| Poplar is an important economic and ecological value woody plants of dicotyledonous. Black poplar, especially P. deltoides Marshall and P. euramericana, grows fast and is the representation to study height growth. Height growth of one years old seedings occupy an important position in height growth studying of morphogenesis. To investigate the molecular basis of morphogenesis of height growth, and to deternine the materials and sampling strategy of molecular mechanism of heterosis, tests of height growth morphogenesis and heterosis were conducted from the morphology, histology, biochemistry and molecular biology. The results show as follow:By location observation to Lingfeng poplar 1, poplar 347 and N3930, summarized with the following characteristics in the seedling stage: (1) Not all internodes are elongating at certain time during growth season. The number of elongating internode is limited, generally within six internodes. There are different numbers of elongating internode in different seasons. The frequence distribution of elongating internode number follows right-skewness in deltoides and euramericana population, while it approximately follows normal distribution from one to six internodes. The frequence of three to four internodes is the highest. The most numbers of elongating internode are eight. (2) The contribution of internode number and internode length to tree height growth is different in different growth stages. The more internode frequency happens higher, the more height growths faster. Internode number is the most important factor contrast to internode length, and internode number is the most significant morphologic marker close to height. (3) During the whole growing season, height growth of deltoides and euramericana follows'S'shape curve law. There are few reports about the first and the second law. The guiding significance of the first law to sample of tree growth is important. After the second law was discovered, internode number should be regarded as a key factor of poplar conventional breeding, molecular marker-assisted breeding and gene cloning. Application scope and mechanism of the two laws were discussed. Overall, linkages between the cells of tip of the II and IV are relatively compact, the same as to between phloem, cambium, xylem. The cell length is shorter, cells are also smaller. Starting from the inter-section VI, the contact between the epidermis, cortex, phloem, xylem and other tissues are loose, elongation growth tends to stop.The transverse and longitudinal map of the stem tip show that the meristem differentiate leaf and stem. Stem tip is meristematic zone. The boundary of between meristematic zone and elongation zone exist in the first internode. Section VI is divided between the elongation zone and the mature zone, which is the same as observation results.Seen from the results of determination of endogenous IAA, the content of endogenous IAA of apical bud, apical internode and young leaf are all july's content higher than May's content. The increment of July's internodes is higher than May's also. On the surface a positive correlation is conducted between the two. To Lingfeng 1 poplar, its internode number of July is higher than May, the same as height. The content of ABA is like IAA. The internode number increments are different in different developmental stages, which may be related to IAA and ABA content. However, different clones'height are different, which can not be predicted early by content of endogenous IAA or ABA.Gene IAA9 was cloned from Populus nigra by RACE technology, it is 1786bp.By calculating heterosis, (P.×deltoides'zhongzhu 6')×(P.×deltoides'juba') was regarded as the heterosis experimental material to do gene expression profiling test. Meanwhile, height was identified as target trait from the height, diameter, leaf length and leaf width. According to the results of location observation and biospy, it was determined that height growth was closely related to the apical bud and the first internode. Stem tip can be representative of the target traits. It was determined that the best time to sample was middle ten days of July according to the's'curve of height growth morphogenesis.The paper has created a platform for poplar height growth morphogenesis and molecular mechanism of heterosis. Next step will study the endogenous hormone content ratio and height growth, IAA9 gene function and molecular mechanism of heterosis. |
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