Seed Germination And Seedling Growth Responses Of Six Alfalfa Cultivars To Temperature And Drought

Alfalfa is thought to be the king of pasture,which is the most important forage species for the development of livestock husbandry in our country.In order to develop alfalfa industry in northern China,cold-and drought-tolerant cultivars planting is needed.Cold tolerance of alfalfa can be reflected by cold tolerance at germination and seedling stages.Thus selecting cold tolerant cultivars at germination and seedling growth stages has practical significance for alfalfa production in northern China.However,most studies on the responses of alfalfa to temperature and drought stress has been comparisons between domestic and foreign cultivars.Studies about high quality cultivars from northern China are relatively lacking.Thus we selected six alfalfa cultivars cultivated from northern China and compared their responses to different temperatures and water potentials at germination and seedling growth stages.Our results showed that germination percentages of the six alfalfa cultivars increased with temperature and then decreased.Germination percentage of Gongnong 1 was relatively high at all temperatures,especially high temperatures.Germination percentage of Gongnong 1 was the highest at 5~oC,which was 92%.At 10~oC,germination percentages of Longmu 803,Dongmu 1and Gongnong 1 were significantly higher than the other cultivars.Radicle length of the six cultivars increased with temperature until 30~oC and then decreased.Seedling height of the six cultivars remained unchanged with temperature.Seedlings of Caoyuan 3 grew better at low temperatures.Chlorophyll content,the soluble protein content and the number of stoma at leaf epidermis decreased with temperature and then increased.Chlorophyll content of Dongmu 1was the highest at 30~oC,which was 38.95.Water potential inhibited germination of all alfalfa cultivars obviously.Gongnong 1 had the highest germination percentage in all PEG treatments.For example,germination percentage of Gongnong 1 at-0.2 MPa PEG was 89.2%,only 4.8%lower than that in distilled water.As the water potential of PEG decreased,radicle length and seedling height of the six cultivars decreased.Seedlings of Caoyuan 3 exhibited the best in all PEG treatments.When transferred un-germinated seed in PEG treatments to distilled water,the recovery germination percentage of Gongnong 1 was the highest.