盐渍土壤生境中大果沙枣成年树离子吸收、运输和分配特征研究

罗青红, 阿不都热西提∙热合曼, 李英仑, 周斌, 古丽尼沙∙卡斯木

中国农学通报. 2021, 37(11): 87-94

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中国农学通报 ›› 2021, Vol. 37 ›› Issue (11) : 87-94. DOI: 10.11924/j.issn.1000-6850.casb2020-0294
资源·环境·生态·土壤·气象

盐渍土壤生境中大果沙枣成年树离子吸收、运输和分配特征研究

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Research on the Ion Absorption, Transportation and Distribution of Mature E. angustifolia in Saline Soil Habitat

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摘要

为揭示盐渍土壤中大果沙枣(Elaeagnus angustifolia Linn.)树体矿质离子分布规律,保障大果沙枣高效种植和丰产栽培,以不同盐度土壤中生长的成年大果沙枣树为材料,测定并分析了其根、枝、叶中Na+、K+、Mg2+和Ca2+的吸收、运输和分配特征。结果表明:盐土土壤环境中,大果沙枣叶片对Ca2+和Mg2+具有较强的选择吸收能力,低盐(I~II级)土壤环境中,叶内Na+含量明显上升,而至高盐(III~IV级)中,根部对Na+的吸收量明显高于枝和叶。随着林地土壤盐度的升高,K+、Ca2+、Mg2+在枝部和叶部的积累量明显增大,矿质离子由根部向枝、叶部运输的能力在I~III级盐度土壤环境中逐渐增大,并在IV级盐度土壤环境中受抑。同时,根和枝中K+/Na+和Mg2+/Na+值均是先增大后减小,叶中K+/Na+、Mg2+/Na+变幅较小,根和叶中Ca2+/Na+变幅较大。大果沙枣成年树的盐适应机制主要是通过根对Na+的聚积作用,叶对K+、Mg2+和Ca2+的选择性吸收能力增强来实现的,同时也与枝中相对稳定的K+、Na+、Mg2+和Ca2+的选择性运输能力有关。

Abstract

To reveal the rule of mineral ions distribution of the Elaeagnus angustifolia Linn. in saline soil habitat to ensure the efficient planting and high yield, mature E. angustifolia grown in different salinity soils were used as study materials, the characteristics of absorption, transport and distribution of Na+, K+, Mg2+and Ca2+ in roots, branches and leaves were analyzed. The results showed that in saline soil environment, leaves of E. angustifolia had strong selective absorbing capacity for Ca2+ and Mg2+. In lower salt (from Grade I to II) soil environment, the Na+ content in leaves increased significantly, while in higher salt (from Grade III to IV) situation, Na+ absorbed in roots was more than that in branches and leaves. With the increase of soil salinity, the accumulation of K+, Ca2+ and Mg2+ in branches and leaves increased significantly. The capacity of mineral ions transportation from roots to branches and leaves increased in Grade I-III salinity soil environment, and this capacity was inhibited in Grade IV salinity soil environment. The values of K+/Na+and Mg2+/Na+in roots and branches increased first and then decreased. K+/Na+ and Mg2+/Na+ value in leaves had little variation, and the Ca2+/Na+ value in the roots and leaves varied greatly. The salt adaptation mechanism of mature E. angustifolia is mainly achieved by the accumulation of Na+ in roots and the enhanced selective absorbing capacity of K+, Mg2+ and Ca2+ in leaves, and also related to the relatively stable selective transport capacity of K+, Na+, Mg2+ and Ca2+in branches.

关键词

土壤盐度等级 / 矿质离子平衡 / 离子吸收和分配 / 选择性运输 / 盐离子积累 / 盐适应

Key words

soil salinity grade / mineral ion homeostasis / ion absorption and distribution / selective transportation / salt ion accumulation / salt adaptation

引用本文

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罗青红 , 阿不都热西提∙热合曼 , 李英仑 , 周斌 , 古丽尼沙∙卡斯木. 盐渍土壤生境中大果沙枣成年树离子吸收、运输和分配特征研究. 中国农学通报. 2021, 37(11): 87-94 https://doi.org/10.11924/j.issn.1000-6850.casb2020-0294
Luo Qinghong , Abudurexiti Reheman , Li Yinglun , Zhou Bin , Gulinisha Kasimu. Research on the Ion Absorption, Transportation and Distribution of Mature E. angustifolia in Saline Soil Habitat. Chinese Agricultural Science Bulletin. 2021, 37(11): 87-94 https://doi.org/10.11924/j.issn.1000-6850.casb2020-0294

0 引言

盐胁迫是抑制植物生长发育和限制农林产量的重要环境威胁因素[1]。中国盐渍化土地总面积为3.6×107 hm2[2],在生态环境较为脆弱的西北干旱和半干旱区,土壤盐渍化程度尤为严重[3]。盐胁迫对植物的危害主要体现为渗透胁迫、离子毒害及营养亏缺等,植物正常生理代谢受抑,生长受阻,甚至死亡[2]。但有一些植物(例如大果沙枣)仍能在盐渍化土壤中生长,说明它在长期的进化过程中,产生了与盐土生境相适应的组织结构或内在特有的生理机制,对盐胁迫有了应对措施[4]。植物的耐盐机制相当复杂,一般说来,植物的耐盐性与盐离子在植物体内的吸收、运输、分配,并由此来维持自身细胞离子平衡的能力等密切相关。盐胁迫下,植物体可通过调节盐离子在不同器官、组织或细胞内的区域化分布进行渗透调节,进而减轻离子毒害,但高盐环境会抑制植物对K+、Ca2+和Mg2+等矿质元素的吸收[5],一方面抑制了以K+为主要辅助因子的多种酶的活性,并且抑制了以Ca2+为主的在细胞内起第二信使的作用,另一方面影响了细胞的结构和生理功能、细胞膜的稳定性和植物光合作用,造成植物体内矿质离子比例失调,从而影响植物正常生长[6]。因此,维持和重建细胞内的离子平衡,对保证植物在盐胁迫环境下细胞的正常功能和生理活动意义重大。
大果沙枣(Elaeagnus angustifolia Linn.)是胡颓子属(Elaeagnus L.)大灌木或落叶小乔木,主要分布于中国西部荒漠区,是干旱区的一种重要经济树种[7,8]。大果沙枣耐贫瘠、耐盐碱、生长快易繁殖,是中国盐碱地区及沙区优良的先锋树种[9]。其果实含有氨基酸、果胶、维生素C、微量元素等多种营养成分,尤其是锌含量较高[10],具有很高的营养保健价值,素有“沙漠之宝”的美称[11,12];同时,其果实和枝叶含有类黄酮、生育酚、阿魏酸,鞣质等化合物[13],具有治疗镇痛恶心、腹泻和菌痢、冠心病、哮喘和胀气、慢性气管炎、冠心病等功效[14,15,16]。因此,大果沙枣具有在干旱盐碱区推广应用的巨大潜力和明显的生态价值。目前,有关沙枣耐盐性研究主要集中在幼苗(树),且多采用室内控制试验,测定了膜脂过氧化和保护酶活性[17,18]、叶绿素荧光参数和色素[19,20]、抗氧化酶活性和渗透调节[21,22]、种子萌发及幼苗耐盐性和阳离子吸收、运输与分配[23,24]等方面的指标,而对于野外盐渍土壤自然生长环境下成年植株体内离子运移吸收特性鲜有报导。因此,笔者以大果沙枣成年株为试验材料,研究不同盐度生境下其体内不同器官离子选择运移情况,以探明盐胁迫下离子吸收、运输和分配的关系及其耐盐机理,并为其在盐碱地丰产栽培中的科学管理提供理论参考。

1 材料和方法

1.1 研究区概况

研究区位于新疆喀什的成年大果沙枣纯林中(N:39°17′57″—39°49′00″、E:75°41′23″—76°11′30″),这些沙枣树是20世纪90年代种植于土壤盐渍化程度较高的农田或绿洲外围,作为防护林,以实现防风阻沙的目的。种植当年进行人工灌溉,之后未采取任何人工管理(灌溉、施肥、修剪等)措施,树体近自然生长至今,已进入结果期,兼具生态防护和经济收益双重效益。研究区大果沙枣树目前保留密度为833~1666株/hm2,树高为2.84~6.04 m,胸径为7.49~24.09 cm,叶片组织相对含水量为80.15%~87.09%。林区土壤为沙壤土,含水量为15.88%~32.25%,容重为1.37~1.52 g/cm2,pH 7.81~9.45。
图1可知,总盐及K+、Na+、Mg2+和Ca2+ 4种矿质离子含量的变幅分别为0.67~17.3、0.01~0.19、0.05~1.69、0.05~1.31、0.08~1.50 g/kg。同时,土壤中Ca2+和K+的含量较高,且Ca2+含量显著高于Mg2+ (P<0.05),极显著高于Na+ (P<0.01)。4个样地中,IV级土壤盐度样地中总盐和Ca2+含量极显著高于其他3个盐度的样地(P<0.01),而4个样地间土壤中K+、Na+和Mg2+的含量差异不显著(P>0.05)。对总盐及4种矿质离子含量进行主成分分析,发现仅总盐含量的特征值大于1,且主因素总盐的特征值为4.15,方差贡献率达83.05%。说明影响大果沙枣林地土壤盐度高低的主要因素是总盐含量。
图1 土壤中总盐、矿质离子含量变化趋势

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进一步分析林地土壤总盐的垂直空间上的分布特征,土壤总盐含量为上层(6.77)>中层(4.32)>下层(2.40),但层间差异不显著(P>0.05)。就上层(0~30 cm)而言,IV级盐度林地土壤含盐量显著高于II级林地(P<0.05),极显著高于I级林地(P<0.01),但与III级林地差异不显著(P>0.05)。同时,IV级林地中层(30~60 cm)土壤中总盐含量极显著高于I-III级林地(P <0.01)。I~IV级4个盐度级别林地下层(60~100 cm)土壤中总盐含量差异均不大(P>0.05)。

1.2 研究材料与试验方法

研究材料为大果沙枣林,林地土壤总盐含量分别为0.67~1.47、1.55~1.75、3.57~4.33、7.23~17.3 g/kg,设定为I级、II级、III级和IV级4个土壤盐度等级。2019年7月,在4个土壤盐度区域选择具有代表性的乡镇,每个乡镇选3个大果沙枣林地作为样点,每个样点分别选6棵生长基本一致且彼此相距10 m以上的大沙枣树作为试验样株,从每个样株树冠中部的东南西北4个方向上采集健康的2~3年生枝条和成熟叶片。在距样株主干基部50 cm和100 cm的位置,从4个方向,用根钻采集地下0~100 cm范围内直径≤1 cm的根系。然后将6个样株的枝、叶、根分别混合成1个试验样品,带回室内洗净阴干。同时,在每个样地中随机选择3个样点,用土钻分3层(0~30、30~60、60~100 cm)取土样,同一样地中同层土壤混合,带回室内阴干。

1.3 测定指标与方法

1.3.1 土样总盐及离子含量测定 阴干的土壤经过研碎、过筛后,参考鲍士旦[25]《土壤农化分析》的方法,用质量法测定土壤总盐含量,用乙炔空气火焰的原子吸收分光光度法测定Na+、K+、Ca2+、Mg2+的含量。
1.3.2 植物组织离子含量的测定 大果沙枣根、枝、叶样品经烘干、磨碎、过筛后,参照刘正祥等[3]的测定方法,将HNO3:HClO4=10:1 (V/V)消煮后,用电感耦合等离子体光谱仪(ICP-OES)测定Na+、K+、Ca2+、Mg2+ 4种离子的含量。
1.3.3 离子选择性运输、吸收能力 按照Pitman等[26]的方法计算根、枝和叶不同器官对离子的选择性吸收、运移系数(Sx, Na+),Sx, Na+=库器官[X/Na+]/源器官[X/Na+],X代表K+、Mg2+、Ca2+的含量,Sx, Na+值越大,说明源器官抑制Na+、促进K+、Mg2+或Ca2+元素向库端运输能力越强,即库器官的选择吸收或运输能力越强。

1.4 数据处理与分析

采用Excel 2017和SPSS 22.0软件进行数据的整理和正态分布检验、统计分析和图表制作。

2 结果与分析

2.1 大果沙枣树体内矿质离子分布特征

2.1.1 不同盐度等级林地中树体内四种矿质离子累积特征比较 分析大果沙枣树不同器官不同矿质离子的积累特征可以看出(图2),枝内积累的Na+ (0.11~0.16 g/kg)量均低于根(0.35~3.39 g/kg)和叶(1.03~1.59 g/kg),枝、根和叶三者Na+含量比值为1:9.73:8.63。叶内的K+含量(10.5~12.66 g/kg)远高于根(2.19~3.98 g/kg)和枝(2.74~3.39 g/kg)。Mg2+积累量大小顺序为叶、根、枝,且三者比值为3.15:2.56:1。叶片内积累的Ca2+始终最高(21.56~27.24 g/kg),其次是根(10.19~18.80 g/kg),枝最低(0.90~1.47 g/kg),叶、根和枝3个部位Ca2+浓度比值为21.92:12.77:1。
图2 大果沙枣树体不同部位矿质离子分布特征

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同时,4个盐分梯度林地中,大果沙枣根中Ca2+的积累量最高(10.19~18.80 g/kg),其次是K+ (2.19~3.98 g/kg)和Mg2+ (2.02~3.46 g/kg),Na+最低,仅0.35~3.39 g/kg。枝中含量最高的矿质离子是K+,为2.74~3.39 g/kg,其次是Mg2+ (0.86~1.73 g/kg)和Ca2+ (0.90~1.31 g/kg),Na+最低(0.11~0.16 g/kg)。叶中储量最大的是Ca2+ (21.56~27.24 g/kg),K+次之(10.50~12.66 g/kg),再次是Mg2+ (2.78~4.69 g/kg),Na+最次(1.03~1.59 g/kg)。整体来看,研究区大果沙枣树Na+、K+、Mg2+和Ca2+的含量高低排序为叶、根和枝。
表1大果沙枣树体不同器官矿质离子含量的相关系数可以看出,枝和叶内的Na+、Ca2+含量具有正相关性,且前者达到了极显著水平(r2=0.799,P<0.01),但枝和叶中的K+和Mg2+呈负相关性,且均不显著(P>0.05)。此外,根和叶中的Na+、K+和Mg2+均呈正相关性,Ca2+呈负相关性,且均不显著(P>0.05)。根和枝中4种矿质离子的相关性特征,与根和叶相近。
表1 同一矿质离子的含量在根、枝和叶之间的相关系数
器官 Na+ K+ Mg2+ Ca2+
0.466 0.258 0.264 -0.209
0.440 0.799** 0.174 -0.189 0.361 -0.408 -0.020 0.185
从大果沙枣树体各器官矿质离子积累量间的相关系数可以看出(表2),根系中,K+与Na+、Mg2+和Ca2+含量呈不显著负相关关系(P>0.05),但Na+、Mg2+和Ca2+彼此间为不显著正相关关系(P>0.05)。枝条中,Na+与K+和Ca2+为不显著正相关关系(P>0.05),K+与Ca2+存在显著正相关关系(r2=0.673,P<0.05),Mg2+与Na+和K+呈不显著负相关(P>0.05),与Ca2+存在不显著正相关关系(P>0.05)。叶片中,K+与Na+和Mg2+存在不显著正相关关系(P>0.05),Na+与Ca2+之间存在极显著相关关系(r2=0.714,P<0.01),Mg2+与Na+和Ca2+之间,以及K+和Ca2+之间均存在不显著负相关关系(P>0.05)。
表2 根、枝和叶内各矿质离子之间的相关系数
矿质
离子
Na+ K+ Ca2+ Na+ K+ Ca2+ Na+ K+ Ca2+
K+ -0.375 0.117 0.019
Ca2+ 0.028 -0.044 0.034 0.673 * 0.714 ** -0.342
Mg2+ 0.285 -0.261 0.083 -0.141 -0.065 0.018 -0.320 0.143 -0.167
注:**表示在P=0.01水平上相关性极显著,*表示在P=0.05水平上相关性极显著。下同。
2.1.2 大果沙枣树体内离子比变化特征 由图3不同盐度等级林地中大果沙枣根、枝、叶中K+/Na+、Mg2+/Na+和Ca2+/Na+的变化趋势可知,随着林地土壤盐度的升高,大果沙枣树的根和枝中K+/Na+和Mg2+/Na+值均呈先增大后减小的趋势,且枝的K+/Na+值明显高于根和叶,但叶中K+/Na+、Mg2+/Na+受土壤盐度变化的影响较小,其变幅较小。就Ca2+/Na+而言,其比值随土壤盐度的升高在枝中的变化趋势较为稳定,但在根和叶中的变幅较大。
图3 不同盐度林地大果沙枣各器官K+/Na+、Ca2+/Na+和Mg2+/Na+变化特征

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2.2 树体各器官离子选择性吸收特征比较

大果沙枣根系从土壤中吸收K+、Na+、Mg2+和Ca2+后,会通过树干、枝向叶运输,不同器官对矿质离子的选择性运输最终会体现出不同器官离子积累和分布,最终影响树体的耐盐性。从表3表4可看出,大果沙枣根、枝和叶不同器官间,以及各器官从土壤中吸收离子运输规律均不同。K+和Mg2+从根向枝、叶的运输系数在III级盐度林地中达最大,而Ca2+从根到枝、从枝到叶、从根到叶的运输系数则分别是在IV级、II级和IV级盐度林地达到最大。叶片从土壤中吸收的K+随着土壤盐度的升高而增多,且在IV级林分中SK+,Na+达最大(102.06)。而大果沙枣的根、枝和叶从土壤中选择性吸收Mg2+和Ca2+,以及根和枝从土壤中吸收K+的能力,均是在II级盐度林地中达到最大,之后随土壤盐度的继续升高,这种能力逐渐降低。
表3 不同盐度等级林地大果沙枣树体内矿质离子由根向枝、叶传输的选择性运输系数
土壤盐度等级 SK+,Na+ SMg2+,Na+ SCa2+,Na+
根-枝 枝-叶 根-叶 根-枝 枝-叶 根-叶 根-枝 枝-叶 根-叶
I级 4.67 a 0.55 a 2.58 a 2.03 a 0.63 a 1.27 a 0.36 a 2.52 a 0.92 a
II级 2.54 b 0.36 a 0.91 a 2.77 a 0.15 a 0.42 b 0.28 a 2.84 a 0.81 a
III级 29.11 a 0.35 a 10.24 a 8.11 a 0.36 a 2.89 a 1.05 a 2.32 b 2.45 a
IV级 9.22 a 0.64 a 5.91 a 4.60 a 0.41 a 1.89 a 1.52 a 2.38 a 3.62 a
表4 大果沙枣树各器官对土壤矿质离子的选择性运输系数
土壤盐度等级 SK+,Na+ SMg2+,Na+ SCa2+,Na+
土-根 土-枝 土-叶 土-根 土-枝 土-叶 土-根 土-枝 土-叶
I级 17.75 a 82.98 b 45.82 a 3.77 b 7.66 b 4.79 a 19.25 a 7.02 b 17.68 ab
II级 99.89 a 253.56 a 90.94 a 15.81 a 43.73 a 6.56 a 54.20 a 15.39 a 43.75 a
III级 8.59 a 249.98 a 87.90 a 1.96 b 15.86 b 5.66 a 5.46 a 5.76 c 13.36 ab
IV级 17.28 a 159.28 ab 102.06 a 2.06 b 9.47 b 3.89 a 2.57 a 3.90 c 9.30 b

3 结论与讨论

植物体内的离子平衡是维持细胞内部各种生理活动正常的前提。逆境胁迫通常会破坏组织器官内离子间的动态平衡,引起离子比例失衡和离子毒害,使得植株体对营养元素的吸收困难,从而影响植物正常的生理代谢[28]。离子区隔化是植物一种有效的耐盐方式,也是维持植物细胞内离子平衡的重要机制之一[29]。不同植物因其组织结构不同,离子区隔化方式亦不同,例如唐古特白刺[30]是将Na+优先积累在叶片中,而沙枣[28]、鹅耳枥[31]、侧柏[32]等则是将Na+优先积累在根系中。非盐生植物的耐盐特性主要表现为根系对Na+的限制性吸收,以及叶片中维持较低的Na+浓度[33]。本研究结果显示,随着林地土壤盐度等级的升高,大果沙枣成年树体各器官Na+积累量有不同程度的增加,在低盐土壤环境中,叶片中的Na+含量明显高于根和枝,而随着土壤盐度继续升高,根中的Na+含量则急速上升,此时,大果沙枣树体将Na+聚集在根部,限制其向上运输,以此来减轻盐胁迫对地上部的毒害。同时根系利用Na+进行渗透调节来降低水势,提高树体的吸水能力,减轻生理干旱,这可能是大果沙枣适应盐渍土壤生境的一种生理机制。
钾是植物生长必需的营养元素,主要参与酶活性调节,蛋白质合成等生理过程。同时,K+还是重要的无机渗透调节剂,当植株遭受盐害时,通过调控离子平衡和细胞膨压等来抵制盐害[34]。因Na+和K+具有相近的水合能和离子半径,保持植物细胞内较高的K+含量及较高的K+/Na+值可减轻盐对组织器官的危害,维持机体正常活动[35]。而本研究结果也表明,在不同盐度土壤生境中,大果沙枣成年树体叶片内积累的K+、Mg2+、Ca2+量均明显高于根和枝,同时枝条中的K+/Na+和Mg2+/Na+也明显高于根部,表明大果沙枣成年树通过地上部分对K+、Mg2+、Ca2+的吸收积累来提高渗透调节能力,缓解盐胁迫对树体的伤害。叶片中Mg2+含量高于枝和根,这主要跟叶器官的功能有关,叶片是植物光合作用主要器官,而镁是叶绿素的重要组成元素,在受到盐胁迫危害时,大果沙枣的叶片通过积累更多的Mg2+来避免Mg2+的营养亏缺,由此提高树体光合作用效率来增强抗盐胁迫能力。
钙作为植物细胞膜的组成成分,具有维持细胞膜的结构与功能、参与植物细胞的生长发育、调控酶活性等功能[36],同时它还有助于植物体对K+的选择吸收,维持K+/Na+[31]。有研究表明,适度盐胁迫通常会促进植物对K+的吸收,且抑制Ca2+的吸收[32],而本研究中,在土壤盐度不断升高的过程中,大果沙枣的根与叶中的Ca2+含量有升高趋势,但Ca2+由根向茎和由茎向叶的运输能力也在增强,表明高浓度盐胁迫会促进大果沙枣对Ca2+的吸收,来应对植物生理代谢受阻。树体通过增强叶对Ca2+选择性吸收,增强Ca2+从根部向地上部分的运输,维持地上部相对稳定的Ca2+/Na+值,由此增强细胞质膜的稳定性,减少叶片对Na+的吸收和维持根、枝和叶的钙信号传导,阻止细胞内K+的外流和Na+的大量进入,维持细胞内离子平衡。由于离子区隔化作用,大果沙枣叶中维持了相对较高水平的K+、Ca2+、Mg2+,且枝中K+/Na+和Mg2+/Na+明显高于根系,由此可见,随着土壤盐度的升高,大果沙枣根系将大量的Na+区隔在根中,而选择性运输K+、Ca2+、Mg2+到枝、叶中,由此来维持树体离子平衡,维持叶部的生理活动和信号传导,由此提高树体对高盐胁迫的适应能力,这是大果沙枣适应高盐土壤生境的重要原因。
离子选择性运输系数可反映植物对矿质营养离子向上运输的选择能力,盐胁迫下其值越大,说明植株促进营养离子向上运输的能力就越强,留在根中的Na+越多,其耐盐能力也就越强[37],本研究中,土壤盐胁迫明显增强了大果沙枣树体内K+、Mg2+和Ca2+从根到枝的选择性运输能力,同时也抑制了Ca2+和Mg2+从枝向叶的运输,从而破坏了叶部的离子平衡,导致离子毒害的发生,正常的生长及生理活动的受阻。当林地土壤总盐含量为1.47 g/kg时,Mg2+从枝运输到叶的选择性吸收能力最高,而当土壤含盐量升高至1.75 g/kg时,Ca2+从枝运输到叶的选择性吸收能力达到最高,而当含盐量继续上升至17.3 g/kg时,K+从枝到叶的选择性吸收能力达最高。矿质离子在从根到叶的运输过程中,K+和Mg2+的选择能力在土壤含盐量为4.33g/kg时达最强,Ca2+则在土壤含盐量为17.3 g/kg时达到最大。由此可见,不同程度的盐胁迫会对大果沙枣体内不同矿质离子的选择性运输能力产生不同程度的影响,低盐浓度下,大果沙枣根中K+浓度有轻微升高但Ca2+有轻微降低,而Mg2+浓度变化不大(图3),但叶片Mg2+浓度明显降低且Ca2+明显升高,说明低浓度盐胁迫对Ca2+和Mg2+在根系的吸收影响不大,这对于维持根系细胞膜的稳定性具有重要意义。高浓度盐胁迫下,根系对Ca2+和Mg2+的相对吸收明显降低,但叶片对Ca2+和Mg2+的选择性吸收能力有不同程度增加(图4、5),使Ca2+/Na+、Mg2+/Na+能够在高盐胁迫下不致于下降过多,导致营养失衡。另外,矿质营养离子与盐离子的比值在低浓度和高浓度盐胁迫之间差异不大,说明大果沙枣能够在高盐环境中控制离子的吸收,维持相对稳定的离子比例,保持相对较好的营养状况,这可能也是大果沙枣耐盐的原因之一。
综合本研究结果认为,土壤盐度升高对大果沙枣树体各器官矿质离子选择性吸收、运输和分配会产生影响,对根和叶的影响最为明显,主要体现在增强了叶中K+、Mg2+和Ca2+的积累和根部Na+的吸收,同时促进了Mg2+和Ca2+向上选择性运输,提高了光合器官叶片中矿质营养元素的浓度。总之,研究区大果沙枣成年树对盐渍化土壤生境具有一定的适应性,虽然土壤盐胁迫对树体内的离子平衡产生一定不良影响,但大果沙枣通过离子区隔化功能,优先将Na+储存在根系中,以维持枝和叶相对较高的K+/Na+、Ca2+/Na+、Mg2+/Na+值,同时保持根系和枝条内相对稳定的K+、Ca2+、Mg2+浓度,增强叶片选择性吸收K+、Ca2+、Mg2+的能力,提高渗透调节能力,缓解Na+毒害,并保证地上部矿质元素的供应,从而维持树体正常的生理活动。
在新疆等相似气候的干旱盐碱区,种植大果沙枣不仅能通过增加地表覆盖来降低地表蒸发,而且树体还可以选择吸收土壤中盐离子而降低土壤中盐分含量,达到盐碱地的生物改良效果。盐害通常是因为Na +含量过高造成的,大果沙枣根、枝和叶各器官之间对Na+的区域化分配往往决定着树体整体水平的耐盐能力,通常可以通过增加钾的供应来降低树体对钠的吸收。因此,在大果沙枣的栽培管理中,补充钾肥以维持土壤中较高的K+浓度,不仅可以满足树体生长发育对钾营养元素的需求,而且可促进根系中有机溶质积累,提高细胞液的渗透压,降低Na+危害,从而促进树体组织细胞吸收水分,改善树体对盐胁迫的耐性。

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In pea (Pisum sativum L.) plants the effect of short-term salt stress and recovery on growth, water relations and the activity of some antioxidant enzymes was studied. Leaf growth was interrupted by salt addition. However, during recovery, growth was restored, although there was a delay in returning to control levels. Salt stress brought about a decrease in osmotic potential and in stomatal conductance, but at 48 h and 24 h post-stress, respectively, both parameters recovered control values. In pea leaves, a linear increase in the Na+ concentration was observed in salt treated plants. In the recovered plants, a slight reduction in the Na+ concentration was observed, probably due to a dilution effect since the plant growth was restored and the total Na+ content was maintined in leaves after the stress period. A significant increase of SOD activity occurred after 48 h of stress and after 8 h of the recovery period (53% and 42%, respectively), and it reached control values at 24 h post-stress. APX activity did not change during the stress period, and after only 8 h post-stress it was increased by 48% with respect to control leaves. GR showed a 71% increase after 24 h of salt stress and also a significant increase was observed in the recovered plants. A strong increase of TBARS was observed after 8 h of stress (180% increase), but then a rapid decrease was observed during the stress period. Surprisingly, TBARS again increased at 8 h post-stress (78% increase), suggesting that plants could perceive the elimination of NaCl from the hydroponic cultures as another stress during the first hours of recovery. These results suggest that short-term NaCl stress produces reversible effects on growth, leaf water relations and on SOD and APX activities. This work also suggests that both during the first hours of imposition of stress and during the first hours of recovery an oxidative stress was produced.
[37]
Teakle N L, Flowers T J, Real D, et al. Lotus tenuis tolerates the interactive effects of salinity and water logging by excluding Na+ and Cl- from the xylem[J]. Journal of Experimental Botany, 2007,58(8):2169-2180.
Salinity and waterlogging interact to reduce growth of poorly adapted species by, amongst other processes, increasing the rate of Na(+) and Cl(-) transport to shoots. Xylem concentrations of these ions were measured in sap collected using xylem-feeding spittlebugs (Philaenus spumarius) from Lotus tenuis and Lotus corniculatus in saline (NaCl) and anoxic (stagnant) treatments. In aerated NaCl solution (200 mM), L. corniculatus had 50% higher Cl(-) concentrations in the xylem and shoot compared with L. tenuis, whereas concentrations of Na(+) and K(+) did not differ between the species. In stagnant-plus-NaCl solution, xylem Cl(-) and Na(+) concentrations of L. corniculatus increased to twice those of L. tenuis. These differences in xylem ion concentrations, which were not caused by variation in transpiration between the two species, contributed to lower net accumulation of Na(+) and Cl(-) in shoots of L. tenuis, indicating that ion transport mechanisms in roots of L. tenuis were contributing to better 'exclusion' of Cl(-) and Na(+) from shoots, compared with L. corniculatus. Root porosity was also higher in L. tenuis, due to constitutive aerenchyma, than in L. corniculatus, suggesting that enhanced root aeration contributed to the maintenance of Na(+) and Cl(-) 'exclusion' in L. tenuis exposed to stagnant-plus-NaCl treatment. Lotus tenuis also had greater dry mass than L. corniculatus after 56 d in NaCl or stagnant-plus-NaCl treatment. Thus, Cl(-) 'exclusion' is a key trait contributing to salt tolerance of L. tenuis, and 'exclusion' of both Cl(-) and Na(+) from the xylem enables L. tenuis to tolerate, better than L. corniculatus, the interactive stresses of salinity and waterlogging.

基金

新疆维吾尔自治区重点研发计划项目“大果沙枣良种选育及栽培研究”(2019B00007)
中央财政科技推广项目“大果沙枣良种繁育与栽培技术示范与推广”(新[2021]TG01号)
自治区林业发展补助资金项目“新疆大果沙枣良种高效栽培技术研究”(XJLYKJ-2020-09)

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