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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(80C/50C,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TZ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(oPSII),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CO_2浓度(C_i)和初始荧光(F_0.)逐渐升高。T2和T3的P_n、G_s、T_r、RuBisCO和RCA活性以及ΦPSII,F_v/F_m和F_v’/F_m’的降低幅度还有G_i和F_0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)和谷肤甘肤还原酶(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。
The cucumber seedlings of ’Jinyou 35’ were used as materials to control the soil water content of 80% -90% (T1), 70% -80% (T2), 60% -70% (T3) and 50% -60% (T4). The effects of soil moisture on the photosynthesis and antioxidant enzyme activity of cucumber under low temperature (80C / 50C, day / night) were studied under soil water content of 80% ~ 90%. The results showed that the lowest cold damage index (TZ) and T3 (T1) at low temperature were the highest, the electrolyte leakage rate (EL) was lowest at T2 and T3, and highest at T4. Under low temperature stress, the net photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r), RuBisCO and RuBisCO activase (RCA), and the maximum photosynthetic efficiency (F_v / F_m) and the maximal antenna conversion efficiency (F_v ’/ F_m’) of PSII were significantly lower than those of the control The initial fluorescence (F_0.) Gradually increased. P_n, G_s, T_r, RuBisCO and RCA activities of T2 and T3, as well as the decrease of ΦPSII, F_v / F_m and F_v ’/ F_m’, and the increase of G_i and F_0 were smaller and T1 and T4 were larger. T2 and T3 had the lowest levels of malondialdehyde (MDA) at low temperature. T4 was the highest. The activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) and glucosinolate reductase (GR) High; T1 and T4 were significantly lower. It can be seen that appropriate control of water can effectively regulate the photosynthetic adaptability of cucumber seedlings. The possible mechanism is to enhance reactive oxygen scavenging ability and reduce photoinhibition by increasing antioxidant enzyme activity so as to maintain high photosynthetic activity and enhance low temperature tolerance.