摘要
为探究不同叶果比(leaf fruit ratio,LFR)对设施柑橘秋梢叶片生理生化特征的影响,以设施栽培‘红美人’杂柑为试材,设置高(LFR=100)、中(LFR=80)、低(LFR=60)3个叶果比,测定秋梢叶片中矿质元素、碳氮代谢物、碳氮代谢的关键酶、抗氧化酶活性等生理指标的变化。结果显示,LFR80和LFR100秋梢叶片的磷、钾、镁、淀粉含量较高;丙二醛、脯氨酸、抗坏血酸含量较低;β-淀粉酶、硝酸还原酶、谷氨酰胺合成酶和抗坏血酸过氧化物酶的活性较高;LFR80和LFR100秋梢叶片整体养分含量充足,受胁迫程度较低。结果表明,设施栽培‘红美人’杂柑的叶果比控制在80~100有利用于平衡营养生长和生殖生长,延缓叶片衰老,维持树势强健。
源-库关系是指作物生长发育过程中生产同化产物的源器官和积累同化产物的库器官之间的平衡协调关系。果树生产中通常采用疏花、疏果、摘叶等栽培措施控制叶果比,对源库关系进行调整。叶果比过大则造成树体营养浪费,营养生长过旺,果实对同化物的竞争力降低;叶果比过小会导致光合产物和养分不足,不仅降低果实品质,还会影响翌年果树的植株生长、成花和树
源-库关系与植物光合产物的积累密切相关,库强对源器官的糖分累积、转化、同化物运输与分配具有显著的调节作
源-库关系平衡与否也会影响作物抗逆系统的稳态,源-库失衡会引起抗氧化相关指标的变化。胡敏
源-库关系还影响作物矿质营养的吸收、运输和分配。充足的矿物质营养是果树生长、产量和果实品质形成的必要条件。有研究发现矿质养分的吸收和分配也受到源-库关系的调控。许蓓蓓
‘红美人’杂柑是橘橙类杂交柑橘品种,具有高糖低酸,化渣性好,香气浓郁,经济效益高等特
供试材料为6年生枳砧‘红美人’杂柑,栽植于浙江省黄岩区宁溪镇晨湖果蔬家庭农场(121°15'9″E,28°39'33″N,海拔24 m),株行距为3 m×4 m,土壤为红黄壤(pH 5.69),有机质含量3.14%,速效氮77.00 mg/kg、速效磷160.13 mg/kg、速效钾148.55 mg/kg、有效钙241.50 mg/kg、有效镁66.54 mg/kg、有效硼0.26 mg/kg。
本试验采用完全随机区组设计,选择树体大小相仿、树势一致、栽培管理措施统一的6年生‘红美人’杂柑(株高1.8~2.2 m、冠幅2.5~3.0 m、主干粗度5.0~6.0 cm,整株的叶片数为0.8万~1.5万片、挂果量为80~150个),分别进行高叶果比(叶片∶果实=100∶1,LFR100)、中叶果比(叶片∶果实=80∶1,LFR80)和低叶果比(叶片∶果实=60∶1,LFR60)3个处理,每个处理10棵树。疏果分2个阶段完成(初步疏果和最终定果),2019年6月中旬第二次生理落果完成后,对果树进行初步疏果,程度为目标叶果比的90%,2019年9月中旬最终定果达到目标叶果比。2019年11月20日,每棵树从东、西、南、北4个方向采集树冠外围秋梢的第5~6片叶用于后续实验,每3棵树的叶片混合为1个样品,每个样品3次生物学重复。
采用蒽酮比色法测定淀粉和可溶性糖含量,采用BCA法测定可溶性蛋白含量,采用硫代巴比妥酸法测定丙二醛含量、采用酸性茚三酮法测定脯氨酸含量,采用固蓝盐比色法测定ASA含量,具体方法参见文献[
不同叶果比‘红美人’杂柑叶片的淀粉、可溶性糖和可溶性蛋白分析结果显示,叶果比LFR100秋梢叶片的淀粉含量为55.77 mg/g,显著高于叶果比LFR60和LFR80叶片中的淀粉含量(

图1 不同叶果比‘红美人’杂柑秋梢叶片的淀粉(A)、可溶性糖(B)和可溶性蛋白(C)含量
Fig. 1 The contents of starch (A), soluble sugar (B) and soluble protein (C) in autumn shoot leaves of ‘Hongmeiren’ citrus hybrid with different leaf/fruit ratio
不同小写字母表示不同叶果比处理间差异显著(P<0.05),下同。Different lowercase letters indicate significant differences among different leaf/fruit ratio at the 0.05 level, the same as follows.
由

图2 不同叶果比‘红美人’杂柑秋梢叶片的淀粉酶、蔗糖合酶、硝酸还原酶和谷氨酰胺合成酶活性
Fig. 2 The enzyme activities of amylase, sucrose synthase, nitrate reductase and glutamine synthetasein autumn shoot leaves of ‘Hongmeiren’ citrus hybrid with different leaf/fruit ratios
A:α-淀粉酶 α-AMS; B:β-淀粉酶 β-AMS; C:蔗糖合酶分解方向 Decomposition direction of sucrose synthase; D:蔗糖合酶合成方向 Synthetic direction of sucrose synthase; E:硝酸还原酶 Nitrate reductase; F:谷氨酰胺合成酶 Glutamine synthetase.
LFR60秋梢叶片的MDA含量为85.18 nmol/g,显著高于LFR80和LFR100,分别为LFR80和LFR100中MDA含量的1.57和1.46倍(

图3 不同叶果比‘红美人’杂柑秋梢叶片的丙二醛(A)、脯氨酸(B)和抗坏血酸(C)含量,抗坏血酸过氧化物酶(D)和抗坏血酸氧化酶(E)活性
Fig. 3 The contents of malonaldehyde (A), proline (B), ascorbic acid (C), the enzyme activities of ascorbate peroxidase (D) and ascorbic acid oxidase (E) in autumn shoot leaves of ‘Hongmeiren’ citrus hybrid with different leaf/fruit ratios
由
矿质元素Mineral element | 叶果比 Leaf/fruit ratio | ||
---|---|---|---|
LFR60 | LFR80 | LFR100 | |
氮含量/(g/kg)N content | 27.62±1.63a | 28.09±0.48a | 28.07±1.22a |
磷含量/(g/kg)P content | 1.16±0.09b | 1.17±0.01b | 1.49±0.10a |
钾含量/(g/kg)K content | 9.95±0.95c | 13.44±1.17b | 16.42±1.31a |
钙含量/(g/kg)Ca content | 24.17±1.50a | 21.19±1.08b | 17.50±1.04c |
镁含量/(g/kg)Mg content | 1.44±0.11b | 2.27±0.14a | 2.05±0.15a |
铁含量/(mg/kg)Fe content | 75.07±4.42a | 75.96±4.96a | 64.79±3.83b |
锰含量/(mg/kg) Mn content | 76.91±4.10b | 91.87±6.35a | 77.61±6.55b |
铜含量/(mg/kg) Cu content | 1.95±0.14a | 2.21±0.18a | 2.11±0.14a |
锌含量/(mg/kg) Zn content | 14.94±1.59b | 24.50±1.34a | 15.28±1.22b |
硼含量/(mg/kg) B content | 115.61±8.20a | 83.02±6.55b | 74.97±5.71b |
为了直观地展示叶果比对设施柑橘叶片生理生化特征的影响,对不同叶果比处理下的叶片矿质元素、淀粉、可溶性糖、可溶性蛋白、MDA、脯氨酸含量和AMS、SS、GS、NR等碳氮代谢的关键酶活性,以及APX和AAO等抗氧化酶活性进行分层聚类分析。结果显示,3个叶果比处理中LFR60单独聚为一簇,LFR80和LFR100聚为一簇;生理生化指标中Fe、Ca、B、Pro、MDA、ASA含量和AAO活性聚为一簇,N、P、K、Mg、Mn、Zn、Cu、淀粉、可溶性糖、可溶性蛋白、AMS、SS、NR、GS和APX活性聚为一类。结果表明叶果比LFR80和LFR100处理条件下的叶片生理生化特征比较相似,高叶果比叶片中的K、Mg、Cu、Zn、Mn等矿质元素和淀粉等同化产物含量较高,丙二醛、脯氨酸、ASA等衰老相关指标含量较低(

图4 不同叶果比设施‘红美人’杂柑秋梢叶片生理生化指标的聚类分析
Fig. 4 Cluster heat map analysis of physiological and biochemical indexes in autumn shoot leaves of ‘Hongmeiren’ citrus hybrid with different leaf/fruit ratio
Fe:Fe 含量 Fe content;AAO:抗坏血酸氧化酶活性 Ascorbic acid oxidase activity;Ca:Ca 含量 Ca content;Pro:脯氨酸含量 Proline content;MDA:丙二醛含量 Malondialdehyde content: ASA: 抗坏血酸含量 Ascorbic acid content;α⁃AMS: α⁃淀粉酶活性 α⁃Amylase activity;Mn:锰含量 Mn content; Zn: 锌含量 Zn content;Sta:淀粉含量Starch content;N:N 含量 N content; APX: 抗坏血酸过氧化物酶活性 Ascorbate peroxidase activity;K: K 含量 K content;GS:谷氨酰胺合成酶活性 Glutamine synthetase activity;P:P含量 P content; Spr:可溶性蛋白含量 Soluble protein content; SS⁃Ⅱ:蔗糖合成酶活性(合成方向) Sucrose synthase activity(synthetic direction); Mg:Mg含量 Mg content; Cu:Cu含量 Cu content; β⁃AMS: β⁃淀粉酶活性 β⁃Amylase activity;NR: 硝酸还原酶活性 Nitrate reductase activity;Ssu: 可溶性糖含量Soluble sugar content;SS⁃Ⅰ:蔗糖合成酶活性(分解方向) Sucrose synthase activity(decomposition direction).
源是光合产物的生产者,是库增长的基础;库是光合产物积累、需求、消耗的器官,对源具有反馈调节作用。疏花、疏果和摘叶等栽培管理措施能够有效控制果树的叶果比,进而调控源库之间的平衡,达到增产、稳产和优
丙二醛是植物细胞膜脂过氧化的最终产物,是衡量植物在逆境胁迫下受损程度的指标之一,通常也作为判断叶片衰老的重要指标。在本研究中LFR60秋梢叶片的丙二醛含量显著高于LFR80和LFR100,这表明LFR60叶片细胞膜脂可能受到过氧化胁迫的程度高于LFR80和LFR100,这可能是叶果比过低导致源库失衡引起叶片提前衰老。在逆境胁迫下快速积累脯氨酸能够增强细胞水势,维持细胞的稳态,延缓叶片衰
成熟叶片是柑橘的源器官,也是柑橘树体养分的存储库,叶片矿质养分含量的高低直接影响柑橘的生长、树势、开花和果实的品
综上所述,LFR80和LFR100秋梢叶片的P、K、Mg、淀粉含量较高,丙二醛、脯氨酸、抗坏血酸含量较低,β-淀粉酶、硝酸还原酶、谷氨酰胺合成酶和抗坏血酸过氧化物酶的活性较高,秋梢叶片整体养分含量充足,有利于维持树体正常的生理生化代谢。因此设施栽培‘红美人’杂柑的叶果比控制在80~100,能够平衡营养生长和生殖生长,缓解秋梢叶片早衰,维持树势强健,促进翌年成花。
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