《植物生理学报》 2015, 51(12): 2247-2254

土壤湿度对低温下黄瓜幼苗光合作用及抗氧化酶活性的影响

刘婧, 毕焕改, 李清明, 艾希珍^*

山东农业大学园艺科学与工程学院, 作物生物学国家重点实验室, 农业部黄淮地区园艺作物生物学与种质创制重点开放实验室, 山东省果蔬优质高效生产协同创新中心, 山东泰安271018

通信作者：艾希珍；E-mail: axz@sdau.edu.cn；Tel: 0538-8246218

摘　要：

以‘津优35’黄瓜幼苗为试材, 用称重法控制土壤含水量为80%~90% (T1)、70%~80% (T2)、60%~70% (T3)和50%~60% (T4), 以土壤含水量80%~90%常温处理幼苗作对照, 研究土壤湿度对低温(8℃/5℃, 昼/夜)下黄瓜光合作用及抗氧化酶活性的影响。结果表明: 低温下T2和T3的冷害指数最小, T1最大; 电解质渗漏率(EL)以T2和T3最低, T4最高。低温胁迫使黄瓜幼苗的净光合速率(P_n)、气孔导度(G_s)、蒸腾速率(T_r)、核酮糖-1,5-二磷酸羧化/加氧酶(RuBisCO)和RuBisCO活化酶(RCA)活性以及光系统II (PSII)实际光化学效率(Φ_PSII)、最大光化学效率(F_v/F_m)和光下最大天线转换效率(F_v′/F_m′)均明显降低, 胞间CO₂浓度(C_i)和初始荧光(F_o)逐渐升高。T2和T3的P_n、G_s、T_r、RuBisCO和RCA活性以及Φ_PSII、F_v/F_m和F_v′/F_m′的降低幅度还有C_i和F_o的升高幅度较小, T1和T4的较大。低温下T2和T3的丙二醛(MDA)含量最低, T4最高; T2和T3的超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)和谷胱甘肽还原酶(GR)活性较高; T1和T4明显较低。可见, 适当控水可有效调控黄瓜幼苗的光合适应性, 其可能机理是通过提高抗氧化酶活性增强活性氧清除能力, 减轻低温光抑制, 从而维持较高的光合活性, 增强低温耐受性。

关键词：低温胁迫; 土壤湿度; 光合作用; 抗氧化酶; 黄瓜

收稿：2015-09-15   修定：2015-12-12

资助：“十二五”国家科技支撑计划(2014BAD05B03)和山东省农业重大应用技术创新课题(鲁财农指[2013]136号)。

Effect of Soil Moisture on Photosynthesis and Antioxidant Enzyme Activities in Cucumber Seedlings Under Chilling Stress

LIU Jing, BI Huan-Gai, LI Qing-Ming, AI Xi-Zhen^*

College of Horticulture Science and Engineering, State Key Laboratory of Crop Biology, Key Laboratory of Horticultural Crop Biology and Germplasm Innovation of Agriculture Ministry, Shandong Collaborative Innovation Center for Fruit and Vegetable Production with High Quality and Efficiency, Taian, Shandong 271018, China

Corresponding author: AI Xi-Zhen; E-mail: axz@sdau.edu.cn; Tel: 0538-8246218

Abstract:

The effect of soil moisture on the photosynthesis and antioxidant enzyme activities of ‘Jinyou 35’ cucumber (Cucumis sativa) seedlings under low temperature (8 °C/5 °C, day/night) was investigated. The soil moisture was controlled to 80%~90% (T1), 70%~80% (T2), 60%~70% (T3) and 50%~60% (T4) with weighing method. 80%~90% moisture and normal temperature treatment was used as the control. The results revealed that the chilling injury indexes of T2 and T3 were the lowest and T1 the highest, the electrolyte leakage (EL) of T2 and T3 were the lowest either, but T4 the highest, among the four treatments under chilling stress. Chilling stress leds to significant decreases in photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r), activities of ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) and RuBisCO activase (RCA), actual photochemical efficiency of PSII (Φ_PSII), maximum photochemical efficiency (F_v/F_m), the antenna transformation efficiency (F_v′/F_m′), whereas increases in intercellular CO₂ concentration (C_i) and initial fluorescence (F_o). T2 and T3 showed lower reductions in P_n, G_s, T_r, activities of RuBisCO and RCA, Φ_PSII, F_v/F_m and F_v′/F_m′, and lower increases in C_i and F_o, compared with T1 and T4 under chilling stress. Malondialdehyde (MDA) contents of T2 and T3 were the lowest and T4 the highest among the four treatments. On the contrary, T2 and T3 showed higher activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) than those of T1 and T4 under chilling stress. These data suggest that moderate water control increases the photosynthesis adaptability of cucumber seedlings under low temperature. The mechanism might be the observed increase in scavenging ability of reactive oxygen species by enhancing the antioxidant enzyme activities, alleviating low temperature photoinhibition, consequently maintaining higher photosynthetic activity, and heightening the chillingtolerance.

Key words: chilling stress; soil moisture; photosynthesis; antioxidant enzyme; cucumber