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- Author or Editor: T. T. Kozlowski x
Each of 8 antitranspirants reduced transpiration of 2 species of woody plants. Dow Silicone and CS 6432 were the most effective compounds on Fraxinus americana and Dow Silicone was effective on Pinus resinosa. Keykote, Folicote and Improved Wilt Pruf showed an increased effect on plant water loss and net photosynthesis (measured by net CO2 uptake) of P. resinosa up to 8 days after compound application. Thereafter there was no significant change in the effect of any compound on transpiration or photosynthesis. Effects on F. americana of all compounds except Improved Wilt Pruf decreased with time after application. Scanning electron micrographs of treated leaves suggested that antitranspirant films on F. americana leaves cracked over the guard cell pore, accounting for the decrease in compound effect with time. Antitranspirants apparently reduced water loss of P. resinosa by combining with wax in the stomatal pore and forming an impermeable plug. The compounds tested were toxic to F. americana seedlings and photosynthesis of treated plants decreased with time, even when direct physical effect of a compound had worn off. Pinus resinosa seedlings showed no decrease in photosynthesis with time. F. americana plants treated with Keykote exhibited low rates of water loss and transpiration/photosynthesis ratios that were not significantly different from those of control plants. Folicote was toxic, and Clear Spray increased water loss of F. americana seedlings. Dow Silicone reduced water loss of Pinus seedlings by about 80%, and plants treated with Dow Silicone, Improved Wilt Pruf, Keykote, or Folicote had favorable transpiration/photosynthesis ratios. The effects of antitranspirants on transpiration and photosynthesis were greatly influenced by environmental regimes and by species.
The effects of various combinations of naphthaleneacetic acid (NAA), gibberellic acid (GA), and benzyladenine (BA) at 5 or 50 ppm of each and temperature (22 and 25°C) on root initiation in Salix viminalis, L. cuttings were studied. Highly significant influences of temperature, exogenous growth regulators, and temperature-growth regulator interactions on root initiation were demonstrated. Root formation generally was stimulated by increasing temperature from 22 to 25°. NAA stimulated root formation markedly and its effects were further enhanced for at least 10 days by increasing temperature from 22 to 25°. In contrast to NAA, both GA and BA inhibited root initiation. The inhibitory effect of GA was greater at 25 than at 22°; BA had the greater depressive effect at 22°. Addition of GA or BA, or both, to NAA generally reduced the stimulation of root formation by NAA. As temperature increased toward an optimum for root initiation the balance of endogenous growth regulators and possible cofactors may have changed to bring out the stimulatory effects of auxins over the inhibitory influences of cytokinins and gibberellins.