The Study On Resistant Drought-chill And The Seed Germination Characters Of Three Poa Species At Seedling Stage

The survival ratio of three Poa species are studied after drought again and again, and the changes of relative leave water content, relative electrical conductivity rate, proline content and malondialdehyde(MDA) content of three species at Poa seedling stage have been researched in the pots experiment; and the changes of chlorophy II content, carotenoid content, soluble sugar content, proline content and membrane permeability of these species have been researched at five different temperatures(25℃,5℃,0℃,-5℃,-15℃) under same treated time(12h),and then analysis three Poa species'resistance of drought-chill generally. And the three Poa species seeds are pretreated by 20% PEG-6000, the seed vitality and physiological characters have been studied. The following are the main results:After drought again and again, the survival ratio of three species ordered as Poa.pratensis L.var.anceps Gaud Qinghai >P.pratensisL.CV Baron >P.poophangorum Bor;with the water stress time prolonged, the leave relative water content of each species decreased, while the relative electrical conductivity rate, proline content and MDA content increased. Moreover, the ability of drought tolerance of three species was Poa.pratensis L.var.anceps Gaud Qinghai >P.pratensisL.CV Baron >P.poophangorum Bor, and the result is consistented with the result of survival ratio indicated after drought again and again.The results of chill stress experiments showed, with the chill stress time prolonged , the chlorophy II content and carotenoid content of each species decreased; while the soluble sugar content, proline content and membrane permeability increased. The ability of chill resistance of these species at seedling stage indicated that Poa.pratensis L.var.anceps Gaud Qinghai> P.poophangorum Bor.>P.pratensis L.CV Baron.Evaluated the resistance of three Poa species generally, the drought-chill resistance is ordered as: Poa.pratensis L.var.anceps Gaud Qinghai> P.poophangorum Bor.>P.pratensis L.CV Baron, and the result is consistented with the performance of three Poa species in 3 different region.The pretreatment of 20% PEG could improve germination rate of Poa seed, decrease relative electrical conductivity rate and MDA content, but couldn't improve germination index and germination potential. These showed that lipid peroxidation was slow down, biomembrance repaired easily, then, this could improve seed vitality better in a certain extent.