| Swida Cornus wilsonian (Wanger.) Sojak is a kind of deciduous arbors or shrub belonging to Cornaceae,whose height is 5-18 m and diameter may reach 55 cm.The bark is purple or greyish white with green,which is smooth and maculosus abscission.Its crown is umbrella shape,the leaves are oblong,and its inflorescence is cyme with small white flower.The mature drupes of Swida wilsoniana are sphere with black pericarp,and the seeds are yellowish Swida wilsoniana mainly distributed south of the Huanghe River valley, particularly in these provinces such as Hunan,Jiangxi,Hubei.Its vertical distribution is below elevation 1000 m. Swida wilsoniana is a heliophilous plant which has a strong Suitability to different soil.And Swida wilsoniana is also one kind of oil plant with extensive ecological adaptability. Oil of the fruit and seed richening with oleic acid and linoleic acid was an ideal raw material for producing bio-diesel. Because of its suitable in infertile arid hill mountainous region and non-farming land,it is one of the bio-energy plants with great developing potentiality In recent years the State Government has been supporting the extensive cultivation,process and utilization of this tree species.In this paper researches on floral differentiation of Swida wilsoniana was carried out at forest experimental farm of Hunan Academy of Forestry which located at Shi Gongpo,Changsha city.In the experiment,4-year old grafted,vigorous and healthy adult plants were selected as the research target. All the selected plants were the same variety, and had similar size,located at the same site conditions.Terminal bud and the axial bud from blossom and blossomless plants were collected separately from the selected plants to investigate their morphological and anatomic structures by using conventional wax slicing method,and direct field observations;Meanwhile tender leaves from one year branches of the same plants as buds were collected to analyze the endogenous hormones contents by means of indirect enzyme-linked immunosorbent assay;Also carbohydrate content in the leaves was determined by means of Phenol-sulfuric acid Method. It's the first time to study the flower buds differentiation and development of Swida wilsoniana,and to analyze the correlation between the flower differentiation and endogenous hormones and carbohydrate. The experimental results showed as followings:1. Flower bud differentiation occurred both at terminal buds and axiliary buds. Under the climate conditions of Central part of Hunan Province,the flower bud differentiation started at late February and ended around the end of April. The whole process of flower bud differentiation might be divided into five stages,including pre-differentiation, Inflorescence differentiation,Sepal differentiation,Petal differentiation and Stamens and pistils differentiation stage.2. There was a great difference in content change of endogenous hormones between flowering plants and non-flowering plants of Swida wilsoniana. During floral bud differentiation, IAA and GA3 were at relatively low and steady level,ABA was at a higher level with fluctuation change,ZR firstly was at a relatively low level and increased gradually along with the development of flower. Meanwhile,for the non-flowering plants, both IAA and ZR contents changed as increased and decresased,then increased and decreased again,ABA increased at initial time and then decreased gradually;GA3 firstly increased and then decreased.As to the absolute contents of the four kinds of endogenous hormone,the average content of IAA was obviously lower than that of the other three kinds of endogenous hormone which were analyzed. Of the analized endogene hormones,the average content of ABA was higher,and its change fluctuation was quite large.It's suggested that the dynamic changes of endogenous were related with the flowering process.3. The content of carbohydrate increased unceasingly along with the differentiation of flower bud, and it was higher than that during the earlier stage of flower bud differentiation, which suggested that the accumulation of carbohydrate was advantageous to the differentiation of flower bud.4. Changes of endogene hormone in the flower bud differentiation process of Swida wilsoniana indicated that:Changes of ABA/ GA3 and ZR/IAA were very similar, whose content were stable; the ABA /IAA and ABA /GA3 content were at the low levels during the floral initiation period, then increased gradually during flower bud morphological differentiation, and decreased gradually during the pistil and stamen formation period. Those suggested that the high level of ABA /IAA was advantageous to the morphological differentiation of flower bud, while the low level of ZR /GA3 was advantageous to flower bud initiation. |
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