| Summary: | 碩士 === 中興大學 === 園藝學系所 === 95 === The objective of this study was to find a chemical compound to substitute fenitrothion as the flower advancing agent of wax apple trees. Fenitrothion, classified as an organophosphate pesticide, has been used to advance blooming for some time. Due to its negative side effects on farmers’ health and ecological concern, searching for a new agent as a replacement has become necessary. Various reports indicated that KH2PO4 has been effective in the post-harvest defoliation, and played a role in flower initiation. Thus experiment has been designed to test the possibility of replacing fenitrothion with KH2PO4 in the advancing flower of wax-apple.
By dipping a wax-apple branch in KH2PO4 solution in stem-feeding system, leaves showed signs of abscission and water soaking. The tendency was similar to those treated with ethrel or fenitrothion. Samples treated with KH2PO4, ethrel and fenitrothion were analyzed for their potassium and phosphate contents. KH2PO4 treated had the highest phosphate concentration. Ethylene production was also proportional to the concentration of KH2PO4. Ethylene peaked on the third day after the treatment of 100 mM KH2PO4 and abscission started on the seventh day.
Leaf disc experiments were conducted to determine the ethylene production and CO2 release. Wax-apple leaf-dises treated with KH2PO4 or NaH2PO4 showed that the rate of ethylene release was proportional to the concentration of either compound, though KH2PO4 treated was superior. There was no response in KCl treated disc. This result demonstrated that phosphate was the major factor for inducing ethylene production. Mannitol solution was used as a buffer and no effect on the KH2PO4-induced ethylene production. The leaf discs of releasing rate of ethylene is influenced by light intensity. Effect the ethylene production apparently under high light intensity, as the intensity reduces the releasing rate of ethylene to reduce.
Adding inhibitors AVG, CHI, 1-MCP separately to KH2PO4-treated leaf discs, ethylene production was significantly reduced by AVG and CHI, and not affected by 1-MCP. But inhibition took effect when AVG or CHI was added to the1-MCP treated sample. This seemed to explain that the biosynthesis of ethylene induced by KH2PO4 was similar to the general pathway of ethylene synthesis in the plant.
In field experiments both fenitrothion and KH2PO4 caused a change in carbohydrate concentration and a faster flowering was induced by KH2PO4. After evocation activated by fenitrothion or KH2PO4, chlorophyll and chlorophyll flurometric parameter (Fv/Fm) increased gradually. Wax-apple evocation often limited by climatic conditions but the post-harvest fruit qualities were not affected by either chemical treatment.
According to the results of this study, it shows that KH2PO4 can be a wax-apple flower advancing agent instead of fenitrothion in the field application.
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