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Abscisic Acid Spray on Sunflower Acts Differently under Drought and Irrigation Conditions

Hussain, S., Ma, B.L., Saleem, M.F., Anjum, Shakeel A., Saeed, A., Iqbal, J.
Agronomy journal 2012 v.104 no.3 pp. 561-568
Helianthus annuus, abscisic acid, biomass production, bud initiation, crop yield, developmental stages, drought, environmental factors, field experimentation, flowering, foliar spraying, fruits, irrigation rates, leaf area index, oils
Appropriate use of abscisic acid (ABA), a well-known plant growth regulator, could be beneficial to crop production under certain environmental conditions. A field experiment was conducted in both 2008 and 2009 to determine the appropriate level of ABA and the growth stages at which sunflower (Helianthus annuus L.) are sensitive to exogenous application of ABA. Sunflowers grown in fully irrigated plots or in plots receiving limited irrigation were sprayed with 0, 5, and 10 μM ABA at the bud initiation or early flowering. Growth and yield of sunflower were severely reduced (P < 0.05) by limited irrigation. When irrigation was withheld at the bud initiation, foliar spray of ABA at 5 μM increased (P < 0.05) crop growth rate (6%) and leaf area index (16%) at flowering, and total biomass production (14%), leading to increased achene yield by up to 27% and oil yield by 24%. However, achene and oil yields were often reduced by ABA treatment under drought-free conditions. More improvement of ABA application in growth and yield was observed when drought occurred at bud initiation stage, and when ABA was applied to drought-prone sunflower at 5 μM than at 10 μM concentrations. Our study suggests that timely application of 5 μM ABA could improve sunflower productivity under drought-prone conditions.