Citrus is the main fruit tree crop in the world and therefore has a tremendous economical, social and cultural impact in our society. In recent years, our knowledge on plant reproductive biology has increased considerably mostly because of the work developed in model plants. However, the information generated in these species cannot always be applied to citrus, predominantly because citrus is a perennial tree crop that exhibits a very peculiar and unusual reproductive biology.
Effect of Different Day Temperatures on Flowering and Fruiting in Tosa Buntan Pummelo (Citrus grandis (L.) Osbeck)
The effect of different day temperatures during winter and spring seasons on the flowering and fruiting of 3-year-old potted Tosa Buntan pummelo (Citrus grandis (L.) Osbeck) trees grafted on trifoliate orange (Poncirus trifoliata Raf.) rootstock was investigated. The experiment was conducted in growth chambers with setting day temperatures of 15℃, 20℃, 25℃, 30℃ and 35℃, while night temperature in each chamber was set at a constant 10℃. The temperature treatments were started on December 18, 1989 and terminated on May 1, 1990, except for the 15℃ day temperature treatment which lasted until June 11, 1990. After the temperature treatments in the growth chambers, all trees were grown in the same way in the field condition until harvesting time of November 15, 1990. The lowest day temperature treatment of 15℃ needed considerably more days to flower bud initiation and greatly inhibited flower bud development, thus all flower buds in this regime dropped before and after their opening.