The Study Of Rhythmic Change Of Dormant Buds And Regulation Of Secondary Flowering In Autumn Of Early Pear

The genus Pyrus, a member of the Pomoideae of Rosaceae, is native to Europe, Asia, and Africa. It is distributed widely in China. The yield of pear in our country is about 11324kt in 2005, which amounts to 50% of the whole world yield. The industry of pear plays an important role in the rural economy. But the problem of low yield, low quality and low efficiency has not been solved for a long time. In our south, it is hot and dry in autumn and warm in winter, adding poor facilities in most orchards, severe soil erosion, deterioration in soil fertility and worsening of ecological environment in orchards, all of which lead to secondary flowering in autumn and germination of buds after a lot of fallen leaves in early pear orchards. Secondary flowers in autumn can bear a few fruits but they stop growing gradually as the temperature during October and November decreases, then they drop and lose economical value. The harm of secondary flowering in autumn is so extensive that in our south almost all product areas of early pear with low-altitude have this phenomenon. At present research on this topic is still in perceptual stage and research on efficient control is almost blank. Focusing on factors influencing secondary flowering in autumn of early pear, this paper has done some experiments as follows.Part 1 Study on dormancy - inducing process of buds of early pearThis experiment has studied the rate of germination of branches during different dormant periods, fresh weight of mixed buds, chlorophyll content, water content, dissolvable protein content and total phenol content, and the change of cell cycle by means of field sampling.The results show that from late September to middle November, the rate of germination, the proportion of cells in G2/M, water content decrease gradually and fresh weight of mixed buds increases slowly and dissolvable protein content and total phenol content increase. From middle November to middle and late January, which is midterm of dormancy, these indexes are stable. But from middle and late January to the end of February the change pattern of these indexes is reverse.From the results above we can infer that from late September to middle November, which is the earlier stage of dormancy of early pear, the buds are active; from middle November to middle and late January, the midterm of dormancy, the buds are in real dormancy; and from middle and late January to the end of February, the later stage of dormancy, the buds restore; activity.Part 2 The effect of photoperiod on the dormancy induction of early pearThe experiment of photoperiod demonstrates that there is no significant difference between the effect of 11-hour illumination and the effect of 14-hour illumination on the break of dormancy of early pear, which shows that induction or release of dormant buds is not sensitive to photoperiod too.Part 3 The effect of temperature on the dormancy induction of early pearThis experiment has studied the effect of culturing branches in different temperature indoors on dormancy of early pear.The results show that the speed and rate of germination decrease obviously as the culture temperature lowers. When it is 15℃±1℃, the rate of germination reduces to zero, which shows that 15℃±1℃is the critical temperature of inducing buds of early pear into dormancy, at the same time fresh weight of mixed buds and chlorophyll content increase evidently slowly. With the decrease of temperature, the number of cells in G2/M of mixed buds is inclined to reduce, which proves in reality the number of cells in division lowers. And also the transition of stage S to stage G2/M is inhibited.Part 4 The effect of hormone on the dormancy induction of early pear indoorsWith off-stem bearing branches of early pear as experimental material, this experiment studied the factors influencing dormant process of buds of early pear.The results find that in 25℃both Ethephon of 0.04% and 0.08% and ABA of 0.1mg/L and 0.3mg/L can inhibit germination during a certain period of time. IAA of 0.3mg/L can induce germination while IAA of 0.6mg/L and GA3 haven no significant effect.Part 5 The effect of growth modulator on the rate of secondary flowering in autumn of early pear in the fieldThis experiment studied the effect of spraying different kind and different concentration of growth modulators on control of secondary flowering in autumn of early pear in the field.The results demonstrate that in contrast with the control all the other treatments can control secondary flowering in autumn significantly except ABA of 1.0mg/L. Ethephon and chlormequat chloride(CCC) have a better effect, among which Ethephon of 0.04% and CCC of 0.1% have the best effect.Part 6 The effect of cover on fallen leaves and the rate of secondary flowering in autumn of early pear in the fieldThis experiment studied the effect of cover on control of secondary flowering in autumn of early pear in the field.The results show that cover increases water content in 20cm-deep soil layer and the deeper the soil layer the better the water-containing. Cover lowers the temperature in the earth's surface and in 20cm-deep soil layer, can reduce fallen leaves in autumn and can decrease the proportion of cells in G2/M significantly. Water content of mixed buds in cover treatment 1 is less than that in cover treatment 2 and the control. Cover treatment 1 can decrease the rate of leaf buds, the rate of flower buds and the rate of total germination significantly.