Waddah Hamed
General Commission for Scientific Agricultural Research-
Tartous  Research Center
Faculty of Agriculture, Tishreen University,
2010

Abstract

This study was carried out on 20-year citrus trees at Citrus Research Section in Tartous province during the two growing seasons (2006\2007) and (2007\2008) on three citrus species: Valencia Orange, grapefruit (Marsh seedless) and Clementine(66), and there are all grafted on sour orange rootstock.
This study concluded to abstracted to the following:
-*Telescopic observation of buds as of 12 – 15 January, for all studied varieties according to  sides of tree, showed that flower initiation started from 17 – 25 March for studied varieties.
-*There are three growing seasonal cycles: Spring , Summer, and Autumn.
-*The vegetative buds started to develop from 13-15 February and lasted to 20 May to produce spring growing cycle for all studied varieties, and then resumed growing on 15 June until 25 July to summer growing cycle, while the third growing cycle started from 25 August to 10 October .
-*Excessive length of spring growing cycle over lengths in  the other growing cycles for all varieties.
-*Flowering concentrated in all studied varieties on Summer and Autumn cycles. The spring cycle contained lower number of  flowers on grapefruit (Marsh seedless) and Clementine(66).
-*The mixed inflorescence over-numbered for both Valencia and Clementine(66), while flowering inflorescence over-numbered for Grapefruit (Marsh seedless) variety.
-*The fruit inflorescence with one flower  was superlative in ovule flower’s weight than both flowering and mixed inflorescences, and the mixture excessive on flowering  in terms of ovule flower’s weight.
-*This study showed a high fruit-setting over  mixed inflorescence (leafy and flowering) and flowering inflorescences. The inflorescence growth  mixed with fruit-setting was superlative than flowering inflorescence for all studied varieties.
-*The autumn growing cycle gave higher productivity in Valencia and Grapefruit (Marsh seedless), followed by  summer growing cycle, and the lower productivity  was spring growing cycle, while summer growing cycle gave higher productivity in Clementine(66), and lower productivity in spring growing cycle.
-*Fruits produced from  autumn and Summer growing cycles and leafy-inflorescence, either south and west sides contained a high average of vitamin C and total solid solution  TSS, and total sugar