Aritificial Induction Of2n Pollen In C.Longibracteatum Cv. Cuixian

This study was designed to determine the efficacious period of inducing2n pollen though cytological viewing and mastering the relation between the development of microspores and the external morphological characteristics in C. longibracteatum using the flower buds as material. Different concentrations (0.05%、0.1%、0.15%、0.2%) and different time (24h、48h、72h、96h) of colchicine were employed to determine the efficacious method of inducing2n pollen. The influence induced by colchicines on flower buds, rate and vitality of2n pollen were surveyed. Additionally, the cytological mechanism of inducing2n pollen was probed prelimilarily. The results were as follows.(1)The characteristics in every meiosis period of C. longibracteatum was typical and accordant with the law of diploid meiosis. Cytokinesis was of the simultaneous type and with two-celled mature pollen grains. Bistratal cell wall was visible in each period of male gametophyte when the transverse diameter of bud increased from0.41cm to0.44cm and the white anthers turned into yellow. They can be used as standard to estimate the development stage which correlated with partial external morphological characteristics. The active meiosis period was efficacious to induce2n pollen when the transverse diameter of flower buds increased from0.31cm to0.39cm and the greenish yellow anthers turned into bluish white.(2)The corolla was variable, the bud was susceptible to colchicine and lethiferous inordinately after being induced by colchicine with different concentration or time. The largest variable rate was11.27%. The lethallty rate that can reached46.67%increased with the concentration or induction time of colchicine.(3)Speaking relatively in the design range of combination and time,Treating the flower buds of C. longibracteatum by colchicine of low concentration in combination with long hours or high concentration in combination with short time was benefitial to inducing2n pollen while high concentration colchicine in combination with long time was poisonous, reduced the induction rate and vitality of2n pollen. In terms of the rate and vitality of2n pollen, inducing2n pollen by0.15%colchicines with48hours was optimum in which the2n pollen percent reached2.65%and the comparable vitality was73.72%that was not significantly different from the largest relative vitality(87.5%).The2n pollen of C. longibracteatum whose longitudinal diameter was52.99μm and transverse diameter was45.54μm was legible and bigger than n pollen.2n pollen was ovoid or subround with sculptural sueface,regular shape and smooth rim.(4)Abnormal behaviour of chromosome, abnormal fixed position of spindle, micronucleus and chromosome doubling of gamete appeared in the period of microspore development after colchicine treatment to the flower buds. The monad, dyad, triad and polysporous were observed in the period of tetrad. The percent of predicted2n pollen which came from the rate of dyad and triad was close to the measured value. Additionally, abnormal fixed position of spindle, chromosome doubling of gamete and the existence of dyad and triad were the cytological mechanism of formation of2n pollen in C. longibracteatum.