阳光玫瑰葡萄叶片发育与衰老期间矿质营养与光合能力变化及相关性研究

赵世利,邓蔡妍,曾稚雅,邬梦露,石星儿,段晓妍,程丽兰,南科淼,黄旭明*

(华南农业大学园艺学院,广州 510642)

摘 要:【目的】掌握葡萄叶片光合能力和矿质营养变化规律,探明影响光合功能的关键营养因子。【方法】以平棚架式4~5年生5BB砧阳光玫瑰植株为研究试材,于采后生长季节(9月中)测定同一枝不同节位叶片净光合速率(Pn)及其矿质元素含量;在入秋后追踪固定节位(第8节位)叶衰老过程中Pn、SPAD值和矿质营养含量,进行相关性分析。【结果】第8节位Pn达到与最大值无显著差异水平,说明该节位叶片已经发育充分成熟,而同枝条上衰老叶SPAD和Pn显著下降。叶片氮、磷、钾、铜在第8节位后达到稳态,而钙和锰则随叶位升高(叶龄)呈积累趋势。9月中的衰老叶的氮、磷、钾、锌、硼、铜元素内吸收率分别为44.6%、44.4%、71.1%、25.8%、24.6%和10.5%,钙、铁、镁、锰内吸收率接近0或为负值。不同节位叶片锰含量与Pn值呈显著正相关。入冬衰老叶片仅氮、锌、钾元素含量有所降低,其余营养元素再利用率均为负值,氮含量与Pn呈显著正相关。【结论】阳光玫瑰在生长季节可移动元素再利用率较高,入冬后衰老叶片矿质再利用能力全面降低。锰可能是叶片光合能力形成的限制性营养因子,氮可能是老叶光合能力维持的关键营养因子。

关键词:阳光玫瑰葡萄;叶片发育;叶片衰老;光合作用;矿质元素;内吸收

葡萄(Vitis L.)是世界性果树。2018 年,中国葡萄产业迅猛发展,总产量位居世界第一,面积第二[1]。随着南方葡萄生产技术的进步,华南地区成为了一年双收的葡萄特色产区,广东也迎来了葡萄产业发展的新机遇[2]。源自日本的欧美杂交种阳光玫瑰葡萄,以其优异食用品质和环境适应性,深受广大种植者和消费者的青睐[3]。因其在广东种植综合性状优异[4],成为了广东省发展最快的主栽葡萄品种之一。

光合作用是植物生长和物质积累的基础,对于葡萄养分积累、品质形成和产能可持续性至关重要。叶片的光合功能与矿质营养的摄取密切相关,这些营养参与了光合机构的构建、光合代谢运转和能量转化、光合产物的转运等等,其含量会直接影响光合生理过程。氮素是植物需求最大的必需元素,是叶绿素及结构和功能蛋白的重要组分,氮不足对果树叶片光合功能和寿命有显著影响[5-6]。磷直接参与了光合产物输出、光合碳代谢、电子传递速率及能量转换[7]。钾和镁参与气孔的开放调控、叶绿素合成、Rubisco 酶激活、光合产物输出和光保护等过程[8-10]。铜、铁、锰、锌是光合机构或酶的重要辅因子,参与氧化还原反应和光合电子传递[11]。其中,锰是光系统Ⅱ电子供体侧的放氧复合体的核心元素,直接参与了水的分解,使之成为电子传递链的最终电子供体[12]。硼虽然不直接参与光合机构构建和代谢过程的运转,但它参与了光合产物向库器官运输,缺硼导致生长停止和光合产物积累,对光合作用有反馈抑制效应[13]

随着叶片进入衰老状态,其光合能力减弱,叶片中的营养物质流失,这可能是叶片衰老的原因,并不是叶片衰老的结果[14]。植物衰老死亡部分在脱落前,将其部分营养库物质重新转移到植物其他器官的现象,称为“内吸收”(resorption)[15]。内吸收在衰老的叶片表现最为明显,但不同树种、不同营养元素从叶片“撤离”比率或内吸收率有较大的差异[15-16]

叶片既是果树从土壤获取养分的中转站,又是树体对土壤养分供应最敏感的响应器官,故了解叶片矿质元素含量的动态变化对指导科学施肥具有十分重要的意义[15]。叶片是光合作用场所,其光合功能受制于营养“木桶”的“短板因子”,在叶片发育的不同阶段,光合功能的营养“短板因子”可能有所不同。Fu 等[17]在荔枝、苹果和毛叶枣等跨树种的研究中发现,叶片光合功能构建期间,锰元素可能是光合功能的营养“短板因子”,但在葡萄中尚未见报道。此外,关于葡萄叶片在生长季和冬季的衰老过程中各种矿质营养内吸收情况也未见报道。笔者在本研究中以种植在南亚热带地区(广州)的阳光玫瑰葡萄叶片为试验材料,探究叶片发育及衰老过程中葡萄叶片光合能力的变化规律和矿质营养的动态变化,分析光合能力与矿质元素的相关性,揭示影响光合功能的关键营养因子,分析生长季和冬季衰老叶片各种矿质营养内吸收情况,为指导葡萄的养分管理、促进光合能力构建提供理论参考。

1 材料和方法

1.1 试验材料

本试验于2019年和2020年进行,材料为华南农业大学启林北葡萄试验园中避雨大棚下的4~5年生“T”形平棚架式5BB 砧阳光玫瑰葡萄植株,采用1.5 m×1.0 m×1.0 m(长×宽×高)限根池种植,每池添加约1 m3本地泥土,加300 L泥炭、40 kg发酵鸡粪和10 kg 过磷酸钙,土壤pH=6.8,植株密度3 m×6 m。于2月初进行超短枝(留1~2个冬芽)修剪,2月中旬进行单氰胺促萌处理,促萌前10 d进行充分灌溉,保持土壤湿润;4月初盛花,花穗以上每4片叶摘心,保留顶部副梢生长,其余节位副梢留1 叶绝后摘心。坐果期间,每米主蔓约6个结果枝,每个结果枝保留1 个果穗,花前进行疏花穗,保留穗尖5 cm,并用常规无核化及膨大处理,每穗质量约500 g。采用常规肥水管理:冬季株施精制有机肥25 kg,落叶回填根池;促萌处理至花前期,间隔2 周株施25-5-8(N-PK,后同)+2 MgO 100 g两次,每2 d浇水1次(每次滴灌20 min约20 L),保持土壤湿润;盛花至硬核期间隔2周株施20-5-15+3 CaO+2 MgO+微量元素100 g 三次,保持土壤湿润;硬核后株施0-0-35+5 Mg 200 g一次,灌水减少至5 d 浇水一次;8 月20 日采收后株施20-5-15+3 CaO+2 MgO+微量元素200 g 一次,每10 d 灌水1 次。

1.2 试验处理

于2019年9月15日进行(当日晴天),从不同的5 株长势一致的阳光玫瑰植株中各选1 个生长状况良好且相近的枝梢,自顶向基从第3片新叶开始,逐一测定枝梢第3~16 节位上的叶片光合参数与叶绿素指数(SPAD 值),并选同一枝梢基部明显黄化的衰老叶(在第17 节位以上)测定。在8:30—11:30 完成测定。随后按节位分别采集叶片及衰老叶,用蒸馏水表面漂洗,擦干后将叶片置于65 ℃烘干72 h,逐一称质量并分析矿质元素含量。获得同一叶片的叶绿素指数、光合参数及矿质营养数据,用于相关分析。

于2020年9月10日从5株阳光玫瑰分别选取4个生长状况良好且相近的枝梢并做好标记,将每个枝梢由顶向基的第8节位功能叶片挂牌标记,于9月23 日、10 月23 日、11 月25 日及12 月25 日测定标记叶片和4条邻近枝梢相同叶位叶片光合参数和叶绿素指数后,采集邻近枝的叶片用于测定矿质元素,于12月25日完成对标记叶片进行光合参数、叶绿素荧光参数和叶绿素指数测定后,采集标记叶片。叶样用蒸馏水表面漂洗,擦干后将叶片置于65 ℃烘干72 h,逐一称质量,用于测定矿质元素含量。获得同一叶片的叶绿素指数、光合参数及矿质营养数据,用于相关分析。

1.3 相关指标的测定方法

叶绿素指数(SPAD 值)用SPAD-502 叶绿素仪(日本Minolta)测定。叶片净光合速率(Pn)用CIRAS-3 便携式光合仪(美国PP System)测定。用凯式自动定氮仪进行蒸馏定氮;用钼锑抗比色法测定磷含量;用火焰光度法测定钾含量;用原子吸收光谱法测定钙、镁、铜、锌、铁等必需元素含量。

各种元素在叶片衰老时再利用情况以内吸收率(Resorption rate)表示,参考王文卿等[15]的报道,按以下公式计算:

在不同节位叶片样品中,以光合速率最高的节位(由顶向基16节位)上叶片矿质元素含量作为Xm;以同一枝梢上的衰老叶片矿质元素含量作为Xi。在不同月份的比较试验中,以9 月初标记的功能叶同一节位的叶片元素为Xm,以12月份该叶片衰老时叶矿质元素含量为Xi,计算冬季叶片衰老时矿质元素再利用率。

1.4 数据分析

以上分析均设5 个生物学重复。采用Excel 2016 进行数据整理和作图。使用SPSS 25.0 软件进行方差分析、T测验,利用Duncan’s新复极差法进行多重比较和相关与回归分析。

2 结果与分析

2.1 生长季节不同节位叶片光合参数及矿质营养差异

在广州9 月份葡萄仍维持很强的长势,但枝梢基部的一些节位陆续出现黄化衰老的叶片。不同节位光合参数有显著差异,由顶向基第3 至第10 节位叶片的SPAD 值逐渐增大,并达到与最大值接近水平。叶片Pn也同步提高(表1),在第8节位达到与最大值差异不显著水平。除第12 节位较低外,第10~16 节位SPAD 值保持相对稳定,光合速率维持较高水平,说明叶片趋渐成熟;结果枝基部的叶片(第17节位以上)明显黄化衰老,其SPAD 和Pn均显著降低,光合功能大幅度丧失。从第3~16 节位,叶片逐渐老熟,光合功能不断完善,但在各节位的成熟叶片中,第12节位的成熟叶光合功能最弱。

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氮、磷、钾含量在幼叶中高,并在3至8节位随叶片升高(叶片扩展)而明显降低;而8~16节位的叶片3种元素含量相对稳定,而衰老叶片显著下降;钙、锰总体上随叶龄(节位)提高而积累,说明这些元素的吸收快于叶片生长,而在生长稀释效应下其浓度仍然上升;镁含量相对稳定;铜含量总体上随叶龄提高而减少;锌、硼含量在不同节位的规律性并不明显,但衰老叶显著降低;铁在幼叶中含量较高,在6~15 节位的成熟叶相对稳定,衰老叶再度积累。其中,氮、磷、钾、锌、硼含量在衰老叶中明显下降,意味着这些元素可能在叶片衰老过程中会部分撤出衰老叶片。

Pn值最高的第16节位为代表功能叶,其矿质营养含量与衰老叶含量的差可以反映衰老叶片矿质营养再利用情况,并计算该营养的内吸收率。可见,氮、磷、钾、锌、硼的内吸收率分别为44.6%、44.4%、71.1%、25.8%和24.6%;铜的再利用率为10.5%;而镁和锰内吸收率接近0;钙和铁内吸收率为负数(分别为-16.9%和-16.3%),说明这些元素是持续积累的,在生长季节葡萄衰老叶的钙、铁、镁、锰几乎不可再利用。

由于3~8 节位的叶片处于生长状态,对氮、磷、钾的稀释效应比较明显,故而分析8~16节位的成长叶矿质营养含量与Pn的相关性,结果表明,除锰元素含量与Pn呈现显著正相关外,其余元素含量与Pn

2.2 冬季叶片衰老期间光合速率与矿质营养动态

由表3可见,9月份的功能叶至12月底时,SPAD相关性均不显著(表2)。各节位叶片的Pn值与锰含量的回归分析表明,拟合为二次函数关系(R2=0.652 5,p=0.003)比线性函数关系(R2=0.562 9,p=0.002)更为合适(图1)。根据该二次方程,当锰含量(w,后同)达到66.96 mg·kg-1时,Pn达到极大值。这一结果表明,新成长的叶片光合能力形成可能主要受到锰营养限制,而当叶片锰达到66.96 mg·kg-1时,锰元素不再是光合能力形成的限制因子。和Pn均显著下降,12月份的Pn仅为0.35 μmol·m-2·s-1

图1 不同节位叶片锰元素含量与其净光合速率的线性
和二次方程回归分析
Fig.1 Linear and quadratic regressions between Mn content and net photosynthetic rate

表2 生长季节不同节位叶片矿质营养与其净光合速率的相关性分析
Table 2 Correlations between mineral nutrients and net photosynthetic rate in mature leaves during growth season

注:*表示相关性达到显著水平。
Note:*indicates significant correlation at p <0.05.

矿质营养Mineral N P K C a Mg Cu Zn Fe Mn B显著性Significance(p-value)0.533 0.915 0.161 0.118 0.188 0.463 0.054 0.794 0.039*0.625相关系数Correlation coefficient 0.240 0.042-0.510 0.559 0.484-0.281 0.657 0.102 0.691-0.190

表3 冬季叶片衰老过程中SPAD 值、Pn及矿质营养含量比较
Table 3 Comparison of SPAD value,net photosynthetic rate and mineral nutrient content of functional leaves and senescent leaves of Shine Muscat grapes in different months

注:不同小写字母表示相同状态不同月份差异达到显著水平(p <0.05,Duncan 多重比较)。内吸收率是用9 月份第8 节位成熟叶片及同节位冬季衰老叶片来计算。
Note:Different small letters indicate significant difference between months at p <0.05(Duncan’s multiple range test). Resorption rate is calculated using the mineral contents of functional leaves at node 8 in September and those of senesced leaves in December.

指标Index SPAD净光合速率Pn/(μmol·m-2·s-1)w(N)/(g·kg-1)w(P)/(g·kg-1)w(K)/(g·kg-1)w(Ca)/(g·kg-1)w(Mg)/(g·kg-1)w(Cu)/(mg·kg-1)w(Zn)/(mg·kg-1)w(Fe)/(mg·kg-1)w(Mn)/(mg·kg-1)w(B)/(mg·kg-1)内吸收率Resorption rate/%24.3-79.3 0.6-12.3-17.4-7.7 18.4-58.3-78.3-150.2 9月September 38.70±0.97 a 12.93±0.98 a 20.60±0.56 b 1.74±0.16 b 4.70±0.66 a 26.90±1.44 a 1.38±0.08 a 6.12±0.57 a 31.60±2.60 a 108.00±12.20 b 193.50±41.10 b 52.60±4.66 b 10月October 39.80±1.39 a 6.31±1.28 b 23.69±0.60 a 3.50±0.36 a 5.35±0.40 a 27.48±1.70 a 1.54±0.07 a 5.15±0.30 ab 20.60±2.42 b 115.30±4.60 b 270.50±39.20 ab 106.30±10.70 a 11月December 34.70±1.57 a 3.06±0.93 c 17.90±0.97 c 3.09±0.38 a 5.08±0.53 a 29.40±1.50 a 1.54±0.09 a 3.91±0.36 b 31.10±4.15 a 133.59±12.02 ab 342.19±48.95 a 109.53±14.64 a 12月December 24.00±2.39 b 0.35±0.63 c 15.6±0.69 d 3.12±0.29 a 4.67±0.47 a 30.20±1.93 a 1.62±0.10 a 6.59±0.74 a 25.8±1.65 ab 171.00±19.92 a 345.00±47.62 a 131.60±8.81 a

9至12月期间,同节位叶片光合速率逐渐降低,而叶绿素指数SPAD值仅在12月显著降低,此时,叶片显著黄化,叶片光合功能几乎完全丧失(表3)。不同种矿质元素含量变化规律有所差异。氮含量在9至10月显著增高,之后持续显著下降。磷含量在9至10 月显著上升,之后维持相对稳定,钾含量略有波动,但总体差异不大;钙、镁含量在各月虽无显著差异,但呈现积累趋势;铁、锰、硼含量则随叶片衰老明显积累;铜含量在9 至11 月明显下降,但在12 月又显著上升,锌含量有显著波动,变化规律不明显。

入冬后在短日、低温诱导下,葡萄叶片发生系统性衰老。比较9 月份和12 月份功能叶矿质元素含量,并计算冬季衰老叶的矿质元素内吸收率(表3),发现仅氮、锌、钾再利用率为正值,其中氮、锌的内吸收率分别为24.3%和18.4%,而钾内吸收率非常低,仅0.6%;而磷、钙、镁、铜、铁、锰、硼的内吸收率均为负值,表明这些元素随冬季叶片衰老而积累,会随衰老叶的脱落而丧失。

由表4可见,入冬后叶片衰老期间,仅叶片氮含量与Pn呈显著正相关,而锰和铁含量与Pn呈极显著负相关。其余元素含量与Pn相关性并不显著。对比表2,在生长季节和秋冬衰老季节叶片光合速率与各矿质营养的相关性有很大的差异。在衰老的叶片中,氮营养可能是光合能力维持的关键营养。而锰、铁、硼属于持续积累型营养,随着叶片衰老,体现出与Pn存在明显的负相关。

表4 阳光玫瑰叶片冬季衰老期间各矿质元素含量与净光合速率(Pn)的相关性分析
Table 4 Correlations between the contents of mineral elements and the net photosynthetic rate in senescing leaves of Shine Muscat in winter

注:*和**分别表示在p<0.05 和p<0.01 水平上相关性达到显著水平。
Note:* and ** indicate significant correlation at p<0.05 and p<0.01,respectively.

显著性Significance 0.032*0.297 0.974 0.070 0.092 0.675 0.257 0.005**0.002**0.394矿质元素Mineral element N P K C a Mg Cu Zn Fe Mn B相关系数Correlation coefficient 0.676-0.367-0.012-0.581-0.561-0.152-0.396-0.803-0.850-0.303

3 讨 论

本研究表明,不同生长状态叶片光合能力变化伴随着矿质营养变化。广东地处南亚热带气候区,对于葡萄而言,周年生长时间长[2]。9—10月份北方地区的葡萄开始落叶逐步进入休眠,广州的气温仍然非常适于葡萄的生长。葡萄的梢尖分生组织在生长季可持续分裂,进行器官发生,抽生新叶,直至入冬前,梢尖脱落[18]。在同一枝梢(生长轴)上自顶向基叶片逐渐成熟老化,叶色加深,光合速率提高。其中3~8节位叶片扩大并革质化,光合速率快速提高,涉及光合机构(photosynthetic apparatus)的构建;8~16节位叶片维持相近且较高的光合速率,说明在第8节位的叶片光合机构构建已经基本完善。而枝梢基部的老叶发生黄化,光合速率明显降低,表明此叶片已经进入衰老状态。

植物必需的矿质营养在细胞构建和代谢功能中起了不可替代的作用。这些营养元素直接或间接参与了光合作用,包括光合机构的构建、电子传递、能量转化、碳固定代谢,以及光合产物的转运等,进而对光合作用能力的形成和维持具有重要作用。在生长季,各种营养在同一枝梢不同节位叶片的含量变化趋势有很大差异。氮、磷、钾、铜含量在最幼嫩的叶片中最高,而在3~8节位的叶片氮、磷、钾含量呈现随叶片生长发育而下降趋势,说明叶片这些元素的摄取速度低于叶片生长速度,而体现稀释效应;而在第8节位后,叶片已经停止增大,这些元素含量维持相对稳定的状态,光合速率也总体接近,说明这些叶片达到了功能稳态,而使这些可移动元素含量维持相对稳态,这一稳态可持续到叶片衰老前。钙和锰则随叶片发育(叶龄)呈现积累趋势,其中,钙含量的积累趋势尤其明显,在幼叶生长期含量上升,说明叶片的钙摄取速率超过生长速率。而叶片生长期铁含量一度降低,在叶片成熟后持续积累;其余元素含量变化趋势或差异不明显。不同元素含量变化随叶龄的动态差异机制值得进一步研究,可能与其摄取途径和可移动性的差异有关。分析生长季不同叶龄(节位)矿质元素含量与Pn的相关性可见,仅锰含量与Pn呈现显著正相关,说明锰在葡萄叶片光合能力的形成中一度是限制性营养。锰是PSⅡ电子供体侧放氧复合体中的核心元素[12],由此推测,放氧复合体的构建可能是叶片光合能力形成的限速步骤。Pn随锰含量变化可拟合为二次方程,叶片锰含量为66.96 mg·kg-1时,Pn达到极大值拐点,说明此时锰元素不再是光合能力形成的“短板”营养因子。

生长季节的叶片衰老发生在老龄叶片个体上,而秋冬季节的叶片衰老是系统性的,由短日、低温引发整株叶片群体的衰老[19-20]。本研究表明,在广东地区,阳光玫瑰叶片进入10月份后叶片光合速率持续降低,而系统性叶片衰老黄化主要发生在11 月后。生长季节叶片个体衰老矿质营养变化与秋冬季节叶片系统性衰老过程中矿质营养变化有所差异。生长季节,衰老叶片中,氮、磷、钾、铜、锌、硼含量全面降低,而铁、钙显著积累,其余元素含量变化不明显;而在秋冬季节,仅氮、钾、锌含量略有降低,其余元素均出现不同程度积累。不同作物叶片各种矿质营养随叶衰老的动态不同,再利用情况有较大差异,并受根系供应的影响,而钙作为难以再利用元素,在叶片中持续积累具普遍性[21]。本研究进一步表明,在生长季和秋冬生长停滞季节,葡萄衰老叶片矿质营养的再利用情况有很大差异。在生长季节衰老叶片中的可再利用的元素多,再利用率(内吸收率)更高,其原因可能与生长的梢尖调用衰老叶片矿质能力强有关;而在冬季节,由短日和低温诱导的系统性叶片衰老过程中[18],氮、磷、钾均会发生内吸收,内吸收率可达60%~70%[22],但本叶片再利用的元素种类少,回流树体的比率低。因而,冬季落叶会带走大量的养分,相关的原因尚未探明。根据Sample 等[23]的研究,橡树叶片衰老是由短日引发,而衰老叶氮的大量撤离则是由晚秋的低温(<10 ℃)引发。或许落叶果树葡萄在广州进入11 月短日条件下启动芽休眠和叶衰老[24],但是低于10 ℃的低温发生迟且频率低,可能不利于养分撤离衰老叶片,这一推测有待进一步验证。本研究还表明,秋冬季仅氮含量与Pn具有显著的正相关性,说明氮营养是老叶光合能力维持的关键元素。

综上,不同季节阳光玫瑰叶片衰老后矿质营养的再利用有很大差异。在生长季,叶片不同节位的成熟叶片氮、磷、钾、铜、锌、镁等元素含量呈现稳态,与其光合功能达到稳态对应;在衰老叶片个体中的氮、磷、钾、锌、硼、铜含量显著降低,可再利用,而钙、铁、镁、锰几乎不可再利用。冬季叶片系统衰老期间,衰老叶中仅氮、锌、钾可再利用,且再利用比率远低于生长季的衰老叶,而其余元素随叶片衰老累积,因此,多数矿质元素并不能再利用,会随冬季落叶而损失。在叶片发育过程中,锰一度成为光合能力形成的显著因子;而在秋冬季节老叶光合能力的维持与氮营养密切相关。本研究为阳光玫瑰合理施肥提供重要参考,例如,在叶片发育期间,可以适当补施含锰叶面肥,促进光合能力的形成;氮对叶片功能寿命至关重要,需充足供应;冬季落叶仍含有大量的营养元素,建议做绿肥回土,减少养分损失。

4 结 论

阳光玫瑰由梢尖向基端第8节位叶片光合功能达到最佳状态,说明叶片发育充分完善,该节位以上叶片保持光合高效运转,直至叶片衰老。在生长季节,可移动元素(氮、磷、钾、锌、硼)的再利用率较高,而钙、铁、镁、锰不可再利用;入冬衰老叶片矿质元素再利用能力全面降低,冬季落叶会带走大量矿质营养。在幼叶光合能力形成阶段,锰可能一度是阳光玫瑰叶片光合能力形成的“短板”营养因子,而在叶片衰老过程中,氮可能是光合能力维持的关键营养因子。

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Changes in mineral nutrients and photosynthetic capacity and their correlations during leaf development and senescence in Shine Muscat grape

ZHAO Shili, DENG Caiyan, ZENG Ziya, WU Menglu, SHI Xinger, DUAN Xiaoyan, CHENG Lilan,NAN Kemiao,HUANG Xuming*

(College of Horticulture,South China Agricultural University,Guangzhou 510642,Guangdong,China)

Abstract:【Objective】In recent years, grape production has expanded rapidly in Guangdong province,where climate allows over 9 months of growth season for grape. Leaf senescence and abscission occur in Guangdong much later than in traditional production regions further north. In some cultivars like Shine Muscat and Oriental Star, there is no complete leaf shed throughout winter. During the active growth season, leaf senescence frequently occurs with the ripening of the berry. Mineral nutrients play important roles in performing photosynthetic functions.It is worth to examine mineral nutrient changes in leaves during development and senescence.Also, there has been no study on comparing patterns of mineral changes in senescing leaves during growth season and during short-day induced systematic leaf senescence in late fall.The present study was conducted to understand the change patterns of photosynthetic capacity and mineral nutrients in leaves of Shine Muscat grape during leaf development and senescence and analyze their correlations so as to find out the key elements for photosynthetic capacity development and maintenance during leaf maturation and senescence as well as the reutilization pattern of various nutrients during leaf senescence. These findings will provide important guidance for nutrient management in grape.【Methods】The experiment was carried out in the experimental grape orchard,South China Agricultural University,Guangzhou,China,in 2019 and 2020.Four-to five-year-old Shine Muscat vines on 5BB rootstocks in pergola trellis were used as the experimental materials. One month after berry clusters were harvested, leaves at all nodes of five canes from different vines were sampled during the postharvest tree recovery period in mid September 2019 after they were individually measured for net photosynthetic rate (Pn) with a CIRAS-3 photosynthesis system (PP systems,Amesbury,MA, USA) and chlorophyll index (SPAD value) with an a SPAD-502 portable chlorophyll meter (Minolta,Osaka,Japan).All the measurements were made from 9:00 to 11:00 in the morning in a clear day.The sampled leaves were then taken into the laboratory and individually washed with clean water and oven-dried at 65 ℃for 3 days before used for mineral nutrient analysis.In late September 2020,a functional mature leaf at the 8th node from the tip on 3 canes with each of five vines was tagged for tracing changes in SPAD and photosynthetic parameters from late September to late December at an interval of one month. Leaves at the same node of neighboring canes were sampled for nutrient analysis in late September and late December. Based on differences in mineral nutrients between the functional leaves and the senesced leaves, the resorption rate, which reflects the remobilization ability of nutrients in senescing leaves,was calculated.【Results】(1)Leaf Pn and SPAD values increased as the node position increased.At node 8, Pn value reached a level similar to its maximum value obtained in leaf at node 16,while SPAD increased to a maximal value at node 10 and maintained relatively stable in older leaves,suggesting leaves at the 10th node were fully mature. The senesced and yellowed leaves on the same canes showed significantly reduced Pn and SPAD values compared with the leaves at the 16th node. (2)Concentrations of nitrogen, phosphorous, potassium and copper decreased initially with leaf expansion but maintained stabilized from node 8 up; calcium and manganese accumulated with leaf age and were the highest in the old senescing leaves; iron content decreased during leaf expansion but accumulated later; the remaining elements (magnesium, zinc and boron) showed no defined pattern. (3) During the growth season in mid-September, the yellowed and senescing leaves had lower contents of nitrogen,phosphorus, potassium, zinc, boron and copper compared with the functional mature leaf at the 16th node with the highest Pn value.The resorption rates of nitrogen,phosphorus,potassium,zinc,boron and copper in senescent leaves were 44.6%,44.4%,71.1%,25.8%,24.6%and 10.5%,respectively,indicating these mineral nutrients in senescing leaves can be remobilized at different degrees; the resorption rates of magnesium, manganese, calcium and iron were close to zero or negative, indicating that these mineral nutrients can hardly be reutilized.(4)Correlation analysis between Pn and mineral nutrients contents in functional leaves at different nodes showed that only manganese had a significant and positive correlation with Pn. Manganese content and Pn could be perfectly regressed into a quadratic equation(R2=0.652 5,p=0.003),with a maximal Pn value occurring when manganese content was 66.96 mg·kg-1.(5) During winter, systemic leaf senescence occurred in the vines, and only nitrogen, zinc and potassium had a positive resorption rate (24.3%, 18.4% and 0.6%, respectively), while those of phosphorus,calcium, magnesium, copper, iron, manganese and boron were all negative, indicating that these elements accumulated with leaf senescence in winter and that these nutrients may loss as the leaves drop in winter. (6) During the senescence of leaves in winter, nitrogen was the only nutrient with a significant and positive linear correlation (R2=0.457, p=0.032) to Pn.【Conclusion】Based on the above results, the following conclusions could be drawn:(1)Leaf at the 8th node from the cane apex becomes fully mature and photosynthetic function maintains its maximal level until leaf senescence. (2) During the growth season, nitrogen, phosphorous, potassium, zinc and boron are remobilized in senescing leaves of Shine Muscat grape,but calcium,iron and manganese are not remobilized and accumulated with leaf aging.In winter,systematic leaf senescence occurs,and the mobilizability of all mineral nutrients from senescing leaves loses or becomes weaker in Guangzhou.(3)During the development of young leaves,manganese may be a limiting nutrient element for the formation of photosynthetic capacity in Shine Muscat leaves,while in old leaves,nitrogen serves as the key nutrient element for maintaining photosynthetic capacity.

Key words: Shine Muscat grape; Leaf development; Leaf senescence; Photosynthesis; Mineral nutrients;Resorption

中图分类号:S663.1

文献标志码:A

文章编号:1009-9980(2022)12-2343-09

DOI:10.13925/j.cnki.gsxb.20220001

收稿日期:2022-01-24

接受日期:2022-08-17

基金项目:广东省优稀水果产业技术体系土肥栽培岗(2018LM1130);大学生创新项目(202110564055)

作者简介:赵世利,男,在读硕士研究生,研究方向为果树生理。Tel:15099997925,E-mail:2585380389@qq.com

*通信作者Author for correspondence.Tel:13640319693,E-mail:huangxm@scau.edu.cn