Studies On The Biological Characteristics Of Sweet Cherry In Shanghai And The Effect Of Hygrogen Cyanamide On Dormancy Breaking

In this thesis, we studied the growth characters and flower differentiation process of sweet cherry in Shanghai and determined the chilling requirement and photosynthetic characters of some varieties. Then, the best method for break sweet cherry dormancy was chosen. The theory how the HC （Hygrogen Cyanamide ） was working and the effect of HC on the growth, fruit quality and flower organ was investigated, too. The results were indicated as follows:1. Sweet cherries cultured in Shanghai had earlier phenological stages and longer flowering duration compared with those cultured in Yantai. The fruit developing period of‘Hongdeng’and‘Van’in Yantai reached 38d and 51d, respectively,which were only 29d and 45d in Shanghai. Results showed that the proportion of normal flower organ was lower, ratio of malformed flower was more popular, fruit set percentage was lower. Sweet cherries cultured in Shanghai achieved earlier germination followed by longer flowering stage and shorter fruit developing stage. Meanwhile, the shoots were longer than those cultured in Yantai, resulting in higher proportion of water shoot and lower proportion of spur. The trunk coarseness, tree height and crown diameter of five-year-old‘Hongdeng’were 14.2cm, 435cm and 450cm, respectively, all significantly more than those cultured in Yantai. The process of flower buds differentiation was observed by paraffin section. Results showed that the flower buds differentiation in Shanghai earlier than that cultured in Yantai. However,the differentiation rate slowed down after July 15. The flower buds differentiation completed later than of sweet cherries cultured in Yantai. There was a delay of one month. For sweet cherry cultured in shanghai, there seemed to be a competitive relationship between the flower buds differentiation and shoot elongation. The photosynthetic characteristics of leaves were studied in four sweet cherry varieties in Shanghai. The results showed that the Chl concentration of Brooks and Summit were higher than Labins and Van. There was no interrelation between Pn and Chl in the four cultivars. Labins and Van had higher stomata density but smaller stomata size. The light saturation point of different cultivars was 800μmol·m^-2·s^-1, and the light compensation point of Labins only was 11.7μmol·m^-2·s^-1. Although Brooks had photo inhibition, it had a high utilization ratio to weak light and low concentration CO2, exhibiting some characters of shade plants. The most suitable cultivar for rainy regions was Brooks.2. The chilling requirement of thirty varieties of sweet cherry was determined. There was nine varieties’chilling requirement below 900 hours. The primary energy storage form was sorbitol. The content of sorbitol and starch was decreased with the chilling treatment, while the content of glucose and fructose and the ratio of Protein-N/ noprotein-N were increased.3. Application of HC a month before bud break usually increased the date of bud break and shortened the lasting time of flowering 2-4 days. The ratio of normal ovary was increased to 58% and the fruit set ratio reached to 18.8% with the HC treated. The fruit development period was shortened by application of HC, and the maturity was advanced. Sugar acid ratio of Van’s fruit was increased significantly by treated trees.4. Application of HC accelerated the development of male gamete and advanced the disaggregation of tapetum and the tetrad was formed earlier after meiosis. HC hasten the free pollen grain formation. In Shanghai, the archesporial cell of untreated ovary was appeared on 26th March, while the HC application advanced the date of the archesporial cell formed. These could make the ovary avoid the hurt of high temperature. The corresponding phenological stages of sweet cherry in Shanghai was 3 days before full blooming while the mature embryo sac was formed completely.5. Application of HC led to a significant increase in H₂O₂ and inactivated catalase. The dynamic of POD was likely to H₂O₂. The elevation of H₂O₂ perhaps was one of the reasons to break the sweet cherry dormancy. The content of Pro in phloem was increased and the starch hydrolyzed quickly after the HC application. The decrease of sorbitol and the rise of glucose and fructose indicated the resume of metabolism. The rise of glucose and fructose was finished after bud break then decreased soon, these indicated that there was hexose transport between the phloem and meristem. Application of HC advanced the date of amino acid increasing. There was a contrary trend between the content of amino acid and protein, mean while it is the time that dormancy breaking. The results presented here suggest that change of amino acid and protein in sweet cherry phloem be a good indicator of their dormant state.