关键词: 西瓜, 盐胁迫, CO₂加富, 生长, 生理生化特性

Abstract: In order to provide theoretical basis for improving salt tolerance of protected watermelon, the grafted seedlings of watermelon cultivar Qianli No.1 were used as experimental material,and the mitigative effect and mechanism of CO2 enrichment on watermelon seedlings under salt stress were investigated.The results showed that compared with control,the growth of watermelon seedlings were significantly inhibited under salt stress (400 μmol/mol CO₂ +80 mmol/L NaCl).The leaf relative water content,water potential,the root hydraulic conductance and osmotic potential and net photosynthetic rate(Pn) were also decreased to different extent.Meanwhile,the relative conductivity,MDA content,oxygen production rate,H₂O₂ content and antioxidant enzyme activity were significantly increased(P<0.05).The injury effect of watermelon seedlings were significantly alleviated and the growth was significantly improved by CO₂ enrichment(800 μmol/mol+80 mmol/L NaCl) under salt stress(P<0.05).In comparison with single salt stress treatment,the plant height,stem diameter,dry weight and total root length of salt-stressed watermel on seedlings enriched with CO2 were significantly increased by 25.42%,11.62%,21.61% and 30.49%,respectively,and the salt damage index was significantly decreased by 49.80%;the relative water content,water potential,osmotic potential,root hydraulic conductivity,Pn,superoxide dismutase(SOD),peroxidase(POD),catalase(CAT) and ascorbic acid peroxidase(APX) activities of salt-stressed watermelon seedlings enriched with CO₂ were significantly increased by 21.60%,71.06%,19.05%,17.11%,15.13%,18.77%,13.04%,13.23% and 13.29%,respectively,but the stomatal conductance(Gs),intercellular carbon dioxide concentration(Ci),transpiration rate(Tr),relative conductivity,MDA content,oxygen production rate and H₂O₂ content were significantly decreased by 23.91%,8.12%,14.84%,11.42%,16.00%,13.21% and 20.51%,respectively(P<0.05).In conclusion,CO2 enrichment could alleviate salt stress injury,and improve salt tolerance by improving water absorption and retention capacity,net photosynthetic rate and antioxidant enzyme activity of watermelon seedlings under salt stress.

Key words: Watermelon, Salt stress, CO₂ enrichment, Growth, Physiological and biochemical characteristics