Abstract
The effects of soil drought and temperature on flower bud differentiation of one-year-old satsuma trees (cv. Okitsu Wase) on trifoliate orange were investigated. Potted trees were grown in 15, 20 and 25°C growth chamber rooms and in the field for 6 months from mid June, when new spring leaves turned greenish and the stems were full. Water was supplied at 3 grades of water stress of the trees by monitoring the daily pot weight decrease. Flower bud differentiation was estimated by counting the number of flowers and non-flowering shoots on the trees after defoliating and transferring the trees into the 25°C room in mid December.
Trees at lower temperatures produced more flowers and fewer shoots. Trees with optimum soil moisture and medium drought at 25°C did not produce any flowers, but produced some shoots. Only high drought pots produced many flowers. When the soil was dried, the trees tended to have many flowers, flowering nodes and flowers per node at 20°C and in the field. At 15°C, few shoots sprouted, but many leafless flowers occurred regardless of soil moisture. Low temperature treatments produced many flowers from compound buds in an axillary bud, and drought treatments enhanced these trends. Number of flowers in the field was about the same as in a 20°C room, but less than in a 15°C room.
