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| Effects of Girdling and Chemical Treatments on the Response of Longan Fruit and Layer |
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| DOI：10.16768/j.issn.1004-874X.2023.04.007 |
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| Abstract: |
| 【Objective】The production mode of Hainan longan can be divided into natural flowering on-season longan and off-season longan induced by potassium chlorate. Reasonable fruit loading is extremely important to maintain tree vigor and avoid alternate bearing results. The fruit loading regulation modes in the production of on-season and off-season longan are greatly different. The fruit setting amount of on-season longan is great, which seriously affects the tree vigor and fruit quality, while off-season longan fruit abscission before harvest is a common phenomenon, which seriously affects the yield.Therefore, fruit thinning of on-season longan and fruit preserving of off-season longan are equally important in the production.【Method】The main cultivar Shixia longan was used as the test material, and two tests including fruit thinning of on-season longan and fruit preserving of off-season long were set. The fruit thinning effect was studied by treating the longan ears with different fruit thinning agents, and the fruit preserving effect was studied with the treatment of different fruit preserving agents after artificially induced fruit abscission of off-season longan.【Result】By tracking and monitoring the fruit abscission rate and the separation force of the pedicel abscission layer, it was found that IAA and DMTU treatments delayed fruit abscission process for 2 days, 2,4-D and NAA treatments delayed the fruit abscission process for 3 days in off-season longan, but neither of them could prevent fruit abscission. Treatment of fruit substituted by IAA completely inhibited the pedicel separation in off-season longan. Girdling treatment could induce 100% of on-season longan fruit abscission within 6 days; different concentrations of ethephon, paraquat and 100 g/L urea treatment could induce 11.88%-53.05%, 29.23% and 35.43% of fruit abscission respectively within 10 days. After 10 days, there was very little fruit abscission under urea treatment, while other treatments showed sustained fruit abscission.【Conclusion】The results show that carbohydrate stress, paraquat, ethephon and urea treatment can induce the abscission layer separation of longan pedicel, and these agents have a fruit thinning effect on onseason longan. IAA, 2,4-D, NAA, DMTU can delay the abscission layer separation of fruit pedicel, which can effectively delay the abscission of off-season longan before harvest. All the treatments that can enhance the IAA signal can play a role in fruit preserving, while all the treatments that reduce the synthesis and transport of IAA and the treatments that enhance the ethylene signal have effects on fruit thinning. Therefore, in terms of production, it is suggested that measures should be taken to thin the fruit of on-season longan as early as possible to reduce the consumption of carbohydrates and then ensure the quality and yield of the fruits. In the middle fruiting period of off-season longan, certain fruit preserving measures should be taken to ensure the accumulation of IAA in the fruit to avoid the abscission of fruits. |
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