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首页> 外文期刊>Plant and Soil >Efflux and active re-absorption of glucose in roots of cotton plants grown under saline conditions.
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Efflux and active re-absorption of glucose in roots of cotton plants grown under saline conditions.

机译：在盐水条件下生长的棉花植株根中葡萄糖的外流和主动重吸收。

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The effect of growth under saline condition (100 mol NaCl m-3 in the nutrient solution) on the influx and the efflux of glucose from roots of cotton plants was analysed utilizing the non-metabolisable glucose analogue [14C]-3-O-methylglucose ([14C]3-OMG). Apical segments (1 cm long) excised from cotton roots took up [14C]3-OMG. At each tested concentration (5-500 mmol m-3), the influx was completely inhibited by the presence of the protonophore carbonyl cyanide-m-chlorophenyl hydrazone (CCCP) indicating that it is mediated by a H+-coupled co-transport mechanism. The CCCP-sensitive [14C]3-OMG influx was lower in the root segments excised from plants grown on saline solution than in the controls, and this was particularly evident at lower external concentrations. This difference was not due to a lower H+ apoplastic availability. In fact, the saline condition did not affect the pH of the rhizosphere and indeed the H+-ATPase activity, evaluated in plasma membrane vesicles purified from saline-treatedplants, was higher (+23%) than in the controls. The lower uptake of [14C]3-OMG into saline treated root segments was related to an enhanced value of the apparent Km of the carrier for the glucose analogue. This effect is discussed in relation to eitherthe more positive value of the transmembrane electric potential difference (DELTAPSI) measured in these root segments, or a competitive inhibition of Na+ on the H+ binding site of the carrier. Growth in saline solution slightly affected the efflux of the[14C]3-OMG preloaded in root segments, changing the membrane permeability to the molecule. The results strongly suggest that the higher (2.5 fold) net exudation of glucose, observed in short-term (4 h) collection experiments, from roots of cotton plantsgrown in saline condition, is mainly due to an effect of the saline growth condition on the system involved in the reabsorption of the hexose rather than on its efflux.
机译：利用不可代谢的葡萄糖类似物[14C] -3-O-甲基葡萄糖，分析了在盐分条件下（营养液中100 mol NaCl m-3）生长对棉花根部葡萄糖流入和流出的影响。 （[14C] 3-OMG）。从棉根切下的顶端部分（长1厘米）吸收了[14C] 3-OMG。在每个测试浓度（5-500 mmol m-3）下，质子基团羰基氰化物-间氯苯基（CCCP）的存在完全抑制了流入，表明它是由H +偶联的共转运机制介导的。 CCCP敏感的[14C] 3-OMG流入量从在盐溶液中生长的植物中切除的根段中比对照中的含量低，这在较低的外部浓度下尤为明显。这种差异不是由于较低的H +质外性利用率。实际上，盐水条件不会影响根际的pH值，实际上，在用盐水处理过的植物纯化的质膜囊泡中评估的H + -ATPase活性要比对照高（+ 23％）。盐处理的根段中[14C] 3-OMG的吸收较低，与葡萄糖类似物载体的表观Km值增加有关。关于在这些根段中测得的跨膜电势差（DELTAPSI）的正值或Na +对载体H +结合位点的竞争性抑制，讨论了该效应。盐溶液中的生长会稍微影响预先装载在根段中的[14C] 3-OMG的流出，从而改变膜对分子的渗透性。结果强烈表明，在短期（4 h）采集实验中，从盐渍条件下种植的棉花根部观察到较高的葡萄糖净渗出（2.5倍），主要是由于盐碱生长条件对盐渍化的影响。该系统参与了己糖的重吸收而不是其流出。

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