ARBUSCULAR MYCORRHIZAS AND WATER RELATIONS IN MAIZE UNDER DROUGHT STRESS AT TASSELLING

A greenhouse experiment was conducted to investigate the influence of an arbuscular mycorrhizal (AM) fungus (Glomus intraradices Schenck & S mith) on drought tolerance in tropical maize. Freshly regenerated seed s of selection cycles 0 (cv. C0, drought-sensitive) and 8 (cv. C8, dro ught-resistant) of the lowland tropical population 'Tuxpeno sequia' we re used for this study. Maize plants were subjected to drought stress for three weeks following tasselling (75-95 days after sowing). During the drought stress period, midday leaf water potential (LWP), stomata l resistance (SR) and transpiration rate (TR) were monitored daily, an d green leaf area (GLA) determined at alternate days to assess the eff ects of mycorrhizal inoculation. Mycorrhizal plants of the cultivars C 0 and C8 had higher (less negative) LWP and TR, and lower SR throughou t the experiment. The GLA was 27.5% higher in mycorrhizal than non-myc orrhizal C0 plants under drought conditions. Results indicate that myc orrhizas significantly improve tolerance to moderate drought stress im posed at tasselling, especially for the sensitive C0 maize cultivar.