The Research On Physiological Response Of Three Legume Turfgrasses To Drought Stress

Among three important landscape plants (trees, flowers, lawn), lawn occupies the most area. To maintain its daily growth needs a lot of water. In the case of lack of fresh water resources, how to make the use of limited water efficiently to landscaping becomes a vital and pressing subject for scholars both at home and from abroad.This article aims at studying the physiological basis of the difference in turfgrass drought resistance, and providing reference for turfgrass domestication, drought-resistant grass seed selection and on-the-job management. The research took white clover (’sea’ white clover, Trifolium repens L. cv.’Haifa’), shamrock (’Longdong’ shamrock, Medicago lupulina L. cv.’Longdong’), alfalfa (’clover’1, Medicago sativa L.) as materials, studied influence of the response to Abscisic Acid in the process of seed germination, as well as form growth, photosynthetic characteristics, the ability of antioxidant protection system, the change of the osmotic regulation substances under condition of drought stress and rewatering in budding stage, and then carried comprehensive evaluation of the drought-resistant abilities they have. Here are some main conclusions:(1) Exogenous ABA concentration has certain impacts on seed germination and seedling growth of white clover, shamrock and alfalfa. As the ABA concentration increased, white clover, shamrock, germination potential, germination rate, plant height of alfalfa, germination index, vigor index showed a trend of increase, however, the root length and abnormal seedlings rate rised in the first place, then reduced sooner, which indicated that ABA inhibited seed germination and Its corresponding signal transduction of drought stress could be ABA dependable way. The germination of shamrock to ABA treatment showed a better response. The germination potential, germination rate, germination index, vigor index, root-shoot ratio of shamrock were significantly higher than that of white clover and alfalfa, and its abnormal rate is lower than the white clover, but had no had no significant difference from alfalfa.(2) Under the condition of drought stress, the relative water content of three legume grass leaves had a descending trend, the dry weight of above-ground part and underground part decreased, and the average leaf area reduced. As drought increased, net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), pigment declined, and intercellular CO2 concentration showed a trend of decline after rising in the first place. Their photosynthesis was affected. SOD (Superoxide dismutase, SOD) activity declined along with the increasing drought (except shamrock), Peroxidase (POD) activity rised as stress level increased, and cell membrane permeability as well as Malondialdehyde (MDA) content increased.(3) After drought stress and re-watering, morphological characteristics came back to normal growth trend, net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs) rised, intercellular CO2 concentration decreased, and leaf pigment content increased. Plant seedlings growth environment was improved. SOD and POD activity declined after re-watering. Though H2O2 content increased, MDA content decreased. Permeability of cell membrane and the proline content reduced, but soluble protein content increased.(4) Generally, in three kinds of lawn grass, alfalfa has the strongest ability of drought resistance, white clover becomes the second, shamrock has the weakest ability. Under drought condition, the performance of the alfalfa included:height, leaf area, RWC and leaf pigment content did not significant reduce, root length significantly increased, and the antioxidant enzyme activity increased.(5) Shamrock is recommended as lawn grass in Sichuan area.