Effects Of Different Treatments On Self-pollination And Seed Setting Of Camellia Oleifera ’Huashuo’

Camellia oleifera is an important woody edible oil tree species in China.At present,there are many problems in the production of C.oleifera,such as more flowers and less fruits,low fruit setting rate and low yield,which affect the healthy development of C.oleifera industry in China.In order to develop technical methods to improve the fruit-setting rate of C.oleifera,this study used the methods of pollen germination in vitro,controlled pollination in the field and microscopic observation of tissue anatomy to systematically study the effects of different substances on the pollen germination and the pollen tube growth in vitro of‘HS’,the effects of different treatments on the fruit-setting rate of self-pollination of C.oleifera,and the growth changes of self-pollinated pollen tubes in response to exogenous substances.The purpose is to find out the substances and methods to improve the fruit-setting rate of C.oleifera,and to provide scientific basis for realizing artificial regulation and control in production to improve the fruit rate of C.oleifera.The main results are as follows:1.Identified the main substances promoting pollen germination and pollen tube growth in vitro of C.oleifera.The effects of different exogenous substances on pollen germination and pollen tube growth of ’HS’ were studied by pollen germination in vitro.The results showed that plant growth regulators such as NAA,gibberellic acid(GA3),methyl jasmonate(MeJA)and melatonin(MT),mineral elements such as Ca2+ and Mg2+,and tannase,dicyclohexylcarbodiimide(DCC)and Azacitidine promoted pollen germination and pollen tube growth in vitro at appropriate concentrations.Among them,0.5 mg·L-1 NAA had the most obvious effect on promoting germination,which was significantly increased by 16.51%compared with the control;5 mg·L-1 GA3 promoted pollen tube growth most obviously,and the growth length increased significantly by 245.96 μm.Ethephon,nitric oxide(NO)and reactive oxygen species(ROS)inhibited pollen germination and pollen tube growth,among which 50 mg·L-1 ethephon had the strongest inhibition on pollen germination and pollen tube growth,the germination rate was only 4.37%,and the length of pollen tube was 392.21 μm.The promotion of different exogenous substances on pollen germination and pollen tube growth of ’HS’ provides a basis to increase the fruit-setting rate of self-pollination.2.Identifiedthe substances and methods to improve the fruit setting rate of self-pollination of C.oleifera.The effects of big-bud pollination and different exogenous substances such as MeJA,MT,L-NNA,NAC,DCC,azacytidine and tannase on the fruit setting rate of self-pollination in ’HS’ were studied through field-controlled pollination experiments.The results showed that big-bud pollination,5 g·L-1 tannase and 1 000 μmol·L-1 MeJA treatment could effectively improve the fruit setting rate of self-pollination.At 90 days after self-pollination,the fruit-setting rate of big-bud pollination was 18%,5 g·L-1 tannase was 15%,and 1 000 μmol·L-1 MeJA was 14%,all higher-than that in control group(5%).At 180 days after pollination,big-bud pollination did not drop fruit,and 1 000 μmol·L-1 MeJA and 5 g·L-1 tannase were both 10%,while the control group was 3%.From 180 to 360 days,the fruit setting rate of the three treatments remained basically unchanged.In the end,the highest fruit setting rate was big-bud pollination,which is 18%.followed by 5 g·L-1 tannase(10%),1 000 μmol·L-1 MeJA 8%and control group(3%).The observation results of fruit morphology showed that the dynamic changes of fruit transverse and longitudinal diameter,the phenotype of mature fruit and the number of seeds increased significantly compared with the control group.3.The cytological characteristics of self-pollinated pollen tubes in response to exogenous substances.The effects of big-bud pollination,5 g·L-1 tannase and 1000 μmol·L-1 MeJA on the growth pattern,ovule penetration and double fertilization of self-pollinated pollen tubes were observed by fluorescence observation and paraffin section method,and the field experiment was further verified from the cytological level.The results showed that the growth rates of pollen tubes of three treatments were faster than that of the control at different stages after self-pollination,and the final position of pollen tube growth stagnation was closer to the ovule than that of the control.At 48 hours after self-pollination,the growth of pollen tubes in the control group basically stopped,and a typical self-incompatibility phenotype appeared at the end,but the incompatibility characteristics of pollen tubes in the three treatments were not obvious,and some pollen tubes entered the ovary and reached the ovule.Through a large number of cell sections,it was found that the ovule penetration rate and double fertilization rate of self-pollinated pollen tubes were significantly improved compared with the control.Among them,the ovule penetration rate of single-flower and multi-flower and double fertilization rate were the highest in big-bud pollination,which increased by 3.79%,35.41%and 33.70%respectively compared with the control.To sum up,big-bud pollination,5 g·L-1 tannase and 1 000 μmol·L-1 MeJA can improve the self-pollination fruit-setting rate of C.oleifera ’HS’,and it is possible for the self-pollination pollen tube to alleviate the degree of self-incompatibility in response to different treatments.