxidant activities in tomato plants.

Phytomelatonin: Recent advances and future prospects

“…Abiotic stresses, such as drought, cold, and strong light, elevated temperatures along with heavy metal poisoning, can result in the distortion of the electron transport chain (ETC), leading to photo‐oxidation and sequential reduction in the photosynthetic efficiency in plants . It is also noteworthy that these stressful environments induce ultrastructural changes, particularly in leaf mitochondria and chloroplasts; this leads to excessive production of ROS . The photosynthetic effectiveness is determined by the chlorophyll content as elevated ROS causing a drop in the chlorophyll content in plants .…”

“…Estimating chlorophyll fluorescence is a rapid, persuasive, and reliable method for determining the photosynthesis processes in plants . Remarkably, the primary photosystem (PSII) of the photosynthetic machinery ( F o and F o /F m value) is essential in the transformation of energy and thereby serves as an excellent marker of stress in plants . Clearly, it becomes imperative to alter the effectiveness of this profit‐yielding mechanism for improved growth and development of plants under capricious environments.…”

Exogenous Melatonin Improves Fruit Quality Features, Health Promoting Antioxidant Compounds and Yield Traits in Tomato Fruits under Acid Rain Stress

“…It was hypothesized that melatonin act as the first line defense to protect plants against biotic and abiotic stress, and the mechanisms of melatonin-mediated stress tolerance are involved in arranging biosynthesis of antioxidants, activating related enzyme activities and scavenging ROS directly when plants are exposed to harsh environments such as extreme temperature, cold, drought, salt and oxidative stress [ 26 , 27 , 28 ]. Moreover, our previous studies exposed that exogenous melatonin improved the photosynthesis systems and ROS-scavenging antioxidant activities which lead to enhanced the SAR-stress tolerance in tomato plants [ 29 ]. Currently, it has been demonstrated that the presence of melatonin in different parts of plants such as the roots, stems, leaves, flowers, fruits, and seeds [ 27 ].…”

The Effect of Exogenous Melatonin on Kiwifruit Phenolic Compounds and Antioxidant Capacity under low light environment

“…As shown in Figure 1, the content of TPC, TFC and TFAC in melatonin application group significantly increased than control. Additionally, Debnath et al found melatonin caused increase of phenolic compounds content to scavenge the ROS induced by acid rain [8].…”