摘要
Embryonic development was studied in six cross combinations ofCitrus sinensis x C. tangerina, C. sinensis x C. reticulata, C. sinensis x (C. tangerina + C.reticulata), C. sinensis x Poncirus trifoliate, C.reticulata x C grandis and C. grandis xPoncirus trifoliate. The results showed that on the 30th day after pollination thezygote remained a single cell. On the 40th day, the zygote began to divide. On the50th day, zygotic embryo became globular-shaped while nucellar embryos had notinvaded the embryo sac. On the 55th day, a few nucellar embryos began to invadethe embryo sac. On the 60th day, the zygotic embryo became heart-shaped, and atthe same time, a large number of nucellar embryos invaded the embryo sac. On the80th day after pollination, the zygotic embryo was surrounded by nucellar embryosand it was not easy to distinguish these embryos. The cross combination affected thedevelopments of zygotic embryos, ovules and fruits, which were mainly determined bythe cross parents. As compared with interspecies crossing, the zygotic division ofintergenus crossing began later, the zygotic embryos developed slowlier and theinvading time of nucellar embryos was also delayed.
柑桔类珠心胚现象对研究其进化和种质保存方面有着重要意义，但是给其有性杂交育种工作造成相当大的麻烦：它不仅使杂交后代难于区分合子苗和珠心苗，而且会使合子胚发育中途天折。解决的途径是适时分离合子胚进行单独培养。为此，本工作于柑桔胚胎发育的不同时期取样、固定、观察，研究其合子胚发育规律，确定珠心胚侵入胚囊的时期。结果表明：一般情况下，授粉后３０ｄ，合于处于单细胞状态（Ｆｉｇ．１Ａ）；授粉后４０ｄ；合子开始分裂（Ｆｉｇ．１Ｂ）；授粉后４５ｄ，合子胚形成８－１６个细胞，珠心胚开始分裂（Ｆｉｇ．１Ｃ）；授粉后５０ｄ，合子形成球形胚，珠心胚尚未侵入胚囊（Ｆｉｇ．１Ｄ＆Ｅ）；授粉后５５ｄ，合子胚为球形胚或早心形胚，开始有少数珠心胚侵入胚囊（Ｆｉｇ．１Ｄ＆Ｅ）；授粉后６０ｄ，合子胚为心形胚（Ｆｉｇ．１Ｇ）。授粉后８０ｄ，合子胚为晚心形，珠心胚巨大量侵入并迅速发育（Ｆｉｇ．１Ｈ）。杂交的组合对合子，胚珠及果实发育均有一定影响，主要取决于杂交亲本。与种间杂交相比，属间杂交其合子分裂较迟，合子胚发育较慢，珠心胚侵入时期也较迟（Ｔａｂｌｅｌ，Ｆｉｇ．２）。这种发育速度的差异。
