Effects of gibberellic acid and prohexadione-calcium on growth, chlorophyll fluorescence and quality of okra plant

Abstract

The experiment was conducted to identify the response of three cultivars of okra [Abelmoschus esculentus (L.) Moench] to exogenous hormones [gibberellic acid-(GA3) and prohexadione-Ca] applied as foliar spray. Stem and leaf dry masses and stem length were significantly enhanced by the application of exogenous GA3, but prohexadione-Ca inhibited growth. Control and prohexadione-Ca treated okra plants took more time to bloom than did GA 3 treated plants. In the fruits of all the cultivars a decrease in fructose content was observed, while protein content remained almost unchanged after the application of the two growth regulators. The small changes in chlorophyll a fluorescence characteristics observed under prohexadione-Ca suggested a weakening of the photochemical processes near the photosystem 2 reaction centre. The lowering of ratio between maximum time to reach maximum fluorescence, Fm (Tmax) and Area (sum of F m-Ft for t = 0 to t = Tmax) caused by GA 3 was probably due to the increase of Area rather than to changes in Tmax. © 2007 Institute of Experimental Botany, ASCR.