Observation of morphological and anatomical characteristics of Swida wilsoniana flower bud during differentiation process.

The anatomical characteristics of Swida wilsoniana(Wanger.) Sojak.flower bud during differentiation process were studied by paraffin method,and the external morphology of flower bud was also observed.The results show that both terminal bud and axillary bud of S.wilsoniana can differentiate into flower bud.The differentiation starts at late February and ends around the end of April.The whole differentiation process may be divided into five stages,including flower bud undifferentiation stage,inflorescence differentiation stage,calyx differentiation stage,petal differentiation stage,pistil and stamen differentiation stage,in which the inflorescence differentiation stage can be divided into prophase and anaphase.In the flower bud differentiation process,the flower buds of S.wilsoniana gradually grow larger,and extend longitudinally and radially.Pyramidal cymes are initiated in petal differentiation stage.According to the longitudinal section of flower bud,in flower bud differentiation process,growing tip in the bud grows bigger and protrudes upward.Four calyx primordia arise around the growing tip in calyx differentiation stage.Petal primordia are initiated inside calyx primordia and alternately spaced with calyx primerdia in petal differentiation stage.Stamen primordia appear inside petal primordia in pistil and stamen differentiation stage and meanwhile carpel primordia of pistil are initiated in the center of growing tip.These primordia develop into calyx,petal,pistil and stamen after growth and differentiation.