Effect of different concentrations of potassium and magnesium on mycorrhizal colonization of maize in pot culture

Abstract

The rate of root colonization by mycorrhizal fungi largely depends on the concentration of nutrient elements in roots and soil. In this study, the effects of different concentrations of potassium and magnesium on mycorrhizal colonization of maize grown in pot cultures were studied. This experiment was performed using natural soil containing spores of Glomus spp. Mycorrhizal spores were exposed to 3 concentrations of K solution, that is, 0.61 (soil K content), 0.92 and 1.23 meq/l and 3 concentrations of Mg, that is, 4.8 (soil Mg content), 7.2 and 9.6 meq/l, concurrently in 500 ml pots containing three seedlings of maize per pot. Forty (40) pots were cultured and kept in greenhouse under ambient conditions. Plants were watered every 4 days for 16 days with 50 ml distilled water. A pot with sterilized soil was used as negative control. For study of mycorrhizal colonization, very thin longitudinal sections of plant roots (>1 mm in diameter) were prepared manually and were stained with lactophenol-cottonblue. Mycorrhizal percentage was determined by the grid-line intersect method. Results indicated a significantly (P£0.05) higher percentage of mycorrhizal colonization in natural soil than sterilized soil in all treatments. Percent of mycorrhizal colonization was lower in all treatments as compared to that of natural soil, except in treatments with Mg (7.2 meq/l) and combined treatment of K (0.92 meq/l) and Mg (7.2 meq/l). Latter treatment produced the highest colonization rate (56%). This may suggest the synergistic effect of these nutrients on mycorrhizal development when present in specific concentrations in soil. Key words: Mycorrhizal colonization, maize, vesicular-arbuscular mycorrhiza (VAM)