Effects of exogenous glutathione on ions micro-distribution in leaf and root of tomato seedlings under NaCl stress

ObjectivesNaCl stress is one of the major obstacles during tomato growth in Xinjiang, and glutathione (GSH) spray has been considered as an effective solution. Exploring the effect and mechanism of exogenous GSH on alleviating salt stress in tomato will provide theoretical basis for the efficient use of GSH.

MethodsA hydroponic experiment was conducted and tomato (Solanum lycopersicum L.) cv. Zhongshu No. 4 was used as experimental material. 100 mg/L NaCl was added into the nutrition solution to form NaCl stress growth condition. The solution without NaCl was used as control (CK), and the main treatments included no glutathione spraying (NaCl), GSH spraying (+ GSH), glutathione synthesis inhibitor spraying (+ BSO) and both GSH+BSO spraying (+ BSO + GSH). The ion micro-distribution status and balance of K⁺, Ca²⁺, Mg²⁺, Na⁺ and Cl^– in leaf and root of tomato seedlings were measured.

ResultsUnder NaCl stress condition, both Na⁺ and Cl^– contents were increased significantly, and the K⁺ content and the ratios of K⁺/Na⁺, Ca²⁺/Na⁺ and K⁺/Cl^– were decreased in all the cells of leaf and root of tomato seedlings. It indicated that NaCl stress caused the plant accumulation of harmful ions Na⁺ and Cl^– and the serious damage of intracellular ions steady status in the cells of leaf and root of tomato seedlings. The application of exogenous BSO further intensified the off-balance of the ratio of K⁺/Na⁺ in leaf and root of tomato seedlings under NaCl stress. While the application of exogenous GSH inhibited the absorption of Na⁺ and significantly decreased the relative content of Cl^– and increased the ratios of K⁺/Na⁺, Ca²⁺/Na⁺ and K⁺/Cl^– in leaf and root of tomato seedlings under NaCl stress. Under salt stress with BSO treatments, the application of exogenous GSH also greatly inhibited the absorption of Na⁺ and resulted in the relative content of Na⁺ in cells of all tissues of leaf and in mediopellis, endodermis and stele of tomato root was below the detection limit. Under salt stress with BSO treatments, the application of exogenous GSH significantly decreased the relative content of Cl^– and increased the relative content of K⁺ and Ca²⁺ and the ratios of K⁺/Na⁺,Ca²⁺/Na⁺, K⁺/Cl^– and Ca²⁺/Cl^– in leaf and root of tomato seedlings.

ConclusionsGSH could alleviate the toxicity from salt ions and enhanced salt tolerance in tomato seedlings by inhibiting the absorption of Na⁺, decreasing the absorption of toxic ions and optimizing ions micro-distribution and maintaining ion balance in cells of leaf and root of tomato seedlings under salt stress.