Studies Of High Temperature On Floral Organs Development And Underlying Mechanisms In Protected Cultivation Of Sweet Cherry (Prunus Avium L.)

The research was conducted with 4-year-old protected and 7-year-old protected sweet cherry (Prunus avium L.'Hongdeng') in Shandong Agricultural University during the year of 2008 to 2010. Effects of short time high temperature stress, different increasing rate of temperature and dormancy process on pistils'and stamens'development of protected sweet cherry were studied. And the effects of dormancy process on nutrient contents of flower buds and surrounding tissues of protected sweet cherry were analyzed and physiological mechanism of floral organ's development which effected by high temperature was discussed. The main results are as follows:(1) The promoting effect on flowering of protected sweet cherry was more obvious when the processing time of high temperature was closer to flowering at the period of early spring; And the promoting effect on flowering wasn't obvious when the processing time of high temperature was earlier, however, it can shorten the flowering. The high temperature during pollen mother cell's meiosis stage treatment made the flowering shorter 5 days than contrast; The high temperature treatment made the flowering 7 days earlier than contrast of uninucleate stage.(2) The influences of high temperature treated at different early spring stages on the positions and degree on pistils, stamens and floral organ's development during flowering were different. More abnormal tetrads generated after 4 hours of 35℃treatment during meiosis, which was 14 times of contrast and the production of mature pollen was 7 days earlier than the contrast. However, the microspores began to degenerate in the following time and the remaining pollens were not able to germinate. The development of spores were promoted by 4 hours of 35℃treatment during karyokinesis both in mononuclear microspore stage and mononuclear microspore stage, however, that could make some microspores disappeared. More anthers were found turning brown and shriveling, with low gemination rates of pollens. And the final pollen germinations were 0,11% and 38.9% after high temperature processing, however, the contrast was 70.8%. The influences to megaspore development and normal embryo sac formation were not obvious after short time of high temperature stress during the period of pistil development, and the rates of blasted pistil were 1.4,2.2 and 3.9 times of contrast respectively as well as the rates of curled corolla were 8.5, 12.2 and 17.9 times of contrast respectively.(3) The effects of increasing rate of temperature on germination rate, pistil development and flowering of protected sweet cherry were little at the range of daytime temperature of 12℃-18℃, however, the slower increasing rate of temperature allows the flower opening consistent and tidy. Stamens were more sensitive than the pistils to the increasing rate of temperature, and the faster the increasing rate of temperature the faster the development of stamens, however, there was little influence on the process of pistil development.(4) The pistils and stamens could not develop normally even the appropriate cultivated conditions were gaven if the protected sweet cherry haven't met the normal dormancy. The pistils and stamens were still in the original ungerminated state from beginning to end after cultivation of sweet cherries which were in the shallow dormancy period. After 42 days cultivation of sweet cherry which were in the deep dormancy period, there were 56.8% of microspores of anthers still in the stage of microspore mother cell,16.7% in the stage of tetrad and 26.5% of anthers had produced mononuclear microspore, but only 16% of the pistils have been divided out of the nucellus and integument. After 28 days cultivation of sweet cherries which dormancy has been broken, mature pollen would to be produced and 95% of the pistils had completed the differentiation of ovule and embryo sac after 42 days treatment.(5) The squama of floral bud were more sensitive to environmental changes than any other part and could achieve active state quickly. The inharmony of high activity of amylase in squama of floral bud and the continued decreases of amylase in other parts was one of the reasons that floral bud failed to bloom in the stage of deep dormancy. Otherwise, the increasing of soluble protein content in flower buds and surrounding tissues in the flower buds budding period and the high activity of amylase were favor to flower bud germination and the normal germination of flower bud needed to make good use of starch, sugar and soluble protein in bud scales and growing point. The facilities cultivated environment might be kind of stress that prompted the content of free amino acids to increase and the flower buds could genninat natulally only if the content of free amino acids increased in each part after normal dormancy. The transformation of starch to soluble sugar in buds growing point, the degradation of starch in flower buds cushion and bark, and the transportation of products into growing point were important for flower buds germination.