Effects of high growth-medium temperature under controlled conditions on characteristics of tomato leaves

High temperatures have become a major threat that seriously affects crop growth and yield. The present work aimed to investigate the acclimation process in adjusting plant responses to high root temperatures. Tomato (Solanum lycopersicum L., cv. Micro-Tom) during the flowering time was subjected to heat treatments (day/night temperatures at the root level of 40 or 45 ??C for 4 d) while control plants were maintained at 25 ??C, and the heat-stress treatment effects were analysed in the tomato leaves. The results showed a reduction in the content of chlorophylls a and b as well as chlorophyll a/b ratio at both high temperatures. Further, the increase in the amount of malondialdehyde as an indicator of lipid peroxidation was greater at 45 ??C. The leaf content of hydrogen peroxide was induced in tomato plants subjected to 45 ??C whereas it was markedly decreased in plants maintained at 40 ??C as compared to control plants. Antioxidant enzymes showed higher activity in tomatoes treated at 45 ??C compared to those treated at 40 ??C. Moreover, the highest amount of antioxidants such as carotenoids and ascorbate in tomato plants were found at a temperature of 45 ??C. Collectively, we provide evidence that physiological and biochemical components can be altered depending on the heat level, exposure time, and developmental stage. The interaction of root and shoot under high temperatures must be further characterized in terms of understanding the challenging climate changes.