摘要
Pollen morphology and hydration, ovule development, formation of pollination drop and the pollination process of Taxus chinensis (Pilg.) Rehd were investigated in detail. The results showed that mature pollen was one_celled, irregular in shape, nonsaccate, and the surface was covered with orbicules. When pollen became hydrated, the intine swelled and the exine bursted. The exine usually remained on the surface of water or on the pollination drop all the time, while the rest portion of the pollen sank into the drop of water or the pollination drop. In the late August, the down_curved female buds could be observed in the field trees. The downturning of the female buds was an characteristic feature discriminating from the vegetative buds. At this stage ovular primordium was present in the female bud with a dome_shaped nucellar primordium encircled by a rudimentary integument. The integument grew fast and overgrew the nucellus. In the March of the following year, the ovule formed a micropylar canal about 1?000 μm in length, 200-300 μm in width. Except the micropyle, the other part of the ovule was enclosed by 20-25 scales. During the early stage of the ovule development, the nucellar surface clearly showed cell configuration; but a membrane_like structure covering the nucellar apex appeared in the late stage of the ovule development, and subsequently broke down with nucellar cell disintegration before pollen shedding. The disintegrated cell products might partake in the formation of the pollination drop. Before and during pollination, the nucellar cells contained abundant mitochondria, endospermic reticulum and dictysomes with vesicles; the plasma membrane was undulated and there was no accumulation of electron_dense substances in the pericytoplasm. Pollination drops usually occurred at night, and disappeared by noon in the field tree. 15 days before pollination, the in vitro ovules from the field trees already had the capability of producing pollination drops, which could last for 4-5 days indoors. However,
观察了红豆杉 (Taxuschinensis (Pilg .)Rehd)的花粉形态和水合特性及胚珠发育、传粉滴形成与传粉过程。成熟花粉为单细胞 ,无气囊 ,形状不规则 ,外壁表面具大量乌氏体。花粉水合时 ,内壁膨胀 ,外壁开裂。通常情况下 ,外壁保留在水滴或传粉滴的表面 ,而花粉的其他部分进入水滴或传粉滴内。在 8月下旬 ,可观察到下弯的雌性生殖芽。下弯这一特性是雌性生殖芽区别于营养芽的重要特征。这一时期的雌性生殖芽内已有胚珠原基。胚珠原基由一个丘状突起的珠心分生组织和珠被分生组织构成。珠被生长较快 ,并逐渐包围珠心。在次年 3月份 ,胚珠形成一个约 10 0 0 μm长 ,2 0 0～ 30 0 μm宽的珠孔道。除珠孔外 ,整个胚珠都被鳞片包被。在胚珠发育早期 ,珠心表面细胞轮廓清晰 ;而在后期 ,珠心表面则形成一层膜状结构。这层膜状结构在传粉前随珠心细胞的解体而破裂 ,细胞壁降解产物可能参与传粉滴的形成。在传粉前和传粉期 ,珠心细胞内含大量的线粒体、内质网、高尔基体和小泡 ;细胞膜起伏不平 ,周围细胞质内无明显的高电子密度物质。室外树上的传粉滴通常在夜间产生 ,中午前消失。传粉前 15d离体的胚珠就具有在室内产生传粉滴的能力 ,室内产生的传粉滴可在珠孔端保持 4～ 5d。授粉不能引起传粉滴的明显收缩 ,传粉滴?
基金
TheNationalNaturalScienceFoundationofChina!(39770 0 50 )
TheResearchGrantofTheChineseAcademyofSciences !(KZ952_S1_1 2 8)
