关键词: 紫花苜蓿, 氮营养, 根系形态, 输导组织, 解剖结构

Abstract:

This paper is to explore the effects of regulation of exogenous nitrogen on early root external morphology and internal structure of alfalfa. In order to simulate soil nutrient that could be absorbed by plants, the study was based on two nitrogen forms (nitrate nitrogen and ammonium nitrogen) and five nitrogen levels (0,105,210,315,420 mg·L^-1). ‘Gannong No.3’ alfalfa was used as the experimental material by using sand culture supplied with different nutrient solutions,and observation of paraffin section and the photomicrography of roots. The results showed that under each level of two kinds of nitrogen forms, the root biomass, length, surface area and volume, average diameter were significantly higher than that of controls (P <0.05). With the levels of nitrogen increase, each root indexes were increased at the beginning and then decreased. When two kinks of nitrogen forms were 210 mg·L^-1, the root growth and morphological indexes were maximum, and NH₄⁺-N treatments were better than NO₃^--N. Root conduction tissue anatomy also showed the same trend as root morphology. When NH₄⁺-N treatment was 210 mg·L^-1, the root anatomy of conducting tissue (vascular area, xylem area, phloem area and the number of catheter) showed the best performance. The result showed that NH₄⁺-N 210 mg·L^-1 level can effectively promote roots outside morphogenesis, improve internal conducting tissue structure.

Key words: Alfalfa, Nitrogen, Root morphology, Conducting tissue, Anatomical structure