Arbuscular mycorrhizal fungi colonization and physiological functions toward wetland plants under different water regimes

https://doi.org/10.1016/j.scitotenv.2020.137040Get rights and content

Highlights

  • P. arundinacea and S. sylvaticus had similar AMF colonization.

  • Lower water regimes are beneficial for AMF colonization in the two wetland plants.

  • AMF improve physiological functions in the two plants at fluctuating water regime.

Abstract

Arbuscular mycorrhizal fungi (AMF) have been widely reported to occur in the association with wetland plants. However, the factors that affect AMF colonization in wetland plants and physiological functions in AMF inoculated wetland plants are poorly studied. This study investigated the effects of four water regimes (below the surface of sands: water levels of 5 cm, 9 cm, 11 cm, and fluctuating water depth (9–11 cm)) on AMF root colonization in two wetland plants (Phalaris arundinacea and Scirpus sylvaticus) which are commonly used in constructed wetland. Results showed that two lower water regimes were the most suitable for the formation of root colonization by AMF. Plant species did not show any significant difference in AMF colonization. The AMF colonization of 15.6–23.3% in the roots of both wetland plants were determined under the water regimes of 11 cm and 9–11 cm. In comparison to the non-inoculated plants, root length, shoot height, biomass, shoot total phosphorus and chlorophyll contents of both wetland plants under the fluctuating water regimes (9–11 cm) were increased by 35.4–46.2%, 13.1–26.6%, 33.3–114.3%, 25.7–80% and 14.3–24%, respectively. Although malondialdehyde (MDA) contents in both AMF inoculated wetland plants were decreased under the lower water levels, the MDA contents under the water regime of 11 cm were still high. Therefore, these results indicated that the physiological functions in wetland plants with high AMF colonization might be improved under a specific water regime condition (e.g. depth of fluctuating water regime).

Introduction

Arbuscular mycorrhizal fungi (AMF) are an important component of the population of the soil microorganisms, they can form symbiotic association with the roots of most plant species (nearly 85%) in all terrestrial ecosystems (Dodd and Perez-Alfocea, 2012; Liu et al., 2014). Numerous researchers have indicated that AMF have large amount of positive effects on terrestrial plants, such as improving the nutrient status of plants (Ansari et al., 2013), enhancing the resistance of plant to the heavy metals, salinity, and cold (Camprubi et al., 2012; Wang et al., 2018b), as well as increasing the activities of rhizosphere microorganisms (Artursson et al., 2005). Therefore, AMF play a key role in terrestrial ecosystems. In the last two decades, more and more studies have confirmed that AMF are also widely present in many species of wetland plants in different wetland systems around the world (Wang et al., 2011; Xu et al., 2016). However, AMF colonization in wetland plant roots is still low due to a variety of negative factors (e.g. wetland environment, water, plants) (Kohout et al., 2012; Xu et al., 2016), and the knowledge of AMF effect on aquatic environment is still scarce.

Wetlands are unique habitats at the interface between terrestrial and aquatic ecosystems, which have ecological significance in natural waste purification, nutrient cycling, and floods preventing (Zedler and Kercher, 2005). AMF can easily survive and colonize in plant roots under an aerobic condition, which is why high AMF colonization is detected in terrestrial plants (Ramírez-Viga et al., 2018; Xu et al., 2016). Compared to terrestrial plants, lower AMF colonization is determined in wetland plant roots, which mainly results from low oxygen content in wetland system (Brundrett, 2009; Stevens et al., 2011). Meanwhile, roots of wetland plants can uptake nutrients directly from water for their growth, which also results in low AMF colonization in wetland system (Xu et al., 2016). Therefore, it is very important to control water content in wetland systems in order to increasing AMF colonization in wetland plants. Previous studies reported that AMF colonization in wetland plants gradually decreased with the increase of water regime (Miller, 2000; Wang et al., 2011). Despite that, increasing evidence demonstrates that AMF are observed in the roots of many wetland plants under different hydrologic sites around the world (Sidhoum and Fortas, 2019; Wang et al., 2018a; Xu et al., 2016). Moreover, AMF can even be detected in submerged wetland plants (Sudová et al., 2015), and also can be found in some pollutant stress conditions (e.g. heavy metals) (Ramírez-Viga et al., 2018). In contrast, some researchers revealed that soil moisture had no significant effect on AMF colonization, as well as the percentage of root in AMF colonization was not related to hydrologic category (Ipsilantis and Sylvia, 2007; Turner et al., 2000). In addition, previous studies showed that AMF colonization were significantly lower in continuously flooding conditions than in intermittent flood conditions (such as drying-rewetting cycles or fluctuating water depth) (Liang et al., 2018; Stevens et al., 2011). Li et al. (2011) and Shi et al. (2015) also indicated that alternation of drying-rewetting, or intermittent operation can bring oxygen into wetlands, which was beneficial to the growth, abundance, and diversity of AMF in wetland ecosystem, and wetland plants growth also can be improved. Therefore, it is necessary to explore which water regime condition can improve AMF colonization and also promote wetland plant physiological functions in wetland systems.

AMF may enhance wetland plants tolerance to environmental stresses (e.g. drought, salt, pollutants) and increase vegetation restoration in wetlands by determining the physicochemical indicators of wetland plants (e.g. biomass, malonaldehyde and chlorophyll) (Bharti and Garg, 2019; Sidhoum and Fortas, 2019; Wang et al., 2018b). However, different wetland plant species colonized by AMF are not consistent, which easily lead to different tolerance of wetland plants to environmental stress (Yan et al., 2008). Therefore, it is necessary to determine AMF colonization in different wetland plants. In general, AMF colonization was higher in dicots (58%) than in monocots (13%) (Xu et al., 2016), and the frequency of AMF hyphae is significant higher in angiosperms than in both Isoetes species (Kohout et al., 2012). Meanwhile, AMF colonization is also related to well-developed aerenchyma in wetland plant roots (Xu et al., 2016). Wang et al. (2018a) studied AMF status in urban wetland plants and its impact factors, results showed that 87.5% of plants (49 of 56 species including Costus speciosus, Polypogon fugax, Adenophora trachelioide, Senecio scandens, Tephroseris palustris, Phragmites australi, Typha orientalis and Glyceria maxima) were colonized by AMF, with colonization ranged from 2% to 72%. Fester (2013) also showed that substantial AMF colonization was observed (colonized root length: 25–80%) in Phragmites australis roots although these fungi were exposed to high concentrations of toxic pollutants. In addition, more and more studies have proved that high AMF colonization can provide a wide range of benefits for the physiological functions of wetland plants (Grilli et al., 2014; Ramírez-Viga et al., 2018; Wang et al., 2018b).

Therefore, the aim of this work was to (1) assess AMF colonization in different wetland plants under various water regimes; (2) evaluate the effects of AMF and water regimes on physiological functions of wetland plants.

Section snippets

Host plants

Phalaris arundinacea and Scirpus sylvaticus were selected from natural ponds in the Czech University of Life Sciences Prague campus. The roots of each plant were surface sterilized with 75% ethyl alcohol for 10 s and 1% sodium hypochlorite (NaClO) for 15 min, washed carefully with sterile distilled water five times. Some roots were selected from each plant to detect AMF colonization before transplanted into the sterilized pots. Finally, P. arundinacea and S. sylvaticus with no AMF colonization

Effect of water regime on AMF colonization

The frequency of mycorrhiza in root system (F%) and the intensity of mycorrhizal colonization (M%) ranged from 34.6% to 88.3% and 0.7% to 23.3%, respectively; while the arbuscule abundance (A%) in all treatments (11 cm, 9–11 cm, 9 cm, and 5 cm) were barely exist (Table 1, Fig. S2). In general, AMF colonization was decreased in the following treatments of 11 cm, 9–11 cm, 9 cm, and 5 cm. Meanwhile, AMF colonization in low water regimes (11 cm and 9–11 cm) were significantly higher than that in

Conclusion

Water regime had a significant impact on AMF colonization with the highest AMF colonization (23.3%) was observed in the roots of S. sylvaticus under the water regime of 11 cm. Meanwhile, physiological functions of AMF inoculated wetland plants (plant height, plant biomass, RWC, and nutrient contents (e.g. TP and TN) can be improved under low water level or fluctuating water. However, MDA, as a lipid peroxidation product in plants, were accumulated under the water regime of 11 cm. Therefore,

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

Shanshan Hu would like to thank the China Scholarship Council for PhD scholarship (CSC, No. 201706760061). This work was financially supported by project IGA (project no. 20184235) and complex IGA (support of students for research in the field of natural and constructed wetlands, project no. 42220/1312/3173) of Faculty of Environmental Sciences, Czech University of Life Sciences Prague.

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