Abstract
One-year-old satsuma trees (cv. Okitsu Wase) on trifoliate orange were grown in a growth chamber where day and night temperature were kept constant at 15, 20, 25 and 30°C for 7 or 9 months. The effects of temperature on vegetative growth and nutrient absorption were investigated.
1. Potted trees were transferred into the growth chamber in April and grown until late October of 1979. Budbreak occurred considerably earlier at higher temperatures. Trees at 15 and 20°C sprouted flushes only in spring and these shoots produced some flower buds during September through October. Trees at 25°C flushed spring, summer and autumn shoots, and those at 30°C had an additional cycle of flush. Total shoot length of the trees at 30°C was the greatest. Fresh and dry matter increased in both tops and roots with rising temperatures, but at 30°C they slightly decreased. The leaves of trees at 20°C contained the highest amount of nitrogen and phosphorus. Calcium and potassium contents increased as temperature rose. Other mineral contents examined were lowest at 15°C. Total amount of mineral elements absorbed by the trees increased with rising temperature from 15 to 25°C, but slightly decreased at 30°C
2. Root growth was observed using root boxes (30×20×25cm) for 9 months from April through December, 1982. High temperature stimulated root growth. At 30°C trees grew rapidly and had five growth cycles for shoots and three for roots. In contrast, root growth of trees at 15°C was severely restricted. In all cases, root growth always followed shoot growth. The rate of root growth increased just after spring and summer flushes, and had two clear peaks, excepting in trees at 15°C. Root growth showed the same pattern at all temperatures above 20°C. At 15°C, however, roots grew slowly but continuously without any peaks. The higher the temperature. the greater the total root length obtained by the end of the experiment.
