| In this study, two experiments were conducted. In the first experiment, water levels and paclobutrazol were applied to 'Royal Gala' apple on M.9 rootstock. The three water levels were drought, normal, and flooded. Four levels of paclobutrazol as a foliar spray were 0, 125, 250, 500 ppm. Paclobutrazol was also applied as a drench at 50 and 100 mg a.i. per plant. In the second experiment, paclobutrazol was foliar applied at 0, 125, and 250 ppm while ABA was applied at 50 and 100 {dollar}mu{dollar}M, and proline at 50 and 100 mM. In both experiments, the experimental design was a split plot where water levels were the main plots and chemical concentrations were the subplots. There was no interaction between water levels and chemical concentrations in both experiments. On the average of the first experiment, water levels influenced plant water potential and proline accumulation in the plant. Both drought and flooded water levels reduced plant water potential. Proline was increased by flooding compared to the control (normal water level). Paclobutrazol influenced plant water potential. Since diffusive resistance increased and transpiration rate decreased, it seems that plant tolerance to drought or flooding may also be dependent on plant water potential, diffusive resistance, and transpiration rate. In the second experiment, flooding increased shoot water potential, proline accumulation, and diffusive resistance but reduced transpiration rate. Tolerance of plants to drought or flooding may be dependent not only on plant water potential, but also on proline accumulation, diffusive resistance, and transpiration rate during water stress. |
