薄壳山核桃‘Mahan’品种雄花发育及花粉粒萌发特性研究

Male flower development and pollen germination of ‘Mahan' pecan

为探究薄壳山核桃雄花发育及花粉粒萌发特性，以‘Mahan’为研究对象，系统观测雄蕊开花习性，从显微结构水平跟踪掌握薄壳山核桃雄花发育过程，利用扫描电子显微镜观察‘Mahan’花粉粒结构及其在雌花柱头表面的萌发特性。结果表明，3月下旬的解剖切片观察到雄花芽内有3束菜荑花序，雄蕊原基形成并分化，至4月中旬雄蕊基本形成；4月下旬雄蕊进一步分化形成小花，花药内形成4个花粉囊，花粉囊壁分为绒毡层、纤维层和中层，其内部花粉母细胞减数分裂形成四分体，至4月底绒毡层解体，四分体也解体形成4个单胞花粉粒；5月上旬花粉粒继续发育形成2．胞花粉粒，此时花粉完全成熟。人工授粉4h后，花粉在柱头表面开始萌发：授粉12～24h花粉普遍萌发，花粉管伸入柱头向下生长；2 d后花粉管继续伸入胚珠，柱头表面花粉管皱瘪；4d后花粉管伸入到胚珠位置。

In order to study the development of male flowers and pollen germination of pecan, ＇Mahan＇ wassystematically observed under microscope using paraffin sections for its staminal flowering habit. The structureand germination characteristics of the pollen grain were also observed using scanning electron microscope. Theresults showed that the male flower primordium took shape on the top of stamen in late March and began to dif-ferentiate in early April. In late April, the pollen sac formed in anther and the pollen mother cell began meiosis totetrad stage. Then the tetrad produced pollen grains of single cell nucleus and the tapetum disappeared graduallyin the developmental process. The pollen grain was fully developed when it had two nuclei. A stigma in the recep-tive period after pollination showed wave crests and papillary cells at the top of the carpel. Pollen germinated on astigma four hours after pollination. More pollen germinated on stigma and pollen tubes grown toward ovary 12hours after pollination. Pollen began collapse 24 hours after pollination and pollen tubes began collapse, and pap-illary ceils at the top of the carpel began depression and collapse 3 days after pollination.