Megagametophyte Devolopment And Abortion In Torreya Grandis

Torreya grandis is a famous nut tree particularly growing in China,with a long economic life and high economic value. Seeds of the Torreya grandis is rich in nutrition and has unique flavor,which lead to big market demands. Torreya grandis has two kinds of cones.One developed normally,while the other one’s development stopped.The abortive cone does not fall off,but stay in the base of the normal cone.This study was to find how the female gametophyte of Torreya grandis developed and the formation mechanism of the abortive cone.On April 24 of 2014,the pollination drop is out of the female cone,which means it’s time for artificial pollination.Collecting female cones every 5 ~ 7 days,using the conventional method of paraffin wax to observe how the female gametophyte developed,in order to make up the research blank in the sexual reproductive cycle of Torreya grandis.We also get statistics of the abortive cone and the normal cone in different location of the one-year-old branches to find a regulation.It takes 4 months from pollination to fertilization in Torreya grandis. Torreya grandis pollinate in the mid to late April,following the formation of megaspore in early May.In early June,the megaspore nucleus divides without cell wall formed.After divides into eight times,every free nucleus forms its cell wall.In late July,two archegonium mother cells appear near the micropyle,and divide into central cell and primary neck cell.The latter divides twice into four neck cells,while the former divides into egg nucleus and canal nucleus which regressive soon.Pollination drop carry the pollen into ovule and store it in the powder chamber.Pollen tubes go through the nucellus into the female gametophyte,release two sperm nucleus into the archegonium.The fertilization begins in mitosis metaphase of egg nucleus and sperm nucleus.The zygote continue to divide into two free nuclei in middle September.Proembryo formed in September 20.The abortive cone failed to develop because of its female gametophyte growth stagnation.The abortion cone does not has full structure. And the abortion is random,no regulation with its location in the one-year-old bearing branches.