Effect of 2,4-Dichlorophenoxyacetic Acid on the Water Relations, the Accumulation and Distribution of Solid Matter, and the Respiration of Bean Plants

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Abstract
Bean (Phaseolus vulgaris) seedlings were sprayed with concentrations of 2,4-dichlorophenoxyacetic acid mixed with Carbowax 1500 as a dispersing agent to determine the toxic effects associated with some of the physiol. responses induced by the acid. Plants sprayed with a 1000 ppm. conc, of the acid were permanently wilted in 5 days and dead in 7 days. During 5 days after treatment the total water transpired was 34% less than that of untreated plants. Water uptake was not immediately limited in treated plants. Leaf growth was markedly inhibited even when sprayed with a conc, of 25 ppm. of the acid. A high conc, of the acid (1000 ppm.) caused a marked decrease in solid matter of the above-ground parts, while lower conc, induced increased accumulation of solid matter in the lower stem regions. The rate of accumulation of water in leaves of sprayed plants was depressed, while in stem tissues it was accelerated. Treated plants had higher % moisture than untreated ones. Respiration of entire plants under 3 temp. conditions was accelerated as much as 40% within 24 hrs. after spraying.