干旱胁迫对2种光合类型C4荒漠植物叶片光合特征酶和抗氧化酶活性的影响

以荒漠C₄草本植物蔷薇猪毛菜(NADP苹果酸酶型，NADP-ME）和粗枝猪毛菜（NAD苹果酸酶型，NAD-ME）为研究对象，采用盆栽控水试验设置正常供水和轻度、中度、重度干旱处理（土壤含水量分别为田间持水量80%、60%、45%和35%），通过测定不同程度干旱胁迫下叶片含水量、C₄光合特征酶和抗氧化酶活性等指标，探讨不同类型C₄荒漠植物光合特征酶和抗氧化系统对干旱逆境的适应机制。结果显示：（1）2种植物叶片含水量均随干旱胁迫的加剧不同程度降低。（2）叶片磷酸烯醇式丙酮酸羧化酶（PEPC）活性在中度干旱胁迫下显著增加而在重度干旱胁迫下急剧下降；蔷薇猪毛菜NAD-ME活性和粗枝猪毛菜NADP-ME活性都很低，且它们基本不受干旱胁迫的影响；随干旱胁迫的加剧，蔷薇猪毛菜NADP-ME活性呈下降趋势，而粗枝猪毛菜NAD-ME活性先显著增加而在重度干旱胁迫下显著降低。（3）随着干旱胁迫的加剧，叶片超氧化物歧化酶（SOD）活性呈下降趋势，过氧化物酶（POD）活性在不同程度干旱胁迫下均有不同程度增加；过氧化氢酶（CAT）活性在中度干旱胁迫下均有不同程度的增加，但在重度干旱胁迫下蔷薇猪毛菜CAT活性降低，而粗枝猪毛菜CAT活性显著增加；丙二醛（MDA）含量随干旱胁迫的加剧均有不同程度的增加。研究认为，一定程度干旱胁迫下，2种荒漠植物的PEPC活性均有增加；不同光合类型C₄植物叶片脱羧酶（NADP-ME和NAD-ME）对干旱胁迫的响应有明显的差异。POD和CAT是这两种C₄植物适应干旱胁迫的主要抗氧化酶，但蔷薇猪毛菜CAT在重度干旱胁迫下没有起到积极保护作用。

C4 Photosynthetic Enzymes and Antioxidant Enzymes Activities in Two Photosynthetic Subtypes of C4 Desert Plants under Soil Drought Stress

Two photosynthetic subtypes of C₄ desert plants,including NADP-malic enzyme (NADP-ME) Salsola rosacea and NAD-malic enzyme (NAD-ME) S.subcrassa,were used to investigate the adaptive mechanism of C₄ photosynthetic enzymes and antioxidant enzymes in respond to soil drought stress.The results showed that:(1) leaf water content decreased as increasing of drought stress;(2) the phosphoenolpyruvate carboxylase (PEPC) activity increased markedly under moderate drought stress and decreased significantly under severe drought stress;the NAD-ME activity of S.rosacea and NADP-ME activity of S.subcrassa were very low,and their activities were almost not affected by drought stress;the NADP-ME activity of S.rosacea was declined with increasing of drought stress,but the NAD-ME activity of S.subcrassa increased firstly and then decreased significantly under severe drought stress;(3) the superoxide dismutases (SOD) activity was declined with increasing of drought stress,and the peroxidase (POD) activity increased under drought stress;the catalase (CAT) activity increased under moderate drought stress,but under severe drought stress,CAT activity of S.rosacea was declined,and that of S.subcrassa increased significantly;the malondialdehyde (MDA) content arose in different degrees as increasing of drought stress,and MDA content under severe drought stress was significantly lower than that under moderate drought stress.These results have showed that PEPC activity increased under a certain degree of drought stress;decarboxylase (NADP-ME and NAD-ME) belonging to two photosynthetic subtypes showed significant differences in response to drought stress;POD and CAT are the major antioxidant enzymes,but CAT for S.rosacea does not remove H₂O₂ efficiently under severe drought stress.