Ca2+在磷酸盐营养诱导黄瓜幼叶系统抗病中的作用

黄瓜第 2叶喷施 75mmol/L K2HPO4 溶液以后 ,每天采取叶片 ,用去离子水、1mol/L氯化钠、2 %醋酸和 5%盐酸 4种浸提液连续提取不同形态的钙 ,其中水溶性钙和果胶酸钙的含量减少而磷酸钙含量明显上升 ,同时 ,叶片中相关的抗病酶活性也持续升高。用焦锑酸钙沉淀的电镜细胞化学方法研究了叶片内Ca2+定位分布的变化后发现 ,与对照比较 ,喷施K2HPO4处理 ,液泡和叶绿体出现大量的钙颗粒分布 ,同时细胞间层中的钙沉淀也变得更为密集。用X 射线能谱仪测得细胞壁上Ca/P明显下降。上述现象表明 ,叶片细胞液泡和叶绿体含钙量增加以及磷酸钙沉淀的形成使得中间层的钙桥键断裂 ,从而引起抗病酶的产生 ,并导致细胞壁分解形成寡聚半乳糖醛酸 ,可诱导黄瓜苗产生系统抗病能力

The role of Ca2+ in the systemic resistance of cucumber young leaf induced by phosphate nutrition

The second leaves of cucumbers were collected every day after spraying the surface of leaves with 75mmol/L K₂HPO₄. Four kinds of solutions, i.e., water, 1mol/L NaCl, 2% CH₃COOH and 5% HCl were used in the sequence to extract different forms of calcium compounds in these leaves. The content of water soluble calcium and calcium pectate decreased, but calcium phosphate increased. Meantime, the activity of resistance related enzymes increased. The changes of Ca²⁺ localization in cells were investigated with calcium antimonate precipitate electromicroscopic cytochemical methods. When the second leaves were sprayed with K₂HPO₄, deposits of calcium antimonate became more in the vacuole and chloroplast stroma. Calcium antimonate became much denser in the middle lamella and the X ray microanalysis showed that the Ca/P ratio in the cell wall decreased obviously. It is, therefore, concluded that increased Ca²⁺ in vacuole and chloroplast and the deposits of calcium phosphate in leaves broke the calcium binding of middle lamella. This process might induce the increase of resistance related enzymes and made cell walls decomposed into oligagalacturonide, which, in turn, induced systemic resistance of cucumber plants to disease.