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.