Flowering Biology And Pollination Characteristics Of Camellia Gauchowensis Chang

Camellia gauchowensis Chang is one of the most important woody edible oil species endemic in southern China,which is characterized by its tall tree,large fruit and high yield per plant,but its premature flower and fruit drop is serious,and the rate of fruit setting is very low.In recent years,there have been a few reports on the cultivation techniques and fruit characters but the study of reproductive physiology and regulatory mechanism is relatively lacking.Therefore,it is of great theoretical and practical significance to study its flowering biology and pollination characteristics.In this paper,the morphological anatomy,scanning electron microscopy,paraffin section and physiological and biochemical techniques were used to study the flower bud differentiation,flower organ structure,pollen development and pollination physiology of C.gauchowensis.The results as follows:?1?The flower bud differentiation starts from mid May to mid October,which included former differentiation stage,sepal forming stage,petal forming stage,as well as stamen and pistil forming stage,ovary and anther formation stage,and tamen and pistil maturity stage.During the period of flower bud differentiation,the ratio of length to width of flower bud increased slowly,while the moisture content of flower bud was generally decreased slowly,the nutrient content of flower bud fluctuated greatly,and the change trend of different elements was different.?2?C.gauchowensi belonged to late flower type,the initial flowering period of which was from early November to mid November,the whole plantation full-bloom stage was from late November to late December,and the last flowering period is from early January to late January,the whole florescence lasted about 90 to 100 days.The corolla was large,pistil and stamens were equally equal,corolla crowns had the largest coefficient of variation in all traits,the length of style,the height of stamens,and the diameter of stamens had the smallest coefficient of variation.The correlation between the flower organ traits was very significant,among them,the length of the style was negatively correlated with most traits,and most of the correlations between the traits except the length of style were significantly positive correlation.?3?The pollen size of C.gauchowensi was medium,polar axis length was of 44.66⁵4.08?m,and equatorial axis length was of 27.38³4.29?m.The shape of pollen was long spherical,long oval in equatorial view and three lobed circular in polar view,the pollen was tricoiporate grains in normal state.The average number of pollen of single anther was 2 699,and the average number of pollen of single flower was 461 186.?4?The pollen viability rose gradually on the first day of flowering,reaching the maximum on the second day,then gradually decreased.The pollen viability during the first three days was more than 80%,but dropped to 57.07%on the seventh day.The regularity of stigma receptivity was similar to that of pollen viability,increased gradually in the first two days,then gradually decreased,reaching the maximum on the second day,the first four days were the highest period of stigma receptivity.Therefore,the artificial pollination of C.gauchowensi should be carried out within three days after flowering.?5?The contents of total N,P,K,Ca,Mg respectively of pollen were 58.72 g·kg^-1,7.73 g·kg^-1,8.65 g·kg^-1,1.94 g·kg^-1,1.22 g·kg^-1,there was little difference with Cenxi soft branch No.2.The contents of total Zn and total B were significantly different from those of Cenxi soft branch No.2,the total Zn content of C.gauchowensi pollen was 135.93 g·kg^-1,77.35%higher than that of Cenxi soft branch No.2,while the total B content was 2.73g·kg^-1,51.40%less than that of Cenxi soft branch No.2.?6?Low temperature and dry conditions were favorable to the storage of C.gauchowensi pollen.Pollen viability remained over 80%within 60 days under the condition of 4?drying,-20?drying and-80?drying.?7?A small amount of pollen grains germinated on the stigma in 4 hours after self-pollination,after 24 hours the pollen tube grew to a quarter of the style,after 48 hours grew to half of the style,after 60 hours grew to two thirds of the style,the pollen tube arrived at the style base and began to pass through the base in 72 hours.?8?The rate of fruit setting of C.gauchowensi was only 4.2%under natural pollination condition,through manual xenogamy pollination,the rate of fruit setting increased by 2.38 times.In hybrid experiments,the rate of fruit setting of C.gauchowensiבGan 77024'and C.gauchowensiבCenxi soft branch No.2'was 0%,while the rate of fruit setting of C.gauchowensiבGanwu 2'reached 22.0%.