College of Life Science, Agriculture and Forestry, Qiqihar University, Qiqihar 161006, P. R. China.
Qiqihar Branch of Heilongjiang Academy of Agriculture Sciences, Qiqihar 161006, P. R. China.
Funct Plant Biol. 2023 Mar;50(3):230-241. doi: 10.1071/FP22047.
Soil salinity is a growing problem in agriculture, plant growth regulators (PGRs) can regulate plant response to stress. The objective of this study was to evaluate the effects of exogenous 6-benzyladenine (6-BA) on photosynthetic capacity and antioxidant defences in watermelon (Citrullus lanatus L.) seedlings under NaCl stress. Two watermelon genotypes were subjected to four different treatments: (1) normal water (control); (2) 20mgL-1 6-BA; (3) 120mmolL-1 NaCl; and (4) 120mmolL-1 NaCl+20mgL-1 6-BA. Our results showed that NaCl stress inhibited the growth of watermelon seedlings, decreased their photosynthetic capacity, promoted membrane lipid peroxidation, and lowered the activity of protective enzymes. Additionally the salt-tolerant Charleston Gray variety fared better than the salt-sensitive Zhengzi NO.017 variety under NaCl stress. Foliar spraying of 6-BA under NaCl stress significantly increased biomass accumulation, as well as photosynthetic pigment, soluble sugar, and protein content, while decreasing malondialdehyde levels, H2 O2 content, and electrolyte leakage. Moreover, 6-BA enhanced photosynthetic parameters, including net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, and transpiration rate; activated antioxidant enzymes, such as superoxide dismutase, catalase, and peroxidase; and improved the efficiency of the ascorbate-glutathione cycle by stimulating glutathione reductase, dehydroascorbate reductase, and monodehydroascorbate reductase, as well as ascorbic acid and glutathione content. Principal component analysis confirmed that 6-BA improved salt tolerance of the two watermelon varieties, particularly Zhengzi NO.017, albeit through two different regulatory mechanisms. In conclusion, 6-BA treatment could alleviate NaCl stress-induced damage and improve salt tolerance of watermelons by regulating photosynthesis and osmoregulation, activating the ascorbate-glutathione cycle, and promoting antioxidant defences.
土壤盐渍化是农业中一个日益严重的问题，植物生长调节剂（PGRs）可以调节植物对胁迫的反应。本研究旨在评估外源 6-苄基腺嘌呤（6-BA）对 NaCl 胁迫下西瓜（Citrullus lanatus L.）幼苗光合作用和抗氧化防御能力的影响。两种西瓜基因型分别进行了四种不同的处理：（1）正常水（对照）；（2）20mgL-1 6-BA；（3）120mmolL-1 NaCl；和（4）120mmolL-1 NaCl+20mgL-1 6-BA。结果表明，NaCl 胁迫抑制了西瓜幼苗的生长，降低了其光合作用能力，促进了膜脂过氧化，降低了保护酶的活性。此外，耐盐品种 Charleston Gray 在 NaCl 胁迫下的表现优于盐敏感品种 Zhengzi NO.017。NaCl 胁迫下叶片喷施 6-BA 显著增加了生物量积累，以及光合色素、可溶性糖和蛋白质含量，同时降低了丙二醛水平、H2O2 含量和电解质渗漏。此外，6-BA 增强了光合作用参数，包括净光合速率、气孔导度、胞间 CO2 浓度和蒸腾速率；激活了抗氧化酶，如超氧化物歧化酶、过氧化氢酶和过氧化物酶；并通过刺激谷胱甘肽还原酶、脱氢抗坏血酸还原酶和单脱氢抗坏血酸还原酶以及抗坏血酸和谷胱甘肽含量，提高了抗坏血酸-谷胱甘肽循环的效率。主成分分析证实，6-BA 改善了两种西瓜品种的耐盐性，特别是 Zhengzi NO.017，尽管通过两种不同的调节机制。总之，6-BA 处理可以通过调节光合作用和渗透调节、激活抗坏血酸-谷胱甘肽循环以及促进抗氧化防御来减轻 NaCl 胁迫对西瓜的伤害，提高其耐盐性。
