Abstract
To investigate the physiological responses of plants to high root-zone temperature (HT, 35 °C) stress mitigated by exogenous glutathione (GSH), cucumber (Cucumis sativus L.) seedlings were exposed to HT with or without GSH treatment for 4 days and following with 4 days of recovery. Plant physiological variables, growth, and gene expression related to antioxidant enzymes and Calvin cycle were quantified. 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, as well as dry weight. The exogenous GSH treatment clearly lessened the HT stress by increasing the above variables. Meanwhile, HT significantly increased soluble protein content, proline and malondialdehyde (MDA) content as well as O2•− production rate, the gene expression and activities of antioxidant enzymes. The GSH treatment remarkably improved soluble protein content, proline content, antioxidant enzymes activities, and antioxidant enzymes related gene expression, and reduced the MDA content and O2•− production rate compared to no GSH treatment in the HT condition. Our results suggest that exogenous GSH enhances cucumber seedling tolerance of HT stress by modulating the photosynthesis, antioxidant and osmolytes systems to improve physiological adaptation.
Highlights
To investigate the physiological responses of plants to high root-zone temperature (HT, 35 °C) stress mitigated by exogenous glutathione (GSH), cucumber (Cucumis sativus L.) seedlings were exposed to High root-zone temperature (HT) with or without GSH treatment for 4 days and following with 4 days of recovery
Compared to normal temperature treatment (NT), plant height, stem diameter, shoot fresh weight, and shoot dry weight of the HT treatment were significantly reduced by 14.8%, 8.1%, 38.1% and 32.6%, respectively, in the HT stress and by 24.0%, 12.6%, 33.5%, 37.7%, respectively, in the recovery period (Table 1; Fig. 1)
Shoot dry weight significantly decreased and shoot water content significantly increased for the High root-zone temperature plus exogenous GSH treatment (HT+GSH) treatment under the HT stress, and stem diameter, shoot fresh weight, and shoot dry weight were clearly decreased in the recovery period compared to the NT treatment
Summary
To investigate the physiological responses of plants to high root-zone temperature (HT, 35 °C) stress mitigated by exogenous glutathione (GSH), cucumber (Cucumis sativus L.) seedlings were exposed to HT with or without GSH treatment for 4 days and following with 4 days of recovery. Growth, and gene expression related to antioxidant enzymes and Calvin cycle were quantified. HT significantly increased soluble protein content, proline and malondialdehyde (MDA) content as well as O2− production rate, the gene expression and activities of antioxidant enzymes. The GSH treatment remarkably improved soluble protein content, proline content, antioxidant enzymes activities, and antioxidant enzymes related gene expression, and reduced the MDA content and O2− production rate compared to no GSH treatment in the HT condition. Proline is important in cellular homeostasis (cell proliferation or cell death) and can act as a signaling molecule to modulate mitochondrial functions and trigger specific genes expression, which is essential for plant recovery from stresses[20]
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