SOME PHYSIOLOGICAL STUDIES ON CITRUS

Abstract

In two field experiments during 1996- 1997, and 1997- 1998, Valencia orange trees were treated with calcium (42, 84 and 126 ppm) or ethrel (100, 200 and 300 ppm) or combination of both calcium and ethrel. Calcium treatments were applied at three spraying dates (November the 15th February the 15th and two equal split doses at November the 15th and February the 15th). Ethrel treatments were applied on March the 15th. Also the internal branch of some trees were bruned (open-heart treatment). The obtained results showed that fruit pull force, firmness, rind chlorophyll and juice acidity increased due to application of calcium, while these treatments decreased the number of dropped fruits per tree. On the other hand, ethrel application decrease fruit pull force, firmness, and rind chlorophyll and increased T.S.S., rind carotenoids and the number of dropped fruits. In combination treatment of both calcium arid ethrel, foliar application of calcium reduced the effect of ethrel in decreasing fruit pull force and firmness and number of fruit dropped. Open heart treatment caused improvement of rind colour in Valencia orange.