ウンシュウミカンの花芽の分化, 発達の温度条件

Abstract

One-year to three-year-old satsuma trees (cv. Okitsu Wase or Miyagawa Wase) on trifoliate orange rootstocks grown at 15, 20, 25 and 30°C in a growth chamber were observed for flower bud differentiation and development.1. One-year-old trees were grown in a growth chamber from March 1 or April 1. On trees grown at 15°C, flowers but no leaves were produce instead of summer flushes. On trees grown at 20°C, a smaller number of leafless flowers and some leafy ones were produced. On trees grown at 25 and 30°C, summer shoots grew vigorously and flower buds did not differentiate.2. In mid-June, when spring shoots ceased their growth and their stems became mature, one-year-old trees were transferred into 20 and 15°C growth chambers. They were kept there for several months, and then transferred to 25°C rooms. On the trees grown at 15°C for 2 months or more and at 20t for 2.5 months or more, flower buds were produced. More flower buds developed on the trees grown at lower temperatures for longer periods. Flowers of trees grown at 15°C or 20°C until flowering had large and flat ovaries. Flowers of trees that were transferred to the 25°C room before flowering had small and long ovaries.3. Three-year-old trees were put in 15, 20 and 25t rooms at the time of morphological flower bud differentiation (March 20) and one month before and after. Flower bud development was observed in February, whereas microscopic evidence of differentiation was not evident. Flowering periods on trees grown at higher temperature were shorter.4. Two-or 3-year-old trees were put in 20 and 25°C rooms at half-month intervals from late September to next March. Flower buds were produced on the trees put at 25°C in late October and later. On the trees put at 20°C in early November and before, few flower buds were produced and they dropped before flowering.