اثر تنظيم كننده هاي رشد و جوانه برداري بر مناسب شدن دانهالهاي مركب براي كوپيوند

EFFECTS OF GROWTH REGULATORS AND PINCHING ON SUITABILITY OF CITRUS SEEDLINGS FOR BUDDING

Citrus plants respond positively to growth regulators especially GA and daylength to increase vegetative growth. The aim of this research was to study the effect of cycocel (CCC), paclobutrazol (PP333). ethephon and pinching following GA3 treatment on trifoliate orange (Poncirus trifoliata L.) and sour orange (Citrus aurantium L.) seedlings to determine the suitability of them for budding. The experiment was carried out during 1988-1999 in the greenhouse at the College of Agriculture. Shiraz University, Shiraz, Iran. Seeds were sown and 3 mo later when seedlings had 4 to 6 leaves, they were sprayed twice with 100 mg 1-1 GA3 at a 2-wk interval. Control plants were not spayed. Two mo after GA3 treatment, uniform trifoliate orange seedlings with 50 cm height were selected, potted and sprayed with PP333 and CCC (500 and 1000 mg 1-1) and pinching was carried out. Also, uniform sour orange seedlings with 45 cm height were sprayed with CCC (500 and 1000 mg 1-1), ethephon (150 and 300 mg 1-1) and pinching was carried out. Results indicated that GA3 increased plant height and internode length in both sour and trifoliate oranges. Using PP333 following GA3 treatment reduced significantly plant height in trifoliate orange. Stem diameter was increased by the use of GAs alone and/or PP333, CCC. ethephon or pinching following GA3 treatment in both sour and trioliate oranges. Ethephon (150 and 300 mg 1-1) reduced chlorophyll content of the leaves in sour orange. GA3 significantly increased fresh and dry weights of shoots when compared to control, whereas, PP333 and CCC reduced this character. Application of these growth regulators reduced the necessary time to reach the budding size.