Attraction of germ tubes and germination of spores of the arbuscular mycorrhizal fungus Gigaspora gigantea in the presence of roots of maize exposed to different concentrations of phosphorus

Abstract

Chemotropism of germ tubes of Gigaspora gigantea to roots of four cultivars of Zea mays (differing in phosphorus-uptake efficiency) mediated by volatile exudates was examined in root-organ culture. Spores and germ tubes were prevented from contacting water soluble exudates from the roots. Cultivars that were inefficient in phosphorus uptake were more effective in attracting germ tubes than were phosphorus-efficient cultivars. The amount of phosphate in the medium affected the ability of the roots to attract germ tubes. For three of the four cultivars, attraction was reduced at the highest concentration of phosphorus tested. Germination of spores was higher in the presence of some cultivars (93%) than in the control (81%), but there was no apparent relationship between stimulation of germination and phosphorus-uptake efficiency of the cultivars. The amount of phosphorus to which roots were exposed did not exert a significant effect on germination of spores.

Key Words:

• chemotropism
• germination
• Gigaspora
• phosphorus effects
• root exudates