富钾植物籽粒苋根系分泌物及其矿物释钾作用的研究

应用１４ Ｃ 同位素示踪技术研究了籽粒苋品种根系分泌物的动态、构成以及对含钾矿物钾素释放的作用。结果表明，具有高效富钾特性的籽粒苋品种， Ｃ Ｏ２ 同化能力强，光合产物向根外分泌的比例大。籽粒苋根系分泌物中的有机酸主要是草酸，占有机酸总量的９５ ％ 以上。不同种属的籽粒苋分泌有机酸的能力不同，一般是 Ａ Ｄｕｂｉｓ＞ Ａ Ｒｅｔｒｏｆｌｅｘｕｓ ＞ Ａ Ｃｒｕｅｎｔｕｓ 。同一种内，则钾素利用高效型品种一般型品种。钾亏缺处理显著提高光合产物向根外的分泌量。钾利用高效型籽粒苋品种的草酸分泌量明显增加。根系分泌物对含钾矿物有明显的解钾作用。草酸含量与根系分泌物解钾量显著相关，籽粒苋的草酸分泌能力是籽粒苋高效吸收利用土壤钾及富钾特性的重要机理之一。

THE ROOT EXUDATION OF GRAIN AMARANTH AND ITS ROLE IN RELEASE OF MINERAL POTASSIUM

Grain amaranth is a pseudo cereal with big biomass and abundant mineral elements. The genotypic variations of Amaranthus spp . with different K use efficiency(KUE) were studied in root exudation and the role of root exudate in solubilizing mineral K by use of hydroponics and 14 C tracing technique. The results showed that high KUE varieties had strong ability of both CO 2 assimilation and exudation of photosynthates. Predominate low molecular weight organic acids (IMWOAs) in root exudate of grain amaranth was oxalic acid, accounting for more than 95% of the total LMWOAs tested. Amaranthus spp . differed in the intensity of root exudation with an order as. A. dubis>A. retroflexus>A.cruentus. In the same species, then, high KUE varieties usually had higher power of excretion. K free treatment promoted excretion of photosynthates, but oxalic acid increased only in high KUE varieties. The root exudate could solubilize K minerals significantly, and the amount of oxalic acid and its K release were closely correlated, which indicated that oxalic acid exudation be one of the key mechanism for Amaranthus spp. to enrich and take up K from K minerals.