NH4+-N对紫花苜蓿输导组织解剖结构的影响

以甘农3号紫花苜蓿(Medicago sativa 'Gannong No.3')为材料,采用石蜡切片技术和光学显微技术,比较研究了5个NH₄⁺-N水平(0,105,210,315,420 mg·L^-1)对紫花苜蓿根、茎和叶输导组织解剖结构的影响。结果表明:随着氮浓度的增加,贯通于根、茎、叶3个器官的维管组织先增大后减小,在NH₄⁺-N浓度为210 mg·L^-1时,维管束面积最大,木质部区域宽,韧皮部发达,导管数目多,其输导能力最强。此外,各营养器官的其他组织也发生了相应的改变,在0~210 mg·L^-1随着氮浓度的增加,根皮层增厚,薄壁细胞体积减小;髓腔呈片状的髓组织,面积增大;叶主脉突起程度增大,表皮由长圆形排列更为紧密的单层细胞组成,在210 mg·L^-1时处于最优状态,再提高浓度效果反而降低。

The Effect of NH4+-N on Anatomical Structure of Alfalfa Conducting Tissue

Gannong NO.3 was used as experimental materials with five different NH₄⁺-N concentrations(0,105,210,315,420 mg·L^-1). Anatomical structure characteristics of three types of organs(roots, stems and leaflets)were observed by using paraffin section techniques and photomicrography. The results showed that vascular tissue throughout the roots,stems and leaflets was increased at the begining, and then reduced with the further increase of nitrogen treatment. When NH₄⁺-N treatment was 210 mg·L^-1, the function of conducting tissue achieved the best performance with more vessels, more multi-vascular bundles, larger and better developed xylem and phloem area as well as more xylem conduits. Changes in other tissues of vegetative organs were also observed, the roots cortex was thicked and parenchyma cell volume decreasesd. The intramedullary cavity had flaky tissue and the area was increased. Leaves midrib became more prominent and epidermis consisted of a layer of oblong, more compactly arranged epidermal cells with increased NH₄⁺-N concentration within a range of 0 to 210 mg·L^-1. The optimal concentration was at 210 mg·L^-1. Further increase of the concentration of NH₄⁺-N concentration reduced the improvement effects instead.