To investigate the physiological responses of plants to high root zone temperature (HT, 35°C) stress mitigated by exogenous glutathione (GSH), seedlings of a cucumber cultivar (Cucumis sativus L. cv. Chunqiuwang NO.2) were exposed to HT with or without GSH treatment for 4 d and then set to recover for 4 d. Plant physiological variables, growth, and antioxidant enzymes related gene expression were measured.
Results/Conclusions
The results showed that HT significantly decreased GSH content, the ratio of reduced to oxidized glutathione (GSH/GSSG), chlorophyll content, photosynthesis and related gene expression, shoot height, stem diameter, and dry weight. The exogenous GSH treatment clearly lessened the HT stress on the above variables. Meanwhile, HT significantly increased soluble protein content, proline content, malondialdehyde (MDA) content, O2•− production rate, catalase (CAT), ascorbate peroxidase (APX) , superoxide dismutase (SOD), guaiacol peroxidase (G-POD), and gutathione reductase (GR) activities and antioxidant enzymes related gene expression. The GSH treatment remarkably improved soluble protein content by 20.6%, proline content by 72.3%, antioxidant enzymes activities, and antioxidant enzymes related gene expression, and reduced the MDA content by 23.3% and O2•− production rate by 27.6% compared to no GSH treatment in the HT condition. Treatment with GSH resulted in a better physiological performance, improved photosynthesis, antioxidant and osmolytes systems, and reduced oxidative stress under the HT stress.
The results suggest that exogenous GSH enhances cucumber seedling tolerance of HT stress by modulating the photosynthesis and antioxidant and osmolytes systems to improve physiological adaptation.