| 摘要: |
| 【目的】研究成熟期（采收前20 d）施用氮肥对富士苹果糖酸含量及糖代谢转运关键基因表达的影响，以期为科学施用氮肥和调控果实品质提供理论依据。【方法】以陕西杨凌地区15年生富士苹果为试材，设置施用氮肥和对照2个处理，其中施氮处理采用环状沟施法，以尿素为氮源，每株环状沟内施用尿素1 kg后浇水并覆土；对照不施氮肥，仅浇满与施氮处理相同水量并覆土，于处理后6，13，20 d取样,研究成熟期施用氮肥对果实氮含量、可溶性固形物含量、含水量、可溶性糖酸、总糖、糖酸比、果实糖代谢及转运关键基因表达量的影响。【结果】与对照相比，成熟期施用氮肥能显著提高果实的氮含量，显著降低可溶性固形物含量，但果实含水量无显著变化；成熟期施氮对果实糖酸含量有较大影响，其中果糖、葡萄糖、半乳糖和山梨醇含量均有所下降，仅蔗糖和苹果酸含量显著增加，果实糖酸比显著降低；施氮后果实中的蔗糖磷酸合成酶基因（MdSPS1、MdSPS6）、果糖激酶基因（MdFK2、MdFK4）和己糖激酶基因（MdHK1）表达量上调，液泡膜糖转运蛋白基因（MdTST1、MdTST2）表达量总体下调，说明施氮可以促进糖的分解，但会抑制糖向液泡的转运。【结论】苹果树成熟期施用氮肥后，果实的糖代谢和转运相关基因表达量发生了变化，己糖含量降低，改变了果实可溶性糖的组成，导致果实甜度和品质降低，因此苹果成熟期采果前不宜施氮。 |
| 关键词: 富士苹果 氮肥 糖含量 糖代谢和转运 |
| DOI： |
| 分类号: |
| 基金项目:国家重点研发计划项目（2016YFD0201100） |
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| Effects of nitrogen application at mature stage on sugar contents and related gene expression of Fuji apple |
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LI Fan,WEI Hua,QI Jianguo,et al
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| Abstract: |
| 【Objective】This study applied nitrogen fertilizer to Fuji apple trees at the mature stage (20 days before harvest) and measured the changes in fruit sugar acid contents and expression of key genes of sugar metabolism and transport to provide basis for scientific application of nitrogen fertilizer and fruit quality regulation.【Method】The experiment was arranged in a 15-year-old Fuji orchard in Yangling,Shaanxi with two treatments of nitrogen fertilizer application and control.In the nitrogen application treatment,urea was used as nitrogen source and 1 kg urea was applied to each tree in the annular ditch before watering and covered with soil.The control did not apply nitrogen fertilizer,only filled with the same amount of water as the nitrogen treatment and soil covering.Samples were collected 6,13,and 20 days after treatment to study the effects of nitrogen fertilizer during fruit ripening period on fruit contents of nitrogen,soluble solids,water,soluble sugar,soluble acid and total sugar,sugar-acid ratio,and expression of key genes of fruit sugar metabolism and transport.【Result】Compared with the control,the application of nitrogen fertilizer could significantly increase nitrogen content in fruit and significantly reduce soluble solid content.There was no significant difference in water content.Nitrogen application had great effects on fruit sugar and acid contents.The contents of fructose,glucose,galactose and sorbitol decreased,contents of sucrose and malic acid increased significantly,and sugar-acid ratio decreased.Relative expression levels of sucrose phosphate synthase (MdSPS1 and MdSPS6),fructokinase (MdFK2 and MdFK4) and hexokinase (MdHK1) were up regulated after nitrogen application,which promoted decomposition of sugar.Expression levels of tonoplast sugar transporters (MdTST1 and MdTST2) were down regulated, inhibiting the transport of sugar to vacuole.【Conclusion】Nitrogen application to apple trees at mature stage changed expression of sugar metabolism and transport related genes,reduced hexose content and changed composition of soluble sugars,resulting in the decrease of fruit sweetness and quality.Thus,nitrogen should not be applied before fruit harvesting at ripening stage. |
| Key words: Fuji apple nitrogen fertilizer sugar content sugar metabolism and transport |
