ABSTRACT
The effect of foliar application of plant growth retardants N, N, N-trimethyl-l-methyl-3-(2′ 6′,6′-trimethyl-2′-cyclohexen-r-yl)-2-propenylammonium-iodide (TMPAI), 2-chloroethyl trimethylammonium chloride (CCC), B-9, and PP333, alone or in combination with the surfactant Agral 90, on the physiology of rice seedlings was investigated. Spraying of aqueous solutions of 300 ppm TMPAI, 500 ppm CCC, 500 ppm B-9, 30 ppm PP333, or 0.4% Agral 90 alone was ineffective in reducing plant height of rice seedlings, but each of these plant growth retardants mixed with Agral 90 significantly reduced plant height. The enhancement of the activity of the growth retardants by Agral 90 may result from solubilizing the epicuticular wax by the surfactant, thus the plant growth retardants readily penetrated into the leaf tissue. In comparison with foliar application of TMPAI or Agral 90 alone, the mixture of both promoted an accumulation of P2O5 and 32P, increased the stomatal resistance, but decreased the photosynthetic rate.
