Study On Shade-tolerance And Photosynthesis Characteristic Of 5 Native Dichondra Repens Forst. In Southwest Of China

Urban afforestation is an organism integrated from arbors,shrubs,and grass.Besides, the main reason for lawn attenuation is light stress from the shade of trees,shrubs,and buildings.Therefore,the key point for lawn planning and landscaping is the shade tolerance of the chosen grass species and it is practically significant to research the serial reaction and adaptation mechanism of Dichondra repens Forst. under shade stress.Southwest of China is abundant with native Dichondra repens Forst., from which 5 accessions of native Dichondra repens Forst.(SD200309,SD200310, SD200411,YD200503, and GD200503) with high value for lawny landscape,strong drought resistance,great fecundity,and together with a reference species (common) imported from America are chosen to do this shade resistance experiment on the basis of previous experiments. More specifically, the research is made on the three aspects of those samples, namely the leaf and stalk morphological feature,chlorophyll content and other physiological and biochemical resistant response, photosynthetic feature under light stress(T0:0%shade,Tl:30%shade, T2:50%shade,T3:70%shade) so as to compare and find out the accessions with optimized shade resistance,and provide a theoretical basis for the cultivation of native Dichondra repens Forst.The experimental result shows that:1. As the increased degree of shade, the materials showed different morphological changes,the mode of plasticity in response was different with others. Evaluation of their morphological plasticity according to the degree of morphological variation in the four light treatments, rankings were: SD200310> SD200309> SD200411> CK> YD200503> GD200503.The morphological variation of CK, SD200411,SD200309 intensifies with the increased of shade; the morphological variation of SD200411 at T3 is extraordinary; the Plasticity of SD200310, YD200503, and GD200503 at T1 are better than that at T2; GD200503 has the slightest variation degree, relatively similar morphological feature under 4 gradients of light treatments, and plasticity was not obvious.2. The leaf length,leaf wild,leaf thickness,leaf stalk diameter,leaf stalk length,plant height,SLW,leaf water content,relative electronic,proline content,MDA content,soluble sugar content,SOD activity and Chlorophyll Content of Dichondra repens accessions vary with different shade intensity level. Dichondra repens accessions were assorted into 3 groups. The 1st group comprises SD200411,SD200309 and SD200310;The 2nd group comprises YD200503 and CK;The 3rd group comprises 1 accessions which was GD200503. Judging by the mean membership indexes of all the morphological indicators and Physiological and biochemical characters, the 1 st group was weakest at shade resistance, the 2nd group the better and the 3rd group the strongest.3. Diurnal variation of Tr was the inter-consequence of many elements. The diurnal mean Tr value of unit area were arranged as follows: SD200310>CK>GD200503> YD200503>SD200309>SD200411. And SD200310 was far more higher than the others.4. The diurnal mean value of available WUE were arranged as follows: SD200411> SD200309>GD200503>CK>YD200503>SD200310. And SD200411 was the highest accession which means it can produce more biomass than other accessions when given the same amount of moisture.5. With natural illumination, Pn diural variations of showed a double-peak curve which the 1st peaked at 12:00 and the 2nd peaked at 16:00. Results showed: GD200503 with high LSP and low LCP which had a strong adaptability with light. SD200411 with low LSP and LCP which is a shade-resistant plant. SD200310 with the highest LSP which means it had a strong light resistance.