Abstract

K. S. Subramanian, V. Tenshia, K. Jayalakshmi and V. Ramachandran

A greenhouse experiment was conducted to assess the nutritional improvement of maize plants (variety COHM5) inoculated with and without arbuscular mycorrhizal (AM) fungus (Glomus intraradices Schenck and Smith) under varying levels of Zn concentration (0, 1.25, 2.5, 3.75 and 5.0 mg kg-1 ). Growth (leaf area index and root morphological attributes) and nutrient status (Zn and P concentrations) were measured at 45 and 75 days after sowing (DAS). Maize grains were analyzed for Zn and tryptophan concentrations. The increasing levels of Zn fertilization have no impact on the total mycorrhizal colonization, but the hyphal growth decreased slightly. Mycorrhizal inoculation consistently increased the root morphological attributes regardless of Zn fertilization. Mycorrhizal inoculation and Zn fertilization exhibited prominent increase in the leaf area index and chlorophyll content of plants and the response to mycorrhizal inoculation was higher at lower levels of Zn fertilization. The mycorrhizal dependency decreased gradually with increase in Zn levels. Mycorrhizal plants had higher P and Zn concentrations in both the stages in comparison to non-inoculated plants. Maize grains of AM+ plants had higher Zn and tryptophan concentrations. The plant available Zn concentration in mycorrhizal fungal inoculated soil was higher than non-inoculated soils, which directly contributed to increase in Zn status of mycorrhizal plants. In conclusion, mycorrhizal symbiosis enhances Zn supply to the host plants by extensive root development enabling the plant to maintain higher nutritional status and produce grains with rich tryptophan concentrations.