(27(3):259-266)Studies on embryo and endosperm development following interspecific crosses in rice

利用栽培稻(Oryza sativa L.)臺中65號與野生稻(O. officianlis Wall)品種雜交之F1為材料，由授粉後1~10日之種子，經固定，脫水，石蠟包埋，作成10~15μ之切片，觀察種子之發育過程，並以人工授粉方式，將去雄後的臺中65號品種為母本，再將臺中65號之花粉授配，以便採取受精相同時日之種子作為對照。 水稻經人工授粉後，正常種子之發育縱向比橫向快，授粉後4日，縱向發育完全，授粉後6日橫向發育完全。雜種F1種子，授粉後1~4日，胚及胚乳之發育與正常種子無甚差別，自第5日開始胚乳由外向內漸漸變成細長一條，胚部變化較小，第6日開始胚及胚乳均已變形，胚乳細胞組織分裂不規則，胚盤異常膨大，第8~10日除胚發育成畸形外，胚乳完全退化，胚乳退化可由組織培養得到雜種第一代，而胚之畸形發育，在吸取叢分上是一阻礙，因此，在育種時，採取1~4日之幼胚培養而獲得雜種F1植株之機會最大。 Rice cultivar Taichung 65 (Oryza sativa L. ) was crossed with O. officiualis Wall, a wild rice for observing the development of F1 seeds. The F1 seeds were sampled between 1 to 10 day after pollination, fixed, paraffin-sectioned (thickness 10-15μ) and examined. Cultivar Taichung 65 was also selfed by pollination and seed development was investigated similarly as comparison. The normal rice caryopsis developed much faster in the longitudinal then in the transverse axis. It attained full length 4 days and full width 6 days after pollination. F1 seeds obtained from the cross O. sativa and O. officinalis showed similar development in embryo and endosperm till 4 days after pollination. However, starting from the 5th day, its endosperm started to degenerate from the peripheral layer. Both embryo and endosperm deformed at the 6th day. There were irregular cell division of endosperm tissue and abnormal enlargement of scutellum. Between 8 and 10 days after pollination, the endosperm was totally degenerated and the embryo showed signifinant deformity. It is possible to obtain healthly F1 plants by embryo culture if the degeneration of hybrid endosperm is the main problem of crosses between cultivated and wild rices. The deformity of embryo might also affect the normal uptake of nutrient from endosperm. It is suggested that culturing young embryo 1 to 4 day after pollination would provide maximum possibility in obtaining F1 plants of interspecific crosses in rice