The Research On Pollination And Fertilization And Fruit Dropping Of Biological Characteristics In Fengtang Plum

In order to reveal the causes of low fruit-setting rate of Fengtang plum,pollination and fertilization of characteristics such as flower comprehensive characteristics,pollen viability,stigma receptivity,pollen tube dynamic growth and endogenous hormone changes was studied.And the physiological characteristics of fruit dropping,such as the falling regularity of young fruit,the growth of new shoots and young fruits,and the dynamic changes of endogenous hormones and mineral elements in young fruits during fruit dropping stage were studied.The influencing factors of low fruit setting rate and the cause of young fruit drop in Fengtang plum were analyzed and elucidated.The main results were listed as follows:1.Results of pollination and fertilization characteristics of Fengtang plum showed that:（1）Fengtang plum produce normal amounts of the pollen grain,about 575 per anther,and there was no significant difference from that of the Qingcui plum.（2）The method of culture in vitro was used to study the factors affecting pollen vigor of plum,it was found that the most suitable culture conditions for pollen germination and pollen tube growth was 25℃,p H 5.0,pollen germination rate reached 44.54%,pollen tube length reached 723.94μm.Sucrose and H₃BO₃had significant positive effects on pollen activity.the optimal basic medium was as follows:150 g/L sucrose+0.10 g/L H₃BO₃+10 g/L agar.Among this medium,the germination rate and pollen tube length could reach 53.68%,1554.70μm,respectively.GA₃ and urea can promote the germination and elongation of pollen tube in Fengtang plum as the best plant growth regulator and nourishing substances.The germination rate reached 69.23%and the length of pollen tube was 1425.58μm at 50 mg/L of GA₃ concentration,however,NAA and6-BA can promote pollen germination,but inhibit pollen tube elongation.Urea was more effective at a concentration of 20 mg/L,its pollen germination rate and pollen tube length could reach 70%,1717.89μm,respectively.However,nutrients such as dipotassium hydrogen phosphate,potassium nitrate,calcium chloride and magnesium chloride significantly promoted the germination of Fengtang plum,but had no significant positive effect on the pollen tube growth.（3）The stigma had receptivity,and part of the stigmas had receptivity at the bud stage,and it was acceptable on 0～4 d after flowering,the stigma reached the highest level on 1 d after flowering,and then the receptivity decreased gradually.（4）The fruit setting rates in natural state,self-pollination and cross-pollination were 23.61%,17.74%and 36.65%,respectively,the fruit-setting rate of across-pollination was significantly higher than the natural and self-pollination treatment.（5）Pollen tubes can into ovary after self-pollination treatment,pollen began to germinate at 2 h after self-pollination,pollen tubes penetrated through stigma at 8 h,entered to the base of style at 96 h,and into ovary at 120 h.However,the growing speed of pollen tubes after self-pollination of Fengtang plum was slower than that of Siyue plum.The pollen tubes of self-pollination of Fengtang plum only extended to 2/3 of the style at 72 h after pollination,while the pollen tubes of Siyue plum had reached the bottom of the style at the same time.The number of pollen tubes from style to ovary was less than the Siyue plum,the self-compatibility of Fengtang plum was not strong.GA₃ in pistils of Fengtang plum was stimulated rapid increase after they was pollinated,the pistils appeared to have much less t Z build-up,while had little effect on the synthesis and accumulation of IAA and ABA.In conclusion,Fengtang plum can produce fertile male gametophytes;stigma is acceptable;the pollen tubes can into ovary.These results indicated that Fengtang plum was self-compatible and there was no obstacle to pollination and fertilization.but the degree of self-compatibility is not high.2.Physiological fruit dropping characteristics of Fengtang plum showed that:（1）The whole fruit dropping time was from 14 to 63 days after flowering and was divided into two stages,one was the rapid time to fruit dropping（from 14 to 28 days after flowering）,the other was the slow time to fruit dropping（from 28 to 63 days after flowering）.The fast time of dropping was the main period of dropping,the peak of fruit drop appeared the 28 d after blooming,which accumulated about 82.73%of fruits,has dropped.（2）In the whole fruit dropping stages,the content of IAA,ZT and GA₃ in normal young fruits and stalks was higher than that in dropping young fruits and stalks,and ABA of normal fruits and stalks was lower than dropping fruits and stalks,high level of growth promoting substances and low level of inhibiting substance in fruit were likely to contribute to the set of young fruits.During the fast time of fruit dropping,the fruit set rate was significant positive related to the new shoot but was negatively corrected with the fruit weight.The content of IAA and IAA/ABA,GA₃/ABA,ZT/ABA and（IAA+GA₃+ZR）/ABA ratio in dropping fruit and stalk was reduced,while the GA₃,ZT and ABA in dropping fruit and stalk was increased.The low level of growth promoting substances and high level of inhibiting substance resulted in rapid fruit dropping in Fengtang plum.During the slow fruit dropping period,there was difference in relation with fruit set rate between the shoot and fruit weight,the fruit set rate was negative related to the new shoot,the rate was negative related to the fruit weight in 35 and 42 d after flowering but was positively corrected with the fruits weight from 49 to 70 d.The change trend of IAA,ZT and ABA content in normal fruits and stalks was similar with that of dropping fruits and stalks,the content of IAA,GA₃,ZT and the ratio of IAA/ABA,GA₃/ABA,ZT/ABA and（IAA+GA₃+ZR）/ABA in dropping fruits and stalks was not inosculated with the fluctuation curves of the fruit drop rate.（3）The contents of N and P in normal fruits were higher than those in dropped fruits,while the contents of K,Ca,Mg,Mn,Cu,Zn and B in normal fruit were lower than those in dropped fruit.