欧亚国际

摘要

以前对细胞激动素以及干旱的研究揭示激素在植物适应限制性条件中可起到积较和消较作用。本研究采用Plantarray生理表型测量系统检测了CK对蒸腾以及气孔活力的影响以及在西红柿 (Solanum lycopersicum) 干旱时反应。在干旱条件下，因降低了全植株蒸腾，叶片保持高水分状态，转基因西红柿过量表达拟南芥（Arabidopsis thaliana）CK降解酶-CK氧化酶//脱氢酶 3 (CKX3) 。蒸腾减少可导致叶面积减小，气孔密度下降。过度表达CKX3脱氢酶的植物与野生植株相比，扁平细胞含量较少，单位叶面积气孔数量较低。对CK含量的操控并未影响到气孔运动或导致脱落酸诱导气孔关闭。另外我们并未发现气孔开度与保卫细胞中CK诱导启动子TCS的活性的相关性。以前研究表明干旱可减低ＣＫ含量，我们称之为抑制生长以及降低气孔密度，两者均降低蒸腾作用，从而增加了对延长干旱条件的耐受性。

Cytokinin activity increases stomatal density and transpiration rate in tomato

Mika Farber, iv Attia, and David Weiss*

Institute of Plant Sciences and Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, Israel

Abstract

Previous studies on cytokinin (CK) and drought have suggested that the hormone has positive and negative effects on plant adaptation to restrictive conditions. This study examined the effect of CK on transpiration, stomatal activ- ity, and response to drought in tomato (Solanum lycopersicum) plants. Transgenic tomato plants overexpressing the Arabidopsis thaliana CK-degrading enzyme CK oxidase/dehydrogenase 3 (CKX3) maintained higher leaf water status under drought conditions due to reduced whole-plant transpiration. The reduced transpiration could be attrib- uted to smaller leaf area and reduced stomatal density. CKX3-overexpressing plants contained fewer and larger pavement cells and fewer stomata per leaf area than wild-type plants. In addition, wild-type leaves treated with CK exhibited enhanced transpiration and had more pavement cells and increased numbers of stomata per leaf area than untreated leaves. Manipulation of CK levels did not affect stomatal movement or abscisic acid-induced stomatal closure. Moreover, we found no correlation between stomatal aperture and the activity of the CK-induced promoter Two-Component Signaling Sensor (TCS) in guard cells. Previous studies have shown that drought reduces CK levels, and we propose this to be a mechanism of adaptation to water deficiency: the reduced CK levels suppress growth and reduce stomatal density, both of which reduce transpiration, thereby increasing tolerance to prolonged drought conditions.