萱草幼嫩花粉原生质体培养启动细胞分裂的超微结构研究

AN ULTRASTRUCTURAL STUDY ON TRIGGERING OF CELL DIVISION IN YOUNG POLLEN PROTOPLAST CULTURE OF HEMEROCALLIS FULVAL

萱草(Hemerocallis fulva L.)幼嫩花粉,即后期小孢子原生质体在培养8天时进入有丝分裂或已形成二个细胞。此外,还观察到游离核分裂、无丝分裂、微核形成等现象。这显示了花粉原生质体分裂方式的多样性。在启动分裂时发生一系列变化:如细胞核移位、大液泡消失、细胞质电子密度增加、细胞器增多、质体不含淀粉等。再生的细胞壁含许多小泡,很少纤丝,表现出现有培养条件下壁的形成能力薄弱。这是今后改进培养技术需要特别注意的问题。

The ultrastructural changes of young pollen protoplasts under culture condition in Heme- rocallis fulva were studied.In comparison with the original pollen grains,the pollen protopla- sts had been completely deprived of pollen wall,but kept the internal structure intact,including a large vacuole,a thin layer of cytoplasm and a peripherally located nucleus.After 8 days of culture a few pollen protoplasts were triggered to cell division:some of them were just under- going mitosis with clearly visible chromosomes and spindle fibers;the others already divided into 2-celled units.The two daughter cells were equal or unequal in size but with similar dis- tribution of organelles inside.Besides cell division,there were also free nuclear division,ami- tosis and formation of micronuclei indicating a diversity of division modes in pollen protoplast culture.A series of changes occurred during the process of induction of cell division,such as locomotion of the nucleus toward the central position,disappearence of the large vacuole,in- crease of electron density of cytoplasm,increase and activation of organelles,diminishing of starch granules in plastids,etc.However,the regeneration of surface wall was not sufficient: it contained mostly vesicles with only a few microfibrils.The wall separating the two daughter cells were either complete or incomplete.The weak capability of wall formation is supposed to be one of the major obstacles which has so far restricted sustained cell divisions of young pol- len protoplasts under current culture condition.