Differential responses of sunflower (Helianthus annuus cv. Modern) towards high and low concentrations of dikegulac sodium

Abstract

In pot experiments, foliar application of dikegulac sodium (2,3:4-6-di-O-isopropylidene-α-L-xylo-2-hexalofuranosate) at 500 and 750 μg/mL inhibited plant growth and decreased growth and dry matter production of the treated leaves of sunflower (Helianthus annuus L. cv. Modern). A concentration of 100 μg/mL, however, increased leaf area and anabolic activities of treated leaves. Increased cambial activity was noted at all concentrations of dikegulac, which resulted in formation of secondary tissues. At 500 and 750 μg/mL RNase and protease activities increased appreciably, while catalase activity was drastically suppressed. The inhibitory effect of dikegulac was also found in newly expanding leaves which developed after treatment. Beneficial effects of dikegulac at low concentration were also reflected in field experiments where increased yield was noted, while high concentrations were distinctly inhibitory. The importance of dikegulac as an agronomically promising chemical for sunflower is discussed.