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 & Smith) on drought tolerance in tropical maize. Freshly regenerated seeds of selection cycles 0 (cv. C0, drought-sensitive) and 8 (cv. C8, drought-resistant) of the lowland tropical population 'Tuxpeno sequia' were 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), stomatal resistance (SR) and transpiration rate (TR) were monitored daily, and green leaf area (GLA) determined at alternate days to assess the effects of mycorrhizal inoculation. Mycorrhizal plants of the cultivars C0 and C8 had higher (less negative) LWP and TR, and lower SR throughout the experiment. The GLA was 27.5% higher in mycorrhizal than non-mycorrhizal C0 plants under drought conditions. Results indicate that mycorrhizas significantly improve tolerance to moderate drought stress imposed at tasselling, especially for the sensitive C0 maize cultivar.