Temperature Effects on Shoot Growth and Flowering of Kumquat Trees

This study investigated the effects of temperature on the shoot growth and flowering of potted kumquat [Fortunella margarita (Lour.) Swingle] trees grown in subtropical conditions of I-Lan County in Taiwan. Temperature treatments included T 25-32, T 17-25, T 22, and T 18. The T 25-32 treatment trees were to the day/night temperatures of 25/18 degrees C for 2 weeks, followed by 28 weeks at 32/25 degrees C. T 17-25 was exposed for 4 weeks to 17/10 degrees C followed by 26 weeks at 25/18 degrees C. T 22 and T 18 were exposed at 22/18 degrees C and 18/13 degrees C, respectively, for the entire duration of the experiment. Control trees were placed in a plastic greenhouse under conditions similar to the natural environment. The kumquat trees exposed to high-temperature environment of 32/25 degrees C showed more frequent and speedy sprouting of new buds, but induced the earlier termination of shoot elongation growth, resulting in decreased vegetative growth. The temperature treatments lower than 22 degrees C suppressed the new shoot production but increased the shoot growth period, resulting in increased shoot length and diameter. Temperatures higher than 25/18 degrees C readily induced flowering, with flowering being advanced under the higher temperature conditions such as 32/25 degrees C. However, flowering was substantially inhibited under temperature conditions lower than 22/18 degrees C, indicating the negative role of relatively lower temperatures on flowering of kumquat trees.