侧柏雌球果及其胚珠的发育(英文)

Cone and Ovule Development in Platycladus orientalis (Cupressaceae)

观察了侧柏 (Platycladusorientalis (L .)France)胚珠的发育过程及后期球果苞片的结构变化。在北京 ,雌球果原基 7月分化。通常一个球果有 4对苞片 ,中部两对可育 ,靠球果顶端一对各产生一枚胚珠 ,其下一对各两枚。胚珠的发育顺序是向顶的 ,下部可育苞片腋部的两枚胚珠源于同一原基。胚珠原基分化成珠心和珠被 ,在发育过程中 ,珠被逐渐包围珠心 ,最后形成烧瓶状的胚珠。 11月到次年 1月 ,球果处于休眠状态。 3月中旬 ,苞片张开露出胚珠接受花粉。传粉后 ,苞片近轴面居间生长迅速 ,形成突起 ,并将苞片推到了水平位置。成熟果鳞有两组维管束 ,远轴面维管束延伸至苞片 ,近轴面延伸到居间生长突起。近轴面维管束发育较晚 ,其木质部朝向远轴面。

Seed cone in Platycladus orientalis (L.) France consists of four or five pairs of decussate bracts. Usually, two pairs of the fertile bracts in the middle of the cone subtend six ovules, which initiate in an acropetal manner. Only one ovule presents on each of the upper fertile bract, while two ovules initiate from a common primordium in the axil of lower bracts. In Beijing, most female cones initiated in July. All parts of the cone formed before dormancy, which occurred during November to the next January. After pollination in March, bract morphology changed dramatically; intercalary growth of the bract base formed a conspicuous protuberance, in which inverted vascular system developed. Furthermore, ovules on different pairs of bracts initiated in an acropetal manner and two ovules in each lower fertile bract initiated from a common primordium, which was different from the basipetal initiation of ovules and independently formed single ovule as reported by Takaso in Calltris