Reproductive Ecology Of Natural Taxus Cuspidata

In the Japanese yew(Taxus cuspidata Sieb.et Zucc.) nature reserve of Muling County in southeastern Heilongjiang province,Adopting the route-checking,we found 271 natural Japanese yew trees for population fecundity investigation,and confirmed 59 individuals for detailed study of sexual reproduction.By using the method of standard branch,29 flowering male trees and 30 flowering female trees were examined for strobilus development,fruiting status,and relationships between the strobilus development,fruiting status,and various ecological factors.1.The sex ratio of trees was 1 m:2 f;the natural Japanese yew tree was sexually reproductive over many years:male trees of diameter at breast height(DBH) ranging from 1.5 cm to 92 cm were reproductive,while female trees of DBH 9.5 - 68.1 cm were reproductive.Male trees typically flowered at ages about 20 years younger than female trees.2.The numbers of microstrobili were 3 times greater than numbers of megastrobili and only 1/10 megastrobili developed into seed.The numbers of strobili and seed correlated with DBH,crown diameter and height of trees;however,no significant differences were observed with other site factors.3.Numbers of strobili decreased from the upper to lower canopy layers,while the quantity of seed decreased from the middle,upper to lower canopy layers;seed-setting rate increased from the upper to lower canopy layers.Numbers of strobili and seed quantity in compass direction of the canopy showed a certain characteristics,but the differences weren't significant.4.The 1000-seed weight of Taxus cuspidata was(39～45)g,which was lower than other yew seeds,is not conducive to breeding.Hard seed coat prevent moisture absorption and gas exchange,and that's one of the reasons leading to seed dormancy.5.The viability of seedlot was tested by TTC(1.0%).The results of showed high seed abortion.anf the percentages of viable seeds were 24.67%.This maybe also a reason of poor natural reproduction.6.When the seed reached maturity,embryo development is not complete,after going through the physical after-ripening,seed embryo cavity filled with embryos and the radicle begin to growth,endosperm imbibition,seed coat cracking,seed germination with the conditions gradually.7.The main storage material of Taxus cuspidata seed is fat and protein,and low soluble carbohydrate.It can be concluded that the degradation of fat in the seeds of Taxus cuspidata is of crucial importance to their germination.These reproductive characteristics of natural Japanese yew reflect long-term adaptions to the environment,including the activities of wildlife and humankind.