| Summary: | 碩士 === 國立宜蘭大學 === 園藝學系碩士班 === 102 === The objectives of the study were to investigate the effects of regulated deficit irrigations (RDI) and temperatures on the fruit qualities of kumquat. The 2-year old potted kumquat（Fortunella margarita（Lour.）Swingle）trees were used in this study.
The duration of RDI treatments applied was from the fruit coloration stage to the harvest. Four treatments were designed, that is, RDI-70, RDI-50, RDI-25, and Control, which were irrigated trees with 70%, 50%, 25%, and 100% of available water, respectively. The total irrigation amount and soil-water content showed significant differences among treatments, with stem water potential also showed significant differences among treatments. Reducing irrigation quantity caused fruit drop rate increasing, fruit size and weight decreasing, and yield reduction. Trees treated by RDI-25 displayed the highest of fruit drop rate, the smallest fruit size and weight, and the least yield. Reducing irrigation quantity significantly increased the total soluble solids（TSS）content and titratable acidity（TA）content in fruits, which the RDI-25 group exhibited the highest TSS and TA, but caused a reduction of the TSS/TA ratio. Consequently, kumquat trees applied with regulated deficit irrigation in the third fruit growth stage increased TSS and TA, which promote flavor of kumquat fruits.
After the first physiological fruit drop, two weeks after fruit set, three day/night temperature treatments of 36/28℃, 28/20℃, and 20/12℃ were designed and the control group was placed in the plastic greenhouse. As the temperature increased, the total fruit drop number and fruit drop rate raise. Therefore, trees in 36/28℃ showed the most fruit drop number. The length and width of fruits reduced as the temperature increased, whereas the fruits of the 36/28℃ were smallest. Because the fruits of 36/28℃ and 28/20℃ groups could not reach maturation, data of them were not excluded to analysis. The fruit TSS of the Control and 20/12℃ groups had no significant differences, however, fruit TA of the 20/12℃ group were significantly higher than that of the Control group. Consequently, the development and qualities of the kumquat fruits were influenced by temperatures. Higher temperature（36/28℃）inhibited fruit growth and made fruit unripe.
The developing fruits of kumquat would fail to further growth and might drop if the high temperature（≧28℃）was encountered. Therefore, pruning shoots on early February and making plant flowering in May should avoid the fruit drop and fruit qualities reduction, which should be caused by high temperatures. Trees applied with available water of 70％ from the fruit coloration stage to the harvest increased the TSS and TA of kumquat fruits, which promoted the fruit flavors. However, the duration of RDI application should not be too long or might make obviously increase of TA and yield reduction.
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