不同氮素形态培养下荞麦叶片中草酸积累的变化

Changes on leaf oxalate content in buckwheat growing under different nitrogen forms

关键词:  氨态氮  荞麦  草酸

Key words:  ammonia nitrogen  buckwheat  oxalate

摘要:

用1/5浓度Hoagland(pH6.0)营养液培养荞麦幼苗3 d后,取其中一部分继续用此营养液(硝态氮); 另一部分用硫酸氨和氯化钙取代硝态氮(氨态氮)的营养液,均培养至荞麦第一片真叶完全展开。结果表明,以氨态氮为唯一氮源培养荞麦时,植株叶片中草酸含量显著下降。进一步研究表明,氨态氮培养下荞麦根中及根分泌草酸的速率也显著下降,结果排除了叶片中草酸含量的下降是由于叶片中草酸向其根系转运或是因为根分泌草酸速率的差异造成的,而可能与其草酸代谢改变有关。氨态氮培养下叶片中与草酸代谢相关的有机酸含量以及相关酶活性也显著下降,这可能意味着荞麦叶片草酸形成积累可能与相关有机酸代谢有关。

Abstract:

Buckwheat(Fagopyrum esculentum)seedling were pretreated for 3 d with 1/5 Hoagland culture solution,before the buckwheat seedling cultured to expanded primary leaves under hydroponic condition with ammonia nitrogen or nitrate nitrogen as the only nitrogen source,then oxalate content was determined in leaves,roots and root exudates. The results showed the oxalate content was very significantly decreased in buckwheat leaves when ammonia was used as the sole nitrogen source,so was in the root and its exudating rate. This implies that the oxalate decrease by ammonia results from the metabolic change rather than the change in transport to the root and in the exudating rate. The leaves had much less some organic acids,activities of several enzymes involved in oxalate metabolism when the plant grew under ammonia nitrogen,indicating these organic acids level involved in oxalate metabolism may be one of the factors controlling oxalate content. Based on the present data,it is concluded that oxalate accumulation in buckwheat leaves is closely related to some organic acids metabolism.