Effect of Photoperiod on Isoenzymic Composition of Citrus and Poncirus

Long day photoperiod treatments given to Dancy and Clementine tangerines (Citrus reticulata Blanco.), the Mineola tangelo (C. parodisi Macf. × C. reticulata Blanco.) and the Rubideaux trifoliate (Poncirus trifoliata (L.) Raf.) produced 1.5 to 2.5 times the stem area, total linear growth and number of branches compared to short day treatments. Growing shoot tips were snbjected lo etectrophoretic analyses of tbe isoenzymic composition of esterases, teucine aminopeptidases, peroxidases and amylases. Differences were observed in the number and activity of the isoenzymes between the sbort and the long day treated plants of the three Citrus species aiid Hnbideaux trifoliate orange. The possible significance of tbese differences is discnssed in relation to Ihe growth in response to the photoperiodic treatments.