Studies on Growth Characteristics and Flowering Regulation of Kumquat (Fortunella margarita (Lour.) Swingle)
Date Issued
2014
Date
2014
Author(s)
Chang, Yung-Chiung
Abstract
The objectives of this study were to compose the complete growth information of kumquat trees (Fortunella margarita (Lour.) Swingle) trees grown in the subtropical conditions of Taiwan and establish functional operation for flowering regulation which might propose crucial strategies for improvement in kumquat industry. The new buds of the second, third, and forth flushes sprouted in mid May, early July, and early Sep., which almost 70-80, 112-122, and 168-178 days after the first flush sprouted, respectively. Flowering potential of the flowering rate of shoot and flower number per shoot was decreased as flush sequences increased. The shoot flowering potential of the first flush, exhibited 4 peaks in 2010 and 5 peaks in 2011. In experiment of 2011, the fruiting potential displayed on the first flush shoot, sprouted in March; besides, a higher proportion of successful fruit set was observed on shoots which fruitlets were formed from flowers of the second flowering sequence, bloomed in mid July.
Temperature treatments included T 25-32, T 17-25, T 22, and T 18. The T 25-32 treatment exposed trees to the day/night temperatures of 25/18°C for 2 weeks, followed by 28 weeks at 32/25°C. T 17-25 was 4 weeks of exposure to 17/10°C followed by 26 weeks at 25/18°C. T 22 and T 18 were for 22/18°C and 18/13°C, respectively, for the entire duration of the experiment. Control trees were placed in a plastic greenhouse under the conditions similar to the natural environment. The kumquat trees exposed to the high-temperature environment of 32/25°C showed the 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 at lower than 22°C suppressed the new shoot production but increased the shoot growth period, resulting in increased shoot length and diameter. Temperatures higher than 25/18°C readily induced flowering, with flowering being advanced under the higher temperature conditions such as 32/25°C. However, flowering was substantially inhibited under the temperature conditions lower than 22/18°C, indicating the negative role of relatively lower temperatures on flowering of kumquat trees.
Three treatments were implemented for two weeks as shoot elongation terminated, that is, Control, RDI 1, and RDI 2, which irrigated trees with 75%, 55%, and 35% available water, respectively. After withholding water for two weeks (stage B), leaf water potential of the RDI 2 group decreased significantly, and the RDI 2 group exhibited the highest integrated leaf water potential index, which indicated the highest stress level that leaves encountered. Results of the net CO2 assimilation rate (Pn), Fv/Fm, and Fv’/Fm’ of the RDI 2 group also significantly decreased after trees were conducted water withholding for two weeks; however, all growth parameters exhibited an obvious re-watering compensation effect after water recovery. Trees of the RDI 2 group exhibited an obvious flowering potential on shoots. The flowering rate of each node in RDI 2 exhibited the highest average rate of 50%, which significantly differed from those of the Control and RDI 1 groups did. The kumquat trees of the RDI 2 group efficiently altered shoot growth phases and obviously concentrated the flowering period, which offers a valuable water management approach for high-quality potted kumquat production.
Subjects
金柑
物候
枝梢
開花
溫度
調虧灌溉
SDGs
Type
thesis
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