Study And Evaluation On Drought Resistance Of Three Cool-Season Turfgrasses

To evaluate the seed drought resistance of the three cool-season turfgrasses, tall fescue, perennial ryegrass and creeping bentgrass which were very popularly cultivated in Suzhou, the effects of drought on germination characteristics of three cultivars were studied under different osmotic potentials of polyethylene glycol 6000(PEG-6000) in germination stage. Pot experiments were also conducted to study the physical and mor-phological characteristics, physiological index of three cultivars under the different drought stresses in seedlings, the drought resistance of three cultivars was compared, as well, in order to give proposal for drought resistant cultivation and breeding of the cool-season turfgrasses in Suzhou. The results indicated as follows:(1) With the increase of PEG-6000 concentration, the germination energies and the germination percentages of three cultivars all decreased. The relationships between germination percentage and stress intensity were significant (p<0.01). The creeping bentgrass was easily affected by the osmotic stress, from the aspects of germination en-ergies and germination percentages.(2) The growths of radicle were inhibited. The radicle lengths of three turfgrasses decreased with the increase of the osmotic intensity.(3) The developments of root systems were affected by drought to some extent. As root length increased, the root surface area and root volume decreased to mild drought stress. But they all decreased significantly with increasing degree of the stress. The root length, root surface area and root volume of three turfgrasses all had a compensative growth after rewatering.(4) Drought promoted the root/shoot ratios of three turfgrasses. But different culti-var responded differently. The stimulation of the root/shoot ratios of tall fescue increased continuously within 20 days, however, perennial ryegrass began to decline at moderate stress, while creeping bentgrass did at severe stress. After rewatering, the root/shoot ratios of three turfgrasses all decreased.(5) The soil water content and relative water content of the leaves all decreased significantly with prolongation of the drought time. The relationships between soil wa-ter content and relative water content of the leaves were significant (p<0.01). After re-watering, the soil water content and relative water improved greatly, but were not re-stored to the CK level.(6) Under mild drought stress, the chlorophyll content of three cool-season turfgrasses increased insignificantly. With increasing the degree of the stress, the chlo-rophyll content of three cultivars decreased significantly. After rewatering, three culti-vars all recovered obviously, but creeping bentgrass was the worst.(7) The MDA and RPP contents of every tested cultivar had a continuous increase during 20 days. The two indexes both increased slowly at the metaphase, while in-creased rapidly at the late stage. The relationships between MDA and RPP were signifi-cant (p<0.01). After rewatering, the MDA and RPP of three cultivars recovered appar-ently, but did not reach identical level with CK.(8) The free proline contents of leaves were accumulated quite a lot by drought among three tested cultivars, and inreased with prolongation of drought time. Further-more, at severe drought stress, the accumulative speed of the free proline content was the quickest and the accumulative speed was the most. The relationships between PRO and RPP were significant (p<0.01). After rewatering, the free proline of three cultivars recovered apparently, but did not reach identical level with CK.(9) During the early period of drought stress, the catalase activities of three cool-season turfgrasses increased slowly, then increased significantly. With the further stress of drought, they decreased sharply at severe drought stress. After rewatering, the catalase activities of three cultivars recovered apparently, and reached an identical level with CK.(10) The stress of drought could lead to increase of the root activities of three cul-tivars. And it increased with the time of drought. After rehydration, the root activities of three cultivars recovered,and the differences were marked among three cultivars. (11) With a study on synthesis appraisement of drought resistance among 3 culti-vars, the results was showed as following: The strongest drought tolerance is tall festuca, the second is perennial ryegrass, whereas the worst is creeping bentgrass.