玉米幼苗地上部/根间氮的循环及其基因型差异

以两个玉米（ZeamaysL.）自交系原引1号（YY1）和综31（Z31）为研究材料，采用盆栽土培的培养方法，在正常供氮（HN,0.15gN/kg干土）和低氮量供应（LN,0.038gN/kg干土）培养条件下对玉米幼苗植株体内氮的循环量及其在地上部/根间的分配量进行了定量地测定、计算。结果表明，在玉米幼苗地上部/根间氮的循环量很高。低氮量供应使玉米幼苗植株吸氮量下降，根中氮的分配比例增加，同时地上部/根间氮的循环量也随之减少。与氮低效自交系Z31相比，氮高效自交系YY1幼苗中地上部/根间的氮循环量大、氮向根的分配量高，因而有利于其根系的生长，表现为根/地上部之比和总根长较高。这可能有利于其中后期对氮素的高效吸收与利用。

Genotypic Difference of Nitrogen Recycling Between Root and Shoot of MaizeSeedlings

Nitrogen (N) recycling between root and shoot in maize seedling was investigated by using two inbred lines (YY1 and Z31) under two N levels, normal N supply (HN, 0.15 g N /kg soil) and low N supply (LN, 0.038 g N /kg soil) in a pot experiment. N recycling diagrams (Figs.1,2) were established by using the method of Amstrong and Kirkby (1979). The results showed that considerable amount of N recycled between roots and shoot (Figs. 1,2). Under LN, N uptake was lower, so was the amount of N recycled, while the amount of N allocated to roots increased by a large amount than under HN (Table 1, Figs. 1,2). YY1, the N-efficient genotype, had larger amount of N recycled between roots and shoot than Z31 (Figs. 1,2), as well as higher percentage of N in roots under the two N levels (Table 2). YY1 had higher root/shoot ratio (R/S) and longer root length per plant though no difference was found in shoot dry weight and shoot N content between the two genotypes (Table 1). We suggest that more N recycling to root in YY1 may result in higher allocation of N to root which enables the plant to build a larger root system at seedling stage, which is favorable for higher N uptake for later plant growth.