龙眼幼苗镁素吸收特性研究

龙眼镁素吸收曲线、电子探针分析以及代谢抑制剂对龙眼镁吸收影响等三方面的研究结果表明，龙眼镁素吸收特性取于介质供镁状况，供镁浓度低（≤0.40mmol/L）时，龙眼对镁的吸收受代谢控制，属主动吸收；供镁浓度高（＞0.40mmol/L）时，属被动吸收。K^ 、Ca^2 对镁的吸收有明显的抑制作用，但其机制并不相同。K^ 4抑制Mg^2 的吸收作用不是由于与Mg^2 竞争载体，是K^＋引起Mg^2 载体蛋白发生变构作用；Ca^2 对Mg^2 吸收的影响可能与膜透性的改变有关。

Characteristics of Magnesium Absorption by Longan (Dimocarpus longana. Lour) Seedlings

The characteristics of magnesium absorption by longan (Dimocarpus Longana.Lour) seedlings were investigated using hydroponic culture, electron x-ray microanalysis and inhibitors. The results indicated that magnesium absorption by longan seedlings depended on magnesium concentration in solution. When magnesium concentration was below 0.4 mmol/L, magnesium uptake was mediated by metabolism. When magnesium concentration was higher than 0.4 mmol/L, mag- nesium uptake was mainly mediated by non-metabolic factors. The presence of K or Ca2 in the solution significantly depressed the Mg2 uptake by longan Beedlings. It seemed that the depres- sion of Mg2 uptake by K might not occur at carrier site but at allosteric binding site, and might bring about conformational chances in the carrier. The depression of Mg2 uptake by Ca2 might be related to the effect of Ca2 on membrane permeability and magnesium transportain.