Study On The Role Of Ethylene And NO In The Removal Of Leaves

By means of pharmacological approach, laser-scanning confocal microscopy and gas chromatographic technique, the roles and the relationship of ethylene, a plant hormone, and NO, a new signal molecule, in the abscission of pulvinus explants in Phaseolus vulgaris L. were studied. The main results are as follows:1. Ethylene synthesis inhibitors aminooxyacetic acid (AOA) and cobalt chloride (CoCl2), and ethylene action inhibitors silver nitrate (AgNO3) and sodium diethyldithiocarbamate (DDC), significantly inhibited the abscission, and their effects on the abscission were dose-dependent. The optimal concentration of AOA, COCl2, AgNO3and DDC was40μM,4mM,10μM and20μM, respectively. AOA largely prevented ethylene release in the explants, but AgNO3did not. These data clearly indicate that ethylene regulated the abscission of pulvinus explants in Phaseolus vulgaris L.2. Sodium tungstate dehydrate (Na2WO4), an inhibitor of nitrate reductase, NG-nitro-L-arg-methylester (L-NAME), an inhibitor of NO synthase in mammalian cells and2-(4-Carboxyphenyl)-4,4,5,5-tetramethylimidazoline-l-oxyl-3-oxide (c-PTIO), a scavenger of NO, obviously inhibited the abscission of the explants and NO production. The effects of Na2WO4, L-NAME and c-PTIO on the abscission were also dose-dependent, their optimal concentration was150μM,2mM and150μM, respectively. The results not only show that NO plays an important role in the regulation of the abscission, but also suggest that both nitrate reductase and NO synthase are responsible for NO synthesis in the abscission of pulvinus explants in Phaseolus vulgaris L.3. Na2WO4, L-NAME and c-PTIO largely prevented ethrel-induced the abscission, but did not affect ethylene synthesis in the explants. AOA, CoCl2, AgNO3and DDC did not depress SNP-led the abscission, but obviously inhibited NO generation in the explants. The data indicates that ethylene regulates the abscission of pulvinus explants in Phaseolus vulgaris L. via inducing NO production.