避雨栽培对梨叶片光合特性与果实品质的影响

吕科良1,曾少敏1,徐 雷2,黄新忠1,姜翠翠1*

1福建省农业科学院果树研究所,福州 350013;2江西省农业科学院园艺研究所,南昌 330200)

摘 要:【目的】探究避雨栽培对梨不同生长发育时期叶片光合特性与果实外观及内在品质的影响,为南方早熟梨产区推广应用避雨栽培模式提供理论依据。【方法】分别于盛花后30、50、70、100和120 d采集避雨栽培和露地栽培模式下绿皮砂梨新品种浙梨6 号叶片和果实样品,测定叶片光合特性、果实品质以及果实糖、酸代谢相关酶活性等生理指标。【结果】相比露地栽培,避雨栽培下各时期浙梨6号果面锈斑少,果实表面光滑,可能与盛花后70~100 d果皮木质素含量显著低于露地栽培有关;避雨栽培增加了浙梨6号叶片叶绿素含量和提高了气孔导度,同时提高了成熟期(盛花后120 d)浙梨6号果实总糖、蔗糖和葡萄糖含量;相关性分析表明,避雨栽培浙梨6号果实高的蔗糖和葡萄糖含量可能分别与蔗糖合成酶(SS)和己糖激酶(HXK)的高活性相关;同时,避雨栽培成熟期(盛花后120 d)浙梨6号果实苹果酸含量显著低于露地栽培,可能与盛花后120 d 的NADP 苹果酸酶(NADP-МE)活性显著升高加速了苹果酸的降解有关。【结论】避雨栽培降低浙梨6号果实表皮木质素含量,减少锈斑形成;同时,增加果实可溶性糖含量、降低有机酸含量,提高糖/酸比。总之,避雨栽培显著提升浙梨6号梨果实外观和内在品质。

关键词:梨;避雨栽培;光合特性;果实品质;酶活性

我国梨(Pyrus L.)栽培历史悠久,2023 年全国梨产量为1986万t,位居世界第一(FAOSTAT)[1]。中国南方地区气候温暖湿润,是早熟梨的优势产区,近年来梨树在江苏、浙江、福建等省大面积种植。在南方梨产区,春季开花坐果阶段常遭遇持续性低温阴雨及晚霜冻害天气侵袭,导致坐果率显著降低;果实发育中前期持续性低温阴雨天气,导致光照严重不足和空气湿度偏高,易造成果实品质低劣、病害严重等问题[2-4],严重制约梨产业的可持续发展。避雨栽培是一种通过设施覆盖手段有效改变微气候环境、构建相对稳定且适宜果树生长的微域空间、防止自然灾害并实现果实成熟期精准调控的栽培模式[5],近年来被广泛应用在梨[6-7]、葡萄[8-9]、桃[10]和樱桃[11]等果树栽培中。

研究表明,避雨栽培可有效减少果树病害的发生,同时对果树的光合作用和果实品质形成具有显著影响。黄新忠等[12]研究表明,避雨栽培能够降低梨树叶部病害发生率,有效抑制梨早期落叶现象;类似地,避雨栽培能有效降低猕猴桃溃疡病的发生[13],避雨栽培还能显著降低葡萄霜霉病和炭疽病的发病率[8-9]。植物叶片的光合作用能够产生其生长发育所需的干物质和有机物,光合作用的强弱决定了作物的生长发育的好坏[14]。猕猴桃上的研究表明,避雨栽培可维持红阳猕猴桃在生长旺盛期的平均净光合速率,优化植株光合作用,提高果实品质[15];郭靖[16]研究表明避雨栽培可以增强夏黑葡萄叶片的光合作用;任俊鹏等[17]研究表明,避雨栽培增加了阳光玫瑰葡萄叶片面积和叶绿素含量,提高了气孔导度,利于其叶片的生长和光合积累。叶片光合作用能力的提升,可增加干物质糖的积累,提升果实品质[14]。杨梅采用避雨栽培后,单果质量、可溶性固形物含量、固酸比和糖酸比显著高于露地栽培[18];甜樱桃避雨栽培模式显著降低果实可滴定酸含量,同时显著提高可溶性蛋白、可溶性固形物及花青苷含量[19];蓝莓避雨栽培显著提升果实的可溶性糖和可溶性蛋白含量,同时降低有机酸含量[20];猕猴桃避雨栽培单果质量、可溶性固形物和可溶性糖含量显著高于露地栽培,维生素C和可滴定酸含量低于露地栽培[21];梨品种翠冠和苏翠1号在避雨条件下可溶性糖积累量升高,特别是蔗糖含量在发育后期显著上升[7]。此外,避雨栽培对果实的着色有一定的影响,孟祥云等[22]研究表明,避雨栽培可以提高葡萄果皮色泽明亮度L*值和黄蓝色度b*值,但红绿色素a*值和色差饱和度c*值均低于露地栽培;在柑橘上的研究表明,避雨栽培可以改善其果实外观品质[23]

果实糖酸积累较为复杂,涉及多种酶的协同或拮抗调控[24]。在蔗糖代谢过程中,蔗糖合酶(SS)、蔗糖磷酸合酶(SPS)与蔗糖转化酶(INV)发挥重要作用[25],其中SS/SPS 活性比与蔗糖含量呈显著正相关,而INV活性则表现相反。己糖激酶(HXK)和果糖激酶(FRK)作为己糖磷酸化核心酶类,直接影响果糖和葡萄糖的生物合成[26]。就果实有机酸而言,其主要与磷酸烯醇式丙酮酸羧化酶(PEPC)、NAD依赖型异柠檬酸脱氢酶(NAD-IDH)、柠檬酸合成酶(CS)、苹果酸酶(NADP-МE)及苹果酸脱氢酶(МDH)等酶的动态调控相关[27]。关于露地栽培下水果果实糖酸积累及相关代谢酶活性研究较多[28-30],然而避雨栽培下果实发育进程中糖酸积累差异及其相关代谢酶活性研究报道较少。

目前关于梨避雨栽培的报道多集中于栽培品种的物候期、生长特性及经济效益等方面的研究,对其不同生长发育时期叶片特性、果实品质及相关酶活性的研究相对较少。笔者在本研究中以最新选育的绿皮砂梨品种浙梨6 号为试验材料,通过比较避雨栽培和露地栽培下梨树不同果实发育时期的叶片光合特性、果实外观、可溶性糖与有机酸含量及其关键代谢酶活性变化等,旨在解析避雨栽培对砂梨品质形成的调控机制,为南方早熟砂梨产区推广避雨栽培模式提供理论依据。

1 材料和方法

1.1 试验地点

试验在福建省建宁县溪口镇枧头村国家梨产业技术体系生产示范园开展。避雨栽培处理采用钢架连栋塑料大棚应用棚架栽培模式(简称避雨栽培),顶高3.5 m,肩高2.7 m,单栋宽4 m,南北走向。对照处理为常规露地棚架栽培模式(简称露地栽培)。供试材料为3年生浙梨6号,树形为双臂顺行式,株行距4 m×4 m。两个栽培区立地和管理条件一致。

1.2 叶片光合分析与果实样品采集

试验于2024 年4 月12 日至2024 年7 月23 日进行。选择天气晴朗的上午9:00—11:00,每株树随机选择3 片树冠中层向阳方向并充分展开的叶片,使用LI-6400XT 型便携式光合作用测量仪(LI-COR)进行光合指标的测定,每3株树为1个重复,每个叶片重复检测3 次;叶片叶绿素含量采用叶绿素仪(SPAD)进行测定。

选择树龄一致、生长健壮树体,于盛花后30、50、70、100、120 d分别收集各测试树体东、南、西、北4个方向的果实,共计150个果;参照《梨种质资源描述规范和数据标准》测定果实单果质量、纵径和横径,然后将果肉与果皮分离,分别保存于-80 ℃超低温冰箱备用。

1.3 果皮不同发育时期酚类物质与木质素含量测定

叶片总酚含量采用福林比色法测定,具体操作参考Yazdani等[31]的测定方法;木质素含量测定采用格锐思公司的木质素含量试剂盒(G0708W48)测定。每个样品设置3个生物学重复。

1.4 果实不同发育时期可溶性糖含量测定

总糖、蔗糖、葡萄糖、果糖和山梨醇含量分别采用格锐思公司的试剂盒(总糖:G0503W,蔗糖、葡萄糖、果糖:G0545W,山梨醇:G0560W)进行测定。每个样品设置3个生物学重复。

1.5 果实不同发育时期有机酸含量测定

有机酸的提取参考王佳悦等[32]的方法。准确称取1.000 0 g 果肉样品,加入5 mL 超纯水,4 ℃研磨匀浆120 s,4 ℃超声30 min,超声后12 000 r·min-1 4 ℃离心10 min,保留上清液,过滤,待上机检测。精确称取5 mg的各标准品置于棕色容量瓶,用超纯水定容至刻度线,作为1 mg·mL-1的单标储备液。移取0.5 mL 的各单标储备液至5 mL 棕色容量瓶中,超纯水定容至刻度,作为0.1 mg·mL-1的标准中间液,标准工作曲线用超纯水配制。采用Agilent HPLC1260高效液相色谱仪进行有机酸含量测定。

1.6 糖代谢相关酶活性测定

采用格锐思公司试剂盒分别检测各果肉样品的己糖激酶(G0810W)、果糖激酶(G0871W)、蔗糖合成酶(合成方向)(G0512W)、蔗糖磷酸合成酶(G0515W)、可溶性酸性转化酶(G0517W)活性,每个样品设置3个生物学重复。

1.7 有机酸代谢相关酶活性测定

采用格锐思公司试剂盒分别检测不同发育时期果肉样品的磷酸烯醇式丙酮酸羧化酶(G0606W)、NADP-苹果酸酶(G0818W)、NAD-苹果酸脱氢酶(G0821W)、NAD-异柠檬酸脱氢酶(G0833W)和柠檬酸合酶(G0834W)活性,每个样品设置3个生物学重复。

1.8 数据分析

采用双尾T检验进行差异显著性分析,P<0.01为极显著差异,P<0.05为显著差异;采用ggplot2软件包进行数据可视化。

2 结果与分析

2.1 避雨栽培对浙梨6号果实外观品质的影响

如图1 所示,盛花后70 d,露地栽培的浙梨6 号果皮表面出现明显的褐色锈斑,且随着果实的生长发育,褐斑面积逐渐增大,并于果实完全成熟期覆盖大部分果表,最终形成褐皮果;而避雨栽培的浙梨6号果面光滑,仅在果实发育后期(盛花后100~120 d)果点附近才出现零星褐色锈斑,但整体果面偏绿。

图1 不同栽培模式下浙梨6 号不同发育期果实外观
Fig.1 The appearances of Zheli No.6 fruits at different development stages under different cultivation patterns

2.2 避雨栽培对浙梨6号果实发育的影响

如图2 所示,盛花后30~100 d,避雨栽培浙梨6号的单果质量、横径和纵径均高于露地栽培,但有且仅有盛花后30 d 的单果质量、横径和纵径较露地栽培显著增大(图2-A~C),果实成熟后避雨栽培浙梨6号的单果质量和纵径显著低于露地栽培。果形指数分析结果显示,仅在盛花后30 d显著低于露地栽培,随着果实的生长发育果形指数与露地栽培表现趋于一致(图2-D)。

图2 不同栽培模式下浙梨6 号不同发育期果实单果质量、纵横径和果形指数变化
Fig.2 Changes of fruit mass,longitudinal and cross diameter,fruit shape index of Zheli No.6 at different development stages under different cultivation patterns

2.3 避雨栽培对浙梨6号果皮总酚与木质素含量的影响

由图3可知,露地栽培的浙梨6号果皮总酚含量在盛花后70 d和120 d显著高于避雨栽培,但在盛花后100 d 避雨栽培的浙梨6 号果皮总酚含量显著高于露地栽培;此外,两种栽培模式下浙梨6号果皮木质素含量均在盛花后70 d 含量最高,而露地栽培浙梨6 号果皮木质素含量极显著高于避雨栽培,但成熟期(盛花后120 d)果皮木质素含量无显著差异。

图3 不同栽培模式下浙梨6 号不同发育期果皮总酚与木质素含量变化
Fig.3 Changes of pericarp total phenol and lignin content of Zheli No.6 at different growth and development stages under different cultivation patterns

2.4 避雨栽培对浙梨6号叶片光合特性的影响

如图4所示,随着果实的发育,两种栽培模式浙梨6 号叶片的叶绿素含量呈逐渐上升的趋势,且避雨栽培盛花后30 d、70 d 和100 d 的浙梨6 号叶片叶绿素含量均显著高于露地栽培(图4-A)。就叶片光合作用分析而言,露地栽培盛花后100 d的浙梨6号叶片净光合速率显著高于避雨栽培(图4-B),而避雨栽培浙梨6号叶片气孔导度则整体显著高于露地栽培,呈先下降后上升的趋势(图4-C);类似地,两种栽培模式的浙梨6号叶片胞间CO2浓度也随着果实发育而呈先下降后上升趋势,且各模式下各发育期的叶片胞间CO2浓度均无显著差异(图4-D)。

图4 不同栽培模式下浙梨6 号不同发育期叶片光合指标变化
Fig.4 Changes of leaf photosynthetic indexes of Zheli No.6 at different growth and development stages under different cultivation patterns

2.5 避雨栽培对浙梨6号果实可溶性糖组分含量的影响

随着果实的发育,两种栽培模式浙梨6号果实总糖、山梨醇、果糖、葡萄糖和蔗糖含量呈逐渐上升的趋势(图5)。露地栽培盛花后30~100 d的浙梨6号果实总糖含量显著高于避雨栽培,但盛花后120 d总糖含量显著低于避雨栽培(图5-A);露地栽培除盛花后30 d浙梨6号果实山梨醇含量显著高于避雨栽培外,其他发育期无显著差异(图5-B);露地栽培盛花后30 d、50 d和100 d浙梨6号果实果糖含量显著高于避雨栽培,其他发育期无显著差异(图5-C);避雨栽培盛花后120 d浙梨6号果实葡萄糖含量和蔗糖含量显著高于露地栽培,其他发育期则显著低于露地栽培(图5-D、E)。

图5 不同栽培模式下浙梨6 号不同生长发育期果实可溶性糖组分变化
Fig.5 Changes of fruit soluble sugar contents of Zheli No.6 at different growth and development stages under different cultivation patterns

2.6 避雨栽培对浙梨6 号果实苹果酸、柠檬酸和奎宁酸含量的影响

避雨栽培盛花后50~70 d 的浙梨6 号果实苹果酸含量显著高于露地栽培,而盛花后120 d苹果酸含量显著低于露地栽培(图6-A);除盛花后100 d 外,其他发育期避雨栽培浙梨6号果实柠檬酸含量显著高于露地栽培(图6-B);避雨栽培盛花后50、100 和120 d 的浙梨6 号果实奎宁酸含量显著高于露地栽培,而盛花后70 d 奎宁酸含量则显著低于露地栽培(图6-C)。

图6 不同栽培模式下浙梨6 号不同生长发育期果实苹果酸、柠檬酸和奎宁酸含量变化
Fig.6 Changes of fruit malic acid,citric acid and quininic acid contents of Zheli No.6 at different growth and development stages under different cultivation patterns

2.7 避雨栽培对浙梨6号果实糖代谢相关酶活性的影响

随着果实的发育,两种栽培模式浙梨6 号果实的果糖激酶(FRK)活性变化趋势基本一致,避雨栽培盛花后100 d 的浙梨6 号果实FRK 活性显著低于露地栽培,而盛花后120 d浙梨6号果实FRK活性显著高于露地栽培(图7-A);两种栽培模式浙梨6号果实己糖激酶(HXK)活性随着果实的生长发育逐渐升高,盛花后120 d 浙梨6 号果实的HXK 活性无显著差异(图7-B);两种栽培模式浙梨6号果实蔗糖合成酶(SS)活性随着果实的生长发育总体呈上升的趋势,避雨栽培盛花后120 d浙梨6号果实的SS活性显著高于露地栽培(图7-C);两种栽培模式浙梨6号果实的蔗糖磷酸合成酶(SPS)活性随着果实的生长发育呈逐渐下降的趋势,盛花后120 d 浙梨6 号果实SPS活性无显著差异(图7-D);两种栽培模式浙梨6号的可溶性酸性转化酶(S-AI)活性随着果实的发育呈逐渐下降的趋势,避雨栽培盛花后100~120 d的浙梨6号果实S-AI活性显著高于露地栽培(图7-E)。

图7 不同栽培模式下浙梨6 号不同生长发育期果实糖代谢相关酶活性变化
Fig.7 Changes of enzyme activities related to fruit sugar metabolism of Zheli No.6 at different growth and development stages under different cultivation patterns

2.8 避雨栽培对浙梨6号果实有机酸代谢相关酶活性的影响

图8显示,随着果实的生长发育,两种栽培模式浙梨6 号果实的磷酸烯醇式丙酮酸羧化酶(PEPC)活性变化趋势一致,都呈下降的趋势,盛花后30~70 d避雨栽培浙梨6号果实PEPC活性显著高于露地栽培(图8-A);盛花后30~70 d,两种栽培模式浙梨6号NADP-苹果酸酶(NADP-МE)活性变化趋势一致,都呈上升-下降的趋势,盛花后120 d 避雨栽培模式浙梨6 号果实的NADP-МE 活性显著高于露地栽培(图8-B);随着果实的发育,两种栽培模式浙梨6 号果实NAD-异柠檬酸脱氢酶(NAD-IDH)活性呈逐渐下降的趋势,避雨栽培浙梨6号果实的NAD-IDH活性显著高于露地栽培(图8-C);盛花后30 d,避雨栽培浙梨6 号果实的NAD-苹果酸脱氢酶(NADМDH)活性显著高于露地栽培,盛花后120 d两种栽培模式浙梨6号果实的NAD-МDH活性无显著差异(图8-D);盛花后100 d 露地栽培浙梨6 号果实的柠檬酸合酶(CS)活性显著高于避雨栽培,而盛花后120 d避雨栽培浙梨6号果实的CS活性显著高于露地栽培(图8-E)。

图8 不同栽培模式下浙梨6 号果实有机酸代谢相关酶活性分析
Fig.8 Changes of enzyme activities related to fruit organic acid metabolism of Zheli No.6 at different growth and development stages under different cultivation patterns

2.9 浙梨6号果实可溶性糖与有机酸含量及其相关代谢酶活性的相关性分析

果实可溶性糖含量与有机酸含量的相关性分析如图9-A所示,两种栽培模式浙梨6号果实可溶性糖含量与有机酸含量均呈负相关;避雨栽培浙梨6 号果实果糖、葡萄糖含量与柠檬酸含量呈显著负相关;露地栽培果糖含量与柠檬酸含量呈显著负相关,蔗糖含量与奎宁酸含量呈显著负相关。

图9 不同栽培模式下浙梨6 号果实可溶性糖与有机酸及其代谢酶活性的相关性分析
Fig.9 Analysis of the correlation between fruit soluble sugars,organic acids and their metabolic enzyme activities in Zheli No.6 under different cultivation patterns

FRK.果糖激酶;HXK.己糖激酶;SS.蔗糖合成酶;SPS.蔗糖磷酸合成酶;S-AI.可溶性酸性转化酶;PEPC.磷酸烯醇式丙酮酸羧化酶;NADPМE. NADP-苹果酸酶;NAD-IDH. NAD-异柠檬酸脱氢酶;NAD-МDH. NAD-苹果酸脱氢酶;CS. 柠檬酸合酶;*. 表示处理间差异显著(P<0.05);**.表示处理间差异极显著(P<0.01)。
FRK.Fructokinase;HXK.Hexokinase;SS.Sucrose synthase;SPS.Sucrose phosphate synthase;S-AI.Soluble acid invertase;PEPC.Phosphoenolpyruvate carboxylase;NADP-МE.NADP-malic enzyme;NAD-IDH.NAD-malate dehydrogenase;NAD-МDH.NAD-isocitrate dehydrogenase;CS.Citrate synthase;*.Indicate a significant differences(P<0.05);**.Indicate a highly significant differences(P<0.01).

进一步研究了浙梨6号果实可溶性糖含量与有机酸含量及其相关代谢酶活性的相关性。结果表明避雨栽培浙梨6 号果实的山梨醇含量与FRK、HXK活性呈显著正相关,果糖、葡萄糖含量与HXK 活性呈显著正相关,蔗糖含量与SS 活性呈显著正相关;露地栽培浙梨6 号果实的果糖含量与HXK 活性呈显著正相关,葡萄糖含量则与FRK、HXK 活性均呈显著正相关(图9-B);避雨栽培浙梨6号果实不同发育时期苹果酸、奎宁酸含量与PEPC、NADP-МE 活性呈显著正相关,柠檬酸含量与NAD-МDH活性呈显著正相关(图9-C)。

3 讨 论

避雨栽培作为一种果树保护性栽培方式,可避免果实因淋雨导致着色不均等问题,在桃[33]、柑橘[23]、樱桃[34]等果树上采用避雨栽培可有效改善果实外观品质。本研究中应用避雨栽培的浙梨6号果面锈斑少,果实表面光滑,外观品质得到明显改善。研究表明木质素是梨果皮果锈的主要成分[35-36]。衡伟等[37]研究表明,花后75~125 d 是砀山酥梨芽变褐皮品种锈酥梨褐皮形成的关键时期,此时木质素含量显著升高;Jiang 等[38]研究表明盛花后50 d 是褐皮梨新玉木质素积累的关键时期,本研究中盛花后70~100 d 露地栽培的浙梨6 号果皮木质素含量显著高于避雨栽培,进一步证实了前人的研究结果。

避雨栽培除对果实外观品质有影响外,对果实大小及果形指数也有显著影响。陈佳鑫等[21]等研究表明,避雨栽培猕猴桃果实单果质量、纵径和横径均显著高于露地栽培;宋莎等[39]研究了贵州中部避雨栽培下7个甜樱桃品种果实性状,表明不同品种间的单果质量和果形指数受避雨栽培影响差异较大;肖金平等[33]研究表明,避雨栽培下丹霞玉露和迟玉露两个桃品种单果质量显著低于露地栽培;与露地栽培相比,避雨栽培的苏翠1号、翠冠、黄冠和粤引早脆果实单果质量显著提高[40-42],而晚翠和黄花果实的单果质量则显著低于露地栽培[6]。本研究中,果实成熟期(盛花后120 d)避雨栽培浙梨6号果实的单果质量显著低于露地栽培,果形指数差异不显著,表明避雨栽培对果实单果质量和果形指数的影响因品种不同而表现不同。

叶片光合作用的强弱决定了果实的产量和果实品质。净光合速率、气孔导度、蒸腾速率和胞间CO2浓度是反映光合作用的重要指标[43]。戴美松等[44]研究表明葡萄避雨栽培净光合速率显著低于露地栽培,其主要原因是避雨设施棚顶覆膜对阳光的削弱与遮挡的影响,使避雨栽培光照度显著低于露地栽培,影响叶片光合效率,但是避雨设施内相对弱光环境可以促进叶片叶绿素含量提高[42,45];任俊鹏等[17]研究也表明,避雨栽培下葡萄叶片蒸腾速率、气孔导度和胞间CO2浓度均高于露地栽培,而净光合速率则低于露地栽培;杨俊强等[46]的研究表明,避雨设施虽然降低了设施内的光合有效辐射,但是减弱了光抑制现象,净光合速率不受影响。本研究中,避雨栽培浙梨6号叶片的气孔导度显著高于露地栽培,净光合速率在果实成熟期无显著差异,表明避雨栽培并没有影响梨叶片的净光合速率。同时,避雨栽培有效增加了梨叶片叶绿素含量,有利于对光能的捕获和吸收,从而有效利用弱光,提高植株的光合效率[47]

研究表明,叶片高的光合效率可以增加光合产物,为果实糖合成及积累提供物质保障[48]。本研究中,盛花后120 d 避雨栽培浙梨6 号果实的总糖、蔗糖和葡萄糖含量显著高于露地栽培,与李刚波等[40]报道相一致,这可能与避雨栽培下浙梨6 号植株高的光合效率有关。类似地,避雨栽培也能促进桃果实的蔗糖和果糖积累,其含量可达露地栽培的两倍以上[33]。此外,果实的糖含量还与糖代谢相关酶活性密切相关[49-50]。研究表明,SS、SPS 和INV 活性与蔗糖代谢合成相关,HXK和FRK直接影响果糖和葡萄糖的生物合成[25-26]。张琮[51]研究发现避雨栽培东魁杨梅果实的SPS 活性显著高于露地栽培,且蔗糖含量与SPS活性呈显著正相关,与SS活性无显著相关性。本研究中避雨栽培浙梨6 号果实SS 活性显著高于露地栽培且与蔗糖含量呈显著正相关,而SPS活性在两种栽培模式下无显著差异且与蔗糖含量无相关性,表明不同物种影响蔗糖含量的代谢酶活性不同。HXK 是植物中唯一可以磷酸化葡萄糖的酶,是糖酵解途径的关键限速酶,在植物生长和发育过程中也起着至关重要的作用[52]。梨中有10 个HXK 基因,其中PbrHXK1PbrHXK3 与其酶活性变化趋势一致,且与己糖积累呈显著正相关[53],本研究中两种栽培模式下浙梨6 号果实HXK 活性均与果糖、葡萄糖含量呈显著正相关。

有机酸含量也是影响梨果实品质的重要因素,苹果酸、柠檬酸和奎宁酸是梨果实中最主要的有机酸[54]。李刚波等[7]研究表明,避雨栽培翠冠和苏翠1号梨果实中的苹果酸、柠檬酸和奎宁酸含量显著低于露地栽培;王晓庆等[55]研究表明避雨栽培梨果实的有机酸含量显著低于露地栽培;猕猴桃[55]和杨梅[56]上也研究表明,避雨栽培可以降低果实中有机酸的含量,提高糖酸比。本研究结果显示,花后120 d 避雨栽培浙梨6 号果实的苹果酸含量显著低于露地栽培,与前人研究结果相一致。研究表明果实有机酸含量主要与PEPC、NAD-IDH、CS、NADPМE和МDH等酶的动态调控相关[27]。通过对3种酸与有机酸代谢相关酶进行相关性分析,发现避雨栽培浙梨6 号果实不同发育时期苹果酸、奎宁酸含量与PEPC 和NADP-МE 活性呈显著正相关,表明PEPC、NADP-МE 是导致避雨栽培浙梨6 号梨果实苹果酸含量低于露地栽培的两个关键酶。

4 结 论

综上所述,避雨栽培可降低浙梨6 号果皮木质素含量,有效抑制果面锈斑形成,使梨果面光滑美观;避雨栽培增加了浙梨6 号叶片叶绿素含量和提高了气孔导度,增加了干物质糖的积累,特别是总糖、葡萄糖和蔗糖含量;相关性分析表明,避雨栽培高的蔗糖含量可能与蔗糖合成酶(SS)活性相关,高的葡萄糖含量可能与己糖激酶(HXK)活性相关,而避雨栽培低的苹果酸含量与发育后期高的依赖细胞质NADP的苹果酸酶(NADP-МE)活性相关,增大果实糖酸比;总之,避雨栽培可显著提升梨果实外观品质和内在品质,可在南方梨产区推广应用。

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Effects of rain-shelter cultivation on leaf photosynthetic characteristics and fruit quality in pear

LÜ Keliang1,ZENG Shaomin1,XU Lei2,HUANG Xinzhong1,JIANG Cuicui1*
(1Fruit Research Institute,Fujian Academy of Agricultural Sciences,Fuzhou 350013,Fujian,China;2Horticultural Research Institute,Jiangxi Academy of Agricultural Sciences,Nanchang 330200,Jiangxi,China)

Abstract:【Objective】Rain-shelter cultivation has been widely implemented in fruit production to cope with adverse environmental stresses and enhance the fruit quality. However, its physiological effects on photosynthetic parameters, sugar-acid metabolism and related metabolic enzymatic activity in pear remain poorly understood. This study investigated the impact of rain-shelter cultivation on leaf photosynthetic performance, fruit appearance, and internal quality of the green-skin pear cultivar Zheli No. 6 at various developmental stages. This study aims to provide theoretical reference for optimizing cultivation practices in the humid and rainy pear-growing regions of southern China.【Мethods】Field experiments were conducted at the National Pear Industry Technology System Production Demonstration Orchard in Jiantou Village, Xikou Town, Jianning County, Fujian Province, to compare the aforementioned indicators of pear trees grown in rain-shelter (plastic greenhouse) and open-field cultivation patterns. Leaf and fruit samples from Zheli No. 6 pear trees were collected at 30, 50, 70, 100, and 120 days after full bloom(DAFB).Leaf photosynthetic parameters,including chlorophyll content,net photosynthetic rate,stomatal conductance,and intercellular CO2 concentration,were measured using a chlorophyll meter(SPAD)and a portable photosynthesis system(LI-6400XT),respectively.Fruit internal quality traits,such as soluble sugars,pericarp lignin,and phenolic compounds,were analyzed using spectrophotometric methods, and the levels of organic acids were quantified via the high-performance liquid chromatography (HPLC). In addition, the activities of sugar metabolism- and organic acid metabolismrelated-enzymes were quantified using commercially available reagent kits, comprising sucrose synthase (SS), hexokinase (HXK), fructokinase (FRK), sucrose phosphate synthase (SPS), soluble acid invertase (S-AI), and phosphoenolpyruvate carboxylase (PEPC), NADP-malic enzyme (NADP-МE),NAD-malate dehydrogenase(NAD-МDH),as well as NAD-isocitrate dehydrogenase(NAD-IDH),and citrate synthase (CS). Furthermore, the Pearson correlation analysis of soluble sugars, organic acids,and their key metabolic activities were performed to identify key factors contributing to metabolic differences between cultivation systems.【Results】For fruits of Zheli No.6 grown under open-field cultivation, the brown russet unevenly appeared on the skin beginning at 70 DAFB, and the russet area expanded progressively during fruit development.At fruit maturity (120 DAFB), the russet area covered most of the fruit skin and resulted in rough brown-skin fruits.However,for fruits of Zheli No.6 grown under rain-shelter cultivation, same russet spots appeared near lenticels starting at 100 DAFB, and the fruit skins kept a smooth green surface until fruit maturity.The significantly lower lignin content in the skin of rain-shelter cultivation fruits(with no or sparse russet)compared to open-field cultivation fruits(with more russet)at the same developmental stage,might be associated with the changes in lignin content.At the early fruit developmental stage (30 DAFB), the single fruit mass, transverse diameter, and longitudinal diameter of Zheli No. 6 under rain-shelter cultivation were significantly higher than those under open-field cultivation; however, no significant differences were observed in these traits between cultivation methods during 50-100 DAFB.By contrast,at fruit maturity(120 DAFB),these traits under rain-shelter cultivation were significantly lower than those under open-field cultivation.Compared with open-field cultivation, Zheli No. 6 under rain-shelter conditions had significantly higher leaf chlorophyll content and stomatal conductance, while the net photosynthetic rate remained comparable between the two cultivation patterns.This suggested that rain-shelter cultivation did not impair leaf photosynthetic efficiency.Rather,leaves under rain-shelter conditions likely underwent adaptive regulation to enhance photosynthetic capacity and increase assimilate production,thereby potentially supporting sugar accumulation in developing fruits. Analysis of soluble sugar content revealed that sorbitol was the most abundant sugar at early fruit development stage. Fructose, glucose, and sucrose levels increased steadily throughout development, with fructose becoming the dominant sugar at maturity. Significant differences in total and individual sugar contents were observed between the two cultivation systems in mature fruits.Under rain-shelter cultivation,mature Zheli No.6 fruits had significantly higher levels of total sugars, sucrose, and glucose than those grown in open fields. Correlation analysis showed that sucrose content was significantly and positively associated with SS activity, while glucose content was positively correlated with HXK activity. These findings suggested that elevated SS and HXK activities may contribute to the increased sucrose and glucose levels under rain-shelter cultivation. Organic acid profiling showed that malic,citric,and quinic acids followed similar accumulation patterns in both cultivation systems, with malic acid being the predominant component. However, the malic acid content in mature fruits was significantly lower under rain-shelter cultivation,while the citric and quinic acid contents were significantly higher.The differences in total organic acid content were mainly driven by variations in malic acid levels. Correlation analysis revealed significant associations between malic acid content and the activities of PEPC and NADP-МE, indicating that these enzymes played key roles in the reduced malic acid content observed under rain-shelter cultivation.【Conclusion】Rain-shelter cultivation can significantly enhance both the appearance and internal quality of pear fruits and is suitable for application in the humid,and rain-rich pear-growing regions of southern China.

Key words:Pyrus pyrifolia; Rain-shelter cultivation; Photosynthetic characteristics; Fruit quality; Enzyme activity

中图分类号:S661.2

文献标志码:A

文章编号:1009-9980(2025)09-2028-15

DOI:10.13925/j.cnki.gsxb.20250290

收稿日期:2025-05-23

接受日期:2025-07-17

基金项目:国家梨产业技术体系福州综合试验站项目(CARS-28-35);“十四五”福建省种业创新与产业化工程项目(zycxny2021010);中央引导地方科技发展资金项目(2023L3025)

作者简介:吕科良,男,助理研究员,博士,研究方向:果树遗传育种与发育生理。E-mail:lvkelianglkl@163.com

*通信作者Author for correspondence. E-mail:cuiliao2046@163.com