Study On Drought Resistance Of Dichondra Repens J.R. Forst. In Southwest China

In this study, 5 wild accessions (Dichondra repens)(SD200308, SD200309, SD200310, GD200503 and GD200504) were collected from Sichuan and Guizhou, imported materials Dichondra (Dichondra repens JR Forst.)was selected as control. The morphological characteristics and physiological and biochemical characteristics under different drought stress were analyzed in drought simulated pilot study to comprehensively evaluate the drought resistance of 5 materials and to explore the physiological mechanisms of drought resistance, these main results are as follows:1. Under the drought stress, there were some adaptive changes happened in external morphology of all materials tested, with the degree of drought stress, plant growth was restrained and the leaves curled , turned yellow, and gradually wither until the death of the last water. Under drought stress for the test material, the thickness of the blade thined with a decline in soil moisture.2. By observing the trial of paraffin sections for Dichondra leaf material, changes in the leaf caused by drought stress were divided into three stages: the beginning of the drought stress, epidermal cells began to shrink, the chloroplast in vascular bundle sheath cells move near to edge; with drought stress increased, contraction degree of epidermal cell increased, the chloroplasts in vascular bundle sheath cell moved to the edge, some chloroplast were damaged and then disintegration; at the highest level of drought stress, the leaves were almost completely destroyed, epidermal cells shrinked due to the excessive water loss, vascular bundle sheath cells confused. Tests showed that for all tested materials affected by drought stress, the time for changes of the leaves in three stages was inconsistent. 3. During the drought stress, leaf relative water content for Dichondra materials showed a downward trend in both, and with the time of drought, increased drop.4. In the course of drought stress for the Dichondra materials tested, leaf chlorophyll content in both reduced with vary degrees. In the initial drought stage, leaf chlorophyll content decreased marginally, with time extened, the level of stress depened, leaf chlorophyll content decreased to approach the minimum value. Analysis showed that in varying degrees, to decline after the peak, the soil water content and chlorophyll content were highly significant positive correlation (r: 0.992).5. With the decline in soil moisture, the degree of drought stress enhanced, MDA has increased for the leaves of Dichondra, but in the early stages of drought stress, malondialdehyde content growed slowly, with time for stress extened, it kept rising, indicating that the enhanced role of drought-induced oxidation (soil water content and MDA content was negatively correlated, correlation coefficient -0.875).6. The free proline content for materials tested increased gradually with the increase of soil drought stress (soil water content and proline content showed significant negative correlation, correlation coefficient -0.944).7. The fuzzy membership function was used to comprehensively evaluate the indicators after drought stress for the material tested, the results showed that the order of drought resistance for the tested Dichondra materials: GD200503> GD200504> SD200310> SD200309> CK> SD200308.