钙对亚适温弱光下黄瓜幼苗Ca^(2+)分布及叶绿素荧光参数的影响

Effects of Calcium on Leaf Cell Ca^(2+) Distribution and Chlorophyll Fluorescence Parameters of Cucumber Seedlings under Suboptimal Temperature and Low Light Intensity

以津优3号黄瓜幼苗为试验材料,采用焦锑酸钙沉淀的电镜细胞化学方法,研究了CaCl2预处理对亚适温(昼/夜18℃/12℃)弱光(100μmol·m-2·s-1)下黄瓜幼叶细胞中Ca2+分布、Ca2+-ATP酶活性及叶绿素荧光参数的影响.结果显示:正常温光条件(CK)下,黄瓜幼叶细胞Ca2+主要存在于液泡和液泡膜上,细胞质中含量较低;经亚适温和弱光处理7d后,叶片细胞质和细胞膜中形成较大的钙沉淀颗粒,液泡中的Ca2+颗粒聚集成团,膜组织边缘模糊,Ca2+-ATPase活性降低;胁迫前用CaCl2预处理的细胞质中Ca2+颗粒略有增加,且分布较均匀,膜组织完整,Ca2+-ATPase活性与CK差异不显著;而经LaCl3、EGTA和CPZ预处理的Ca2+多呈大颗粒状聚积在细胞质、液泡膜或细胞壁上,Ca2+-ATPase活性大幅度下降.在7d亚适温弱光处理后,各处理黄瓜叶片的Fv/Fm变化不大,而ΦPSⅡ、qP和ETR显著降低;与水预处理相比,叶片ΦPSⅡ、qP和ETR在CaCl2处理下显著增加,而在EGTA和CPZ处理下显著减小,LaCl3处理的无显著变化.研究表明,亚适温弱光处理能打破黄瓜幼苗细胞内的Ca2+平衡,使其膜组织受到一定程度破坏;CaCl2可维持胞内较高的Ca2+-ATP酶活性,保持Ca2+平衡,保护细胞膜组织结构完整,并参与了光合作用光能捕获和光合效率的调控,能有效减轻亚适温弱光对黄瓜幼苗光合作用的不良影响.

The effect of exogenous CaCl2 on Ca^2＋ distribution in leaf cells,Ca^2＋-ATPase activity and chlorophyll fluorescence parameters of cucumber （Cucurnis sativa L. cv ＇Jinyou 3＇） seedlings under suboptimal temperature （day/night 18 ℃/12 ℃ ） and low light intensity （100μmol·m^-2·s^-1） were investigated with calcium antimonate precipitate-electromicroscopic-cytochemical methods. The results showed that the calcium antimonate deposits, which indicate calcium distribution, were localized mainly in vacuole and vacuole membrane at the optimum growth condition, and smaller amounts of calcium precipitate randomly resided in cytoplasm. After treated under subbptimal temperature and low light intensity for 7 d,larger Ca^2＋ deposit developed and localized on the cytoplasm, cell membrane,and vacuole of leaves. Suboptimal temperature and low light intensity stress also led to blur in cell membrane edge, and decrease in Ca^2＋-ATPase activity. Treated with CaCl2 before exposure to the stress,a little more calcium precipitate well-distributed in cytoplasm, the membrane maintained integrity, and the Ca^2＋-ATPase activity showed no significant difference compared with that of control. However, if seedlings were pretreated with LaCl3, EGTA or CPZ, a lot of Ca^2＋ deposited together in cytoplasm, vacuole membrane, or cell wall, and the Ca^2＋-ATPase activity decreased with a big margin. Suboptimal temperature and low light intensity made no significant difference in Fv/Fm ,but led to remarkable decrease in ΦPSⅡ ,qP and ETR. Compared with water-treatment,the ΦPSⅡ ,qP and ETR of CaCl2-treatment increased, while EGTA-,CPZ-treatments decreased significantely. No significant differences were detected between LaCl3 and water treatments. These data suggest that the Ca^2＋-homeostasis in leaf cells of cucumber seedlings was broken by suboptimal temperature and low light intensity, and the membrane was damaged in a certain degree. CaCl2 had the beneficial effects on maintaining higher Ca^2＋-ATP activity,stabilizing the Ca^2＋-homeostasis, and protecting the membrane structure. It participates in regulation of capture efficiency for solar energy and photosynthetic efficiency, and alleviates the harmful effect of suboptimal temperature and low light intensity on photosynthesis in cucumber seedlings.