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全世界20%的耕地和接近半数的灌溉土地受到土壤盐渍化影响,面对日益稀缺的耕地及其产生的潜在粮食危机[1],如何合理开发利用盐渍化土地是目前研究的焦点问题之一。通过研究植物的耐盐机制,采用生物措施筛选、引种和培育新的耐盐经济植物,利用其耐盐基因增加困难立地粮食产量,并对现有盐渍化土壤的生态环境进行修复已成为国内外研究的热点[2]。
黑果枸杞(Lycium ruthenicum)广泛分布于西北干旱及半干旱地区,是一种典型的具有明显防风固沙效益和药食两用的经济型盐生植物,被视为治理西北干旱区荒漠区盐碱地的主要植物资源之一[3-5]。目前黑果枸杞耐盐性的研究包括以下几方面:幼苗耐盐阈值[6-7],形态解剖学[8],抗氧化酶系统[9]和离子分布及基因表达[10]。证明黑果枸杞幼苗耐受MgSO4的阈值是6 g/L,茎具有较发达的表皮、维管束和较厚的栅栏组织,且随着盐浓度增加,CAT、SOD酶活性先增大后减小,不同器官K+和Ca2+含量略有降低以及保存K+基因LrKUP8显著上调等特征。虽然上述研究表明,黑果枸杞经过短期盐胁迫,从器官到细胞生理均会发生变化,但Jose等人[11]认为盐胁迫应该包括短期与长期两种行为。长期盐胁迫会使植物发生离子毒害,导致K+和Ca2+亏缺,养分失去平衡和生物量累积量减少,对于长期盐胁迫研究,仅杨万鹏等[12]设置30 d培养实验对黑果枸杞耐盐性进行了分析,而目前研究植物长期盐胁迫的时间均较短,耐盐锻炼对长期盐胁迫的黑果枸杞植株生长及果实发育影响的研究仍显不足。
已有研究表明,短期盐胁迫黑果枸杞器官离子区隔化存在一定差异,然而基于长期(至少一个物候期)盐生环境盐胁迫,黑果枸杞果实的生长发育规律及各器官离子区隔化适应盐生环境的规律仍需进一步探究。Flowers等[13]、Jose等[11]提出盐生植物通过器官协同作用以及改变K+和Ca2+浓度适应Na+盐胁迫且长期胁迫对植物更具危害[14],上述文献提出Na+富集区域在叶片。因此笔者提出以下假设,长期盐胁迫下:(1)黑果枸杞不仅通过增加叶K+、叶Ca2+浓度和根系Ca2+浓度提高其耐盐性,而且提高茎Na+富集能力也对其提升耐盐性有一定贡献。(2)黑果枸杞内源Ca2+调控K+/Na+的位置主要发生在根和叶。实验通过调查广泛分布于中国新疆维吾尔自治区黑果枸杞生物学性状,分析不同器官内源K+、Na+和Ca2+含量变化规律,以验证上述假设。
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研究地位于新疆维吾尔自治区阿拉尔市国家农业开发园区,地理位置81°11′ ~ 81°20′E、40°31′ ~ 40°32′N,距塔里木河2 km。自然地理特征为塔克拉玛干沙漠北缘,暖温带极端大陆性干旱荒漠气候,极端最高气温40 ℃,极端最低气温−33.2 ℃。研究区太阳辐射年均559.6 ~ 612.4 kJ/cm2。年均日照2 556.3 ~ 2 991.8 h,日照率为5 869%。年均降水量为40.1 ~ 82.5 mm,年均蒸发量1 876.6 ~ 2 558.9 mm。植被有黑果枸杞、胡杨(Populus euphratica)、多枝柽柳(Tamarix galli)和盐爪爪(Kalidium miq)等。
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黑果枸杞种子及幼苗经过1年耐盐锻炼,于2016年4月1日将幼苗移栽至4 hm2的大田,大田土壤总盐和pH值如表1。根据土壤溶液Na+浓度将实验地划分为低盐胁迫(MSS) < 200 mmol/L[13]、200 mmol/L < 中盐胁迫(HSS) < 400 mmol/L和高盐胁迫(SS) > 400 mmol/L。
表 1 土壤溶液平均NaCl浓度和pH值
Table 1. Average NaCl concentration and pH value of soil solution
土层深度
Soil depth/cm高盐胁迫
High salt
stress (SS)中盐胁迫
Middle salt
stress (HSS)低盐胁迫
Low salt
stress (MSS)pH NaCl/
(mmol·L−1)pH NaCl/
(mmol·L−1)pH NaCl/
(mmol·L−1)0 ~ 20 8.84 690 8.57 382 8.32 180 0 ~ 40 8.95 475 8.79 305 8.44 150 40 ~ 60 9.06 386 8.49 217 8.16 102 -
2017年5月15日调查每一盐分梯度7个样方(10 m × 10 m)黑果枸杞成活率,合计21个样方。在2017年5月15日(花期),7月15日(初果期)和9月15日(果实完全成熟期)采集每一植株果实并测定其直径。根据植株上、中、下3层果实数量,按比例随机选取一定数量果实,用游标卡尺测量果实直径求其加权平均值。9月15日,采集每一植株根际土壤。9月16日收获整株植物,用水冲洗掉根系泥土,根、茎和叶分别收集装至信封袋,备用。
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用20 mmol/L CaCl2冰溶液冲洗根2次,使Na+、K+和Ca2+从细胞壁渗出,用去离子水冲洗掉茎和分枝表层盐离子,然后将根、茎和分枝以及叶在80 ℃杀青3 d,处理过的干物质用10 mL的100% HNO3萃取24 h,随后在90 ~ 100 ℃培养2 h。将硝化的样品稀释10倍,水溶性Na+、K+和Ca2+用原子吸收光谱仪测定[14],土壤K+、Na+、Cl−测定采用常规方法,每一样品重复3次。
植株选择吸收K+拮抗Na+的能力(SA)以及选择性转运系数(STC)用下列方程来评价[15]。
$$ \begin{aligned} & {\rm{SA}} = ({\text{整株}}{{\rm{K}}^ + }/{\rm{ N}}{{\rm{a}}^ + })/({\text{根围土壤}}{{\rm{K}}^ + }/{\rm{ N}}{{\rm{a}}^ + })\\ & {\rm{STC}} = ({\text{地上部}}{{\rm{K}}^ + }/{\rm{N}}{{\rm{a}}^ + })/{\rm{ }}({\text{根中}}{{\rm{K}}^ + }/{\rm{N}}{{\rm{a}}^ + }) \end{aligned} $$ -
不同器官Na+、K+、Ca2+以及果实相对生长速率均用平均值 ± 标准差表示。One-way ANOVA(Duncan-test)检测各梯度测试指标的差异显著性(P < 0.05, P < 0.01,n = 7),并用二次函数模拟土壤溶液NaCl浓度与黑果枸杞成活率的关系,PCA分析各因素(根际土壤K+/Na+、器官Na+、K+、Ca2+,不同器官干质量以及根形态)对植株适应盐生环境的贡献。
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3种盐胁迫黑果枸杞成活率存在极显著差异(P < 0.01)。HSS黑果枸杞成活率显著高于MSS和SS,分别比MSS和SS高16.9%和57%(图1a)。黑果枸杞成活率与土壤NaCl浓度关系符合二次函数模型,即y = 65.91 + 0.298 8x − 0.000 813 6x2,R2 = 0.865。由此推算土壤NaCl浓度导致黑果枸杞理论致死剂量是355.88 mmol/L,当土壤NaCl浓度小于183.63 mmol/L成活率随之增大而增加(图1b)。
图 1 不同盐渍化土壤黑果枸杞植株成活率及模型
Figure 1. Survival rate and model of L. ruthenicum with different salinized soil
前期(5月15日至7月15日),MSS处理的果实相对生长速率极显著高于HSS和SS,HSS和SS之间没有显著差异,但前者略低于后者。后期(7月15日至9月15日),SS、HSS和MSS处理的果实相对生长速率之间具有极显著差异,且SS > HSS > MSS。前后两个时期相比,后期MSS和HSS处理果实相对生长速率极显著低于前期,然而后期SS果实相对生长速率明显快于前期(图2)。
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不同盐胁迫植株相同器官Na+、K+和Ca2+含量具有一定差异。MSS根中Na+含量显著低于HSS,与SS处理根中Na+含量没有显著差异,略低于SS处理。HSS处理茎Na+显著高于MSS处理。HSS处理叶Na+含量显著低于MSS处理,低于SS处理。SS根中Na+含量显著低于HSS,SS茎Na+略低于HSS而高于MSS,SS叶Na+含量显著低于MSS。MSS根中K+含量显著低于HSS。HSS根中K+含量显著高于SS。叶K+随盐渍化程度增加而显著增加。MSS处理根和茎中Ca2+含量显著高于HSS和SS。叶Ca2+含量表现出显著差异,SS > HSS > MSS。
相同盐胁迫黑果枸杞各器官Na+、K+、Ca2+具有明显差异。MSS处理的叶Na+显著高于根和茎,茎显著高于根。HSS处理的根、茎、叶Na+含量具有显著差异。MSS处理的茎、叶K+含量显著高于根。HSS处理的叶K+含量显著高于根和茎,根和茎之间没有显著差异。SS处理的叶中Na+和K+含量显著高于茎和根,茎显著高于根。MSS处理的根Ca2+含量显著高于叶和茎。HSS处理的叶和根中Ca2+含量显著高于茎,前两者之间没有显著差异。SS处理的叶和根中Ca2+含量显著高于茎,叶和根之间没有显著差异(表2)。
表 2 3种盐渍化土壤黑果枸杞根、茎、叶中Na+、K+和Ca2+含量
Table 2. Contents of Na+, K+ and Ca2+of root, stem, leaf of L. ruthenicum in three kinds of salinized soil
g/kg 指标
IndexMSS HSS SS 根 Root 茎 Stem 叶 Leaf 根 Root 茎 Stem 叶 Leaf 根 Root 茎 Stem 叶 Leaf Na+ 0.63cB 2.22bB 23.31aA 1.11cA 3.12bA 9.51aB 0.70cB 3.00bAB 10.00aB K+ 6.04cB 13.34bA 33.83aC 7.84bA 8.84bB 36.93aB 5.80cB 12.41aB 38.28aA Ca2+ 53.24aA 26.88bA 9.12cC 28.63aC 18.57bC 27.62aB 42.38aB 23.29bB 45.90aA 注:不同小写字母表示相同盐渍化水平不同器官Na+、K+和Ca2+含量差异显著,不同大写字母不同盐渍化水平相同器官Na+、K+和Ca2+含量差异显著(P < 0.05)。Notes: different lowercase letters represent significant differences in Na+, K+ and Ca2+ contents of different organs under the same salinization level. Different capital letters represent significant differences in Na+, K+ and Ca2+ contents of same organs under varied salinization levels (P < 0.05). -
相同盐渍土根K+/Na+均显著高于茎和叶。SS处理茎和叶K+/Na+表现出显著差异,HSS和MSS中没有显著差 异;HSS茎中K+/Na+低于叶,MSS处理茎K+/Na+高于叶(图3a)。根中Ca2+/Na+也显著高于茎和叶,茎中Ca2+/Na+均显著高于叶(图3b)。
图 3 不同盐渍化土壤各器官K+/Na+和Ca2+ / Na+变化规律
Figure 3. Variations in K+/Na+ and Ca2+/Na+ of varied organsunder different salt stress levels
MSS和SS处理根中K+/Na+显著高于HSS,前两者没有显著差异。随着盐渍化程度增加,植株茎K+/Na+具有显著增加趋势。HSS和SS处理叶中K+/Na+显著高于MSS,HSS和SS没有显著差异(图3a)。MSS和SS处理根中Ca2+/Na+显著高于HSS,MSS和SS没有显著差异。MSS和SS处理茎中Ca2+/Na+显著高于HSS。HSS和SS处理叶Ca2+/Na+显著高于MSS。随着盐渍化程度增加,叶Ca2+/Na+呈增加趋势(图3b)。
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HSS选择性吸收系数显著高于MSS和SS,SS显著低于MSS(图4a)。HSS选择性转运系数显著低于MSS和SS,后两者之间没有显著差异,SS略低于MSS(图4b)。
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植株K+/Na+与Ca2+含量显著正相关,与根际土壤K+/Na+极显著正相关,与根Na+极显著负相关。根中K+/Na+与植株和根际土壤K+/Na+呈极显著正相关,与根Na+含量呈极显著负相关。根际土壤K+/Na+与根Na+含量呈显著负相关,茎Na+含量与根Na+含量呈极显著正相关,根Na+含量与植株Ca2+含量呈显著负相关(表3)。
表 3 不同器官及根际土壤K+/Na+、Na+和Ca2+ Pearson相关性分析
Table 3. Pearson correlation analysis on K+/Na+, Na+ and Ca2+ of different organs and rhizosphere soil
项目
Item根K+/Na+
Root K+/Na+植株K+/Na+
Whole plant K+/Na+根际土壤K+/Na+
Rhizosphere soil K+/Na+茎Na+
Shoot Na+根Na+
Root Na+植株Ca2+
Whole plant Ca2+根 K+/Na+ Root K+/Na+ 1 0.988** 0.784** −0.296 −0.657** 0.397 植株 K+/Na+ Whole plant K+/Na+ 1 0.702** −0.286 −0.652** 0.496* 根际土壤K+/Na+ Rhizosphere soil K+/Na+ 1 −0.218 −0.598* 0.107 茎 Na+ Stem Na+ 1 0.629** −0.418 根 Na+ Root Na+ 1 −0.488* 植株 Ca2+ Whole plant Ca2+ 1 注:*和**分别代表P < 0.05, P < 0.01相关性显著。下同。Notes: * and ** represent significant correlations at P < 0.05 and P < 0.01, respectively. The same below. 植株和根K+/Na+与SA极显著正相关,与STC极显著负相关,与地上器官干质量显著负相关。根际土壤中K+/Na+与SA显著正相关,与STC极显著负相关,与茎和地上部器官干质量显著负相关。根Na+含量与SA极显著负相关,与STC显著正相关,与叶干质量、茎干质量和地上器官干质量极显著正相关。植株Ca2+含量与SA显著正相关(表4)。
表 4 不同器官干质量、K+/Na+、Na+和Ca2+相关性分析
Table 4. Correlation analysis on K+/Na+, Na+ and Ca2+of different organs or organ dry mass
项目
Item选择吸
收系数
SA选择性转
运系数
STC主根平
均直径
Main root
diameter (MRD)侧根平
均直径
Lateral root
diameter (LRD)根干
质量
Root dry
mass (DW)叶干
质量
Leaf DW茎干
质量
Stem DW地上器官
干质量
Aboveground
organ DW根K+/Na+ Root K+/Na+ 0.931** −0.722** −0.127 −0.184 −0.379 −0.444 −0.532* −0.521* 植株K+/Na+ Whole plant K+/Na+ 0.975** −0.647** −0.059 −0.174 −0.385 −0.451 −0.508* −0.512* 根际土壤 K+/Na+
Rhizosphere soil K+/Na+0.537* −0.983** −0.408 −0.081 −0.197 −0.478 −0.586* −0.569* 茎Na+ Stem Na+ −0.284 0.132 −0.116 −0.268 0.08 0.259 0.298 0.297 根Na+ Root Na+ −0.618** 0.568* 0.139 0.048 0.505* 0.703** 0.752** 0.775** 植株Ca2+ Whole plant Ca2+ 0.509* −0.073 −0.033 0.084 −0.462 −0.155 −0.334 −0.264 SA与STC呈显著负相关。STC与叶干质量、茎干质量和地上部器官干质量显著正相关。主根平均直径与茎干质量和地上器官干质量显著正相关,侧根平均直径与根干质量显著正相关。根干质量与叶干质量显著正相关,与茎干质量和地上器官干质量极显著正相关,叶干质量与茎和地上器官干质量极显著正相关,茎干质量和地上器官干质量极显著正相关(表5)。
表 5 植株选择性吸收盐离子能力,耐盐性与植株根系形态及不同器官干质量相关性分析
Table 5. Correlation analysis on selective absorption of salt properties, salt toleranceand plant root morphology and dry mass of different organs
项目
Item选择吸
收系数
SA选择性转
运系数
STC主根平
均直径
MRD侧根平
均直径
LRD根干
质量
Root DW叶干
质量
Leaf DW茎干
质量
Stem DW地上器官干质量
Aboveground
organ DW选择吸收系数 SA 1 −0.485* 0.053 −0.159 −0.39 −0.431 −0.444 −0.466 选择性转运系数 STC 1 0.433 0.064 0.167 0.495* 0.582* 0.575* 主根平均直径 MRD 1 0.378 0.462 0.467 0.503* 0.517* 侧根平均直径 LRD 1 0.494* 0.231 0.153 0.203 根干质量 Root DW 1 0.600* 0.722** 0.706** 叶干质量 Leaf DW 1 0.767** 0.934** 茎干质量 Stem DW 1 0.945** 地上器官干质量 Aboveground organ DW 1 主成份1(PCA1)和主成份2(PCA2)可以解释黑果枸杞适应盐生环境盐渍化胁迫73.9%的信息。PCA1可解释黑果枸杞盐渍化胁迫57.8%信息,地上器官干质量对PCA1贡献最大,与之呈极显著正相关,按照对PCA1贡献率大小排序为叶干质量、茎干质量、根干质量和主根平均直径;PCA1与地上器官Na+含量和侧根平均直径显著负相关,并且各指标之间存在显著正相关。根Ca2+含量、地上器官K+/Na+、根干质量、主根直径与PCA1显著正相关。植株K+/Na+、根K+/Na+、根际土壤K+/Na+、根Ca2+含量、地上器官Ca2+含量可以解释PCA2耐盐性的16.1%,上述指标均与PCA2呈显著负相关。也显示出MSS处理根系Na+强烈影响黑果枸杞耐盐性,而HSS处理植株耐盐性受地上器官干质量的显著影响,SS处理植株耐盐性与K+/Na+极显著相关(图5)。
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研究结果显示,MSS、HSS和SS处理黑果枸杞植株成活率存在极显著差异,HSS处理分别比SS,MSS,分别高出57% 和16.9%(图1a),表明适度的盐胁迫更有利于提高其存活率,但超出一定范围会使植物死亡,这一结果在枸杞属其他物种已证实[16]。在另一些盐生植物研究中也得出了相似结论[17],即土壤盐含量大于2.38 g/L,随着盐浓度增加水稻(Oryza sativa)幼苗成活率显著降低。导致上述结果的原因可能是因为适度盐胁迫有利于维持植物代谢、抗性以及细胞程序性死亡的平衡。高胁迫则可能需要维持高代谢及能量损耗而加速植物死亡,低胁迫时植物需要消耗更高能量建立系统抗性激活了部分细胞死亡程序,导致植物部分死亡[18]。
土壤溶液NaCl浓度与黑果枸杞成活率之间符合二次函数模型 y = 65.91 + 0.298 8x − 0.000 813 6x2,R2 = 0.865,由此推算土壤NaCl浓度导致黑果枸杞理论致死剂量是355.88 mmol/L (图1b),与我们在田间观测测定结果一致,但略高于室内培养得出的NaCl浓度致死剂量350 mmol/L[6],可能是因为本次试验在黑果枸杞种子及幼苗阶段进行了抗性锻炼而获得更强耐盐性。另外,根系分泌了一些小分子酸溶解了根际土壤中CaCO3,抑制了Na+与根际之间置换反应[1]。Katschnig等人[19]研究指出海篷子(Salicornia europaea)最适NaCl浓度是300 mmo/L,致死剂量是500 mmol/L,小于最适浓度的NaCl可以促进海篷子生长和生物量累积。盐生植物芦苇(Phragmites karka)的最适盐浓度则是100 mmol/L NaCl,低于该浓度也可促进其生长[20]。由此说明,不同物种耐盐性明显不同,且最适盐胁迫阈值和致死剂量存在显著差异[21-22],经过抗性锻炼的植株可适应更高浓度盐胁迫。
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离子区隔化是盐生植物进化出适应盐生环境胁迫的重要方式,盐生植物为了适应高浓度盐胁迫,某些组织或器官会发生离子区隔化[13]。对于多年生盐生木本植物来说,优先富集Na+于地上衰老器官[23],更有利于其适应高浓度盐胁迫。高盐浓度胁迫下,根将过量Na+和Cl−运输至地上器官某些衰老组织,并显著增强K+吸收能力,从而增强植株耐盐性[24]。Fall等人[25]利用不同盐浓度处理鼠尾粟属毛鼠尾粟(Sporobolus robustus),发现高盐浓度处理组地上器官Na+显著高于根。本次研究得出了相似结论,即高浓度盐胁迫黑果枸杞主要将Na+区隔至地上器官,其中叶储存量最多,茎中Na+也有一定程度的富集(表2)。结果也表明:随着盐渍化程度增加,茎中也富集较多Na+,同时K+、Ca2+含量先减少,后增加(表2),此结果与前人结论略不同,Flowers[13]认为这是不同器官协同分摊Na+毒害的结果。
达到最适浓度之前,随着土壤盐渍化程度增加,黑果枸杞叶中Na+、K+和Ca2+含量均显著增加(表2)。这与Khan等人[26]研究结果相反,其认为Na+和Cl−分别达到1 391和1 673 mmol/kg干质量之前,叶中K+、Mg2+和Ca2+随着盐浓度增加显著减小。但Kaya等人[27]也曾报道玉米(Zea mays)受到盐胁迫相对生长速率降低,盐敏感型植株叶中的Na+、Cl−、Na+/K+和Na+/Ca2+比例明显增加。Shabala[18]指出随着叶Na+累积,植株Ca2+含量显著增加,Ca2+信号增强,细胞膜发生极化降低Na+通量,从而减弱Na+毒害作用[28]。而Ca2+含量增加的原因也可能因为细胞本身释放Ca2+,其中的储存钙转化成游离钙以适应高盐胁迫。由此可知,Na+区隔化程度与Ca2+及其产生的信号密切相关。
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Nrgrão等人[29]认为一般线性回归或非线性回归不能完全表征植株耐盐性信息,因而,建议使用诸如PCA、结构方程或复杂网络等方法或模型进行分析,以综合体现一些重要特征或参数对植物耐盐性的贡献。使用植株K+/Na+与土壤介质K+/Na+表征植物耐盐性,虽然能够表示植株对钠离子的吸收能力,却仅能反映出植物生理行为。本次研究中选取了生理指标植物内源K+、Na+、Ca2+,形态学指标主根直茎、侧根直茎,根、茎、叶生物量等多个指标可以解释黑果枸杞植株73.9%耐盐性。本研究也显示PCA分析能够相对全面表征黑果枸杞的耐盐性,并明确了不同指标对植株耐盐性的贡献。研究表明不同盐胁迫条件下,植株应对胁迫的策略略有差异,当土壤溶液NaCl大于400 mmol/L,黑果枸杞主要依赖于调控植株体K+/Na+;而在200 ~ 400 mmol/L盐胁迫下,耐盐性主要受根系Na+含量影响(图5),这与前人的研究结果略不同。
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土壤溶液NaCl浓度小于183.63 mmol/L可以促进黑果枸杞茎和果实的生长,致死剂量是355.88 mmol/L。另外,随着盐胁迫程度增加,根中维持高水平Ca2+调控植株体K+/Na+,不同器官储存Na+的能力具有明显差异,茎富集Na+能力随着盐胁迫程度增加显著增强,说明黑果枸杞倾向于不同器官之间协同分担盐渍化胁迫,从而适应长期盐渍化土壤环境。这些结果为其在修复西北干旱区及半干旱区盐碱地生态环境提供了理论参考,也将为逆境种质资源的选育提供科学依据。
Characteristics of Lycium ruthenicum adapting to salinization stress after salt tolerance training
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摘要:
目的 明确耐盐锻炼黑果枸杞适应长期盐渍化胁迫的机理,为其修复极端干旱区盐渍化土壤提供依据。 方法 应用回归分析及主成分分析低盐胁迫(MSS)、中盐胁迫(HSS)和高盐胁迫(SS)土壤黑果枸杞各器官K+、Na+和Ca2+区隔化特征,器官干质量和根系形态对盐胁迫的响应。 结果 (1)NaCl浓度小于183.63 mmol/L,耐盐锻炼黑果枸杞植株成活率随着NaCl浓度增加而增大,NaCl浓度 ≥ 355.88 mmol/L植株全部死亡。随着NaCl浓度升高,花期到初果期果实相对生长速率显著减缓,初果期到果实完全成熟期果实相对生长速率加快。(2)HSS处理的根K+和Na+显著高于MSS和SS,茎中K+、Na+和Ca2+含量均显著低于MSS和SS。HSS处理的根和茎中K+/Na+和Ca2+/Na+差异不显著。SS处理的叶Ca2+分别是MSS和HSS的5和3倍。SS处理的根和茎Na+含量没有显著差异,根和叶Ca2+含量也没有显著差异。胁迫程度从MSS上升到SS,茎中Na+含量平均增加0.78 g/kg。(3)PCA分析表明,主成份1(PCA1)和主成份2(PCA2) 共解释了黑果枸杞适应盐胁迫的73.9%。PCA1可解释黑果枸杞盐胁迫的57.8%信息,其中,地上器官干质量对PCA1贡献最大,按照对PCA1贡献率大小排序为叶干质量、茎干质量、根干质量和主根直径。PCA1与根Na+含量、地上器官Na+含量和侧根直径呈显著负相关。株高、根Ca2+含量、茎粗、地上器官K+/Na+、根干质量、主根直径与PCA1呈正相关。植株K+/Na+、根系K+/Na+、根际土壤K+/Na+、根Ca2+含量和地上器官Ca2+含量可以解释PCA2盐胁迫的16.1%信息,上述指标均与PCA2呈显著负相关。 结论 随着盐胁迫程度增加,叶维持高浓度Ca2+调控植株体K+/Na+,根和茎富集储存Na+能力显著增强,说明经过耐盐锻炼黑果枸杞倾向于不同器官协同分担盐胁迫以适应长期盐胁迫。 Abstract:Objective For soil salinization restoration and sustainability in extreme arid areas, we investigated Lycium ruthenicum adapting to long-term salinization stress. Method The K+, Na+ and Ca2+ compartmentalization of organs of L. ruthenicum in low salt stress (MSS), middle salt stress (HSS) and high salt stress (SS) soil were analyzed by regression analysis and principal component analysis, as well as the responses of dry mass and root morphology to salt stresses. Result (1) If concentration of NaCl at soil solution was below 183.63 mmol/L, the survival rate of salt-tolerance training plants increased with increasing concentration of NaCl, and all the plants died if concentration of NaCl was above 355.88 mmol/L. With increase of NaCl concentration, the relative growth rate of fruit significantly slowed down from flowering to early fruit, while accelerated from early fruit to full maturity. (2) The root K+ and Na+ treated by HSS were significantly higher than those treated by MSS and SS, and the contents of K+, Na+ and Ca2+ in stems were significantly lower than those treated by MSS and SS. There was significant differences neither K+/Na+ nor Ca2+/Na+ between roots and stems in HSS. The leaf Ca2+ in SS treatment was 5 and 3 folds of MSS and HSS, respectively. There was no significant difference in Na+ content between roots and stems, and no significant difference in Ca2+ content between roots and leaves. The stress increased from MSS to SS, the content of Na+ in the stem increased by 0.78 g/kg on average. (3) PCA analysis showed that principal component 1 (PCA1) and principal component 2 (PCA2) explained 73.9% information of L. ruthenicum under salt stress. PCA1 explained 57.8% of the salt stress of L. ruthenicum. Among them, dry mass of over-ground organs contributed the most to PCA1. According to these contributions to PCA1, leaf dry mass, stem dry mass, root dry mass and taproot diameter were to be top four. PCA1 was negatively correlated with Na+ content both in roots and aboveground organs and lateral root diameter. Plant height, root Ca2+ content, stem diameter, aboveground organ K+/Na+, root dry mass and taproot diameter were positively correlated with PCA1. The content of plant K+/Na+, root K+/Na+, rhizosphere soil K+/Na+, root Ca2+ and aboveground organ Ca2+ could explain 16.1% of PCA2. Conclusion With the increase of salt stress, leaves maintained high concentration of Ca2+ to regulate plant K+/Na+, and root and stem enrichment and storage capacity of Na+ were significantly enhanced, which indicate that L. ruthenicum tends to share salt stress cooperatively in different organs to adapt to long-term salt stress after salt tolerance training. -
Key words:
- half lethal dose /
- ion compartmentalization /
- Lycium ruthenicum /
- salt stress /
- salt-tolerance training
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图 1 不同盐渍化土壤黑果枸杞植株成活率及模型
a. 不同盐渍化土壤黑果枸杞植株成活率,不同小写字母表示各处理植株成活率差异显著(P < 0.05);b. 植株成活率与土壤NaCl浓度二次函数模型。a, plant survival rates of L. ruthenicum in different salinized soil,different lowercase letters mean significant differences in plant survival rate among treatments (P < 0.05); b, quadratic model equation between plant survival rate and NaCl concentration of soil.
Figure 1. Survival rate and model of L. ruthenicum with different salinized soil
图 2 花期至初果期和初果期至果实完全成熟期果实相对生长速率对土壤盐胁迫的响应
不同小写字母表示不同盐渍化程度相同时期差异显著,不同大写字母表示不同时期相同盐胁迫果实相对生长速率差异显著(P < 0.05)。Different lowercase letters represent significant differences in varied salinized degree at the same period; different capital letters represent significant differences in the relative growth rate of fruit in different periods under same salt stress degree (P < 0.05).
Figure 2. Relative growth rates of fruit response to soil salinized stress during the two periods, respectively from flowering to early fruiting stage and from early fruiting to fructescence-later stage
图 3 不同盐渍化土壤各器官K+/Na+和Ca2+ / Na+变化规律
不同大写字母表示不同盐渍化土壤相同器官差异显著,不同小写字母表示同一盐渍化土壤不同器官差异显著(P < 0.05)。Different capital letters indicate significant differences among varied organs under different salinized soils. Different lowercase letters indicate significant differences among varied organs under same salinized soil (P < 0.05).
Figure 3. Variations in K+/Na+ and Ca2+/Na+ of varied organsunder different salt stress levels
表 1 土壤溶液平均NaCl浓度和pH值
Table 1. Average NaCl concentration and pH value of soil solution
土层深度
Soil depth/cm高盐胁迫
High salt
stress (SS)中盐胁迫
Middle salt
stress (HSS)低盐胁迫
Low salt
stress (MSS)pH NaCl/
(mmol·L−1)pH NaCl/
(mmol·L−1)pH NaCl/
(mmol·L−1)0 ~ 20 8.84 690 8.57 382 8.32 180 0 ~ 40 8.95 475 8.79 305 8.44 150 40 ~ 60 9.06 386 8.49 217 8.16 102 表 2 3种盐渍化土壤黑果枸杞根、茎、叶中Na+、K+和Ca2+含量
Table 2. Contents of Na+, K+ and Ca2+of root, stem, leaf of L. ruthenicum in three kinds of salinized soil
g/kg 指标
IndexMSS HSS SS 根 Root 茎 Stem 叶 Leaf 根 Root 茎 Stem 叶 Leaf 根 Root 茎 Stem 叶 Leaf Na+ 0.63cB 2.22bB 23.31aA 1.11cA 3.12bA 9.51aB 0.70cB 3.00bAB 10.00aB K+ 6.04cB 13.34bA 33.83aC 7.84bA 8.84bB 36.93aB 5.80cB 12.41aB 38.28aA Ca2+ 53.24aA 26.88bA 9.12cC 28.63aC 18.57bC 27.62aB 42.38aB 23.29bB 45.90aA 注:不同小写字母表示相同盐渍化水平不同器官Na+、K+和Ca2+含量差异显著,不同大写字母不同盐渍化水平相同器官Na+、K+和Ca2+含量差异显著(P < 0.05)。Notes: different lowercase letters represent significant differences in Na+, K+ and Ca2+ contents of different organs under the same salinization level. Different capital letters represent significant differences in Na+, K+ and Ca2+ contents of same organs under varied salinization levels (P < 0.05). 表 3 不同器官及根际土壤K+/Na+、Na+和Ca2+ Pearson相关性分析
Table 3. Pearson correlation analysis on K+/Na+, Na+ and Ca2+ of different organs and rhizosphere soil
项目
Item根K+/Na+
Root K+/Na+植株K+/Na+
Whole plant K+/Na+根际土壤K+/Na+
Rhizosphere soil K+/Na+茎Na+
Shoot Na+根Na+
Root Na+植株Ca2+
Whole plant Ca2+根 K+/Na+ Root K+/Na+ 1 0.988** 0.784** −0.296 −0.657** 0.397 植株 K+/Na+ Whole plant K+/Na+ 1 0.702** −0.286 −0.652** 0.496* 根际土壤K+/Na+ Rhizosphere soil K+/Na+ 1 −0.218 −0.598* 0.107 茎 Na+ Stem Na+ 1 0.629** −0.418 根 Na+ Root Na+ 1 −0.488* 植株 Ca2+ Whole plant Ca2+ 1 注:*和**分别代表P < 0.05, P < 0.01相关性显著。下同。Notes: * and ** represent significant correlations at P < 0.05 and P < 0.01, respectively. The same below. 表 4 不同器官干质量、K+/Na+、Na+和Ca2+相关性分析
Table 4. Correlation analysis on K+/Na+, Na+ and Ca2+of different organs or organ dry mass
项目
Item选择吸
收系数
SA选择性转
运系数
STC主根平
均直径
Main root
diameter (MRD)侧根平
均直径
Lateral root
diameter (LRD)根干
质量
Root dry
mass (DW)叶干
质量
Leaf DW茎干
质量
Stem DW地上器官
干质量
Aboveground
organ DW根K+/Na+ Root K+/Na+ 0.931** −0.722** −0.127 −0.184 −0.379 −0.444 −0.532* −0.521* 植株K+/Na+ Whole plant K+/Na+ 0.975** −0.647** −0.059 −0.174 −0.385 −0.451 −0.508* −0.512* 根际土壤 K+/Na+
Rhizosphere soil K+/Na+0.537* −0.983** −0.408 −0.081 −0.197 −0.478 −0.586* −0.569* 茎Na+ Stem Na+ −0.284 0.132 −0.116 −0.268 0.08 0.259 0.298 0.297 根Na+ Root Na+ −0.618** 0.568* 0.139 0.048 0.505* 0.703** 0.752** 0.775** 植株Ca2+ Whole plant Ca2+ 0.509* −0.073 −0.033 0.084 −0.462 −0.155 −0.334 −0.264 表 5 植株选择性吸收盐离子能力,耐盐性与植株根系形态及不同器官干质量相关性分析
Table 5. Correlation analysis on selective absorption of salt properties, salt toleranceand plant root morphology and dry mass of different organs
项目
Item选择吸
收系数
SA选择性转
运系数
STC主根平
均直径
MRD侧根平
均直径
LRD根干
质量
Root DW叶干
质量
Leaf DW茎干
质量
Stem DW地上器官干质量
Aboveground
organ DW选择吸收系数 SA 1 −0.485* 0.053 −0.159 −0.39 −0.431 −0.444 −0.466 选择性转运系数 STC 1 0.433 0.064 0.167 0.495* 0.582* 0.575* 主根平均直径 MRD 1 0.378 0.462 0.467 0.503* 0.517* 侧根平均直径 LRD 1 0.494* 0.231 0.153 0.203 根干质量 Root DW 1 0.600* 0.722** 0.706** 叶干质量 Leaf DW 1 0.767** 0.934** 茎干质量 Stem DW 1 0.945** 地上器官干质量 Aboveground organ DW 1 -
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