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2017 Volume 39 Issue 7
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Rong-fei LI, Kang-ping ZHANG, Qiao HE, et al. Impact of Tree Training Systems on the Physiological Characteristics of Leaves on Different Branches of Citrus grandis var. Long' anyou and on Its Fruit Quality[J]. Journal of Southwest University Natural Science Edition, 2017, 39(7): 36-43. doi: 10.13718/j.cnki.xdzk.2017.07.006
Citation: Rong-fei LI, Kang-ping ZHANG, Qiao HE, et al. Impact of Tree Training Systems on the Physiological Characteristics of Leaves on Different Branches of Citrus grandis var. Long' anyou and on Its Fruit Quality[J]. Journal of Southwest University Natural Science Edition, 2017, 39(7): 36-43. doi: 10.13718/j.cnki.xdzk.2017.07.006
shu

Impact of Tree Training Systems on the Physiological Characteristics of Leaves on Different Branches of Citrus grandis var. Long' anyou and on Its Fruit Quality

  • 1.

    School of Horticulture and Landscape Architecture, Southwest University, Chongqing 400715, China

  • 2.

    Guang'an District Agricultural Bureau, Guang'an Sichuan 638500, China

  • 3.

    Guang'an Science and Technology Development and Training Center, Guang'an Sichuan 638500, China

More Information
  • Corresponding author: Qi-gao GUO
  • Received Date: 25/11/2016
    Available Online: 20/07/2017

  • MSC: S666.3

  • In this paper, Citrus grandis var. Long' anyou trees with different crowns formed by three kinds of training system, i. e. natural round shape, open center shape and Y-shape, were used as experimental materials, the water content, nutrient contents and photosynthetic physiological characteristics of the leaves on their vegetative shoots and bearing branches were compared, and the correlation of the above-mentioned parameters with their fruit quality was analyzed. The results showed that the leaf dry matter content (LDMC), leaf area (LA), water use efficiency (WUE) and net photosynthesis rate (Pn) of the vegetative shoots were significantly higher than those of the bearing branches, and there was a similar tendency in all the three kinds of training system. These parameters were in the order of Y-shape > open center shape > natural round shape. The leaves on the vegetative shoots of the round-crowned trees had the highest transpiration rate (Tr=3.18 mmol/m2·s). The leaves of the open-centered trees had higher contents of the major nutrient elements N, P, Ca and Mg than those of the other two training systems, and the four elements were higher in the vegetative shoot leaves than in the bearing branch leaves of all the three training systems. The contents of trace elements (Fe, Mn, Zn, Cu and B) were the lowest in the leaves of the trees with an open-centered crown. Moreover, Fe, Zn and B in the bearing branch leaves were significantly more than those in the vegetative shoot leaves, but the reverse was true of Mn and Cu. The fruit color, fruit weight and fruit shape index of the Y-shaped trees and the open-centered trees were better than those of the natural round-shaped trees. Moreover, the fruit weight of the open-centered trees was 1.12 times that of the natural round-shaped trees. The Y-shaped trees had significantly higher soluble solids (10.33%), vitamin C (0.618 mg/g), reducing sugar (3.81%), solid/acid ratio (16.78%) and sugar/acid ratio (13.54%) than the other two training systems, but titratable acid, invert sugar, sucrose and total sugar showed no significant difference among the three. Correlation analysis showed that the measured physiological parameters influenced the fruit quality. Net photosynthesis rate (Pn) was positively correlated with soluble solids, vitamin C, total sugar, solid/acid ratio and sugar/acid ratio.
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Impact of Tree Training Systems on the Physiological Characteristics of Leaves on Different Branches of Citrus grandis var. Long' anyou and on Its Fruit Quality

    Corresponding author: Qi-gao GUO
  • Received Date: 25/11/2016
  • Available Online: 20/07/2017

Abstract: In this paper, Citrus grandis var. Long' anyou trees with different crowns formed by three kinds of training system, i. e. natural round shape, open center shape and Y-shape, were used as experimental materials, the water content, nutrient contents and photosynthetic physiological characteristics of the leaves on their vegetative shoots and bearing branches were compared, and the correlation of the above-mentioned parameters with their fruit quality was analyzed. The results showed that the leaf dry matter content (LDMC), leaf area (LA), water use efficiency (WUE) and net photosynthesis rate (Pn) of the vegetative shoots were significantly higher than those of the bearing branches, and there was a similar tendency in all the three kinds of training system. These parameters were in the order of Y-shape > open center shape > natural round shape. The leaves on the vegetative shoots of the round-crowned trees had the highest transpiration rate (Tr=3.18 mmol/m2·s). The leaves of the open-centered trees had higher contents of the major nutrient elements N, P, Ca and Mg than those of the other two training systems, and the four elements were higher in the vegetative shoot leaves than in the bearing branch leaves of all the three training systems. The contents of trace elements (Fe, Mn, Zn, Cu and B) were the lowest in the leaves of the trees with an open-centered crown. Moreover, Fe, Zn and B in the bearing branch leaves were significantly more than those in the vegetative shoot leaves, but the reverse was true of Mn and Cu. The fruit color, fruit weight and fruit shape index of the Y-shaped trees and the open-centered trees were better than those of the natural round-shaped trees. Moreover, the fruit weight of the open-centered trees was 1.12 times that of the natural round-shaped trees. The Y-shaped trees had significantly higher soluble solids (10.33%), vitamin C (0.618 mg/g), reducing sugar (3.81%), solid/acid ratio (16.78%) and sugar/acid ratio (13.54%) than the other two training systems, but titratable acid, invert sugar, sucrose and total sugar showed no significant difference among the three. Correlation analysis showed that the measured physiological parameters influenced the fruit quality. Net photosynthesis rate (Pn) was positively correlated with soluble solids, vitamin C, total sugar, solid/acid ratio and sugar/acid ratio.

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  • 树形培养是依据果树生长特性和栽培目的，结合自然条件和管理技术水平，选择恰当的整形修剪方法，调整树体结构，从而形成具有稳定树形及生长发育空间的一项技术措施.已有研究证实，不同的树形将影响树冠内的光照分布、光合特性及叶片的生理状况，从而影响果实的品质和产量[1].因此，分析树形对叶片和果实品质、产量的影响，对于果树栽培中选择适宜的树形及其他栽培措施来提高果实品质和产量、增加果农的经济效益都具有重要意义.

    龙安柚(Citrus grandis var. longanyou)是四川省广安市国家地理标志保护农产品，连续4次荣获国家柚类评比金杯奖，是当地果农增收的支柱产业之一.龙安柚1年可抽梢次数较多，成枝量大，自然生长的树形常为内膛郁闭的自然圆头形，光照不良，对其产量与品质影响较大[2-3].因此，选择龙安柚优质高效树形已成为龙安柚生产栽培中亟待解决的问题.对柑橘[4]、梨[5]、桃[6]、苹果[7]等果树的研究表明，Y字形和开心形均在不同程度上提高了果实的产量与品质.研究还发现，叶片可通过调节自身生理过程来适应整形修剪，但现有报道主要集中于营养枝叶片的养分生理[9-11]及光合生理[12-14]，而结果枝在研究过程中则易被忽视[15].因此，本研究以龙安柚的Y字形、开心形和自然圆头形3种树形的营养枝与结果枝作为研究对象，测定不同树形龙安柚的营养枝和结果枝叶片的含水量、大量元素的质量分数、微量元素的质量分数、光合特性和果实品质，并进行营养枝、结果枝叶片生理状况各指标与果实品质的相关性分析，以期能更全面地反映龙安柚整形修剪效应，并为龙安柚生产栽培中适宜树形筛选奠定基础.

1.   材料与方法

    1.1.   试验材料

  • 以5年生龙安柚为试材，于2015-2016年在广安市前锋区代市镇大田村进行试验.当地(106°76′E，30°50′N)气候表现出西南地区高温多雨的特征，肥力中等.于2010年培养3种树形，分别为Y字形、开心形以及自然圆头形.每年定期对龙安柚进行树形维护工作，2014年10月于同一片栽培地的3种树形中选取树势一致，无病虫害且分布较集中的龙安柚各10株作为试验材料.

    • 1.2.   试验方法

    1.2.1.   光合测定

  • 果实进入成熟期后，于晴天上午9：00~11：00进行.采用LCPRO+光合作用测定仪测定.测定部位：选取当年生春稍营养枝和结果枝的顶部第3片叶，每个处理测定15片叶，重复3次.测定的主要光合指标包括净光合速率、蒸腾速率、气孔导度、胞间CO2浓度以及水分利用效率(水分利用效率=净光合速率/蒸腾速率).

    • 1.2.2.   叶片采集、处理及测定

  • 7月中旬，在每株试验采样树树冠外围的东南西北4个方位，高度1.5~2.0 m处，采集30片长势一致(当年春稍顶部第3片叶)的成熟健康叶片，将所有样品分别装入塑料袋密封后，立即放入冰盒，24 h内带回实验室处理.参照庄伊美的方法[15]进行清洗和烘干等处理.用蒸馏水冲洗干净，轻轻擦干后，再用电子天平称量叶片鲜质量(mLFW)，然后置入85 ℃烘箱中烘干至恒质量称其干质量(mLDW)，并计算叶片含水量(含水量=叶片鲜质量-叶片干质量)和干物质质量比(干物质质量比=叶片干质量*1 000/叶片鲜质量).将烘干样品粉碎，保存，放置备用.

    • 1.2.3.   叶片营养元素测定

  • 叶片营养元素的测定参照庄伊美、李彩和刁莉华等人的方法[15-17]. N的测定：采用凯式定氮法. S的测定：采用硫酸钡比浊法. P的测定：采用钼锑抗比色法.金属元素K，Ca，Mg，Fe，Mn，Zn，Cu的测定：均采用原子吸收法. B的测定：采用干灰化-甲亚胺比色法.

    • 1.2.4.   果实品质测定

  • 果实成熟期，在每株试验采样树树冠外围的东南西北4个方位，高度1.5~2.0 m处，各方位采1个果实，每个处理3次重复.带回实验室洗净、擦干后测定果实外观品质，再榨汁测定果实内在品质.内在品质可溶性固形物、可滴定酸、Vc、总糖、还原糖等指标按国家标准GB8210-87方法测定.外观品质测定：用电子天平测定单果质量；果皮厚度、果实纵横径用游标卡尺测定，并计算果形指数=果实纵径/果实横径.果实颜色描述采用当前最通用的L*，a*，b*色度空间方法，即在每个果实赤道部的4个不同方位，用日本美能达CR-10色差仪测定[18].

    • 1.3.   数据整理和分析

  • 用Excel进行数据整理，用SPSS Statistics 17.0软件进行统计分析、差异显著性检验和相关性分析.

2.   结果与分析

    2.1.   3种树形不同枝类的叶片水分和光合特性

  • 由表 1可知，3种树形的干物质质量比和叶面积均表现为营养枝高于结果枝，其中开心形营养枝叶片的干物质质量比最高，为437.69 mg/g，Y字形营养枝次之. 3种树形的水分利用效率、净光合速率等分析结果显示，不同树形的营养枝高于结果枝(表 2).由于结果枝叶片着生于冠层中下部较多，因此在同一冠层中，结果枝净光合速率显著低于营养枝，且净光合速率从大到小的顺序均为：Y字形、开心形、自然圆头形，说明树形培养显著地提高了叶片的光合特性.水分利用效率是反映植物生长中能量转化效率的重要指标，Y字形与开心形水分利用效率较高，表明这两种树形能量转化效率高于自然圆头形. Y字形和开心形叶片的蒸腾速率表现为营养枝低于结果枝，而自然圆头形则相反；其中自然圆头形营养枝叶片蒸腾速率最大，为3.18 mmol/m2·s，开心形营养枝最小，前者是后者的1.31倍.不同枝类叶片水分和光合特性的各指标多达到极显著水平.综上所述，不同枝类叶片的干物质质量比、叶面积、水分利用效率、净光合速率均表现出营养枝高于结果枝，且3种树形相比，从大到小依次为：Y字形、开心形、自然圆头形.

    • 2.2.   3种树形不同枝类叶片的营养元素的质量分数

  • 叶片营养状况是树体养分情况的反应，根据柑橘叶片营养元素的质量分数及丰缺评价标准，我们发现参试龙安柚3种树形均表现出N，P，K，Zn的质量分数不足；Ca的质量分数偏高；Mg的质量分数和Fe，Mn，Cu，B的质量比均适量.由表 3可知，大量元素N，P，Ca，Mg均表现为营养枝高于结果枝，最大值分别为2.45%，0.11%，6.54%，0.40%；Y字形和开心形稍高于自然圆头形，但3种树形间差异不显著.由表 4可知，微量元素Mn，Cu的质量比表现为营养枝叶片的质量比高于结果枝，且Y字形和自然圆头形多于开心形；B元素的质量比表现为营养枝低于结果枝，且3种树形的B元素质量比从大到小的顺序为：自然圆头形、Y字形、开心形.综合表 3和表 4结果发现，大量元素的质量分数，多表现为营养枝高于结果枝，开心形高于其他两种树形；微量元素Mn，Cu的质量比，也为营养枝高于结果枝，但Y字形和自然圆头形较多.

    • 2.3.   3种不同树形龙安柚果实品质分析

  • 从果实外部品质来看(表 5)，3种树形的果形指数和果皮亮度L*值的差异不具有统计学意义，但开心形和Y字形均优于自然圆头形.其中，Y字形树形的果实红色指标a*值(-2.31)、黄色指标b*值(61.51) 及a*/b*值(-0.04) 显著高于其他树形；且其果皮色泽亮度L*值(71.66) 最大，果面颜色较深，说明Y字形的果皮色泽最好，该树形有利于提高果实色泽. 3种树形的单果质量、纵横径及果形指数等从大到小的顺序均为：开心形、Y字形、自然圆头形，开心形单果质量是自然圆头形的1.12倍.由表 6可知，Y字形可溶性固形物质量分数、Vc质量比、还原糖质量分数、固酸比、糖酸比显著高于其他树形；但3种树形的可滴定酸、转化糖、蔗糖和总糖的差异不具有统计学意义，且以Y字形最高.结合表 5和表 6可知，未进行修剪的自然圆头形果实品质较差，Y字形和开心形较好.

    • 2.4.   龙安柚不同枝类叶片生理状况与果实品质的相关性分析

  • 营养枝与果实品质的相关性分析发现，叶片中N元素的质量分数与可溶性固形物的质量分数、固酸比、总糖、糖酸比和单果质量均为正相关，而与可滴定酸、Vc质量比呈负相关；P，Mg元素的质量分数与可滴定酸的质量分数、单果质量呈正相关，而与其他果实品质呈负相关；水分利用效率与可溶性固形物的质量分数、可滴定酸的质量分数、固酸比、总糖的质量分数、Vc质量比呈负相关；净光合速率与可溶性固形物的质量分数、固酸比、糖酸比、总糖的质量分数、Vc质量比均呈正相关(表 7).结果枝与果实品质的相关性分析发现，叶片中N元素的质量分数与可溶性固形物的质量分数、可滴定酸的质量分数、固酸比、总糖的质量分数、糖酸比和Vc质量比均为正相关，与单果质量呈负相关；P，Mg元素的质量分数与可滴定酸、单果质量呈正相关，与其他果实品质呈负相关；水分利用效率与可溶性固形物的质量分数、糖酸比、固酸比、总糖的质量分数、Vc质量比呈负相关；净光合速率与可溶性固形物的质量分数、固酸比、糖酸比、总糖的质量分数、Vc质量比均呈正相关(表 8).根据表 7和表 8可知，结果枝和营养枝叶片净光合速率与果实品质多数指标呈正相关，即不同枝类叶片光合速率均影响果实品质.可见，营养枝和结果枝叶片养分含量、生理指标与果实品质均有相关性.

3.   讨论

  • 水分利用效率是生产和水分管理间的关键环节.王建林[13]、曹生奎[19]等提出植物叶片水分利用效率的提高是光合速率提高和蒸腾速率降低共同作用的结果.根据前人研究发现，不同树形间水分、光合特性有所差异，而同一种树形冠层中不同枝类叶片的水分、光合特性也有所差异[20-21].本研究发现，龙安柚不同树形叶片干物质质量比、叶面积、水分利用效率、净光合速率、气孔导度均表现为营养枝显著高于结果枝，且3种树形的这几项指标从大到小的顺序依次为：Y字形、开心形、自然圆头形.但自然圆头形的蒸腾速率大于Y字形和开心形，这说明龙安柚Y字形和开心形的水分利用效率均高于自然圆头形，而龙安柚叶片水分利用效率的提高是光合速率提高和蒸腾速率降低共同作用的结果.

    由于7月中旬为幼果膨大期，对营养元素的需求量大，测定此时的营养元素含量更能反映其与果实品质之间的关系. 3种树形不同枝类上叶片的营养元素含量差异具有统计学意义，营养枝大量元素的含量多数高于结果枝，微量元素中Mn和Cu的质量比也为营养枝显著大于结果枝，这可能是因为取样时为幼果膨大期，该物候期营养中心为果实，根据果树营养就近原则，此时期果实上的营养主要来自于结果枝的叶片，从而导致结果枝叶片营养元素的质量比低于营养枝.根据不同树形间营养元素含量比较发现，开心形中大量元素含量高于其他两种树形；而微量元素含量在Y字形和自然圆头形较多.这说明树体的养分含量，不仅与土壤中矿物元素的有效含量有关，还与树体对矿质营养的吸收和利用能力有关[22]，及其与树体自身遗传差异有关[23].根据王仁矶[24]、Morgan[25]、樊卫国等人[26]提出的有关柑橘叶片营养元素含量及丰缺评价标准，本研究测定的营养元素的质量分数均表现出：N，P，K，Zn含量不足，Ca含量偏高，Mg，Fe，Mn，Cu，B含量适量.说明试验地土壤中N，P，K，Zn的有效含量可能偏低，但由于本文侧重于树形对叶片和果实品质的影响，故土壤中矿质元素含量差异，以及根据其差异进行配方施肥等与果实产量品质的相关性研究，笔者将结合肥效试验研究结果另文报道.

    龙安柚不同树形果实的外观品质和内部品质存在显著差异，Y字形和开心形显著地提高了果实外观品质，与张华[4]、Widmer [7]、张晶楠[27]等人在苹果、柑橘上的研究结果一致.叶片营养元素含量对果实品质的影响错综复杂，养分含量与果实品质间呈现不同程度的相关性，但不同研究者对叶片中矿质营养元素与果实品质的相关性研究结果存在一定差异[28-29]，可能是树种、品种、土壤条件、栽培条件及采样时间等因素差异导致的，具体原因有待进一步分析.本研究发现，不同树形龙安柚营养枝、结果枝叶片的鲜质量，净光合速率，Mg，Mn，Cu，B和果实品质相关性一致，其它测定指标与果实品质间的相关性则不一致.其中营养枝、结果枝叶片的净光合速率与可溶性固形物的质量分数、固酸比、糖酸比、总糖的质量分数、Vc质量比均呈正相关，且二者的水分利用效率与可溶性固形物的质量分数、固酸比、总糖的质量分数、Vc质量比呈负相关.说明营养枝和结果枝对果实品质均有影响，龙安柚修剪管理过程应以适当比例去留不同枝类，具体留枝比例待进一步研究.

    综上，对龙安柚不同树形的营养枝与结果枝叶片的对比分析，能更全面的反映龙安柚整形修剪效应.当然，继续对不同树形在主要物候期的营养枝与结果枝叶片的生长发育动态，以及修剪中不同枝类选留比例等进行比较研究，将对后续龙安柚适宜树形筛选及科学合理修剪技术的应用有重要意义.

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