Growth and Physiological Characteristics of Flue-cured Tobacco (Nicotiana Tabacum L.) under Selenate-Se Stress

Selenate is chemically similar to sulfate and can be taken up and assimilated by plants. Although selenium (Se) has not been shown to be essential for higher plants, Se is toxic to many crops in excess. To obtain better insights into the effects of the possible mechanism of how plants alleviates the toxicity of selenate-Se stress, the growth, Se subcellular distribution of fresh leaves, antioxidant enzyme activities and photosynthetic traits of flue-cured tobacco (FCT) through a hydroponic experiment were studied. Results revealed that the growth of FCT reduced remarkably, meanwhile the content of proline and malonaldehyde (MDA) enhanced significantly with selenate-Se stress. Selenium was mainly stored in the cytoplasm and the cell wall in fresh leaves. Cell membrane of lipid peroxidation was aggravated, and it stimulated the improvement of the activities of superoxide dismutase (SOD) and catalase (CAT), and reduced the activity of peroxidase (POD) with the selenate-Se stress. The net photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r), and intercellular CO₂ concentration (C_i) of FCT were significantly reduced with selenate-Se treatments; whereas chlorophyll a, chlorophyll b, and total chlorophyll contents (chlorophyll a + b) were not significantly difference between the treatments. The above declared that it had inhibitory effect on physiological characteristics and photosynthesis of FCT with selenate-Se stress. It was inferred that the reasons of photosynthesis reduction were the main limiting factors of stomatal closure and supplying of CO₂ deterioration of FCT with selenate-Se stress. Meanwhile, synthesized protein or/and amino acids storage in cytoplasm and fixed by cell wall of Se were the important methods to alleviate the toxicity and enhance the tolerance of selenate-Se stress to FCT.