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细枝木麻黄(Casuarina cunninghamiana)属于木麻黄科(Casuarinaceae)木麻黄属常绿乔木,具有耐干旱、耐瘠薄、抗盐碱生物固氮等特性[1]。随着不断深入研究,木麻黄属植物已经运用在固氮改土、盐碱地植被恢复和建立农林复合系统等方面[2]。有研究表明木麻黄对铅的耐受浓度可达1800 mg·kg−1[3]。经本课题组预实验发现细枝木麻黄在600 mg·kg−1铅处理下受到胁迫但不致死。
Frankia菌作为放线菌中的一个属,可以与非豆科植物共生结瘤[4]。作为木麻黄属植物重要的共生菌,Frankia菌在固定氮素、培肥地力、提高植物生长势和土壤生态修复等方面有着独特优势,目前已有研究表明木麻黄属植物和Frankia菌之间的生物组合与木麻黄属植物的固氮量密切相关[5]。另有研究表明Frankia菌株体内具有结合重金属的蛋白质,因此具有积累Pb等重金属的特性[6-9]。
铅(Pb)毒性强、持久,残留在土壤中可严重危害动植物生长。研究表明,随着Pb进入土壤,土壤中的酶活性、土壤微生物生物量碳和微生物活性等都能受到一定抑制,土壤的理化性状受到一定程度的影响[10]。近些年,我国重金属污染土壤修复技术发展迅速,不断创新,常见的例如:隔离包埋技术,固化稳定技术,氧化还原技术,微生物修复技术和植物修复技术等[11]。
随着对Frankia菌的相关研究越来越深入,大量研究证明Frankia菌与木麻黄属植物建立共生关系可以提高木麻黄对干旱、盐碱、金属毒害的抗性[12]。其中有研究证明木麻黄属植物可以积累大量重金属,且各林龄木麻黄对重金属均有很好的富集作用,且根是木麻黄属植物富集重金属的主要部位[13,14]。然而,关于Frankia菌与木麻黄属植物细枝木麻黄共生体系对土壤Pb污染的响应的影响还鲜有报道。本研究通过盆栽试验,分析接种Frankia菌对细枝木麻黄结瘤量、矿质元素吸收,丙二醛、渗透调节物质含量及其根系活力的影响,以期为Frankia菌接种到植物中增加植物对重金属的抗性提供理论基础。
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由表1可知,在600 mg·kg−1Pb胁迫下,施用Frankia菌20 mg·株−1时,细枝木麻黄结瘤量相比接种10 mg·株−1增加了33.32%,接种Frankia菌10、20 mg·株−1,结瘤率均为100%。
处理/(mg·株−1)
Treatment
(mg per plant)结瘤量/个
Nodulation number
per plant结瘤率/%
Nodulation rate0 0 0 10 21 100% 20 31 100% 注:图中结瘤量为平均值。
Note: The number of nodules in the figure is the average of all the treatments.Table 1. Effect of Frankia bacteria on nodulation amount of Casuarina cunninghamiana under Pb treatment
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由图1分析可得,在相同Pb处理下,随着接种量的增加,细枝木麻黄体内矿质元素出现了不同的趋势:与CK相比,10~20 mg·株−1Frankia菌处理细枝木麻黄枝条中Pb含量显著下降(P<0.05),20 mg·株−1处理时,Pb含量相比对照下降了58.06%;图2表明K含量在10 mg·株−1处理时达到最低值,仅为对照的66.95%,当接种量上升到20 mg·株−1时,K含量升高到对照的84.83%,与对照差异不显著;Cu含量随Frankia菌浓度升高呈现先上升后下降的趋势,10 mg·株−1处理时,Cu含量达到最大值,比对照上升了64.0%。
Figure 1. Effects of Frankia bacteria on Pb accumulation in aboveground part of Casuarina cunninghamiana under Pb, Cu and Mn stress
Figure 2. Effects of Frankia bacteria on K, Ca and Mg contents in aboveground part of Casuarina cunninghamiana under Pb stress
由表2分析可得,在相同浓度的Pb胁迫下,Frankia菌接种量与细枝木麻黄枝条中Pb含量呈极显著负相关,细枝木麻黄枝条中Pb含量与Mn、K元素含量呈显著正相关,说明Frankia菌接种量可以与细枝木麻黄地上部Pb含量变化有着密切的关系。
Frankia菌接种量
Frankia inoculationPb Cu Mn Ca Mg K Frankia菌接种量
Frankia inoculation1 Pb −0.879** 1 Cu 0.201 −0.274 1 Mn −0.398 0.744* −0.205 1 Ca −0.625 0.655 0.288 0.663 1 Mg −0.299 0.410 0.432 0.486 0.785* 1 K −0.342 0.715* −0.410 0.961** 0.500 0.399 1 注:*.在0.05水平(双尾)相关性显著;**.在0.01水平(双尾)相关性显著。
Note: * indicates the correlation is significant at 0.05 level (double tail); * * indicates the correlation is significant at 0.01 level (double tail).Table 2. Correlation between metal content in aboveground part of Casuarina cunninghamiana and inoculation amount of Frankia
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由表3分析可得,当Frankia菌浓度为10 mg·株−1时,MDA含量相比对照显著上升了22.87%,20 mg·株−1处理时,MDA含量相比对照下降了37.51%(P < 0.05)。
Frankia接种量 Frankia inoculation/ (mg·株−1) 丙二醛MDA/(nmol·g−1FW) 游离脯氨酸Pro/(µg·g−1) 可溶性糖SS/(µg·g−1) 0 13.63±1.10b 34.51±9.22a 26.52±0.30a 10 16.75±1.28a 26.25±5.22ab 16.68±0.29c 20 8.51±0.73c 15.17±1.09b 23.84±1.39b 注:表中数值为平均值±标准误,同列数据中不同字母表示处理间差异显著(P<0.05)。
Note: The values in the table are mean ± SE, and different letters in the same column indicate significant differences between treatments (P < 0.05).Table 3. Effects of Frankia bacteria on stress physiological index of Casuarina cunninghamiana under Pb treatment
表3分别显示了Pb胁迫下,不同接种量细枝木麻黄枝条中游离脯氨酸与可溶性糖的含量。可溶性糖含量随着接种量的上升,呈现先减少后升高的趋势,接种量为10 mg·株−1时,可溶性糖比对照组下降了37.10%;接种量为20 mg·株−1时,可溶性糖含量相比对照下降了10.10%。接种量为10 mg·株−1时,游离脯氨酸小幅上升,但与对照差异不显著,接种量上升到20 mg·株−1时,游离脯氨酸显著变化(P < 0.05),相比对照降低了56.04%。
图3显示了,Frankia菌接种量为10 mg·株−1时,细枝木麻黄根系活力小幅增强;接种量为20 mg·株−1时细枝木麻黄的根系活力TTC还原强度最强,与对照相比上升了87.12%。
Response of Frankia and Casuarina cunninghamiana Symbiotic System to Soil Pb Pollution
doi: 10.12172/202105140002
- Received Date: 2021-05-19
- Available Online: 2022-01-14
- Publish Date: 2022-03-02
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Key words:
- Frankia bacteria /
- Casuarina cunninghamiana /
- Pb stress /
- Mineral content
Abstract: In order to explore the response of Frankia bacteria and Casuarina cunninghamiana symbiont to soil Pb pollution in soil, pot experiments were conducted to study the effects of Frankia wet bacteria 0 (CK), 10, 20 mg·plant−1 on nodulation amount, contents of Pb, K, CA, Mg, Cu, Mn in the aboveground parts, stress physiology and root activity of Casuarina cunninghamiana under certain Pb treatment. The results of the pre-experiment showed that Casuarina cunninghamiana was stressed but not lethal under 600 mg·kg−1 lead (PB), so the Pb concentration was set at 600 mg·kg−1 in the formal experiment. The results showed that the application of 20 mg·plant−1 Frankia wet mycelium could significantly increase the nodulation rate of Casuarina cunninghamiana. The nodulation rate of Casuarina cunninghamiana was 100% when inoculated with 10 mg·plant−1 or 20 mg·plant−1 Frankia wet mycelium. Compared with CK, the Pb content in aerial parts of Casuarina cunninghamiana decreased significantly with the application of Frankia wet mycelium 10 and 20 mg·plant−1. When the inoculation amount was 10 mg·plant−1, the K content in aerial parts of Casuarina cunninghamiana decreased significantly, while the Cu content increased significantly. The change of Ca, Mg and Mn was not significant (P < 0.05). The free proline and soluble sugar in Casuarina cunninghamiana decreased by 56.04% and 10.10% respectively, and the TTC reduction intensity of root activity increased by 87.12% when Frankia inoculation was 20 mg·plant−1. In conclusion, under the same Pb stress, high inoculation amount (20 mg·plant−1) of Frankia bacteria could enhance the resistance of Casuarina cunninghamiana to Pb pollution in soil.