The Preliminary Investigation On The Mechanism Of Contents Breakdown In Garlic Scape Parenchyma Cells In Course Of Senescence

Base on our previous works in morphology level and speculated the wither process of garlic bulb belonged to PCD. In this study, the DNA in the parenchyma cells(PC) of garlic was analyzed using the agarose electrophoresis to certify the PCD process from biochemical level. Acid Phosphatase(APase) and Adenosine Triphosphatase(ATPase) were also localized by cytochemical method; the ultrustructure of plasmodestama (PD) was researched by the transmission electron microscope(TEM).We want to investigate the withdrawing mechanism of cell contents.Here we can see clearly that the DNA of PC during dormancy period was not degraded and the DNA during releasing dormancy was specialized disassembled by DNAase. Results showed the typical DNA ladder appeared on the gel and became clear with the development and growth. This result provides a good evidence for PCD from biochemical level and contributes to the study of breakdown mechanism.The distribution of APase and ATPase activity in PC of garlic during germination were studied using the lead precipitation method and the two kinds of enzymes activitiy enhanced greatly with the growth of the new bud. APase was localized slightly in the primary pit field during the mature period, but the precipitation was not rich. ATPase was slightly localized in plasma membrane (PM), nucleus(N) and pit field too. As the new bud started to growth, the contents transported out of the PC, and the enzyme activity enhanced with the enhanced metabolism, some contents with APase activity or ATPase activity appeared in the intercellular space(IS). Enzymes activity were highest in IS and PD during the germination period. These results indicated that the APase and ATPase activities have apparently dynamic change. These results proved that the wither of PC was a active, orderly, energy-depended process and suggested that the degradation, transformation and export contributed to contents complete transportation. PD which lies in the cell wall between living and dead cell underwent dynamic changes during the plant development. The length of PD expanded, ruptured, and it developed to be ectodesmata-like at the germination period. This structure assured the successful, complete transportation of contents which make contributions to the new bud growth. The result proved that the appearance of ectodesmata-like is the functional need during the development of plants.Combine with the above results, we speculated that the cell contents were hydrolyzed...