Evaluating alder-endophyte (Alnus acuminata-Frankia-Mycorrhizae) interactions

Evaluating alder-endophyte (Alnus acuminata-Frankia-Mycorrhizae) interactions

Background 

The study examines the interactions between Alnus acuminata (a nitrogen-fixing tree), Frankia (a nitrogen-fixing actinomycete), and vesicular-arbuscular mycorrhizae (VAM), specifically Glomus intra-radices. These symbiotic relationships are significant in upland areas of Costa Rica, Colombia, and Venezuela, where A. acuminata grows alongside pastures. Frankia forms root nodules that fix atmospheric nitrogen, while VAM enhances phosphorus uptake, crucial for plant growth in nutrient-poor soils. The study aims to understand the effects of these interactions on nitrogen fixation and seedling development under varying phosphorus levels.

Goals and Methods 

The experiment evaluates the combined effects of Frankia and VAM on Alnus acuminata seedlings grown under three phosphorus levels (10, 50, 100 ppm). Seedlings were divided into four groups: control, Frankia inoculation, VAM inoculation, and dual inoculation (Frankia + VAM). Growth was assessed using parameters like leaf dry weight, nodule fresh weight, and nitrogenase activity, measured via acetylene reduction. Conducted in a greenhouse at Yale University, the research sought to identify the synergistic impact of dual inoculation under different phosphorus conditions.

Conclusions and Takeaways

Dual inoculation significantly enhanced nitrogen fixation at low phosphorus levels (10 ppm), where nitrogenase activity was 150% higher than other treatments. At 50 ppm, dual inoculation improved leaf and nodule biomass but did not maximize acetylene reduction, while high phosphorus levels (100 ppm) reduced VAM effectiveness, likely due to decreased symbiotic dependency. This study highlights the potential of integrating Alnus acuminata, Frankia, and VAM in agroforestry to enhance soil fertility and plant growth in phosphorus-deficient environments.

Reference: 

Russo RO. Evaluating alder-endophyte (Alnus acuminata-Frankia-Mycorrhizae) interactions. Plant and Soil. 1989;118(1-2):151 - 155. doi:10.1007/BF02232801.