阳离子对黄瓜苗期猝倒病菌果胶酶活性的影响

 本文首次从寄主-寄生物相互关系角度系统研究了阳离子对黄瓜苗期猝倒病菌Pythium aphanidermatum产生的果胶酶活性的影响,胚轴胞壁Ca²⁺含量很大,而且随苗龄增加,其含量也有规律的增加。细胞壁Ca³⁺含量变化与胚轴抗病菌果胶酶能力密切相关。不同阳离子对病菌在寄主体内、外产生的PG活性有明显影响,并随反应时间而变化。病菌在寄主体内和体外合成的PG对阳离子敏感程度不同。低浓度Ca²⁺有激活PG的作用,高浓度Ca²⁺则抑制PG活性。Na⁺超过一定浓度时有抑制PG活性的作用。PGTE比PMTE对Ca³⁺抑制作用敏感。

EFFECT OF CATIONS ON ACTIVITIES OF PECTINASES FROM PATHOGEN OF CUCUMBER SEEDLING DAMPING-OFF

The effect of cations on activities of pectinases produced from Pythium aphanidermatum causing cucumber seedling damping -off were first studied systematically on the basis of host-parasite relationship. There were five kinds of cations detected in healthy hypocotyl cell wall, in which the highest contents of Ca²⁺ and Na⁺ were found. It was interested that seedlings increased calcium contents and resistance to degradation of hypocotyl cell wall by pectinases, as seedling age grew. There were obvious influences of various cations on activities of PG produced in vitro or in vivo, and these influences from the cations changed as reaction time lasted. PG had different sensitivity to cations, depending on the PG produced in vitro or in vivo. Moreover, Ca²⁺ was considered to expose double affection on PG activity, i. e. Ca²⁺ at lower concentration tended to stimulate PG activity, at higher concentration to inactivate PG activity. Na⁺ could inhibit PG activity if it accumulated to enough concentration. PGTE was more sensitive to Ca²⁺ than PMTE.