外源葡萄糖对山定子生长及根系氮素代谢的影响

以有机质含量仅为0.65%的低碳冲积沙土为栽培基质,以当年生山定子幼苗为试材,分别添加与土壤本体微生物生物量碳(MBC)等量的碳量(2 g·kg^-1)、5倍MBC碳量(10g·kg^-1)的葡萄糖,以不添加葡萄糖为对照,处理后0~30 d内定期采集根系样品,研究外源葡萄糖对低碳土壤中山定子幼苗生长、根系构型及氮素代谢的影响.结果表明:5倍MBC碳源处理后山定子幼苗的株高、总生物量、总根长和根表面积分别显著增加12.3%、26.4%、23.2%和14.6%,而茎粗、根体积和平均直径无显著变化.等量及5倍MBC碳源处理均显著提高了山定子的根系活力,分别在第3和15天达到峰值,高于对照119.1%和75.7%.在整个处理期间,等量及5倍MBC碳源处理显著增加了根中NO_3^-、NO_2^-和NH_4^+含量;整体上,等量及5倍MBC碳源处理均显著增强根系中硝酸还原酶、谷氨酰胺合酶、谷氨酸脱氢酶、谷氨酸合酶、谷草转氨酶和谷丙转氨酶的活性,其中5倍MBC处理的作用最显著.5倍MBC的外源葡萄糖浓度更有利于促进低碳土壤中山定子根系中氮素的吸收代谢过程,诱导植株生长、干物质积累和根系构型改变.

Effects of exogenous glucose on growth and root nitrogen metabolism in Malus baccata.

To examine the effects of external glucose on growth, root architecture and nitrogen metabolism of Malus baccata seedlings in low carbon soil condition, Malus baccata seedlings were grown in sandy soil with the concentration of soil organic matter being 0.65%. The experiment consisted of three treatments: Control, with 2 g·kg^-1 glucose that equal to the ambient microbial biomass carbon (MBC), and with 10 g·kg^-1 glucose that was five times higher than the ambient MBC. The plant height, biomass, total root length and superficial area of the five times MBC group were 12.3%, 26.4%, 23.2% and 14.6% higher than that of the control, respectively. Root diameter, root volume and average diameter exhibited no significant difference under glucose treatments. The root activity was significantly increased under equal and five times MBC-glucose treatments, and reached its peak at 3 d and 15 d, about 119.1% and 75.7% higher than the control, respectively. Exogenous glucose addition significantly enhanced the concentrations of NO₃^-, NO₂^- and NH₄⁺ in roots. The activities of nitrate reductase, glutamine synthetase, glutamate dehydrogenase, glutamate synthase, glutamic-oxalacetic transaminase and glutamic-pyruvic transaminase were substantially increased in the roots, especially under five times MBC treatment. Five times higher than the ambient MBC of external carbon source promoted biomass accumulation, root growth, morphogenesis and N absorption of plants in low carbon sandy soil.