【摘要】 对桔梗（ＰｌａｔｙｃｏｄｏｎｇｒａｎｄｉｆｌｏｒｕｓＡ．ＤＣ）小孢子发生和雄配子体发育过程超微结构的观察表明，减数分裂过程中发生第一次细胞质改组，表现为：粗线期／双线期，核糖体数量消减，质体和线粒体结构简化，末期Ⅰ，核糖体数量恢复；四分体时期，质体和线粒体获得正常结构。单核靠边期到二细胞花粉时期，发生第二次细胞质改组，表现同第一次细胞质改组相似。两次核糖体消减过程，均涉及到粗面内质网的活动。在减数分裂前期和有丝分裂前期均存在核周腔膨大形成核液泡现象。结果表明，核糖体数量的恢复可能与核仁的活动有关；核糖体数量的周期性变化，推测在孢子体向配子体转换过程中发挥一定作用。更多还原

【Abstract】 The ultrastructural changes are observed during microsporogesis and development of malegametophyte in Platycodon grandiflorus。The main results are as follows: the first cytoplasmicreorganization takes place during meiosis,expressed in the fall in ribosome number, structuralsimplication of plastids and mitochondria at the stage of pachytene/diplotene, and increasing inribosome number at the stage of talophase I and plastids and mitochondria retaining normal struc-ture at the stage of tetrad. From vacuolation stage of uninucleate microspore to the stage of two一celled pollen grain, the second cytoplasm reorganization takes place, expressing as the same asthe firtst one。Rough endoplasmic reticulum is involved in two times of fall in ribosome number.At prophase of meiosis and mitosis, nuclear vacuoles formed by invagination of the nuclear enve-lope occur accompaning the local breakdown of nuclear envelope。 Restoration of ribotsome innumber is connected with nucleolar activity; periodic changes of ribosome in number may be haverelation to sporo一gametophytic transition。更多还原