施氮时期对库尔勒香梨坐果率、萼片发育过程中木质素积累的影响

郭凯璐1,2,3,王澜霏1,2,3#,余明杨1,2,3,范玮璠1,2,3,包建平1,2,3*

1塔里木大学园艺与林学学院,新疆阿拉尔 843300;2新疆生产建设兵团塔里木盆地生物资源保护利用重点实验室,新疆阿拉尔 843300; 3南疆特色果树高效优质栽培与深加工技术国家地方联合工程实验室,新疆阿拉尔 843300)

摘 要:【目的】研究施氮时期对库尔勒香梨萼片脱落的影响,探讨氮素对库尔勒香梨萼片脱落的作用,从而筛选出促进库尔勒香梨萼片脱落的适宜施氮时期。【方法】以库尔勒香梨为试材,在不同生长阶段用尿素(0.24 kg·株-1)作为氮肥进行一次性施肥处理,调查不同处理的坐果率、脱萼率、萼筒氮素含量、萼筒木质素含量及相关合成酶(PAL、POD、PPO)活性。【结果】与对照相比,不同施氮时期的库尔勒香梨坐果率和脱萼率有显著差异。花芽膨大期(3 月26 日)施氮肥的坐果率最高,为35.30%,而未施肥的对照脱萼率最高,为50.50%。萼筒全氮含量呈先升后降的趋势。花芽膨大期(3月26日)施氮处理木质素含量最高,在盛花期宿萼木质素含量(w,后同)为115.64 mg·g-1、脱萼为112.49 mg·g-1;盛花期后10 d宿萼木质素含量为125.73 mg·g-1、脱萼为103.69 mg·g-1;不同施氮时期在盛花期和盛花期后10 d宿萼和脱萼萼筒的木质素含量与PAL、PPO活性均呈先升后降再上升再下降的变化趋势。【结论】在花芽膨大期施氮处理可以有效提高萼筒木质素含量,有利于库尔勒香梨坐果,不利于库尔勒香梨脱萼,反之不施氮肥有利于库尔勒香梨萼片的脱落。

关键词:库尔勒香梨;施氮时期;坐果率;萼片脱落;木质素

库尔勒香梨(Pyrus brestschneideri Rehd.)简称香梨,属于蔷薇科梨亚科的白梨系统[1],为西洋梨和新疆梨自然杂交所产生的后代,以其独特的口感和丰富的营养价值广受消费者的喜爱,是新疆主栽的梨品种[2]

库尔勒香梨分为宿萼果(公梨)和脱萼果(母梨),形态口感差异大[3]。宿萼果萼端凸起,果皮粗糙,果形不正,脱萼果萼端凹陷,果形端正,此差异由库尔勒香梨在盛花期花萼的萼片部位是否脱落决定。影响脱萼的因素包括砧木、光照、树龄、温度、水分、营养、授粉品种、花序序位和植物激素等[4]

在果树的不同生长发育阶段,对营养元素的需求及利用率是不同的。在苹果、枸杞和柑橘的相关研究中,在控制施肥量的同时也将施肥时期作为重要的控制变量[5-7]。氮是果树生长的必需元素,对果树生长发育有重要的影响,与植物细胞木质化程度有关。李付国等[8]的研究表明,桃经过施氮处理后坐果率显著高于不追施氮肥的处理。Meng 等[9]研究表明,铵态氮处理提高了甘薯贮藏根形成过程中根系的PAL 和POD 活性,促进了木质素的合成,增强了根系的活性。在小麦孕穗期追施氮肥能提高茎秆中PAL、TAL、POD 活性和木质素含量[10]。PAL、POD、PPO等酶在木质素合成中发挥着关键作用,其酶活性直接影响木质素的合成[11-13]。在梨果实中,木质素含量与各合成酶的活性之间存在显著相关性[14-16]。与此同时,有研究者发现植物器官脱落与氮元素同样存在相当程度的关联性[17]。在大豆相关研究中发现,在植株叶片衰老脱落的同时,植株自身氮含量显著降低[18]。而在甘蓝型油菜的相关研究中,研究者发现脱落叶片中积累了大量氮元素。脱落叶片由于氮元素利用效率低,释放出缺少氮元素的错误信号,导致植物体不断向叶片输送氮元素[19]。在狼尾草种粒脱落的相关研究中,通过对全长转录组分析,得出植物器官脱落与木质素直接相关。此外,研究者发现玫瑰花瓣脱落过程中,在POD 表达水平显著上调的同时,木质素沉积[20]

笔者在本研究中以萼筒为研究对象,通过测定萼筒全氮、木质素含量及PAL、POD、PPO 等酶的活性,旨在筛选库尔勒香梨适宜的施氮策略,为生产提供理论依据。

1 材料和方法

1.1 试验材料

试验前期处理于2023 年3—4 月在新疆生产建设兵团第一师阿拉尔市塔里木大学库尔勒香梨园进行,该地属暖温带大陆干旱荒漠气候,年蒸发量约1 403.65 mm,降水量44.3 mm。试验地土壤厚实,无植被覆盖物,主要为砂质土壤,光照充足,昼夜温差大,常年采用大水漫灌,以砀山酥梨为授粉树进行自然授粉。选用长势一致、株高约4.5 m的库尔勒香梨树为试材,南北排列,树龄25 a(年),株行距为2 m×4 m。试验肥料选择一次性施尿素0.24 kg·株-1 处理,选用尿素作为施用的氮肥。

1.2 试验设计

试验选取24 株长势相近的库尔勒香梨树,在不同的生长阶段休眠期1(3 月1 日)、休眠期2(3 月15日)、花芽膨大期(3 月26 日)、大蕾期(4 月1 日)、盛花期(4 月10 日),分别选取4 株树进行施氮肥处理(尿素0.24 kg·株-1),并分别标记为T1、T2、T3、T4、T5,并设置4 株树不施氮肥为对照组(CK),每处理间隔1 株树进行隔离。鉴于库尔勒香梨幼果萼片离区在盛花期出现,而在盛花期后10 d 萼片完全脱落。在盛花期(4 月10 日)当天施氮前和盛花期后10 d(4 月20 日)两个时间点,分别采集T5 处理的宿萼果和脱萼果,并从中提取花萼样品。

1.3 试验方法

1.3.1 库尔勒香梨花序坐果率和脱萼率的调查 在4 月1 日,分别从休眠期1、休眠期2、花芽膨大期、大蕾期和盛花期各选取5 枝花序调查5 个施肥处理和对照库尔勒香梨的开花数量,统计花朵数。4 月30日,调查5 个施肥处理和对照的坐果率。5 月10 日,统计坐果花序果实总数和脱萼果数量,最终统计每个处理的脱萼率。

1.3.2 萼筒全氮含量的测定 将盛花期和盛花期后10 d 的库尔勒香梨萼筒样品带回实验室,洗涤顺序为自来水→0.1%洗涤剂→自来水→蒸馏水,洗涤时间不超过2 min。吸去多余水分,在105 ℃干燥箱中杀青20 min,80 ℃烘至恒质量,研磨并过筛。花萼全氮含量用微量凯氏定氮法测量,采用王冠力[21]和李嘉欣[22]的方法并加以改进。

1.3.3 木质素含量的测定 使用北京索莱宝科技有限公司的试剂盒进行测定。

1.3.4 萼筒PAL、POD、PPO 等酶活性的测定 将超低温冰箱中的试验样品加液氮研磨至粉末,使用北京索莱宝科技有限公司的试剂盒(微量法)进行测定。

1.4 数据分析方法

试验数据采用Microsoft Excel 2019 和DPS 7.05进行分析,用LSD 法评估显著性(p<0.05)。用Origin 2021 软件对各项指标进行相关性分析,采用GraphPad Prism 9绘制图片。

2 结果与分析

2.1 施氮时期对库尔勒香梨坐果率和脱萼率的影响

2.1.1 施氮时期对库尔勒香梨坐果率的影响 由图1 可知,不同时期施氮后库尔勒香梨坐果率先升后降。T1、T2、T3、T4处理与对照有显著差异,而T5与对照无显著差异。5 种施氮处理的坐果率均高于对照,其中T3 处理坐果率最高,为35.30%,比对照增加了6.95%。可见,花芽膨大期施氮肥有利于库尔勒香梨坐果。

图1 不同施氮时期对库尔勒香梨坐果率的影响
Fig. 1 Effects of different periods of nitrogen application on fruit set of Kuerlexiangli pear

2.1.2 施氮时期对库尔勒香梨脱萼率的影响 由图2 可知,不同时期施氮后库尔勒香梨脱萼率先降后升再降。对照脱萼率为50.50%,T1、T3、T4、T5 处理的脱萼率显著低于对照,T2 处理与对照无差异,T1~T5 处理的脱萼率分别下降了8.37%、1.94%、16.80%、21.50%、21.23%。说明施氮处理不利于库尔勒香梨花萼的脱落,越延后施氮肥,脱萼率越低。

图2 不同施氮时期对库尔勒香梨脱萼率的影响
Fig. 2 Effects of different periods of nitrogen application on the rate of decalcification of Kuerlexiangli pear

2.2 施氮时期对萼筒全氮含量的影响

由图3可知,T1、T2、T3、T4、T5处理和对照的萼筒全氮含量呈先升后降趋势,除T1 时期盛花期后10 d 宿萼全氮含量与对照无显著差异外,施氮处理的萼筒全氮含量均显著高于对照。盛花期和盛花期后10 d 宿萼的全氮含量普遍高于脱萼。T4 处理的宿萼与脱萼萼筒全氮含量(w,后同)均高于其他处理,分别为5.48、5.27、6.14、5.88 g·kg-1

图3 不同施氮时期对库尔勒香梨萼筒全氮含量的影响Fig.3
Effects of different periods of nitrogen application on the total nitrogen content of the calyx cylinder of Kuerlexiangli pear

2.3 施氮时期对库尔勒香梨萼筒木质素含量及其相关酶活性的影响

2.3.1 施氮时期对库尔勒香梨萼筒木质素含量的影响 由图4 可知,不同施氮处理盛花期及盛花期后10 d的萼筒木质素含量呈现先升后降再上升再下降的趋势,且宿萼萼筒的木质素含量高于脱萼萼筒。在盛花期和盛花期后10 d,T1、T3、T4、T5处理与对照组相比,萼筒的木质素含量均显著增加,其中T3处理的宿萼木质素含量增幅最大,达到21.28 mg·g-1,而T2处理则导致木质素含量下降4.90 mg·g-1;脱萼萼筒中,T3 处理的木质素含量增幅最大,达到21.41 mg·g-1,T2处理下降2.03 mg·g-1。在盛花期10 d后,宿萼木质素含量增幅最大的为T3 处理,达到26.87 mg·g-1,而T2处理的木质素含量下降0.65 mg·g-1;T3和T4处理脱萼木质素含量的增幅最大,分别为16.10 mg·g-1和16.08 mg·g-1,T2 处理则下降3.98 mg·g-1。综上所述,在T1、T3、T4 和T5 时期施氮增加萼筒木质素含量,在T2时期施用降低木质素含量。

图4 不同施氮时期对库尔勒香梨花萼萼筒木质素含量的影响
Fig. 4 Effeets of different nitrogen application periods on lignin content in sepals of Kuerlexiangli pear

2.3.2 施氮时期对萼筒木质素合成相关酶活性的影响 由图5 可知,不同施氮处理萼筒木质素合成相关酶活性均存在显著差异。由图5-A 可知,盛花期和盛花期后10 d,T1、T3、T4 和T5 处理的宿萼萼筒PAL 活性显著增强,T4 增幅最大为33.76% 和35.79%,T2处理显著下降8.15%和8.30%;脱萼萼筒的PAL 活性在T4 处理下增幅最大,为36.21%和35.83%,T2处理显著下降14.73%和12.33%。由图5-B可知,在盛花期和盛花期后10 d,T1、T3、T4、T5施氮处理的PPO 活性显著高于对照,且宿萼萼筒的PPO活性高于脱萼萼筒。T3 处理在两个时期中的PPO活性最高,分别为12.94、11.30、14.03、12.37 U·g-1,T2处理显著下降0.67 U·g-1和0.70 U·g-1。由图5-C 可知,施氮处理显著提高了宿萼与脱萼萼筒的POD活性,T3 处理的增幅最大,其中宿萼萼筒的POD 活性分别在盛花期和盛花期后10 d 达到64.11%和80.68%的增幅,脱萼萼筒的POD 活性在盛花期和盛花期后10 d 达到67.16%和60.65%的增幅。

图5 不同施氮时期对库尔勒香梨萼筒 PAL、PPO、POD 活性的影响
Fig. 5 Effects of different periods of nitrogen application on the activities of PAL, PPO and PODin the calyx cylinder of Kuerlexiangli pear

2.4 坐果率、脱萼率与萼筒全氮、木质素含量及相关酶活性的相关性分析

由图6 可知,盛花期和盛花期后10 d 的萼筒全氮含量与库尔勒香梨萼片坐果率呈极显著正相关(r>0.707 9)。盛花期POD 活性与坐果率呈显著(0.576 0<r<0.707 9)正相关。

图6 坐果率、脱萼率与萼筒全氮、木质素含量及相关酶活性的相关性分析
Fig. 6 Correlation analysis of fruit set and decalcification rate on total nitrogen, lignin content and related enzyme activities of calyx tube

盛花期和盛花期后10 d的萼筒全氮含量与库尔勒香梨萼片脱萼率之间存在极显著负相关(r>0.707 9)。盛花期和盛花期后10 d 木质素含量与萼片脱萼率呈显著负相关(0.576 0<r<0.707 9)。盛花期和盛花期后10 d的PAL活性与脱萼率呈极显著负相关(r>0.707 9);盛花期和盛花期后10 d 的PPO活性与脱萼率呈极显著负相关(r>0.707 9)。

3 讨 论

3.1 施氮时期对花萼全氮含量的影响

相关研究表明,氮素是植物生长发育过程中至关重要的矿质元素之一[23],不仅对植物的营养生长和生殖生长产生影响,更是决定作物产量的关键因素[24]。骆建珍[25]发现,当偏施氮肥时,黄金梨树脱萼率较低,于新刚等[26]也认为施氮肥时梨树的脱萼率降低,笔者在本研究中发现施氮处理可以提高库尔勒香梨的坐果率,研究结果与前人研究基本一致。笔者在本研究中注意到施氮处理增加了库尔勒香梨花萼的全氮含量,刘卫星等[27]发现施氮量可影响不同土壤肥力条件下冬小麦叶片全氮含量,与不施氮肥相比,施氮处理显著增加了顶三叶的全氮含量,这与本试验研究结果一致。本研究结果表明,施氮有助于库尔勒香梨坐果,但会增加宿萼果,降低脱萼率。

3.2 施氮时期对库尔勒香梨花萼木质素含量及其相关酶活性的影响

木质素是细胞壁重要成分,木质次生细胞壁在植物生长中起关键作用,对植物体内水分、营养输送、生物和非生物胁迫的抵抗能力至关重要[28]。章霄云等[29]在研究中指出,PAL、POD、PPO 在木质素合成过程中具有关键的调控作用。氮素影响植物体内酶活性,调控木质素、纤维素合成,直接参与木质化过程。

笔者在本研究中发现不同施氮时期处理的库尔勒香梨花萼木质素含量均高于未施氮处理。萧长亮等[30]的研究结果表明,氮素对水稻的抗倒伏性能具有显著影响,刘笑鸣[31]研究发现,不同施氮处理玉米节间木质素含量均高于不施氮处理,这与本试验研究结果一致。高珍妮等[32]证实,适量地施氮可提高胡麻作物茎秆的PAL、POD 活性。黄秀兰[33]认为,PAL、PPO、POD 酶活性的激活对木质素的积累有重要作用,且梨果实中相关合成酶活性与木质素含量之间存在显著相关关系。笔者在本研究中发现,PAL、PPO 和POD 活性与木质素含量之间存在正相关性,其次是与脱萼率之间同样呈现负相关性。

4 结 论

施氮对库尔勒香梨花萼脱萼有显著影响。适量施氮可提高坐果率,但可能会导致宿萼果增多,从而降低花萼的正常脱萼。在花芽膨大期进行施氮处理可以增加萼筒的木质素含量,盛花期宿萼木质素含量为115.64 mg·g-1,脱萼为112.49 mg·g-1;盛花期后10 d 宿萼木质素含量为125.73 mg·g-1,脱萼为103.69 mg·g-1。木质素含量的增加可能增强萼筒的结构,有利于水分的运输,从而提高香梨的坐果率,而不利于萼片的脱落。盛花期和盛花期后10 d库尔勒香梨萼筒木质素含量、PAL 活性、PPO 活性、POD活性与坐果率呈正相关,但与脱萼率呈负相关,这些酶在木质素的生物合成过程中起着关键作用,进而影响花萼脱落。

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Effects of nitrogen application time on fruit setting rate and lignin accumulation during sepal development of Kuerlexiangli pear

GUO Kailu1,2,3, WANG Lanfei1,2,3#, YU Mingyang1,2,3, FAN Weifan1,2,3, BAO Jianping1,2,3*
(1College of Horticulture and Forestry, Tarim University, Alar 843300, Xinjiang, China; 2Key Laboratory of Biological Resources Protection and Utilization of Tarim Basin, Xinjiang Production and Construction Corps, Alar 843300, Xinjiang, China; 3Efficient and High-Quality Cultivation and Deep Processing Technology of Characteristic Fruit Trees in Southern Xinjiang National and Local Joint Engineering Laboratory, Alar 843300, Xinjiang, China)

Abstract:【Objective】 Sepal shedding of Kuerlexiangli pear (Pyrus brestschneideri Rehd.) is a key factor in determining fruit quality and economic value. Nitrogen is an essential element for the growth of fruit trees, and has a profound influence on the growth and biochemical processes of fruit trees. However, there are limited studies on how the timing of N application affects sepal shedding in Kuerlexiangli pear. In this experiment, we used Kuerlexiangli pear trees as test materials to investigate the effects of nitrogen application times on the sepal shedding of Kuerlexiangli pear, so as to screen out the appropriate fertilization period for increasing the sepal shedding of Kuerlexiangli pear. 【Methods】 Four Kuerlexiangli pear plants with the same growth were set up in each treatment, and nitrogen fertilizer application (urea 0.24 kg per plant) was carried out at different stages, that is, dormancy 1 (1 March), dormancy 2 (15 March), flower bud expansion (26 March), large bud stage (1 April), and full blooming stage(10 April). The fruit set rate was assessed on 1 April, and calyx abscission rate was assessed on 10 May.In view of the fact that sepal abscission in young fruits of Kuerlexiangli pear occurs at the time of full blossom and sepals are completely abscissa 10 days after full blossom. The calyx samples of 5 treatments were collected before N application on the day of full bloom (10 April) and 10 days after full bloom (20 April). The collected samples were used for the determination of the lignin content and related enzyme activities. 【Results】 The fruit setting rate and calyx shedding rate between the nitrogen application periods and the control showed significant differences. The fruit setting rate and the calyx shedding rate of the different nitrogen application periods were also significantly different from those of the control. The highest fruit setting rate (35.30%) was observed when nitrogen fertilizer was applied during the flower bud expansion period (March 26), which was an increase of up to 6.95% compared with the control. In contrast, the highest calyx shedding rate (50.50%) was recorded in the unfertilized control group. A positive correlation was observed between the total nitrogen content in the calyx tube and the fruit setting rate of sepals. The total nitrogen content in the calyx tube exhibited an initial increase followed by a subsequent decrease. The nitrogen application period had a significant impact on the lignin content and the activity of related enzymes in the calyx tube. The highest lignin content was found when nitrogen was applied during the flower bud expansion period (March 26), with 115.64 mg·g-1 in the persistent calyx during full blooming, 112.49 mg·g-1 in the calyx after shedding; 125.73 mg·g-1 in the persistent calyx 10 days after full bloom, and 103.69 mg·g-1 in the calyx after shedding. The lignin content and the activities of PAL and PPO enzymes in the calyx tube at full blooming and 10 days after full blooming showed a trend of increasing, then decreasing, and then rising and falling again across different nitrogen application periods. 【Conclusion】 Applying nitrogen fertilizer during the period of flower bud expansion was more beneficial for the fruit setting rate of Kuerlexiangli pear, but not for its calyx shedding rate. No-nitrogen fertilizer treatment was more beneficial for the calyx removal rate of Kuerlexiangli pear. The lignin content and related enzyme activities of the calyx sepals and detached sepals during the peak flowering period and 10 days after the peak flowering period showed a trend of first increasing and then decreasing. The lignin content, PAL activity, PPO activity, and POD activity of the calyx tube of Kuerlexiangli pear during the peak flowering period and 10 days after the peak flowering period were positively correlated with fruit setting rates and were negatively correlated with the rate of calyx detachment. These enzymes wouild play a key role in the biosynthesis of lignin and thus affect calyx detachment. Applying nitrogen during the period of flower bud expansion could increase the lignin content in the calyx tube, which would be beneficial for water transport and thus improve the fruit setting rate of Kuerlexiangli pear, but would not be conducive to the shedding of sepals.

Key words:Kuerlexiangli pear; Nitrogen application period; Fruit setting rate; Sepals detachment; Lignin

中图分类号:S661.2

文献标志码:A

文章编号:1009-9980(2025)03-0568-09

DOI:10.13925/j.cnki.gsxb.20240404

收稿日期:2024-08-08

接受日期:2024-12-15

基金项目:兵团财政科技计划项目(2022CB001-11);国家自然科学基金项目(32360722)

作者简介:郭凯璐,女,在读硕士研究生,研究方向为果树栽培与生理。E-mail:1417243325@qq.com。#为共同第一作者。

*通信作者 Author for correspondence. E-mail:baobao-xinjiang@126.com