EFFECT OF PLANT-GROWTH REGULATORS AND ORANGE JUICE ON GROWTH OF CALLUS FROM FRUIT TISSUES OF WASHINGTON NAVEL ORANGE

The effect of the plant growth regulators kinetin, gibberellic acid (G A(3)), and 2,4-dichlorophenoxyacetic acid (2,4-D), either alone or in combination with orange juice, on the in vitro growth of mesocarp and endocarp explants from 90-120 day old Washington Navel Citrus sinensis orange fruits has been determined. Both fruit tissues formed callus. From endocarp 100% callus was formed in all cultures, even without gro wth regulators in the culture medium, while callus growth was lower fr om mesocarp. The addition of orange juice at a final concentration of 15% (v/v) to the basal medium without growth regulators increased the callus growth, specially that derived from endocarp. However, the high stimulant effect of orange juice observed on callus growth was marked ly dependent on the addition of 2,4-dichlorophenoxyacetic acid, maximu m callus growth from endocarp or mesocarp tissues being obtained with orange juice 15% (v/v) and 10 mu M 2,4-D.