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GROWTH REGULATORS APPLICATION AFFECTS VEGETATIVE AND REPRODUCTIVE BEHAVIOUR OF ‘BLOOD RED’ SWEET ORANGE

BASHARAT A. SALEEM^*, A.U. MALIK, M.A. PERVEZ AND A.S. KHAN

Abstract: Two plant growth regulators (GA₃ and 2, 4-D) were exogenously applied in different concentrations alone and their combinations on Blood Red sweet orange trees during full bloom. The experiment was performed at the Experimental Fruit Garden Sq # 9 Institute of Horticultural Sciences, University of Agriculture, Faisalabad; laid out according to RCBD with 13 treatments including control replicated thrice.  A single tree was taken as treatment unit. Vegetative and reproductive behaviours of the treated trees were studied to evaluate the effect of exogenous application of plant growth regulators on leaf age, vegetative growth and final fruit set. The leaf drop was significantly reduced by all treatments compared with control. The mixture treatments at all concentrations retained maximum spring leaves ranging between 38.5% (20 mg L^-1) - 58.38% (45 mg L^-1). The control trees had negligible number of spring leaves (3.09%). Number of leaves per flush, flush length, number of male flowers and flower drop intensity had also significant differences among treatments but no linear trend could be determined. Bud drop, hermaphrodite flowers, fruit on old shoots and fruit on current shoots were not significantly affected by the treatments. The final fruit set was significantly affected by all GA₃ treatments individually as well as in mixture with maximum fruit set of 32.32% in 45 mg L^-1 GA₃ treated trees compared with control. Fruit yield, in terms of number of fruit per tree as well as kg per tree was significantly affected by the treatments compared with control. There was positive correlation between number of fruit and weight of fruit per tree.

Institute of Horticultural Sciences, University of Agriculture, Faisalabad, Pakistan

^*E-mail: basharatuaf@yahoo.com