元江干热河谷不同居群猪屎豆营养器官旱生结构比较

为揭示同一河谷不同地段猪屎豆在旱生结构方面的差异性，按照水热条件的不同将元江干热河谷不同地段生长的猪屎豆划分成3个居群，收集不同居群植株的根、茎、叶组织。采用石蜡切片和光学显微镜观察进行解剖结构分析，运用隶属函数法测定不同居群的抗旱能力。结果表明：3个居群根茎叶的旱生结构存在明显差异，其中元江居群根木质部厚度高达2 004.97 μm，是元阳居群的1.26倍、河口居群的1.35倍；根木质部厚度与根横切面面积的比率达到60.45%，有利于吸收水分。元阳居群茎的皮层厚度远高于其他2个居群，其中元阳居群371.63 μm、河口居群222.12 μm、元江居群275.56 μm，有利于减少水分散失。元江居群的栅栏组织厚度为137.52 μm，分别是元阳居群和河口居群的2.1倍和2.2倍，其叶片栅栏组织厚度与海绵组织厚度比值达118.18%。3个居群的抗旱能力为：元江居群>元阳居群>河口居群，与居群的立地环境条件基本一致。

Comparative Analysis of Vegetative Organ Anatomy Among Different Populations of Crotalaria pallida in Yuanjiang Hot-dry Valley

As one of the pioneer species in the afforestation of barren hills and wastelands, Crotalaria pallida shows some typical features in conservation of soil and water. It is characteristic of being resistant to heat, drought, acid and barren soil, due to its developed root system and strong regeneration ability. In order to reveal the mechanism of being tolerant to these environmental factors, comparative anatomy of vegetative organs among different populations of C.pallida along the Yuanjiang Hot-Dry Valley was carried out by paraffin section. It showed that there exists an outstanding difference among 3 populations in the respects of anatomy in the roots, stems and leaves. In the root anatomic structure, the largest thickness of xylem existed in the plants of Yuanjiang population, which is 1.26 times and 1.35 times of Yuanyang and Hekou populations, respectively. The ratio between the Xylem thickness and whole root cross-section area reached up to 60.45% in Yuanjiang population, indicating the highest efficiency to absorb water in three populations. In the stem structure, the cortical thickness of Yuanyang population is the highest, which is the most helpful to reduce the loss of transpiration. In the anatomic structure of leaves, the plants in Yuangjiang population owned the largest thickness of palisade tissue with the number of 137.52 μm, which is 2.1 times and 2.2 times of those in Yuanyang and Hekou populations, respectively. According to the comparative data, it suggested that the plants in Yuanjiang population would be the most resistant to the heat and drought in three populations while the plants in Yuanyang would be more resistant than those in Hekou population. This suggestion was consistent with the varied amounts of water and heat in different populations.