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  农业环境科学学报  2021, Vol. 40 Issue (6): 1159-1166  DOI: 10.11654/jaes.2020-1453
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引用本文  

马永佳, 梁婵娟. 外源钙对模拟酸雨胁迫下水稻质膜组分和钙形态的调节[J]. 农业环境科学学报, 2021, 40(6): 1159-1166.
MA Yong-jia, LIANG Chan-juan. Regulation of exogenous calcium on plasma membrane compositions and calcium forms of rice roots under simulated acid rain stress[J]. Journal of Agro-Environment Science, 2021, 40(6): 1159-1166.

基金项目

国家自然科学基金项目(31971407,31370517);江苏省自然科学基金项目(BK20161131);江南大学研究生科研与实践创新计划项目(JNKY19_057)

Project supported

The National Natural Science Foundation of China(31971407, 31370517); The Natural Science Foundation of Jiangsu Province (BK20161131); The Postgraduate Research and Practice Innovation Program of Jiangnan University(JNKY19_057)

通信作者

梁婵娟, E-mail: liangchanjuan@jiangnan.edu.cn

作者简介

马永佳(1994-), 女, 江苏连云港人, 硕士研究生, 主要研究方向为环境生态。E-mail: mayongjia2020@126.com

文章历史

收稿日期: 2020-12-16
录用日期: 2021-03-02
外源钙对模拟酸雨胁迫下水稻质膜组分和钙形态的调节
马永佳1,2 , 梁婵娟1,2     
1. 江苏省厌氧生物技术重点实验室, 江南大学环境与土木工程学院, 江苏 无锡 214122;
2. 江苏省水处理技术与材料协同创新中心, 江苏 无锡 214122
摘要:为了探寻减轻植物酸致伤害的有效方法,采用水培法研究了外源钙(Ca,5 μmol·L-1)对模拟酸雨(SAR,pH 4.5/3.0)胁迫下水稻根系质膜稳定性、质膜组分以及钙形态的影响。结果表明:低强度SAR(pH 4.5)对水稻根系膜稳定性无显著影响,而高强度SAR(pH 3.0)显著降低水稻根系膜稳定性,且水稻根系质膜磷脂(磷脂酰胆碱和磷脂酰甘油)、膜蛋白和非水溶性钙含量显著减少,胞内水溶性钙含量显著增加,恢复5 d后仅SAR(pH 3.0)组上述指标仍显著低于对照。与单一SAR和单一Ca2+处理组相比,pH4.5+Ca2+组水稻根系膜稳定性无显著变化。pH 3.0+Ca2+组水稻根系质膜稳定性、磷脂(磷脂酰胆碱和磷脂酰甘油)、膜蛋白和非水溶性钙含量显著低于对照但高于单一SAR(pH 3.0)组,水溶性钙含量仍显著高于对照但低于SAR(pH 3.0)组,且恢复5 d后上述指标均达到对照水平。外源Ca2+增强水稻根系质膜耐受SAR胁迫能力与其维持水溶性钙-非水溶性钙平衡及缓解磷脂和膜蛋白的降解有关,且缓解效果受酸雨强度限制。
关键词外源钙    酸雨    水稻    质膜组分    钙形态    
Regulation of exogenous calcium on plasma membrane compositions and calcium forms of rice roots under simulated acid rain stress
MA Yong-jia1,2 , LIANG Chan-juan1,2     
1. Jiangsu Province Key Laboratory of Anaerobic Biological Technology, School of Environmental and Civil Engineering, Jiangnan University, Wuxi 214122, China;
2. Jiangsu Cooperative Innovation Center of Technology and Material of Water Treatment, Wuxi 214122, China
Abstract: To explore effective ways to reduce damage on plants caused by acid rain, the effect of exogenous calcium(Ca, 5 μmol·L-1)on the membrane stability, plasma membrane compositions, and calcium forms in rice roots under simulated acid rain(SAR, pH 4.5/3.0)were studied through hydroponic experiments. Low intensity SAR(pH 4.5)had no significant effect on membrane stability in rice roots. High intensity SAR(pH 3.0)decreased the membrane stability, contents of phospholipids(phosphatidylcholine and phosphatidylglycerol), and membrane protein in rice roots and increased the content of water-soluble calcium. After a 5-day recovery, the above indicators in rice roots treated with pH 3.0 SAR were still lower than the control. Compared with rice treated with single SAR or Ca2+, pH 4.5+Ca2+ treatment had no effect on the membrane stability in rice roots. pH3.0+Ca2+ decreased the membrane stability as well as the contents of phospholipids, membrane proteins, and non-water-soluble calcium in rice roots, and these parameters were higher than those treated with pH 3.0 SAR. Water-soluble calcium in rice roots treated with pH 3.0 + Ca2+ was increased and lower than the pH 3.0 SAR treatment. After a 5-day recovery, the above indicators in rice roots treated with pH 3.0+Ca2+ were close to the control. Briefly, exogenous Ca2+ enhance the tolerance of rice to SAR stress and that is related to maintaining the balance of water-soluble calcium and non-water-soluble calcium as well as alleviating the degradation of phospholipids and membrane proteins. The alleviating effect is limited by the intensity of acid rain.
Keywords: exogenous calcium    acid rain    rice    plasma membrane compositions    calcium forms    

酸雨是全球性环境问题。酸雨对植物的直接影响主要表现在破坏细胞膜完整性[1]、降低叶绿素含量、抑制光合速率[2]、阻碍营养吸收[3]等,还能通过影响土壤的营养成分[4]、土壤中污染物赋存状态[5]、土壤微生物活性等间接影响植物生长、产量和品质[6],给农林业造成巨大的经济损失。面对全球人口增长对食品安全的挑战,以及当下酸雨污染尚不能有效控制的严峻现实,如何减轻酸雨对植物的危害迫在眉睫。

钙(Ca)既是植物必需的营养物质,也是植物细胞第二信使,在调节植物耐受盐、干旱、重金属、酸雨等非生物胁迫方面发挥重要的作用[7-9]。前期研究发现,外源Ca2+能上调植物质膜H+-ATPase基因表达从而提高H+-ATPase活性,这一方面缓解了酸雨引起的胞内H+增加,维持胞内pH稳定,另一方面保障了植物营养吸收所需质子梯度势[10-11]。然而植物质膜H+- ATPase活性不仅受翻译表达和磷酸化修饰的调控,也受质膜环境的影响。胁迫条件下,质膜中磷脂、糖脂、膜蛋白含量以及膜蛋白与脂质间的相互作用均会发生适应性变化,致使质膜稳定性改变,影响细胞内各类代谢活动的有序进行[12]。而植物质膜上磷脂与蛋白质结合能力或脂质重新分布均会受到细胞内Ca2+含量或Ca2+形态转化的影响[13]。如能从质膜环境角度探究外源Ca2+对植物耐酸性的影响,不仅为丰富植物酸致伤机理提供新思路,也能为理清Ca2+调控植物抗逆性的内在机制提供新数据。

鉴于此,本文通过测定水稻质膜组分(磷脂、糖脂以及膜蛋白含量),评价了外源Ca2+对模拟酸雨胁迫下水稻根系膜稳定性的影响;通过观察水稻根系中各种形态钙的含量,从钙形态角度阐明外源Ca2+对酸雨胁迫下水稻根系质膜组分和稳定性的调节。这些研究结果有助于弄清外源Ca2+缓解植物酸致伤的作用机理,为寻找环境友好型调控方法以增强植物耐酸性提供参考,也为减轻酸雨造成的农林业损失提供理论依据。

1 材料与方法 1.1 试验材料培养

试验用水稻品种为“五优308”(Oryza sativa L.)。用0.1% HgCl2将种子消毒10 min后洗净,并用去离子水浸泡24 h。浸泡后的水稻种子在25 ℃光照培养箱中萌发4 d,继而转入蛭石中培养14 d。取长势一致的水稻幼苗转移到6.88 L周转箱中用营养液培养(pH 5.6)。培养环境的湿度为70%~80%,温度为25 ℃/ 20 ℃(日/夜),光强度为250 µmol·m-2·s-1,光周期为13 h/11 h(日/夜)。营养液采用的是国际水稻研究所(IRRI)常规水稻营养液配方[14],每3 d更换一次。

1.2 试验方法

培养10 d后对水稻幼苗按如下试验设置进行处理:pH 4.5、pH 3.0、Ca2+(5 mmol · L-1)、pH 4.5 + Ca2+(5 mmol·L-1)、pH 3.0+Ca2(+ 5 mmol·L-1),并以不加模拟酸雨或Ca2+的水稻幼苗作为对照(CK)。按照浓硝酸和浓硫酸1∶3(V/V)的比例配制模拟酸雨(Simulated acid rain,SAR)母液[15],并用SAR母液将营养液调为pH 4.5或3.0的SAR溶液。用去离子水稀释SAR母液(pH 4.5/3.0),每日上午10:00喷施水稻幼苗地上部,滴液为限。对照组喷洒pH 7.0去离子水。外源Ca2+以CaCl2的形式加入营养液中,搅拌至完全溶解。连续胁迫5 d后(胁迫期),在对照条件下继续培养水稻幼苗5 d(恢复期),分别在处理的第6 d和11 d收集水稻根系测定指标。

1.3 指标测定方法

采用Singh等[16]的方法测定水稻根系质膜稳定性指数。参照Palmgren等[17]的方法分离水稻根系质膜后,用Kates等[18]方法分离水稻根系质膜总脂质。将提取的水稻根系质膜总脂质用磷钼酸比色法[19]测定总磷脂含量,用蒽酮法[20]测定总糖脂含量。采用薄层色谱法分离并测定磷脂和糖脂各组分含量。植物质膜蛋白提取和BCA法蛋白含量测定试剂盒购于上海贝博生物科技有限公司。采用萃取法依次萃取水稻根系硝酸钙和氯化钙、水溶性钙、果胶钙、磷酸钙和碳酸钙、草酸钙和硅酸钙,并通过原子吸收测定钙含量[21]

1.4 数据处理和分析

所有数据均为3次独立试验的平均值±标准误差(Mean±SD),并采用SPSS 19.0软件对数据进行差异显著性分析,不同字母表示显著性差异(P < 0.05),用Origin 8.5软件制图。

2 结果与讨论 2.1 外源Ca2+对酸雨胁迫下水稻根系膜稳定性的影响

质膜是非生物胁迫作用于植物细胞的靶位。胁迫下质膜稳定性越低,植物受伤害程度越严重,耐受性越低[22]图 1是外源Ca2+对SAR胁迫下水稻根系膜稳定性指数的影响。与CK相比,pH 4.5 SAR对水稻根系膜稳定性无显著影响(P>0.05),pH 3.0 SAR显著降低了水稻根系膜稳定性(P < 0.05),降幅达17.7%。单一Ca2+和pH 4.5+Ca2+组水稻根系膜稳定性与CK无差异(P>0.05),pH 3.0+Ca2+组水稻根系膜稳定性低于CK(12.6%),但高于pH 3.0 SAR组(P < 0.05),说明外源Ca2+可以在一定程度上缓解高强度SAR(pH 3.0)对水稻根系膜稳定性的破坏。这可能与外源Ca2+提高质膜H+-ATPase活性从而维持胞内pH稳定有关[11],也可能是外源Ca2+诱导抗氧化酶活性增加防止脂质过氧化所致[23]。恢复5 d后,pH 4.5 SAR组水稻根系膜稳定性仍处于CK水平(P>0.05),pH 3.0 SAR组水稻根系膜稳定性低于CK且与胁迫期无明显差异。SAR(pH 4.5/3.0)+Ca2+组水稻根系膜稳定性均恢复至CK水平(P>0.05)。以上结果表明低强度SAR(pH 4.5)未超出水稻根系膜稳定性的耐受范围,而高强度SAR(pH 3.0)对水稻膜稳定性的破坏不可逆。外源Ca2+可以在一定程度上缓解高强度SAR(pH 3.0)对水稻根系膜稳定性的破坏,并促进水稻根系膜稳定性的恢复。

不同小写和大写字母分别表示胁迫期和恢复期处理间差异显著(P < 0.05)。下同 Different lowercase and uppercase letters indicate significant differences among treatments during the stress and recovery periods at P < 0.05, respectively. The same below 图 1 外源Ca2+对模拟酸雨胁迫下水稻根系膜稳定性指数的影响 Figure 1 Effect of exogenous Ca2+ on membrane stability index of rice roots under simulated acid rain stress
2.2 外源Ca2+对酸雨胁迫下水稻根系磷脂含量的影响

磷脂是植物质膜的主要成分,其中磷脂酰胆碱(Phosphatidylcholine,PC)、磷脂酰甘油(Phosphatidylglycerol,PG)、磷脂酰肌醇(Phosphatidylinositol,PI)、磷脂酰丝氨酸(Phosphatidylserine,PS)是双层脂,磷脂酰乙醇胺(Phosphatidylethanolamine,PE)为非双层脂。胁迫导致的植物质膜稳定性下降通常与磷脂含量减少及双层脂与非双层脂比例(PC/PE)下降有关,最终表现为植物抗逆性降低[24]表 1是外源Ca2+对SAR胁迫下水稻根系质膜磷脂含量的影响。如表 1所示,PC、PE和PG是水稻根系质膜主要磷脂组分,约占总磷脂的80%。与CK相比,pH 4.5 SAR处理组水稻质膜总磷脂、PC、PE和PG含量分别增加了24.1%、26.4%、24.5% 和41.3%(P < 0.05),PC/PE无显著变化(P>0.05)。pH 3.0 SAR组水稻根系PE增幅大于pH 4.5 SAR组,但总磷脂、PC和PG含量,以及PC/PE分别降低了19.7%、35.0%、48.4% 和53.6%(P < 0.05)。结合膜稳定性变化分析(图 1),SAR诱导的水稻膜双层脂(PC和PG)减少和PC/PE比例下降可能是破坏膜稳定性的原因之一。低强度SAR(pH 4.5)下水稻根系磷脂增加是水稻对酸雨胁迫的适应性反应,以维持水稻根系膜稳定性,避免质膜受到SAR的伤害。前人也发现植物通过增加质膜磷脂含量应对低温和盐胁迫[25]。单一Ca2+处理对水稻根系磷脂组分无影响(P>0.05)。SAR(pH 4.5/3.0)+Ca2+处理的水稻根系总磷脂、PC和PG含量显著高于单一SAR处理,但pH 3.0+Ca2+处理的水稻根系PG含量和PC/PE分别较CK低30.0%和39.1%(P < 0.05)。结合膜稳定性变化分析(图 1),外源Ca2+提高水稻根系磷脂(尤其是双层脂)含量和PC/PE,有利于缓解高强度SAR(pH 3.0)对水稻根系膜稳定性的破坏。然而,当pH 4.5 SAR强度未影响水稻根系膜稳定性时,外源Ca2+也可以增加pH 4.5 SAR胁迫下水稻根系双层脂含量,这可能在一定程度上提高水稻的耐酸性。因为带负电荷的PG和PC增强了磷脂对Ca2+的亲和力,有利于维持植物质膜的完整性[26]。Savithramma等[27]研究也发现施加Ca2+的蔬菜中总磷脂和总糖脂含量明显增加,脂质过氧化程度减轻,生长状况更好。恢复5 d后,pH 4.5 SAR组水稻根系磷脂含量均恢复至CK水平(P>0.05),而pH 3.0 SAR组水稻根系PE含量仍高于CK(17.8%)(P < 0.05),总磷脂、PC、PG含量以及PC/PE分别较CK降低22.2%、25.0%、45.5% 和36.8%(P < 0.05)。而添加外源性Ca2+后,在恢复期,SAR(pH 4.5/3.0)+Ca2+处理的水稻根系总磷脂和PC/PE的水平基本能保持与CK一致(P>0.05)。低强度SAR(pH 4.5)引起的水稻磷脂应激增加在胁迫解除后消失,再次证明磷脂含量的微增加是水稻对SAR胁迫的适应性反应。高强度SAR(pH 3.0)对水稻磷脂组分造成不可逆破坏,导致水稻根系膜稳定性仍较低(图 1)。外源Ca2+促进SAR胁迫后水稻磷脂组分恢复,这可能是SAR+Ca2+处理组水稻根系膜稳定性得以恢复的重要原因之一。

表 1 外源Ca2+对模拟酸雨胁迫下水稻根系质膜磷脂含量的影响(mg·g-1 Table 1 Effect of exogenous Ca2+ on phospholipid content of rice roots under simulated acid rain stress(mg·g-1)
2.3 外源Ca2+对酸雨胁迫下水稻根系糖脂含量的影响

植物细胞膜糖脂主要包含双半乳糖甘油二酯(Digalactosyl diglyceride,DGDG)和单半乳糖甘油二酯(Monogalatosyl diglyceride,MGDG)。胁迫条件下植物细胞膜DGDG/MGDG比值的下降,会降低细胞膜微黏度[28],从而破坏膜稳定性。表 2是外源Ca2+对SAR胁迫下水稻根系质膜糖脂含量的影响。与CK相比,pH 4.5 SAR组水稻根系总糖脂、DGDG和MGDG含量以及DGDG/MGDG比值无显著变化(P>0.05),而pH 3.0 SAR组总糖脂、DGDG含量和DGDG/MGDG比值分别增加了18.5%、20.1% 和19.2%(P < 0.05)。单一Ca2+和pH 4.5+Ca2+组水稻根系总糖脂、DGDG和MGDG含量以及DGDG/MGDG比值与CK差异不显著(P>0.05),pH 3.0+Ca2+组水稻根系的上述参数显著高于CK(P < 0.05),且增幅大于pH 3.0 SAR组。以上结果说明低强度SAR(pH 4.5)对水稻根系糖脂水平无影响,而高强度SAR(pH 3.0)促进水稻根系糖脂双层脂的形成,触发水稻根系质膜的脂质重塑。这可能是SAR诱导DGDG合成酶基因DGD1/DGD2转录水平增加[29],致使糖脂大量生成取代磷脂,以应对SAR对水稻质膜伤害。相比较而言,外源Ca2+促进了高强度SAR(pH 3.0)下水稻根系糖脂双层脂的进一步累积,但水稻根系膜稳定性依然低于CK(图 1)。推测糖脂双层脂的增加虽然有助于维持膜稳定性,但磷脂中非双层脂大面积形成导致膜双层结构中断,细胞膜呈现高通透性,因而pH 3.0+Ca2+组水稻根系质膜稳定性较低但明显优于pH 3.0 SAR处理组(图 1)。高温和干旱胁迫下也发现了植物DGDG增加有利于维持细胞膜结构与功能[30-31]。恢复5 d后,pH 3.0 SAR组水稻根系的总糖脂和DGDG含量,以及DGDG/MGDG仍高于CK和胁迫期,pH 4.5 SAR和SAR(pH 4.5/3.0)+Ca2+组水稻根系糖脂相关参数均恢复至CK(P>0.05)。这说明解除胁迫后,水稻仍需通过提高糖脂含量缓解高强度SAR(pH 3.0)对质膜的伤害,但仍难恢复至正常水平。而外源Ca2+促进糖脂组分的恢复,致使水稻根系膜稳定性得以恢复。

表 2 外源Ca2+对模拟酸雨胁迫下水稻根系质膜糖脂含量的影响(mg·g-1 Table 2 Effect of exogenous Ca2+ on glycolipids content of rice roots under simulated acid rain stress(mg·g-1)
2.4 外源Ca2+对酸雨胁迫下水稻根系质膜蛋白含量的影响

植物质膜蛋白与脂质分子相结合可以加固膜结构,膜蛋白脱离会导致细胞膜稳定性降低,从而引起质膜功能变化。图 2是外源Ca2+对SAR胁迫下水稻根系质膜蛋白含量的影响。与CK相比,pH 4.5 SAR组水稻根系的质膜蛋白含量增加了45.1%,而pH 3.0 SAR组水稻根系的质膜蛋白含量减少了20.3%(P < 0.05)。单一Ca2+组水稻根系的质膜蛋白含量无显著变化(P>0.05),然而pH 4.5+Ca2+组水稻根系的质膜蛋白含量高于CK(P < 0.05),且与pH 4.5 SAR组无显著差异(P>0.05)。pH 3.0+Ca2+组水稻根系的质膜蛋白含量高于CK 45.7%,且高于pH 3.0 SAR组(P < 0.05)。结合水稻磷脂含量和膜稳定性变化分析(表 2图 1),外源Ca2+提高SAR胁迫下水稻根系膜蛋白含量,有利于加固质膜结构,从而缓解磷脂和膜蛋白降解导致的膜结构破坏。这可能是由于外源Ca2+减轻了酸雨中H+与膜上Ca2+的置换,促进Ca2+与质膜磷脂和蛋白的结合,提高细胞膜紧密度[32]。恢复5 d后,pH 4.5 SAR组水稻根系质膜蛋白含量恢复至CK水平(P>0.05),而pH 3.0 SAR组水稻根系质膜蛋白含量仍低于CK16.2%(P < 0.05),SAR(pH 4.5/3.0)+Ca2+组水稻根系质膜蛋白含量仍高于CK和胁迫期(P < 0.05)。这表明解除胁迫后,水稻根系质膜蛋白含量的自我恢复受SAR强度的限制,外源Ca2+可以维持SAR胁迫后的水稻根系膜蛋白含量处于较高水平。这可能与Ca2+增强质膜蛋白表达有关,质膜蛋白丰度的增加对增强植物耐酸性有益[33]

图 2 外源Ca2+对模拟酸雨胁迫下水稻根系质膜蛋白含量的影响 Figure 2 Effect of exogenous Ca2+ on membrane protein content of rice roots under simulated acid rain stress
2.5 外源Ca2+对酸雨胁迫下水稻根系钙形态的影响

逆境胁迫下植物细胞中的钙通过形态转化进行再分配,以完成适应逆境的生理调控。如水溶性钙(多为游离Ca2+)在植物细胞中移动和利用,参与信号传递;果胶酸钙和草酸钙则担负着调节逆境下植物细胞内外Ca2+平衡,保护细胞膜结构,维持生长发育的功能[34]表 3是外源Ca2+和SAR胁迫下水稻根系钙形态的分布。与CK相比,pH 4.5 SAR组水稻根系的水溶性钙增加了18.8%,硝酸钙-氯化钙减少了24.2%(P < 0.05)。pH 3.0 SAR组水稻根系水溶性钙增幅高于pH 4.5 SAR处理组,且高于CK 57.2%,硝酸钙-氯化钙、果胶酸钙和磷酸钙-碳酸钙分别减少34.8%、28.9% 和32.9%(P < 0.05)。这些结果表明,SAR会引起水稻根系水溶性钙增加,非水溶性钙流失。魏金卓等[35]也发现SAR引起水稻胞内游离Ca2+增多。因此,可以推测低强度SAR(pH 4.5)诱导硝酸钙-氯化钙转化为水溶性钙,并向下游传递SAR胁迫信号。这种Ca2+信号可以提高脂酰转移酶活性,促使磷脂的合成[36],进而稳定植物细胞膜组成。然而,胁迫下植物细胞持续升高的游离Ca2+激活磷脂酶D,磷脂大量被水解,导致离子渗透加剧[37]。因此,高强度SAR(pH 3.0)下水稻根系水溶性钙的过量累积可能是降低磷脂含量的重要原因。单一Ca2+处理提高了水稻根系草酸钙含量(P < 0.05),pH 4.5+Ca2+组水稻根系水溶性钙与pH 4.5 SAR处理组无显著差异,但果胶酸钙和磷酸钙-碳酸钙含量较CK分别提高了76.4% 和26.2%(P < 0.05)。pH 3.0+Ca2+组水稻根系果胶酸钙和磷酸钙-碳酸钙含量均与CK无差异(P>0.05),水溶性钙仍高于CK 19.7%但低于pH 3.0 SAR组(P < 0.05)。由此可见,外源Ca2+促进SAR胁迫下水稻根系水溶性钙转化为非水溶性钙。这既维持了水稻根系非水溶性钙水平,也避免了水溶性钙累积,从而有效缓解SAR胁迫下水稻细胞膜脂和膜蛋白的降解,维持细胞膜稳定性(图 1~图 2表 1~表 2)。另外,植物细胞果胶酸钙减少易引发植物细胞壁解体,阻碍细胞伸长。前人研究发现外源Ca2+减轻SAR对水稻相对生长速率的抑制[38],可以推测果胶酸钙的增加可能是造成这一结果的原因之一。恢复5 d后,除pH 3.0 SAR处理组水稻根系水溶性钙、果胶酸钙和磷酸钙-碳酸钙仍低于CK(P < 0.05)外,pH 4.5 SAR组与SAR(pH 4.5/3.0)+Ca2+组的水稻根系各种形态钙含量均维持在CK水平(P>0.05)。这表明,解除胁迫后,高强度SAR(pH 3.0)处理组水稻根系钙流失无法恢复,而SAR(pH 4.5/ 3.0)+Ca2+复合处理为SAR胁迫下水稻根系质膜组分的合成和膜稳定性的恢复提供充足的钙源。

表 3 外源Ca2+和模拟酸雨胁迫下水稻根系钙形态的影响(mg·g-1 Table 3 Effect of exogenous Ca2+ on calcium forms of rice roots under simulated acid rain stress(mg·g-1)
3 结论

(1)低强度SAR(pH 4.5)对水稻根系膜稳定性未造成影响,而高强度SAR(pH 3.0)引起水稻根系水溶性钙过量累积,非水溶性钙流失,质膜磷脂双层脂和膜蛋白降解,对膜稳定性造成不可逆伤害。

(2)外源Ca2+可以提高SAR(pH 4.5/3.0)胁迫下非水溶性钙水平,促进水溶性钙转化为非水溶性钙,缓解质膜磷脂双层脂和膜蛋白降解,减轻高强度SAR(pH 3.0)对水稻根系膜稳定性的伤害,并促进水稻根系膜稳定性的恢复。

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