Effect of arbuscular mycorrhizal fungi on growth of Gmelina arborea in arsenic-contaminated soil

Abstract

Arsenic (As) in the soils of South-Eastern Bangladesh is not only a threat for the health of millions of people but also a problem for plant growth due to its higher concentration in soil. Gmelina arborea Linn. is a promising fast growing tree species in Bangladesh which has also a potential to be planted in arsenic contaminated areas. This study assessed the role of arbuscular mycorrhizal (AM) fungi on the growth of G. arborea in arsenic amended soils at nursery stage. Before sowing seeds, soils were treated with four different concentrations (10 mg·kg−1, 25 mg·kg−1, 50 mg·kg−1, and 100 mg·kg−1) of Arsenic. Growth parameters (length of shoot and root, collar diameter, fresh and dry weight of shoot and root) of the plant, and mycorrhizal root colonization and spore population in the rhizosphere soil of G. arborea were recorded. Mycorrhizal seedlings showed better growth than non-mycorrhizal seedlings. Mycorrhizal seedlings planted in soil with 10-mg·kg−1 arsenic showed best performance in terms of growth, biomass and mycorrhizal colonization, compared to other treatments with higher concentration of arsenic. With increasing arsenic concentration, growth of seedlings, mycorrhizal infection rate and spore population, all decreased significantly (p<0.05). The mycorrhizal seedlings had as much as 40% higher increment in total growth and 2.4 times higher increment in biomass compared to non-mycorrhizal seedlings. The study clearly indicated that mycorrhizal inoculation could reduce the harmful effects of arsenic on the initial growth of G. arborea Linn. in degraded soil at nursery stage.