Anatomical Study On Stone Cell And Preliminary Analysis Of Synthesis Pathway Of Lignin In Pyrus Bretschneideri Cv.

Pyrus bretschneideri cv. is one of the export pears in China. However, it affected the quality of Pyrus bretschneideri cv. that stone cell content increased, taste more than java and flesh became coarse as a result of variety degradation or mismanagement in recent years. Therefore, this experiment studied the development of stone cells, understanding the relationship between the development of stone cell and parenchyma; explore the metabolism of lignin on the forming of stone cells; and preliminary study the path of lignin metabolism in Pyrus bretschneideri cv.. Designed to investigate the mechanism of stone cells, in order to provide theoretical basis for controlling the forming of stone cells, understanding the relationship between the forming of stone cells and lignin metabolism, and provide the ways for studying lignin metabolism farther of pear. Key findings are as follows.1 Unequal thickness of fruit parenchyma cells'wall forms thick wall cell, thick wall cells developed to stone cell through cell wall re-thickness in pear. Stone cell formed through thickening of secondary wall of parenchyma. Part of unequal thickness wall was dyed red by Safranine. The thickness began at took place in the cell, and than extended to the entire cell wall.2 The forming of stone cell mostly started at DPA15 and it commenced largely within a week. The stone cells gathered and emerged at DPA23 and the diameter of stone cell group enlarges. The max diameter of stone cell group came forth at 67DPA. At the same time, the Parenchyma cells grew and enlarged with two different methods, strip and ellipsoid. The content of stone cell increased firstly, and then descended during pear fruit development. The max content of stone cell came forth at 51DPA(18.95%). Some of the parenchyma could develop into stone cells, the others would expand and maturate. The content of stone cell was determined the forming of stone cell and the expansion of parenchyma cells during fruit development.3 Synthesis of lignin affected the forming of stone cell. The content of stone cell and lignin was significant correlation during development of pear fruit, correlation coefficient R2=0.9847. The activity of ammonia-lyase, peroxidase, polyphenol oxidase are all relatively high during the forming of stone cell in pear fruit. And then the activity of PAL, POD, PPO were relatively low. PAL, POD, PPO affected the forming of stone cell and synthesis of lignin in pear. But the distribution of stone cell is related to the degree of division as expanding of parenchyma..4 The experiment detected the cinnamic acid and P-coumalic acid in pear fruit of development. Cinnamic acid is the product of Benzene propane metabolic and starting substance of metabolic pathway-specific of lignin. P-coumaric is the important branch of pathway-specific of lignin and translated from cinnmic acid. Therefore, the synthesis of lignin may be through p-cumaric acid into the lignin-specific pathway in pear fruit.5 The content of stone cell and lignin was positive correlation in five different genotype pear fruit- Pyrus bretschneideri cv, Gong pear, Fung pear, Korla fragrant pear and apple-pear. The parts of high stone cell content have high lignin content also. It is unclear of the relationship between the content of stone cell and the activity of PAL, POD, PPO in different genotypes pear.