石斛气生的兰科菌根组织结构及其对御旱研究

基于过去对铁皮石斛（Dendrobium candidum Wall．Ex Lindl．）气生的兰科菌根适应干旱环境胁迫机理的研究鲜为涉及，现开展了培养基质的不同水分质量分数（W（水）1=43．6％、16．8％、5．5％）对兰科菌根的外部形态以及内部组织结构影响的研究。研究结果表明：基质水分质量分数降低使石斛菌根外部形态发生多样变化；随着基质水分质量分数的不断降低，石斛的生长受到显著的抑制。当基质水分质量分数为5．5％时，石斛的多数生长指标均小于其它处理，但是根冠比（R／S）增加显著，高达2．22；通过不同切片多重镜检测定和图像分析，发现菌根的形态结构产生了天然的适应突变，独特的根被组织细胞层数多达5层以上，细胞壁相对加厚，细胞腔内网、羽状结构比其它两处理明显增多，石斛菌根通过形态结构的改变来适应水分胁迫并维持其生长发育，石斛菌根组织结构的这些改变大大提高了石斛御旱的能力；水分质量分数高低与菌根感染率呈负相关，越是干旱条件菌根真菌繁衍越活跃，菌丝团结构相持时间越长，菌根的这些适应性响应都提高了石斛的抗旱能力。

Tissue structure of aerial orchidaceous mycorrhiza and its effect on drought resistance of Dendrobium

Thestudy on drought resistance mechanism of aerial rchidaceous mycorrhiza of Dendrobium candidum Wall.Ex Lindl. was few reported. Focus on this issue, this paper studied the effect of different moisture content （43.6 %, 16.8 %, 5.5 % ） of growing media on the morphology and the internal tissue structure of orchidaceous myeorrhiza..Obvious changes in external morphology of orchidaceous mycorrhiza were observed when the moisture content of growing media changed. It suggests that orchidaceous my- corrhizamaintain could maintain its growth through the modification of internal structure to resistance drought stress. The growth of Dendrobium were inhibited when the moisture content of growing media decreased. When the moisture content was decreased to 5.5%, the morphology and internal tissue structure of aerial orchidaceous myeorrhiza changed significantly. The growth indices such as shoot length, root length, shoot diameter, shoot diameter and root number were significantly decreased, while the ratio of root to shoot increased to 2.22. The scanning electron microscope （SEM） suggested that the layers of tissue cell of velamen was up to 5 lay- ers with cell wall thickening and plume structure cell cavity significantly increased than the other two treatments. These changes in morphology and internal tissue structure of aerial orchidaceous mycorrhiza greatly promoted the drought-resistant ability of Den- drobium. The moisture content was negatively correlated with mycorrhizal infection rate, the more droughty the better active prolif- eration of mycorrhizal fimgi, and hyphae group structure stalemated a long time, which improved the drought resistance capability.