The effects of exogenous GSH(reduced glutathione)on photosynthetic characteristics,photosystem Ⅱ efficiency,absorbed light energy allocation and the H_2O_2-scavenging system in chloroplasts of salt-stressed tomato(Solanum lycopersicum L.)seedlings were studied using hydroponic experiments in a greenhouse.Application of exogenous GSH ameliorated saline-induced growth inhibition,the disturbed balance of Na^+ and Cl^- ions and Na^+/K^+ ratios,and the reduction of the net photosynthetic rate(P_n).GSH also increased the maximal photochemical efficiency of PSⅡ(F_v/F_m),the electron transport rate(ETR),the photochemical quenching coefficient(q_P),and the non-photochemical quenching coefficient(NPQ).In addition,GSH application increased the photochemical quantum yield(Y(Ⅱ))and relative deviation from full balance between the photosystems(β/α–1)and decreased the PSⅡ excitation pressure(1–q_P)and quantum yield of non-regulated energy dissipation(Y(NO))in leaves of salt-stressed tomatoes without BSO(L-buthionine-sulfoximine,an inhibitor of key GSH synthesis enzymeγ-glutamylcysteine synthetase)or with BSO.Further,the addition of GSH depressed the accumulation of H_2O_2 and malondialdehyde(MDA),induced the redistribution of absorbed light energy in PSⅡ reaction centers,and improved the endogenous GSH content,GSH/GSSH ratio and activities of H_2O_2-scavenging enzymes(including superoxidase dismutase(SOD),catalase(CAT),peroxidase(POD)and key enzymes in the AsA-GSH cycle and Grx system)in the chloroplasts of salt-stressed plants with or without BSO.Therefore,GSH application alleviates inhibition of salt-induced growth and photosynthesis mainly by overcoming stomatal limitations,improving the PSⅡ efficiency,and balancing the uneven distribution of light energy to reduce the risk of ROS generation and to mediate chloroplast redox homeostasis and the antioxidant defense system to protect the chloroplasts from oxidative damage.Thus,GSH may be used as a potential tool for alleviating salt stress in tomato plants.
以西葫芦品种"绿优"为试材,在日光温室中,灌溉定额为629.87 mm,设置2个灌水频率(高频2 d 1次和低频7 d 1次)和2个施氮量(高氮565 kg·hm-2和适氮375 kg·hm-2)水平,4个处理分别为:低频适氮(处理Ⅰ)、高频适氮(处理Ⅱ)、低频高氮(处理Ⅲ)、高频高氮(处理Ⅳ),分析不同处理对西葫芦的影响,为明确科学合理的灌水频率和施肥量提供参考依据。结果表明:在同一施氮水平下,高频灌水处理的西葫芦的叶面积大小、干物质积累、产量以及水分利用效率均高于低频灌水处理。在定额灌水量下,灌水频率对西葫芦水分利用效率的影响程度大于施氮量;在适氮水平下,西葫芦产量对于灌水频率敏感,高频灌水较低频灌水产量增加13.90%,而对于高氮处理,提高灌水频率,产量增加不显著,产量对灌水频率增加的敏感程度低。整个生育期,高频灌水处理土壤保持较好的土壤含水率,减少了深层下渗,降低了西葫芦的耗水量。综合各指标表明,处理Ⅱ>处理Ⅳ>处理Ⅲ>处理Ⅰ。处理Ⅱ灌水处理更有利于西葫芦的生长和产量的提高,推荐最佳温室西葫芦田间管理的灌水频率和施氮量为处理Ⅱ。
