Objective:The biological characteristics and the effects of different environmental factors on seed germination of five Cycas species with extremely small populations were explored.Methods:The morphological characteristics and germination index were determined.Moreover the seed germina-tion characteristics were studied under different texts of temperature,light,water and growing media.Results:There were some differences in seed traits of five Cycas species.Among them,the seed of Cy-cas dolichophylla was the biggest,with the biggest transverse diameter,longitudinal diameter,edge diameter and seed weight.The germination rates of five Cycas species were generally high and differ-ent.The seed germination rate of Cycas bifida and Cycas dolichophylla were the highest and the low-est,92.73%and 75.39%respectively.The proper temperature for seed germination ranged from 25℃to 30℃.With the increase of PEG 6000 concentration,the inhibition of seed germination was strength-ened,the seed could not germinate under the treatment of 20%concentration.The 40%to 60%of the whole light were favorable for the seed germination.Loose growing medium with good air permeability was suitable for the seed germination of Cycas.Conclusion:Five Cycas species had the specific adapt-ability to the ecological factors,the optimum conditions for seed germination of Cycas were suitable moisture,relative light 40%to 60%and temperature 25℃to 30℃.
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