The Development And Chromosome Doubling Of The Microspore In Ginkgo Biloba L.

Ginkgo biloba L. is a multiple-use economic tree species in China. Now availabling genetic improvement methods can increase its leaves and timber outputs; however, in terms of its economic, ecological and medical value the professionals are still on the process of discovering.Based on the gametogenesis and development of microgamete,chromosome doubling of microgamete of Ginkgo biloba were studied.The results of these researches included four points showed as follows.(1)The meiosis stages of pollen mother cells(PMCs) were observed,which was correlative with the diversification of male flower. Usually, the PMCs meiosis of Ginkgo biloba finishes at the end of March.It took short time to finish what happened from pachytene to diakinesis and the duration of leptotene is very long. The synchronization of meiosis were greatly different in different clones,floral branches from the same clones, male flowers from the same floral branches and even anthers of the same flower of Ginkgo biloba.(2)The male flowers of Ginkgo biloba treated by artificial climate chest could resist high temperature.The optimum period of doubling pollen chromosome of Ginkgo biloba was diakineses and the effectual temperature was 40℃.The highest average percentage of unreduced pollen by treating flowers for 2 hours at 40℃was 2.3%.(3)Pronamide and colchicines were the effectual reagents for doubling pollen chromesome of Ginkgo biloba. These reagents have an effect on doubling pollen chromosome. But the ratio of unreduced pollen induced with them was lower. The highest percentage of unreduced pollen by treating flowers for 24 hours with 100μΜpronamide was 1.9%. The highest percentage of unreduced pollen obtained by treating flowers for 72 hours with 0.6% colchicines was 4.3%.(4)The unreduced pollen from flowers treated with the"wood tree heater"was not gained. The height of Ginkgo biloba limited the function of"wood tree heater".It led to using the heater treating flowers of Ginkgo biloba with high temperature difficultly.