低分子有机酸水溶肥提升梨叶片光合、养分吸收及果实品质

邵 微1,2,徐国益1,于会丽1,高登涛1,刘 远1,司 鹏1*

1中国农业科学院郑州果树研究所,郑州 450009;2河南农业大学林学院,郑州 450002)

摘 要:【目的】从梨叶片光合特性、养分吸收及果实品质方面,探讨低分子有机酸(Low Molecular Weight Organic Acid,LMWOAs)对梨树体生长与果实品质的作用效果。【方法】以红宝石梨为试材,设置5%与10%的苹果酸(LM 与HM)、柠檬酸(LC与HC)及草酸(LO与HO)与氮磷钾肥配施处理(其中5%与10%分别表示LMWOAs占氮磷钾肥料总量的5%与10%),以单独施用氮磷钾肥为对照,测定不同有机酸含量对果实叶片生长量与光合参数、养分吸收以及果实品质等指标的影响。【结果】与对照相比,LMWOAs处理下叶绿素Ⅱ含量均有提高,其中柠檬酸处理(LC与HC)较对照显著提高7%与16.6%。草酸处理下净光合速率(Pn)较对照显著提高47.86%与57.79%,而水分利用率(WUE)则分别显著提高92.63%与127.92%。从叶片功能得分表可知,LMWOAs处理能显著提高梨叶片功能,综合得分为草酸>柠檬酸>苹果酸。苹果酸处理(LM与HM)、5%柠檬酸(LC)与草酸(LO)显著提高了梨产量,其中LM处理的产量最高,较对照提高39.25%。比较各LMWOAs处理果皮着色指标发现,LM处理的着色最佳,而HM处理的着色最为不理想。LM、LC及HO处理的可溶性糖含量显著高于对照,其中LM处理最高,较对照升高22.98%。LM处理糖酸比显著高于其他处理,较对照显著上升18.61%,较HC处理显著升高38.15%。由果实品质得分可知,LM处理的得分最高,而以草酸处理的(LO与HO)得分最低。比较5%(LM)与10%苹果酸(HM)处理可知,苹果酸含量对于果实品质排名影响较大。另外,LM处理的叶片与果实中的P、K含量均高于对照,其中K含量显著高于对照。【结论】苹果酸、柠檬酸及草酸处理均能显著提升叶片功能与果实品质,其中草酸处理对叶片功能生长促进效果最佳,而5%苹果酸对于果实品质的提升效果最佳。

关键词:红宝石梨;低分子有机酸;叶片光合;养分吸收;果实品质;果皮色差

近年来,果园土壤板结、酸化以及盐渍化等问题[1-3]导致树体养分失调、果实产量与品质下降的现象屡有发生[4]。随着果树产业转型升级与果品提质增效要求的提出[5],现代果园对土壤健康与生态环境友好更加重视,并通过科学施肥与研发新型果树专用肥等手段加快了果园环境友好型栽培技术的发展[6]。低分子有机酸(low molecular weight organic acid,LMWOAs)是水果中重要的风味物质与营养成分,包括苹果酸、柠檬酸及草酸等,具有促食欲与助消化的功效,其组分与含量决定了水果风味与品质的差异[7-10]。另外,研究发现,LMWOAs能够显著抑制果实在冷藏过程中冻伤、电解质渗漏以及过氧化氢与丙二醛的积累,因此常用于鲜切果品加工与采后贮藏[11-13]。作为植物体内重要产物,LMWOAs 参与碳素和还原力载体在细胞质与细胞器以及细胞器之间碳素和还原力的传递,是细胞多种代谢途径的连接者[14-15]。LMWOAs 具有较强的螯合力,能够与多种金属离子形成复合物,最终促进植物对金属离子的吸收[16]。因此,LMWOAs具有成为氮磷钾水溶肥增效剂的潜力,但其对果树生长、果实品质及养分吸收等方面的影响尚未清楚。

笔者以红宝石梨[17]为试验对象,研究不同含量的苹果酸、柠檬酸及草酸对梨叶片生长、养分吸收及果实品质的影响,探讨LMWOAs作为增效剂对于梨果实品质提升的潜力,确定最适种类LMWOAs 与含量,为新型果树专用水溶肥的研发以及果业绿色高效发展提供理论依据与技术支撑。

1 材料和方法

1.1 试验地基本情况

试验在河南省郑州市中国农业科学院郑州果树研究所国家园艺种质资源库梨分库(34°42′47″N,113°41′49″E)进行。该地区属于黄河流域,年平均降水量约为542.15 mm,表层土壤pH为7.16,有机质含量(w,后同)0.93%,有效磷含量131.80 mg·kg-1,有效钾含量241.02 mg·kg-1,铵态氮含量10.25 mg·kg-1,硝态氮含量14.85 mg·kg-1

1.2 试验布置

2019 年选取长势一致5 年生红宝石(Bayuehong(hybrid cultivar)×Suli(Pyrus bretschneideri))梨(4 m×1 m)为试验材料。设置7个试验处理(表1),包括对照(氮磷钾肥)、LM(苹果酸5%)、HM(苹果酸10%)、LC(柠檬酸5%)、HC(柠檬酸10%)、LO(草酸5%)和HO(草酸10%)。其中,5%与10%是指LMWOAs质量占LMWOAs与全年施肥量总质量的比植(LMWOAs与氮磷钾肥直接混合称样),用量分别为84.72 与178.86 kg·hm- 2。全年施肥量为N(367.5kg·hm-2)-P2O5(247.5kg·hm-2)-K2O(315kg·hm-2)。每个处理设置4 次重复,完全随机排列。施肥时间为萌芽期(4 月11 日)、第一次膨大期(5 月5 日)、第二次膨大期(6月14日)及采摘前20 d(8月2日)4个时期,用施肥枪施入树冠2/3处,其他栽培与病虫害等相关田间管理均保持一致。2019 年8 月22 日采集果实与叶片样品,实验室检测各项指标。

表1 不同LMWOAs 处理对红宝石梨叶片指标的影响
Table 1 Leaf indexes of Hongbaoshi pear with different LMWOAs

注:同一列数据后不同小写字母表示处理间差异达0.05 显著水平。下同。
Note: Different small letters indicate significant differences at p <0.05.The same below.

叶绿素含量Chlorophyll content 22.41±0.30 c 22.79±0.48 c 24.25±0.44 b 24.00±0.39 b 26.13±0.36 a 24.52±0.45 b 23.53±0.37 bc处理Treatment百叶干质量Hundred leaf dry weight/g 47.84±0.99 a 47.00±0.75 a 48.44±0.99 a 50.50±1.83 a 48.91±1.52 a 48.62±1.90 a 48.05±2.90 a对照Control LM HM LC HC LO HO叶面积Leaf area/cm2 42.55±0.80 ab 43.47±1.13 ab 43.97±0.98 ab 44.47±1.00 a 42.56±0.76 ab 41.19±0.80 b 43.92±0.70 ab百叶鲜质量Hundred leaf fresh weight/g 117.39±2.29 a 116.92±1.20 a 119.74±3.90 a 122.68±4.97 a 116.01±3.57 a 116.12±5.46 a 112.29±5.95 a

1.3 测定项目与方法

1.3.1 叶片相关指标 叶绿素含量采用Hansatech的Chlorophyll Content Meter CL-01 测定;叶面积采用便携式叶面积仪CI-203CA 测定;净光合速率Pn(net photosynthetic rate)、胞间二氧化碳浓度Ci(Intercellular CO2 concentration)、蒸腾速率Tr(Transpiration rate)、气孔导度Gs,水分利用率WUE(water use efficiency)于果实采摘前7 d 采用PPsystems 的CIRAS-3测定。

1.3.2 叶片与果实氮磷钾含量测定 叶片与果实氮磷钾含量采用H2SO4-H2O2消煮法[18]测定;叶片与果实氮含量采用全自动间断化学分析仪(Clever Chem 380,德国)测定;叶片与果实中的磷含量采用钼蓝比色法测定;叶片与果实钾含量采用原子吸收法(AAS ZEEnit 700P,Jena,德国)测定。

1.3.3 果实色泽参数测定 LabCh°植均采用便捷式色差仪(CR-400,Konica Minolta,日本)测定。L植表示色泽光度,ab植表示色方向(a植越大表示颜色越红,越小颜色越绿;b植越大颜色趋向黄色,越小趋向蓝色),h°植为色度角,C植为色泽饱和度[19-20]

1.3.4 果实品质参数测定 果实硬度采用硬度计(GY-1,浙江托普仪器有限公司,中国)测定;可溶性固形物含量采用手持式数字折光仪(PR-101;ATAGO)测定;可溶性糖含量使用蒽酮法测定[21];维生素C含量采用2,6-二氯酚靛酚法测定[22];可滴定酸(Titratable Acid,TA)含量采用NaOH 滴定法测定[18]。果实纵径和横径采用游标卡尺测量,果形指数为纵径与横径的比植。

1.4 数据分析

采用Microsoft Excel 2007 进行数据处理与作图;用SPSS 17.0进行单因素方差分析与综合得分分析,以p <0.05作为显著性的标准;用主成分分析法(Principal Component Analysis,PCA)分析相关指标数据,采用Canoco 4.5分析与作图。

2 结果与分析

2.1 不同LMWOAs处理对梨叶片的作用效果

不同处理下梨叶片指标如表1所示。与对照相比,LMWOAs 处理下叶绿素含量均有提高,其中柠檬酸处理(LC 与HC)较对照显著提高7%与16.6%。而就叶面积而言,LMWOAs 处理与对照之间无显著差异,但LC处理显著高于LO处理。各处理间百叶鲜质量与百叶干质量均无显著差异,而LC处理百叶鲜质量与百叶干质量最高。

不同处理的梨叶片光合指标如图1所示。LMWOAs 处理下叶片Ci(除LM 处理外)显著低于对照,其中LO处理与HO处理分别较对照下降45.72%与51.08%。LMWOAs 处理下的PnWUE 较对照均有所提高,其中LO处理与HO处理的Pn植较对照显著提高47.86%与57.79%,而WUE 则分别显著提高92.63%与127.92%。LMWOAs 处理降低了GsTr,其 中LO 处 理 与HO 处 理 的Gs 较 对 照 降 低 了41.91%与45.83%,而Tr则均显著降低了25.47%。

图1 不同LMWOAs 处理下红宝石梨叶片的胞间CO2浓度、净光合速率、蒸腾速率、气孔导度及水分利用率
Fig.1 Intercellular CO2 concentration,photosynthesis rate,transpiration rate and stomatal conductance and water use efficiency of Hongbaoshi pear leaves with different LMWOAs

不同小写字母表示处理间某指标差异达0.05 显著水平。下同。
Different small letters indicate significant difference at p <0.05. The same below.

LMWOAs 处理下梨叶片的氮磷钾含量如图2所示,不同LMWOAs处理对梨叶片氮磷钾含量的影响不同。与对照相比,LC处理显著降低了叶片氮含量,HC处理显著高于LO处理、HO处理及LC处理,而其他处理与对照之间无显著差异。比较各LMWOAs处理叶片钾含量发现,LM处理显著高于其他处理,而HO 处理显著低于其他处理。各处理叶片磷含量无显著差异。综上所示,LM 处理叶片中的氮磷钾含量均高于对照,其中钾含量显著高于对照。

图2 不同LMWOAs 处理下红宝石梨叶片实氮磷钾含量
Fig.2 Macronutrient concentrations of Hongbaoshi pear leaf with different LMWOAs

如图3梨叶片参数的主成分分析所示,提取2个主成分,第一主成分(PC1)为90.1%,第二主成分(PC1)为7.5%。取第一、二个主成分得分作图来表征不同含量与种类的LMWOAs 处理对梨叶片参数的作用效果,处理间样品的距离表示处理间的相似程度,距离越近,相似程度越高。苹果酸与柠檬酸样点距离较近分布在PC1 负轴端,而草酸与对照样点距离较近分布PC1正轴。这表明柠檬酸与苹果酸处理下梨树叶片参数较为相似,而草酸与对照处理下梨树叶片参数较为相似。另外,低含量苹果酸与柠檬酸样点分布在PC2 正轴端,而高含量苹果酸与柠檬酸分布在PC2负轴端。这表明柠檬酸与苹果酸的低含量与高含量对梨树叶片参数影响较大。从表2可知,LMWOAs 处理能够显著提高梨叶片功能,综合得分为草酸>柠檬酸>苹果酸,比较各LMWOAs的低含量与高含量处理对于叶片功能的影响发现,高含量的柠檬酸与苹果酸优于低含量的柠檬酸与苹果酸,而低含量的草酸则优于高含量的草酸处理。

图3 不同LMWOAs 处理下红宝石梨叶片参数的主成分分析
Fig.3 PCA of Hongbaoshi pear leaves with different LMWOAs

表2 不同LMWOAs 处理对红宝石梨叶片生长量、养分及光合影响的综合分析
Table 2 Comprehensive PCA results of the effects of different LMWOAs application onthegrowth,nutrients and photosynthesisof Hongbaoshi pear leaf

处理Treatment排名Rank对照Control LM HM LC HC LO HO主成分1得分Principal component score 1-2.02主成分2得分Principal component score 2-1.50主成分3得分Principal component score 3-0.47综合得分Comprehensive score-0.84-1.42-0.85-1.60 1.08 1.50 3.30-2.21 0.49 3.35-0.22 0.28-0.18-0.38 0.34-0.65 1.62 1.48-1.89-0.83-0.05 0.23 0.44 0.62 0.45 7 654312

2.2 不同LMWOAs对梨果实品质的作用效果

不同LMWOAs处理下梨单果质量、产量及果形指数如表3 所示。LMWOAs 处理能够明显提高红宝石的单果质量,其中苹果酸处理(LM 与HM)与LC处理显著高于对照,分别增长20.62%、24.54%及19.30%。同时,苹果酸处理(LM 与HM)、低含量的柠檬酸(LC)处理与草酸(LO)处理显著提高了梨产量,其中LM处理产量最高,较对照提高39.25%。比较不同LMWOAs 处理对果形指数的影响时发现,5%苹果酸与5%柠檬酸(LM与LC)处理均不能改变果形指数,而10%苹果酸与草酸则能显著改变梨的果形指数。

表3 不同LMWOAs 处理对红宝石梨果实单果质量、产量及果形指数的影响
Table 3 Effects of different LMWOAs on fruit weight,yield and fruit shape index of Hongbaoshi pear

处理Treatment对照Control LM HM LC HC LO HO单果质量Mean fruit mass/g 321.25±14.74 c 387.50±11.54 ab 400.00±9.23 a 383.25±12.63 ab 371.75±11.54 abc 354.75±18.58 abc 342.25±28.04 bc产量Yield/(t·hm-²)38.17±1.67 d 53.15±1.80 a 45.34±1.31 bc 45.85±1.67 bc 37.37±0.36 d 48.01±2.70 ab 41.31±3.17 cd果形指数Fruit shape index 1.38±0.01 c 1.38±0.01 c 1.41±0.01 b 1.38±0.01 c 1.41±0.01 b 1.44±0.00 a 1.41±0.01 b

不同LMWOAs 处理下果实色泽指标见表4,效果见图4。与对照相比,LMWOAs 处理能够显著降低梨果皮明亮度L植与色度角植,同时增加了果皮的色泽饱和度C,即LMWOAs处理均能改善果皮着色。比较各LMWOAs 处理果皮着色指标发现,LM 处理的植显著低于其他处理,C 植显著高于其他处理,果皮红色覆盖面积最大,色泽最佳,其次为HC 与LO 处理;另外,HM 处理在LMWOAs 处理中着色最不理想,这表明5%苹果酸(LM)处理有利于梨果皮着色,而10%苹果酸则抑制果皮着色。

图4 不同LMWOAs 处理下红宝石梨果实
Fig.4 Hongbaoshi pear fruit with different LMWOAs

表4 不同LMWOAs 处理对红宝石梨果实色泽的影响
Table 4 Effects of different LMWOAs on fruit color of Hongbaoshi pear

处理Treatment对照Control LM HM LC HC LO HO明亮度L 28.26±0.48 a 25.33±0.20 d 26.74±0.28 b 25.92±0.26 bcd 25.79±0.21 cd 26.53±0.23 bc 26.57±0.18 bc色泽饱和度C 30.50±0.85 c 33.19±0.38 a 31.22±0.43 bc 32.00±0.46 abc 32.59±0.46 ab 32.64±0.32 ab 31.80±0.40 abc色度角H°27.15±0.27 a 18.35±0.33 f 23.31±0.29 b 20.98±0.28 d 20.18±0.18 e 20.78±0.32 de 22.08±0.18 c

不同LMWOAs 处理下梨果实品质指标如表5所示。3 种LMWOAs 处理对梨果实品质的作用效果不一,而LMWOAs处理(除LM外)均提高了果实的硬度,其中HM、LC 与HO 处理较对照显著提高9.77%、11.40%及12.33%。LM、LC 及HO 处理可溶性糖含量显著高于对照,其中LM处理最高,较对照升高22.98%。LM、LC、HC 及LO 处理可溶性固形物含量显著高于其他处理,其中LM 处理较对照提高18.04%。不同LMWOAs 处理下维生素C 含量与对照无显著差异,而LM 处理较HC 处理显著提高49.77%。HC处理较其他处理显著提高了果实中TA含量,其中较对照提高21.43%。LM 处理糖酸比显著高于其他处理,较对照显著提高18.61%,较HC处理显著高38.15%。

表5 不同LMWOAs 处理对梨果实品质的影响
Table 5 Effects of different LMWOAs on fruit quality of pears

处理Treatment对照Control LM HM LC HC LO HO硬度Firmness/(kg·cm-2)4.30±0.11 b 4.26±0.09 b 4.72±0.11 a 4.79±0.03 a 4.51±0.16 ab 4.35±0.08 b 4.83±0.15 a w(可溶性糖)Total soluble sugar/(mg·g-1)80.13±5.68 c 98.54±2.39 a 81.44±3.38 c 95.36±2.99 ab 83.79±3.99 bc 86.83±4.70 abc 92.21±0.87 abc w(可溶性固形物)Soluble solids content/%13.03±0.07 c 15.38±0.11 a 13.07±0.09 c 13.48±0.08 b 13.52±0.17 b 13.38±0.08 b 12.99±0.05 c w(维生素C)Vitamin C/(mg·100 g-1)2.44±0.42 ab 3.25±0.20 a 2.50±0.21 ab 2.53±0.31 ab 2.17±0.21 b 2.38±0.15 ab 2.74±0.29 ab w(可滴定酸)Titratable acid/%0.42±0.03 b 0.42±0.01 b 0.45±0.01 b 0.44±0.02 b 0.51±0.02 a 0.45±0.01 b 0.42±0.02 b糖酸比Sugar acid ratio 31.32±2.11 b 37.15±1.64 a 29.31±0.30 bc 30.90±1.49 bc 26.89±1.17 c 29.69±0.31 bc 30.71±0.92 bc

不同LMWOAs 处理下果实氮磷钾含量见图5。不同LMWOAs处理下果实中氮含量较对照无显著差异,其中LM、LO 及HO 处理显著低于HM 处理。LM 处理的果实钾含量显著高于其他处理,较对照显著提高9.59%,较HO 处理提高48.97%。柠檬酸(LC与HC)处理与草酸处理(LO与HO)较对照显著降低了果实钾含量。LMWOAs 各处理的磷含量(除LO外)较对照明显提高,与对照相比,HM、LC与HO 处理分别显著提高53.17%、39.75%及43.10%。

图5 不同LMWOAs 处理下红宝石梨果实氮磷钾含量
Fig.5 Macronutrient concentrations of Hongbaoshi pear fruit with different LMWOAs

如图6 梨果实养分与品质的主成分分析所示,提取了2 个主成分,第一主成分(PC1)为95.2%,第二主成分(PC1)为4.6%。柠檬酸与草酸样点分布在PC1 负轴端,对照与苹果酸样点分布在PC1 正轴端。3 种LMWOAs 均随着含量的增加沿PC2 负轴分布。苹果酸样点(LM 与HM)距离与柠檬酸(LC与HC)及草酸(LO 与HO)较远,这表明在对果实品质的影响方面,苹果酸处理与其他两种酸差别较大。不同LMWOAs 处理对红宝石梨果实养分与品质影响的综合分析见表6,LMWOAs 处理能显著提升梨果实品质,其中在各处理中以LM 处理得分最高,而以草酸(LO 与HO)处理得分最低。比较5%(LM)与10%苹果酸(HM)处理可知,苹果酸含量对果实品质排名影响较大。

图6 不同LMWOAs 处理下红宝石梨果实品质参数的主成分分析
Fig.6 PCA of Hongbaoshi pear fruit with different LMWOAs

表6 不同LMWOAs 处理对红宝石梨果实养分与品质影响的综合分析
Table 6 Comprehensive PCA results of the effects of different LMWOAs application on the fruit nutrients and quality of Hongbaoshi pear

处理Treatment对照Control LM HM LC HC LO HO主成分1得分Principal component score 1-3.57 5.17-1.34 0.61-0.59 0.25-0.53主成分2得分Principal component score 2-3.08-1.70 1.03 1.17 1.53-0.06 1.12主成分3得分Principal component score 3 0.26 0.45 1.85 1.44-1.13-2.49-0.37主成分4得分Principal component score 4-0.11 0.09 1.10-0.24 1.26 0.50-2.61综合得分Comprehensive score-2.44 2.32-0.03 0.76 0.00-0.22-0.39排名Rank 7142356

3 讨 论

3.1 LMWOAs与氮磷钾肥配施对梨叶片光合作用的影响

LMWOAs 如柠檬酸与苹果酸作为三羧酸循环的主要产物[23],在光合作用中发挥着重要作用,而草酸虽然不是光合作用的直接产物,但由光合途径中的前体合成,与光合作用及碳代谢密切相关[24-25]。LMWOAs 与氮磷钾肥配施明显提高叶片的叶绿素含量、PnWUE。Chen等[26]也同样发现苹果酸能够增加秋华柳叶片中的叶绿素含量,同时减缓重金属的胁迫以提高叶片光合能力进而促进植物生长。本次研究与Arsenov等[27]保持一致,即在90 d柠檬酸处理显著提高了蒿柳叶片的光合作用效率,同时显著降低气孔导度。从不同LMWOAs 处理对红宝石梨叶片生长量、光合作用及养分吸收的综合分析发现,不同LMWOAs 对叶绿素含量和光合作用的影响依次为草酸>柠檬酸>苹果酸。这也与Song 等[28]的研究结果一致,草酸对于水曲柳叶片叶绿素与光合作用的影响大于柠檬酸。Han 等[29]与王鸿燕等[30]分别在研究柠檬酸对嗜盐鸢尾与马蔺生长影响时发现,柠檬酸能够提高叶片的叶绿素含量且低含量效果优于高含量。本次研究则发现,柠檬酸处理(LC与HC)叶绿素Ⅱ含量显著高于对照,但HC 处理显著高于LC 处理。由此可知,LMWOAs 对作物的作用效果与LMWOAs含量、作物种类与类型及土壤性质相关,因此需进一步研究才能确定LMWOAs最佳施用含量[27]。不同LMWOAs 对叶片叶绿素含量及光合作用的影响因素可以归结于LMWOAs 的化学结构、解离常数及有机配体-金属离子的稳定等的差异性[28];同时,LMWOAs 能够提高植物体保护酶系统的活力,增强抗逆性,但不同的LMWOAs 效果不一;另外,LMWOAs 能够缓解重金属引发的各种植物氧化应激;而不同LMWOAs参与细胞多种代谢途径不同,作为碳素和还原力载体在细胞质与细胞器以及细胞器之间传递碳素和还原力也不一[14-15]

3.2 LMWOAs与氮磷钾肥配施对梨养分吸收的影响

在自然界中,LMWOAs 作为根际分泌物的一类,通过影响根系周围pH 与氧化还原电位(oxidation-reduction potential,Eh)以驱动根际微生物群落的改变,进而促进某些难溶性养分离子的溶解度,从而提高根际元素的溶解度与有效态含量[17,31-32]。梨果实采摘7 d后取树冠2/3处土壤,发现柠檬酸与草酸显著降低了0~20与20~40 cm土层土壤pH。10%苹果酸处理显著降低0~20 cm 土层土壤pH,对于20~40 cm 土层无显著影响,而5%苹果酸则对于土壤pH无显著影响。

磷作为第二重要的关键元素,对植物早期发育中生殖原基的形成至关重要,同时能够促进根生长与发育,提高植物活力与抗病性[33]。LMWOAs通过溶解几乎不溶的无机磷以此增加植物可利用的磷,土壤中磷溶解度[水溶性无机磷(Pi)和有机磷(Po)的含量]驱动因素受苹果酸、草酸及柠檬酸等3 种LMWOAs影响[34-35],随着LMWOAs含量的增大而磷活化潜能提升[36],因此随着苹果酸与草酸含量的升高,梨果实中磷含量显著提高。段立珍等[37]也发现,不同含量苹果酸处理对土壤磷吸附和释放的影响关系符合Peal-Reed等7种数学模型,而苹果酸显著降低了土壤对磷的吸附,因此随着苹果酸含量的增加,土壤对磷的最大吸附量和最大缓冲容量都呈现下降趋势,最终提高了土壤磷的利用率。另外,缺磷植物根系对磷的吸收过程与LMWOAs 密切相关。当根尖感知缺磷时,一方面由质膜上的未知sensor 所识别,级联激活转录因子STOP1,从而激活ALMT1-MATE1(编码跨膜蛋白的MATE1ALMT1 基因分别的诱导柠檬酸与苹果酸的分泌)表达,提高根际柠檬酸与苹果酸含量,进而促进土壤铝铁结合态磷的活化;另一方面,低磷状态下STOP1 的激活能够调控ALMT1 基因转录,同时促进了苹果酸和Fe3+之间的结合,进而提高Pi 的利用率并影响根尖的生长[38-39]

钾元素作为植物所需的第三种必需营养元素,主要通过钾溶解微生物产生LMWOAs 等形式溶解不可溶的钾,因此LMWOAs 的含量、种类与土壤中的钾含量存在密切关系[40]。对水果中有机酸与钾肥的研究发现,钾肥的施用可增加果实的可滴定酸含量尤其是苹果酸含量[41-43]。果实成熟时的苹果酸含量通常与灰分碱度呈正相关,而灰分碱度与钾含量密切相关[44-46]。因此,5%苹果酸与氮磷钾复配(LM)时较其他LMWOAs 与对照显著提高了叶片与果实中的钾含量。这可能归结于苹果酸在酸性水解和络合溶解双重作用的表面化学反应过程中,较其他LMWOAs更易释放含钾矿物与土壤中的钾,从而促进钾元素的吸收[47]。另外,Wang等[48]发现外源添加钾与水稻酸代谢之间的关系紧密,即钾的添加显著提高了植株中柠檬酸合酶与苹果酸脱氢酶活性,同时苹果酸含量较对照显著提高,而柠檬酸含量虽有提高但差异不显著。

3.3 LMWOAs与氮磷钾肥配施对果实品质的影响

LMWOAs 作为水果中重要的风味物质与营养成分,具有促食欲与助消化的功效,而其组分与含量直接决定了水果风味与品质的差异[8-10]。LMWOAs与氮磷钾肥配施显著降低了梨果皮的色度角,提高了色泽饱和度与果实可溶性糖含量,进而改善了果皮着色与果实口感。其中,5%苹果酸(LM)显著提高了梨的可溶性固形物含量与糖酸比,这可能是由于5%苹果酸提高了钾元素的吸收,而果实钾元素的提高也利于糖类物质的运输与转运,进而提高果实的可溶性糖含量[49-50]。综合分析3种LMWOAs对果实品质的作用效果可知,低含量苹果酸(LM)>柠檬酸>草酸(LO与HO),而与叶片排名恰好相反,这可能是因为草酸与柠檬酸促进了果树树体营养生长,而5%苹果酸则促进了梨果实品质的提升。但目前LMWOAs 与氮磷钾肥配施对果实品质影响的研究仍处于基础阶段,其机制的探索尚需要进一步深入。

4 结 论

LMWOAs 与氮磷钾复配能够提升梨叶片的光合作用效率,改善梨果实品质与着色,促进了树体对氮磷钾养分的吸收。对叶片营养功能的影响排名,草酸>柠檬酸>苹果酸;而对果实品质与养分的排名,5%苹果酸与氮磷钾肥料复配>柠檬酸>草酸。其中5%苹果酸与氮磷钾肥料复配显著提高叶片与果实钾含量,同时提高果实中可溶性糖含量。

参考文献

[1] 卢树昌,陈清,张福锁,贾文竹.河北果园主分布区土壤磷素投入特点及磷负荷风险分析[J].中国农业科学,2008,41(10):3149-3157.LU Shuchang,CHEN Qing,ZHANG Fusuo,JIA Wenzhu.Characteristics of soil phosphorus input and phosphorus load risk in major orchards region of Hebei[J]. Scientia Agricultura Sinica,2008,41(10):3149-3157.

[2] 董彩霞,姜海波,赵静文,徐阳春.我国主要梨园施肥现状分析[J].土壤,2012,44(5):754-761.DONG Caixia,JIANG Haibo,ZHAO Jingwen,XU Yangchun.Current fertilization in pear orchards in China[J].Soils,2012,44(5):754-761.

[3] 于会丽,司鹏,邵微,徐国益,乔宪生,王玉红,杨晓静.海藻酸水溶肥对梨树生长与果实产量及品质的影响[J].果树学报,2019,36(5):603-611.YU Huili,SI Peng,SHAO Wei,XU Guoyi,QIAO Xiansheng,WANG Yuhong,YANG Xiaojing. Effect of water soluble alginic acid fertilizer on the growth,yield and quality of pear[J].Journal of Fruit Science,2019,36(5):603-611.

[4] 丁邦新,刘雪艳,何雪菲,陈波浪,柴仲平.‘库尔勒香梨’园测土配方推荐施肥研究[J].果树学报,2019,36(8):1020-1028.DING Bangxin,LIU Xueyan,HE Xuefei,CHEN Bolang,CHAI Zhongping. Recommendation of fertilization for‘Kuerlexiangli’pear orchards based on soil testing[J]. Journal of Fruit Science,2019,36(8):1020-1028.

[5] 陈学森,郭文武,徐娟,丛佩华,王力荣,刘崇怀,李秀根,吴树敬,姚玉新,陈晓流. 主要果树果实品质遗传改良与提升实践[J].中国农业科学,2015,48(17):3524-3540.CHEN Xuesen,GUO Wenwu,XU Juan,CONG Peihua,WANG Lirong,LIU Chonghuai,LI Xiugen,WU Shujing,YAO Yuxin,CHEN Xiaoliu. Genetic improvement and promotion of fruit quality of main fruit trees[J]. Scientia Agricultura Sinica,2015,48(17):3524-3540.

[6] 薛永发.生态果园栽培模式[J].果农之友,2010(6):14.XUE Yongfa. Ecological orchard cultivation models[J]. Fruit Growers'Friend,2010(6):14.

[7] 李佳秀,张春岭,刘慧,吕真真,刘杰超,焦中高.不同果汁中有机酸的组成及差异性分析[J].果树学报,2017,34(9):1192-1203.LI Jiaxiu,ZHANG Chunling,LIU Hui,LÜ Zhenzhen,LIU Jiechao,JIAO Zhonggao. Composition and variability of organic acid in different fruit juices[J].Journal of Fruit Science,2017,34(9):1192-1203.

[8] 关军锋. 果品品质研究[M]. 石家庄:河北科学技术出版社,2001:11-15.GUAN Junfeng. Fruit quality research[M]. Shijiazhuang:Hebei Science&Technology Press,2001:11-15.

[9] 陈发兴,刘星辉,陈立松.果实有机酸代谢研究进展[J].果树学报,2005,22(5):526-531.CHEN Faxing,LIU Xinghui,CHEN Lisong. Advances in research on organic acid metabolism in fruits[J]. Journal of Fruit Science,2005,22(5):526-531.

[10] 周先艳,朱春华,李进学,高俊燕,龚琪,沈正松,岳建强.果实有机酸代谢研究进展[J].中国南方果树,2015,44(1):120-125.ZHOU Xianyan,ZHU Chunhua,LI Jinxue,GAO Junyan,GONG Qi,SHEN Zhengsong,YUE Jianqiang.Advances in research on organic acid metabolism in fruits[J]. South China Fruits,2015,44(1):120-125.

[11] WANG Z,CAO J K,JIANG W B.Changes in sugar metabolism caused by exogenous oxalic acid related to chilling tolerance of apricot fruit[J].Postharvest Biology and Technology,2016,114:10-16.

[12] YANG C,CHEN T,SHEN B R,SUN S X,SONG H Y,CHEN D,XI W P. Citric acid treatment reduces decay and maintains the postharvest quality of peach (Prunus persica L.) fruit[J].Food Science&Nutrition,2019,7(11):3635-3643.

[13] 梁晓璐.鲜切梨果贮藏品质变化及控制技术[D].泰安:山东农业大学,2012.LIANG X L. Quality changes and control technology of freshcut pear during storage[D]. Tai’an:Shandong Agricultural University,2012.

[14] 宋超,张立军,贾永光,崔国瑞,崔震海,朱延姝.植物的苹果酸代谢和转运[J].植物生理学通讯,2009,45(5):419-428.SONG Chao,ZHANG Lijun,JIA Yongguang,CUI Guorui,CUI Zhenhai,ZHU Yanshu. Malate metabolism and transport in plants[J]. Plant Physiology Communications,2009,45(5):419-428.

[15] FERNIE A R,MARTINOIA E.Malate.Jack of all trades or master of a few?[J].Phytochemistry,2009,70(7):828-832.

[16] 许衡,杨和生,徐英,毛志泉,束怀瑞.果树根际微域环境的研究进展[J].山东农业大学学报(自然科学版),2004,35(3):476-480.XU Heng,YANG Hesheng,XU Ying,MAO Zhiquan,SHUHuairui. Research progress on rhizosphere environment of fruit trees[J]. Journal of Shandong Agricultural University(Natural Science Edition),2004,35(3):476-480.

[17] 李秀根,杨健,王龙,王苏珂,薛华柏,苏艳丽.红皮梨新品种‘红宝石’的选育[J].果树学报,2016,33(12):1588-1591.LI Xiugen,YANG Jian,WANG Long,WANG Suke,XUE Huabai,SU Yanli. Breeding of a new red pear cultivar‘Hongbaoshi’[J].Journal of Fruit Science,2016,33(12):1588-1591.

[18] 鲁如坤.土壤农业化学分析方法[M].北京:中国农业科技出版社,2000.LU Rukun.Analytical methods of soil and agricultural chemistry[M].Beijing:China Agriculture Scientech Press,2000.

[19] WEI Y Z,HU F C,HU G B.Differential expression of anthocyanin biosynthetic genes in relation to anthocyanin accumulation in the pericarp of Litchi chinensis Sonn.[J]. PLoS One,2011,6(4):e19455.

[20] XU F,SHI L Y,CHEN W,CAO S,SU X,YANG Z. Effect of blue light treatment on fruit quality,antioxidant enzymes and radical-scavenging activity in strawberry fruit[J]. Scientia Horticulturae,2014,175:181-186.

[21] 王学奎,黄见良.植物生理生化实验原理与技术[M].北京:高等教育出版社,2015.WANG Xuekui,HUANG Jianliang.Principles and techniques of plant physiological biochemical experiment[M]. Beijing:Higher Education Press,2015.

[22] 曹建康,姜微波,赵玉梅.果蔬采后生理生化实验指导[M].北京:中国轻工业出版社,2007.CAO Jiankang,JIANG Weibo,ZHAO Yumei. Physiological and biochemical experiment guidance after fruit and vegetable harvest[M].Beijing:China Light Industry Press,2007.

[23] ARAÚJO W L,NUNES-NESI A,NIKOLOSKI Z,SWEETLOVE L J,FERNIE A R. Metabolic control and regulation of the tricarboxylic acid cycle in photosynthetic and heterotrophic plant tissues[J].Plant,Cell&Environment,2012,35(1):1-21.

[24] STUTZ R E,BURRIS R H. Photosynthesis and metabolism of organic acids in higher plants[J].Plant Physiology,1951,26(2):226-243.

[25] TAVANT H. Fixation de14CO2 et absorption de glucose-U-14C par des feuilles de Begonia semperflorens Link et Otto. Etudedes conditions de la genese de l’acide oxalique[J].Physiology,1967,5:57-69.

[26] CHEN H C,ZHANG S L,WU K J,LI R,HE X R,HE D N,HUANG C,WEI H. The effects of exogenous organic acids on the growth,photosynthesis and cellular ultrastructure of Salix variegata Franch. under Cd stress[J]. Ecotoxicology and Environmental Safety,2020,187:109790.

[27] ARSENOV D,ŽUPUNSKI M,BORIŠEV M,NIKOLIĆ N,PILIPOVIC A,ORLOVIC S,KEBERTB M,PAJEVICA S. Citric acid as soil amendment in cadmium removal by Salix viminalis L.,alterations on biometric attributes and photosynthesis[J]. International Journal of Phytoremediation,2020,22(1):29-39.

[28] SONG J F,QI H Y,CUI X Y,PENG H M.Effects of organic acids on chlorophyll contents and photosynthesis of Fraxinus mandshurica seedlings[J].Advanced Materials Research,2011,393:713-716.

[29] HAN Y L,ZHANG L L,GU J G,ZHAO J,FU J.Citric acid and EDTA on the growth,photosynthetic properties and heavy metal accumulation of Iris halophila Pall. cultivated in Pb mine tailings[J]. International Biodeterioration & Biodegradation,2018,128:15-21.

[30] 王鸿燕,佟海英,黄苏珍,原海燕.柠檬酸和草酸对Pb 胁迫下马蔺生长和生理的影响[J]. 生态学杂志,2010,29(7):1340-1346.WANG Hongyan,TONG Haiying,HUANG Suzhen,YUAN Haiyan. Effects of citric acid and oxalic acid on the growth and physiology of Iris lactea var. chinensis under Pb stress[J]. Chinese Journal of Ecology,2010,29(7):1340-1346.

[31] JONES D L. Organic acids in the rhizosphere-a critical review[J].Plant and Soil,1998,205(1):25-44.

[32] 韩振海,沈隽,王倩. 园艺植物根际营养学的研究:文献述评[J].园艺学报,1993,20(2):116-122.HAN Zhenhai,SHEN Tsuin,WANG Qian. Studies on rhizosphere nutrition of horticultural crops:Literature review[J].Acta Horticulturae Sinica,1993,20(2):116-122.

[33] SHARMA S B,SAYYED R Z,TRIVEDI M H,GOBI T A.Phosphate solubilizing microbes:Sustainable approach for managing phosphorus deficiency in agricultural soils[J]. Springer-Plus,2013,2(1):587.

[34] HOU E Q,TANG S B,CHEN C R,KUANG Y,LU X,HEENAN M,WEN D. Solubility of phosphorus in subtropical forest soils as influenced by low-molecular organic acids and key soil properties[J].Geoderma,2018,313:172-180.

[35] ORAL A,UYGUR V. Effects of low-molecular-mass organic acids on P nutrition and some plant properties of Hordeum vulgare[J].Journal of Plant Nutrition,2018,41(11):1482-1490.

[36] 刘丽,梁成华,王琦,杜立宇,吴玉梅,韩巍.低分子量有机酸对土壤磷活化影响的研究[J].植物营养与肥料学报,2009,15(3):593-600.LIU Li,LIANG Chenghua,WANG Qi,DU Liyu,WU Yumei,HAN Wei. Effects of low-molecular-weight organic acids on soil phosphorus release[J]. Plant Nutrition and Fertilizer Science,2009,15(3):593-600.

[37] 段立珍,汪建飞,赵建荣,王力.苹果酸对温室土壤磷释放与吸附的影响[J].土壤通报,2007,38(1):81-84.DUAN Lizhen,WANG Jianfei,ZHAO Jianrong,WANG Li. Effects of malic acid on the release and absorption of phosphorus in greenhouse soil[J]. Chinese Journal of Soil Science,2007,38(1):81-84.

[38] LIU J P,MAGALHAES J V,SHAFF J,KOCHIAN L. Aluminum-activated citrate and malate transporters from the MATE and ALMT families function independently to confer Arabidopsis aluminum tolerance[J]. The Plant Journal:for Cell and Molecular Biology,2009,57(3):389-399.

[39] SILVA G B P D,ZANELLA C M,DELATORRE C A,CHAVES M S,MARTINELLI J A,FEDERIZZI L C. Organic acid carriers in tolerance to toxic aluminum in wheat[J]. Ciência Rural,2018,48(10):e20180106.

[40] SHANWARE A S,KALKAR S A,TRIVEDI M M. Potassium solublisers:occurrence,mechanism and their role as competent biofertilizers[J]. Inttrnational Journal Curront Microbiology and Applied Sciences,2014,3(9):622-629.

[41] CUMMINGS G A,REEVES J. Factors influencing chemical characteristics of peaches[J]. Journal of the American Society of Horticultural Science,1971,96:320-322.

[42] DU P M. Effect of fertilisation on fruit quality[J]. Deciduous Fruit Grower,1985,4:138-140.

[43] BIAIŁCZYK J,LECHOWSKI Z.Malic acid synthesis in relation to K+ and Cl- availability in Phaseolus coccineus L. pulvini[J].Biochemie Und Physiologie Der Pflanzen,1989,184(1/2):79-86.

[44] GENEVOIS L,PEYNAUD E. Composition de neuf variétés de prunes[J].Revue Horticole,1947,30:317-318.

[45] SOUTY M,PERRET A,ANDRÉ P. Premières observations sur quelques variétés de pêches destinées à la conserve [J].Annales de Technologie Agricole,1967,16:55-68.

[46] LOBIT P,GENARD M,SOING P,HABIB R.Modelling malic acid accumulation in fruits:Relationships with organic acids,potassium,and temperature[J]. Journal of Experimental Botany,2006,57(6):1471-1483.

[47] 王东升,王君.低分子量有机酸作用下土壤矿物钾释放机制[J].辽宁工程技术大学学报(自然科学版),2009,28(S2):259-261.WANG Dongsheng,WANG Jun. Mechanism of soil mineral potassium release extracted by low-molecular-weigh organic acids[J]. Journal of Liaoning Technical University (Natural Science),2009,28(S2):259-261.

[48] WANG Y P,WU Y H,ZHENG G H,ZANG J P,XU G D. Effectsof potassium on organic acid metabolism of Fe-sensitive and Fe-resistant rices (Oryza sativa L.)[J].Australian Journal of Crop Science,2013,7(6):843-848.

[49] 李康宁.海藻肥和S-诱抗素对‘红地球’葡萄果实着色及相关基因表达的影响[D].雅安:四川农业大学,2016.LI Kangning. Effects of seaweed fertilizer and S-ABA on coloring physiological and related gene expression of fruits of‘Red Globe’[D].Ya’an:Sichuan Agricultural University,2016.

[50] 张绍阳,杨军,刘桂华.钾营养水平对艳光油桃果实品质的影响[J].安徽农业大学学报,2008,35(2):289-292.ZHANG Shaoyang,YANG Jun,LIU Guihua.Effects of K nutrition levels on fruit quality of“Yanguang”nectarine[J]. Journal of Anhui Agricultural University,2008,35(2):289-292.

Low molecular weight organic acid water-soluble fertilizer improves leaf photosynthesis,nutrient absorption and fruit quality of pear

SHAO Wei1,2,XU Guoyi1,YU Huili1,GAO Dengtao1,LIU Yuan1,SI Peng1*
(1Zhengzhou Fruit Research Institute, Chinese Academy of Agricultural Sciences, Zhengzhou 450009, Henan, China;2College of Forestry,Henan Agricultural University,Zhengzhou 450002,Henan,China)

Abstract:【Objective】Excessive application of chemical fertilizers for high yield causes problems such as soil compaction, acidification, and salinization in the orchard, leading to nutrient imbalance of fruit trees and decline of fruit yield and quality.With the upgrading of the fruit industry and the urgent requirements for fruit quality and efficiency,more reasonable fertilization regimes have been developed through the development of new types of fertilizers for fruit trees and the other achievements for soil health. Low molecular weight organic acids (LMWOAs), are involved in the transportation of carbon and reducing power between the cytoplasm and organelles, and are the linkers of multiple metabolic pathways in cells.Moreover,LMWOAs have strong chelating power and can form complexes with various metal ions to increase the absorption of metal ions by plants.The study aimed to detect the effects of LMWOAs in fertilizers on the growth and fruit quality in pear through evaluating pear leaf photosynthesis,nutrient absorption and fruit quality.We explored the potential of LMWOAs as a synergist for increasing the efficiency of pear fertilizers,and then determined the kind of best organic acid(s)and its optimal concentration as a synergist for fruit trees,in order to develop a new type of special water-soluble fertilizer for pears industry.【Methods】Hongbaoshi pear trees were used as experimental materials, 5%and 10% malic acid (LM and HM), citric acid (LC and HC), and oxalic acid (LO and HO) combined with NPK fertilizers were set as treatments, NPK fertilizer without additive organic acid was used as control to determine the effects of different organic acids on fruit leaf growth and photosynthetic parameters, nutrient absorption and fruit quality.【Results】Compared with the control, the LMWOAs increased the content of chlorophyll Ⅱ, and LC and HC significantly increased it by 7% and 16.6% , respectively. The LMWOAs increased the Pn (net photosynthetic rate) and WUE (water use efficiency)value. While the LO and HO increased the Pn values by 47.86% and 57.79%, and increased the WUE value by 92.63% and 127.92%, respectively. Furthermore, the leaf function score table showed that organic acid treatments could significantly improve the leaf function of pear leaves. The comprehensive scores were: oxalic acid>citric acid>malic acid.The LM, HM, LC and LO significantly increased the yield of pear and the LM increased the yield by 39.25%The coloring indexes of the peels showed that the LM significantly decreased the H°value, increased the C value, and improved fruit coloring. The HM reduced the fruit coloring.The HM, LC and HO treatments increased the fruit firmness by 9.77%,11.40% and 12.33%l. The LM, LC and HO treatments significantly increased the total soluble sugar content of the fruits,and the highest value was obtained by the LM(22.98%higher than that of the control).The sugar-acid ratio of the LM was 18.61%higher than that of the control and 38.15%higher than that of the HC.The fruit quality scores showed that the score of the LM was the highest,while the score of the oxalic acid(LO and HO)was the lowest.The concentration of malic acid had a greater impact on fruit quality ranking.The nitrogen content in the leaves was significantly reduced by the LC.The nitrogen content in the leaves of the HC was significantly higher than those of the LO, HO and LC, while there was no significant difference between other treatments and the control. There was no significant difference in the N content of the fruits between the treatments and the control, and the N contents of the fruits of the LM, LO and HO were significantly lower than that of the HM. However, the P and K contents were both higher than those of the control,and the K content in the leaves and the fruits of the LM was significantly higher than that of the control.【Conclusion】The leaf function and fruit quality were significantly improved by malic acid,citric acid and oxalic acid.Among them,5%and 10%oxalic acid had a better effect on promoting leaf function growth,and 5%malic acid had the best effect on improving fruit properties.

Key words: Hongbaoshi pear; Low molecular weight organic acid; Leaf photosynthesis; Nutrient absorption;Fruit quality;Peel color difference

中图分类号:S661.2

文献标志码:A

文章编号:1009-9980(2022)06-0992-12

DOI:10.13925/j.cnki.gsxb.20210523

收稿日期:2021-10-25

接受日期:2022-02-25

基金项目:特色林果业(红枣、苹果、香梨和葡萄)简约栽培标准化模式研究与示范推广(2019AA004);国家重点研发计划(2016YFD0200405);中国农业科学院基本科研业务费专项院级统筹项目(Y2021XC07-1)

作者简介:邵微,女,在读博士研究生,主要从事果树营养与施肥技术研究。Tel:0371-55900886,E-mail:shaowei2012bn@126.com

*通信作者Author for correspondence.Tel:0371-55900886,E-mail:sipeng@caas.cn