THE EFFECT OF SIMULTANEOUS APPLICATION OF ETHEPHON OR 2,4-D ON THE ABSORPTION, TRANSLOCATION AND BIOCHEMICAL ACTION OF ASULAM IN BRACKEN FERN (Pteridium aquilinum (L.) Kuhn)

Abstract

The effects of ethephon and 2,4-D on the absorption, translocation and biochemical action of asulam were examined in field- and pot-grown bracken (Pteridium aquilinum (L.) Kuhn). In pot plants, asulam was observed to translocate basipetally to the rhizome system, greater accumulation being evident in the buds and apices compared to the rhizome per se. Although 2,4-D increased absorption of 14C-asulam, neither 2,4-D nor ethephon significantly affected total basipetal translocation. Ethephon was found to reduce accumulation of 14C-asulam within the target meristematic tissues of the rhizome system; this may account for the reduction in bracken control with asulam (4.40 kg a.i. ha−1) + ethephon (0.33 kg a.i. ha−1) compared to asulam alone (65 and 81% control, respectively). September application of asulam (4.40 kg a.i. ha−1) significantly reduced frond density in the following season. The incorporation of 14C-leucine into protein, and the folate levels were reduced in buds and apices treated with asulam. Simultaneous application of 2,4-D (0.33 kg a.i. ha−1) had no significant effect on the activity of asulam (4.40 kg a.i. ha−1) with respect to frond density and the reduction of folate levels, although there was evidence of antagonism with respect to protein synthesis. Free folate levels in rhizome apices treated with asulam + ethephon were greater than in those treated with asulam alone.Key words: Bracken, asulam, absorption, translocation, biochemical action