三叶木通大小孢子发生和雌雄配子体发育研究

Sporogenesis and Gametogenesis of Akebia trifoliata

三叶木通(Akebia trifoliata)属于木通科(Lardizabalaceae)木通属(Akebia),为雌雄异花,雌雄同株的木质藤本植物,具有药食两用的经济价值。本文运用石蜡切片技术观察了三叶木通的大小孢子发生和雌雄配子体发育过程中胚胎学特征,以期了解三叶木通有性生殖过程,分析该物种自然条件下结实率低的生殖原因,为其后续进行杂交育种和新品种培育提供理论基础。结果表明:三叶木通雄蕊6枚,每枚花药具4个小孢子囊,花药壁完全分化时由外到内依次为1层表皮、1层药室内壁、2~3层中层及1层绒毡层,且绒毡层为分泌型绒毡层。小孢子母细胞减数分裂的胞质分裂为同时型,小孢子四分体为四面体型排列,从四分体分离出来的小孢子经过进一步发育形成2-核成熟花粉细胞。小孢子囊中的小孢子四分体时期存在少量败育现象。雌蕊具1室子房,为侧膜胎座,胚珠横生,多枚,双珠被,厚珠心。大孢子母细胞减数分裂后形成的大孢子四分体呈线型排列,靠珠孔端的3个大孢子退化,合点端的1个大孢子发育成为功能大孢子,经3次连续有丝分裂并进一步发育为七细胞八核的蓼型胚囊。雌花中的雄蕊早期发育正常,但小孢子发育至单核靠边期不在进一步发育,花药壁不开裂。雄花中的心皮早期发生退化,心皮愈合不完全,无胚珠产生。三叶木通大、小孢子发生和雌、雄配子体发育基本正常,不是导致其结实率低的原因,结实率低可能与影响传粉的外部因素有关。

Akebia trifoliatabelongs to Akebia of the Lardizabalaceae family,and it is a dioecious,monoecious woody vine,with economic value for medicine and food. In order to understand the sexual reproduction process of A. trifoliate,analyze the reproductive reasons of the low seed setting rate of this species under natural conditions,and provide a theoretical basis for its hybrid breeding and new variety cultivation,the embryological characteristics of mega-and microsporogenesis and female and male gametophyte development of A. trifoliate were observed by paraffin section technology. The main results showed that A. trifoliata had six stamens with four locules in each,and the anther wall was fully differentiated,and it was composed of epidermis(1 layer),endothecium(1 layer),middle layers(2-3 layer)and tapetum(1 layer)from outside to inside,tapetum belonged to glandular type respectively. The cytokinesis of the microspore mother cell in meiosis was of simultaneous type,and the tetrads were arranged in a tetredraltah,mature pollen grain was two-celled. There were little pollen abortion,and abortion occurred at the microspore tetrad stage. The ovary was one locular,parietal placentation,ovules were hemianatropous,bitegminous and crassinucellate. Its megaspore was of monosporogenesis type,and tetrads were linearly arranged. The chalazal end megaspore developed into functional megaspores,which underwent three times consecutive mitosis and further developed into polygonum embryo sac with seven cells and eight nucleus,another three megaspores degenerated. The early development of the stamens in the female flowers was normal,but the microspores did not develop further until the uninucleate pollen grain stage,the tapetum was not completely degraded,and the anther wall did not crack,the degeneration of the carpel of the male flowers was due to the early lack of development,the carpels heal incompletely,and no ovules are produced. The process of the mega-microsporogenesis and development of female and male gametophyte of A. trifoliata were normal,which was not the reason for the low seed setting rate,but may be related to external factors affecting pollination.