Effect of Heat Stress on Root Architecture, Photosynthesis, and Antioxidant Profile of Water Spinach (Ipomoea aquatica Forsk) Seedlings

Abstract

Crop productivity around the world is being seriously affected by adverse environmental conditions. High temperature (HT) stress has severely hampered plant growth, yield, and quality. Water spinach is a significant heat-resilient green leafy vegetable that can mitigate prolonged HT stress. However, the morphological, physiological, and biochemical alterations that occur in its response to heat stress remain unknown. In this study, the physiological response to HT stress in water spinach plants with different temperature (25-control, 30, 35, 40, 45 °C) tolerances was investigated. When plants were subjected to HT over a long period of time, their growth was stunted. The results showed that no significant difference was seen between the control (25 °C) and 30 °C for some traits (root shoot fresh weight, root morphological traits, and leaf gas exchanges parameters). Further, HT (35, 40, and 45 °C) stress significantly reduced the growth status, the gas exchange parameters, the pigment content, the photosystem function, and the root architecture system of water spinach. Conversely, HT stress considerably enhanced secondary metabolites in terms of total phenolics, flavonoids, soluble sugars, and anthocyanin content. Furthermore, heat stress remarkably increased the accumulation of reactive oxygen species (ROS) and caused cellular membrane damage. HT stress effectively altered the antioxidant defense system and caused oxidative damage. Generally, HT has an adverse effect on the enzyme activity of water spinach, leading to cell death. However, the current study found that temperatures ≥35 °C had an adverse effect on the growth of water spinach. Further research will be needed to examine the mechanism and the gene expression involved in the cell death that is caused by temperature stress in water spinach plants.