The Effect Of Growth Regulators On Flowering And Freezing Resistancein Dangshan Su Pear

Many high quality pear producing areas often suffer from late frost, it easily lead to flower bud abscission?pollen cannot crack normally?fruit malformation and some places may absolutely failed,causing great economic losses to pear farmers.This study use Dangshansu pear the largest cultivation as material to explore the effects of GA₃ treatment during the flower bud differentiation and GA₃?NAA?humic acid treatment during the blooming phenophase on internal morphological characteristics and nuitrients conent. Flowers and young fruit during different period were treated at artificial climate chamber for imitating cold wave to study the changes of physiological and biochemical indexs and floral organ morphology. Effects of different auxins on the fruit quality.Those all provide ideas and practical basis for frost hazard.The main results are as follows.?1? Flower bud morphological differentiation began at mid-to-late June and lasted to late August, the overlap of different stages in Dangshan su pear is obvious. Stage of floral primordia begin at mid-July; sepal formed in late-July; stamen formed lasted about one month and formed in mid-August. Gibberellin inhabited the flower bud differentiation, but it had no effect on the period.?2? In the whole process of flower bud differentiation, GA₃ treatments are similar to CK. on content of nuitrient. GA₃ was helpful to improve the content of soluble sugar and soluble protein in the early stage of differentiation, it reduced soluble sugar and soluble protein content from flower bud differentiation phase to petal differentiation phase and stamen differentiation phase to the end of differentiation respectively. During the whole process of bud differentiation, GA₃ treatment decreased the content of free amion acid. The fructose and sucrose content of 50mg/L GA₃ were the lowest among all the treatment in the late stage. The same content of 150mg/L GA₃ were the highest during the formation of stamen to the end of differentiation. 100mg/L GA₃ starch content was lowest during the formation of petal to pistil.150mg/L GA₃ starch content was highest during the formation of pistil.?3? In late March next year, flower buds begin to swell, and then experienced cluster bud, bulb bloom entry first open bloom stages, the flowering phenology of Dangshan su pear ended in mid-April. The gap between first open bloom and half open bloom is short,usually 1-3 days.The growth and development of fruit was mainly after petals fall off. The flower phenophase of GA₃?NAA?humic acid and CK were similar.?4? The frost resistant ability is the strongest during the bulb bud period, and the half open bloom is the weakest.-2? lasted for 2 hours,flower organs have no obvious effects;-4? lasted for 2 hours, the petals have no damage symptom, profile shows that inner ovary has all black;-6? lasted for 2 hours, the whole flower become dark brown. Young fruits are more vulnerable to frostbite than petals.0? lasted for 2 hours has no obvious effects;-1? lasted for 2 hours, fruits become hygrophanous and black core;-2? lasted for 2 hours, fruit shrinked and black.?5? GA₃ could increase the activity of SOD^ POD during bulb bud and first open bloom and decrease the ratio of injury in two weeks after full bloom, it also could lower the content of MDA during bulb bud and one week after full bloom. NAA contributed to the stability of POD, and reduced the ratio of injury during first open bloom and half open bloom. Humic acid had the same effects to GA₃ on MDA. The four treatment all had no obvious effect on the content of proline.