盐胁迫对露花叶片的脱落酸含量及磷酸烯醇式丙酮酸羧化酶昼夜调节特性的影响

兼性CAM植物在转为CAM型后，CAM代谢的关键酶磷酸烯醇式丙酮酸（PEP）核化酶会出现昼夜调节特性的变化（Osmond1978）。关于PEP梭化酶昼夜调节特性的机理存在两种观点：1．PEPK化酶昼夜聚合度发生了变化，白天为二聚体PEPK化酶，对苹果酸抑制敏感；而夜间为四聚体，对苹果酸抑制不敏感（U和Wedding1985）。2·nsv＄化酶昼夜磷酸化状态发生变化，夜间PEPW化酶磷酸化，对苹果酸抑制不敏感；而白天PEP＄化酶脱磷酸化，对苹果酸抑制敏感（Nimmo等1986）。植物生长调节物质如ABA和细胞分裂素对兼性CAM植物PEP＆化酶的表达有诱…

The Effects of Salt Stress on Leaf ABA Content and the Diurnal Regulation Property of Phosphoenolpyruvate Carboxylase in Mesembryanthemum cordifolium

After salt stress, the sensitivitytoward the inhibitory action of L-malateof PEPCase from Mesembryanthemum cordifolium showed diurnal fluctuation(Fig. 1a, b). The day form PEPCasewas more sensitive to the inhibition byL-malate than the night form (Fig.fo). However, there was no differencein molecular weight between the dayform and the night form of PEPCase(Fig. 2). Both salt stress and droughtelevated the leaf ABA level dramatically (Fig. 3A ). The ABA level indrought-stressed leaves decreasedmarkedly after the plants were rewatered (Fig. 3A), but the ABA level insalt-stressed leaves remained unchangedafter soil salts were thoroughly washedout and the plants were well watered(Fig. 3A). External ABA treatment increased the leaf PEPChse activity anddecreased the leaf water content (Fig.3B). Externally applied 6-BA had similar effects on the plants as the ABA(Fig. 4 ). We concluded that: 1. Theday/night difference in the regulatoryaction of CAM form PEPCase was notcaused by any change in the saute of aggregation of the enzyme; 2. The effectSo f ABA and 6-BA on leaf PEPCase level are most likely mediated by leaf water loss they induced.