EFFECT OF 2-(3,4-DICHLOROPHENOXY)TRIETHYLAMINE (DCPTA) ON THE GROWTH AND DEVELOPMENT OF SUGAR-BEET

Foliar application of 2-(3,4-dichlorophenoxy)triethylamine (DCPTA) significantly increased the taproot development, leaf development, and the photosynthetic productivity of sugarbeet (Beta vulgaris L. cv. 811X-S). Photosynthate partitioning in DCPTA-treated sugarbeet plants appeared to be balanced between the demands of plant growth and taproot sucrose accumulation. When compared to controls, the increased taproot fresh weight of 30 μM DCPTA-treated taproots at 88 days after treatment was statistically significant (P < 0.01), and the percentage sucrose content was maintained resulting in an 81% increase in sucrose yield per taproot. Chloroplasts isolated from mature leaves of 30 μM DCPTA-treated plants, as compared with that of controls, showed a 23% increase in the total soluble protein to chlorophyll ratio that parallel an observed increase in activated ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity in vitro per unit chlorophyll. The total activated Rubisco activity per dm2 leaf area of 30 μM DCPTA-treated plants was increased 87% when compared to the value of controls. Increased Rubisco activity largely accounted for the observed increase in net photosynthesis in DCPTA-treated plants. However, intense sink demand for photosynthate and the delayed leaf senescence of older leaves may increase net-carbon assimilation in mature (source) leaves of DCPTA-treated plants. © 1990.