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

在Ca^<2+>饥饿过程中，黄瓜根部的质子挤出量明显减少。缺乏Ca^<2+>的根的囊泡的质子传输速率被抑制到低于对照根的一半。由于Ca^<2+>缺乏，与囊泡相关的K^+-Mg^<2+>- atp酶活性明显降低。从黄瓜根质膜制备部分脂质去化atp酶，并与大豆凝集素结合。对照根重关联atp酶活性明显高于Ca^<2+>缺氧根的活性。从对照根制备的部分脂质耗尽的atp酶的最大激活所需的凝集素的量远低于从Ca^<2+>缺乏的根制备的。Ca^<2+>缺乏可能导致atp酶与磷脂的功能关联降低，这可能是黄瓜根细胞膜受到生理损伤的原因之一。这种增加在蛋白质合成抑制剂的存在下被抑制。与H^+转运活性相关的膜泡特性表明，膜起源于细胞质。与H^+转运活性相关的囊泡的密度梯度离心无明显差异，对照和nacl胁迫根的囊泡的H^+转运活性的ATP Km值相同。这些结果表明，将盐隔离到液泡中是通过与张力质体相关的增加的质子泵进行的。这可能是大麦抗盐胁迫的一种适应机制。1 mM AlCl_3处理后，大麦室中质子的挤出量明显降低。在pH为6.5时，100 M AlCl_3对膜泡的H^+转运活性的抑制作用约为50%，而在pH为7.5时，抑制作用仅为10%。柠檬酸有效地恢复了与Al引起的囊泡H^+转运活性相关的ATP Vmax和Km值。结果表明，Al对植物根系的毒性作用机制之一是抑制H^+的运输活性，从而抑制质子从根中挤出。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