Changes of H^+-pumping activity of the vesicles prepared from plant roots grown under salt stress

在Ca~(2+)~(2+)饥饿过程中，黄瓜根的质子排泄量显著减少。Ca~(2+)饥饿根小泡的质子转运速率被抑制到对照根小泡的一半以下。与囊泡相关的K~(++)-Mg~(2+)&lt；~(2+)-ATPase活性因钙缺乏而显著降低。黄瓜根质膜部分脱脂ATPase与大豆卵磷脂的再结合。对照根的再结合ATPase活性明显高于缺钙根的活性。由对照根制备的部分去脂ATPase的最大激活所需的asolectin量远低于由Ca~(2+)饥饿根制备的。…酶与磷脂结合功能的降低可能是大麦ATPase膜H~(2+)转运活性缺乏引起黄瓜根细胞膜生理损伤的原因之一。200 mMNaC l胁迫下，根数增加。在蛋白质合成抑制剂的存在下，这种增加被抑制。膜泡的性质与H~+-转运活性有关，表明膜是液泡膜来源的。与H~+-转运活性相关的小泡密度梯度离心法没有发现明显的差异，而对照和盐胁迫下小泡H~+~+转运活性的Km值是相同的。这些结果表明，与液泡膜相关的质子泵的增加是将盐隔离到液泡中的过程。这可能是大麦对盐胁迫的一种适应机制。1 mM AlCl3处理大麦根部后，膜泡的H~+-转运活性显著降低，在pH 6.5时，膜泡H~+-转运活性被抑制约50%，而在pH_7.5时，膜泡H~+-转运活性仅被抑制10%。柠檬酸能有效地恢复与Al引起的囊泡H~+转运活性有关的ATP的Vmax和Km值。结果表明，铝毒害植物根的机制之一是抑制H~+转运活性，进而抑制根中质子的排出。较少

Proton extrusion from cucumber roots decrease markedly during Ca^<2+> starvation. The proton transport rate of the vesicles from Ca^<2+>-starved root was repressed to less than half of the vesicles from control roots. K^+-Mg^<2+>-ATPase activity associated with the vesicles decreased markedly by Ca^<2+> deficiency. Partially lipid-depleted ATPase prepared from plasma membrane of cucumber roots reassociated with asolection, soybean lecitin. The activity of reassociated ATPase obtained from the control roots was apparently higher than the activity of Ca^<2+>-starved roots. The amount of asolectin required for maximum activation of the partially lipid-depleted ATPase prepared from control roots was much lower than that prepared from Ca^<2+>-starved roots. A decrease in the functional association of ATPase with phospholipids might be one of the physiological injuries in root cell membranes of cucumber caused by Ca^<2+> deficiency.H^+-transport activity of the vesicles prepared from barley … More roots increased with 200 mM NaCl stress. This increase was suppressed in the presence of inhibitors of protein synthesis. The properties of the membrane vesicles associated with H^+-transport activity suggested that membrane was tonoplast origin. The density gradient centrifugation of vesicles associated with H^+-transport activity showed no detectable difference and Km values for ATP of the H^+-transport activity of vesicles from control and NaCl-stressed roots were the same. These results suggest that the sequestration of the salts into vacuoles is carried out by the increased proton pump associated with the tonoplast. This could be an adaptive mechanism of barley against salt stress.The extrusion of protons from barley roos decreased markedly after the treatment with 1 mM AlCl_3. H^+-transport activity of the membrane vesicles was inhibited by approximately 50% in the presence of 100 M AlCl_3 at pH 6.5 but the inhibition was only 10% at pH 7.5 . The values of Vmax and Km for ATP related to the H^+-transport activity of the vesicles due to Al was effectively restored by citric acid. The results suggest that one of the mechanism of Al toxicity in plant roots is the inhibition of the H^+ transport activity which in turn leads to the inhibition of proton extrusion from the roots. Less