Laccaria bicolor Mobilizes both Labile Aluminum and Inorganic Phosphate in Rhizosphere Soil of Pinus massoniana Seedlings Field Grown in a Yellow Acidic Soil

Abstract

Plant growth is often limited by highly activated aluminum (Al) and low available phosphorus (P) in acidic soil. Ectomycorrhizal (ECM) fungi can improve their host plants’ Al tolerance by increasing P availability while decreasing Al activity in vitro or in hydroponic or sand culture systems. However, the effect of ECM fungi on inorganic P (IP) and labile Al in acidic soil in the field, particularly in conjunction with Al treatment, remains poorly understood. The present study aimed to determine the influence of ECM fungal association on the mobilization of IP and labile Al in rhizosphere soil of host plants grown in the field with external Al treatment and the underlying nutritional mechanism in plant Al tolerance. To do so, 4-week-old Pinus massoniana seedlings were inoculated with three ECM isolates (Laccaria bicolor 270, L. bicolor S238A, and L. bicolor S238N) and grown in a Haplic Alisol field with or without Al treatment for 12 weeks. Results showed that L. bicolor association enhanced the available P depletion and facilitated the mobilization of IP and labile Al, in turn improving the capacity of host plant to use Al-bound P, Ca-bound P, and occluded P, particularly when P. massoniana seedlings were inoculated with L. bicolor S238A. Inoculation with L. bicolor isolates also enhanced the solubility of labile Al and facilitated the conversion of acid-soluble Al into exchangeable Al. Our findings suggested that ECM inoculation could enhance plant Al tolerance in the field by mobilizing IP to improve the P bioavailability but not by decreasing Al activity. IMPORTANCE Here, we reveal the underlying nutritional mechanism in plant Al tolerance conferred by ectomycorrhizal (ECM)-fungus inoculation in the field and report the screening of a promising ECM isolate to assist phytoremediation and afforestation using Pinus massoniana in acidic soil in southern China. This study advances our understanding of the contribution of ECM fungi to plant–ECM-fungus symbiosis and highlights the vital role of ECM-fungus inoculation in plant Al tolerance. In addition, the results described in the present study confirm the importance of carrying out studies in the field rather than only in vitro studies. Our findings strengthen our understanding of the role of ECM-fungus association in detecting, utilizing, and transporting unavailable nutrients in the soil to enhance host plant growth and adaptability in response to adverse habitats.

Differential aluminum tolerance and absorption characteristics in Pinus massoniana seedlings colonized with ectomycorrhizal fungi of Lactarius deliciosus and Pisolithus tinctorius

“…The growth of shoots but not roots of P. strobus seedlings growing in sand treated with 0-100 mg L -1 Al at pH 3.8 was also significantly improved by P. tinctorius (Schier and McQuattie 1995). Other studies (Gu et al 2019(Gu et al , 2020 showed that ECM fungus mobilized inorganic P in rhizosphere soil and facilitated nutrient uptake and transport; thus, both of the fungal species tested in the present study might have similar effects on nutrient mobilization and transport, which improved P. massoniana seedlings' aboveground growth.…”

Comparison of the diversity and structure of the rhizosphere microbial community between the straight and twisted trunk types of Pinus yunnanensis

“…Recent studies have revealed that different species of plants, or even different plant traits of the same species, assemble different rhizosphere microbial communities in the same soil environment (Arafat et al, 2017;Sayer et al, 2017;Bickford et al, 2020). These complex plant-associated microbial communities are crucial for plants because they can affect plant growth, productivity, nutrients and immunity directly or indirectly (Van Wees et al, 2004;Egamberdieva et al, 2010;Erturk et al, 2010;Berendsen et al, 2012;Patel, 2018;Tahir et al, 2019;Gu et al, 2020;Song Q. et al, 2021), as well as affect host phenotypes and adaptability (Herrera Paredes et al, 2018). For instance, Finkel et al (2020) found that rhizosphere microorganisms can promote root growth by affecting plant hormone levels in Arabidopsis.…”

Effects of vertical forest stratification on precipitation material redistribution and ecosystem health of Pinus massoniana in the Three Gorges Reservoir area of China

“…Aluminum can also combine with root cell membrane proteins, thereby causing cell membrane damage (Víctor et al, 2006;Gu et al, 2023). The portion of aluminum that enters the root cells directly affects cellular metabolism by inhibiting the absorption of nutrients such as calcium, phosphorus, and potassium (Gu et al, 2020). At present, it is still unknown which locations within the vertical structure of Masson pine forests are most severely affected by acid rainfall.…”