Abstract：
Riboflavins are secreted under iron deficiency as a part of the iron acquisition Strategy I, mainly when the external pH is acidic. In plants growing under Fe-deficiency and alkaline conditions, riboflavins have been reported to accumulate inside the roots, with very low or negligible secretion. However, the fact that riboflavins may undergo hydrolysis under alkaline conditions has been so far disregarded. In this paper, we report the presence of riboflavin derivatives and products of their alkaline hydrolysis (lumichrome, lumiflavin and carboxymethylflavin) in nutrient solutions of Cucumis sativus plants grown under different iron regimes (soluble Fe-EDDHA in the nutrient solution, total absence of iron in the nutrient solution, or two different doses of FeSO4 supplied as a foliar spray), either cultivated in slightly acidic (pH 6) or alkaline (pH 8.8, 10 mM bicarbonate) nutrient solutions. The results show that root synthesis and exudation of riboflavins is controlled by shoot iron status, and that exuded riboflavins undergo hydrolysis, especially at alkaline pH, with lumichrome being the main product of hydrolysis.
摘要：
作为铁获取策略I的一部分，核黄素在缺铁下分泌，主要是当外部pH为酸性时。在缺铁和碱性条件下生长的植物中，据报道，核黄素在根内积累，分泌非常低或可以忽略不计。然而,到目前为止，核黄素在碱性条件下可能会发生水解的事实一直被忽视。在本文中,我们报告了核黄素衍生物及其碱性水解产物的存在(lumichrome，在不同铁制下生长的黄瓜植物的营养液中的lumiflavin和羧甲基黄素（营养液中的可溶性Fe-EDDHA，营养液中完全没有铁，或两种不同剂量的FeSO4作为叶面喷雾提供)，在微酸性（pH6）或碱性（pH8.8，10mM碳酸氢盐）营养液中培养。结果表明,核黄素的根系合成和渗出受芽铁状态的控制,渗出的核黄素经历水解，尤其是在碱性pH下，lumichrome是水解的主要产物。
