焦核与大核龙眼雌配子体发育、授粉受精及早期胚胎发育的比较研究

利用人工授粉,采用压片法对大核龙眼‘九月乌’和焦核龙眼‘闽焦64-1’、‘闽焦64-2’、‘白核’等的自交与杂交后花粉管的生长特性进行研究,同时应用常规石蜡切片技术对大核与焦核龙眼的雌配子体以及合子胚早期发育进行观察。结果表明,龙眼胚珠在单核胚囊形成前就开始败育,且焦核品种(系)的败育率显著高于大核品种。不同亲本组合的授粉率存在差异,所有授粉组合在授粉36～48 h后均能观察到1个花粉管生长并进入胚囊受精。焦核品种(系)的胚胎在谢花后10 d开始败育,且败育率明显高于大核品种。受精是龙眼子房发育的首要条件,胚珠败育的雌蕊在谢花后10 d不膨大,不能发育形成焦核果实。谢花后10～30 d的早期胚胎败育是形成焦核龙眼的主要原因。焦核品种‘白核’胚乳具有成胚能力。约有24%的‘闽焦64-1’胚珠在胚胎发育过程中,其助细胞、合点端细胞及胚乳发生异常,这可能与早期胚胎败育有关。

Comparison of Megasporecyte Development, Pollination and Early Embryonic Development between Large-and Abortive-seeded Longan (Dimocarpus longan)

The large-seeded longan(Dimocarpus longan Lour.) cultivar ’Jiuyuewu’ and abortive-seeded cultivars,’Minjiao 64-1’,’Minjiao 64-2’ and ’Baihe’ were conducted to inbred or hybrid by artificial pollination,their growth of pollen tube was observed,and the female gametophyte and early zygotic embryo development of two cultivars were investigated by serial paraffin section technique.The results showed that ovule abortion of longan occurred before formation of the mono-nucleated embryo sac,and the abortive rate of ovule in abortive-seeded cultivars were obviously higher than that in large-seeded ones.Pollination rates had difference among different hybrid combinations.Nevertheless,a pollen tube could be observed entering the embryo sac in all combinations tested after pollination 36 to 48 hours.Embryo of abortive-seeded cultivars began to abort 10 days after flowering,which abortion rate was obviously higher than that of large-seeded cultivar.Ovaries did not develop until fertilization occurred.Pistils with abortive ovules did not enlarge 10 days after flowering,and did not develop to abortive-seeded fruits.Early embryo abortion occurring at 10 to 30 days after flowering could be the main factor to form abortive-seeded fruits.The endosperms in abortive-seeded cultivar ’Baihe’ could develop to embryo.The chalazal end cells,synergids and endosperms occurred abnormal development in about 24% ovules of ’Minjiao 64-1’ in ovule development process,which might relate to early embryo abortion.