EFFECTS OF DROUGHT ON NONMYCORRHIZAL AND MYCORRHIZAL MAIZE - CHANGES IN THE POOLS OF NONSTRUCTURAL CARBOHYDRATES, IN THE ACTIVITIES OF INVERTASE AND TREHALASE, AND IN THE POOLS OF AMINO-ACIDS AND IMINO ACIDS

To study the response of non-mycorrhizal and mycorrhizal maize plants to drought, the changes in the pools of non-structural carbohydrates a nd amino acids were analysed in leaves and roots of two maize cvs. Pla nts well colonized by the arbuscular mycorrhizal fungus Glomus mosseae (Nicol. & Gerd.) (60% of root length infected) and comparable non-myc orrhizal plants were subjected to moderate drought stress by reducing the water supply. This stress induced a conspicuous increase in the tr ehalose pool in the mycorrhizal roots, probably because it was accumul ated by the fungal symbiont. Furthermore, glucose and fructose were ac cumulated in leaves and roots of non-mycorrhizal plants but not in the mycorrhizal ones. Starch disappeared completely from the leaves of bo th mycorrhizal and non-mycorrhizal plants in response to drought. Acti vities of soluble acid invertase and trehalase were also measured. Aci d invertase activity increased during drought in the leaves of both no n-mycorrhizal and mycorrhizal plants whilst in the roots it was unaffe cted in non-mycorrhizal plants and decreased in the mycorrhizal ones. Without drought stress, trehalase activity was considerably higher in the leaves and roots of mycorrhizal plants than in those of non-mycorr hizal plants. It increased conspicuously during drought, primarily in the leaves of non-mycorrhizal plants. A drought-induced accumulation o f amino acids as well as imino acids was found in roots and leaves of both mycorrhizal and non-mycorrhizal plants; leaves of mycorrhizal pla nts accumulated more imino acids than those of non-mycorrhizal ones. O ur results show that drought stress and the presence of a mycorrhizal fungus have a considerable effect on carbon partitioning, imino acid a nd amino acid accumulation in maize plants.