EFFECTS OF ARBUSCULAR MYCORRHIZAE ON LEAF WATER POTENTIAL, SUGAR CONTENT, AND P CONTENT DURING DROUGHT AND RECOVERY OF MAIZE

The effect of colonization with the arbuscular mycorrhizal (AM) fungus (Glomus intraradices Schenck gr Smith) in maize (Zea mays L.) under d rought or nondrought conditions, on leaf water potential and sugar and phosphorus status was examined in a greenhouse study. Seeds of select ion-cycles 0 (GO, drought sensitive) and 8 (C8, drought resistant) of the tropical maize cultivar Tuxpeno sequia were used for this experime nt. Maize plants were exposed to 3 weeks of drought (45-65 days after sowing) followed by 3 weeks of recovery (66-86 days) at preflowering s tage. Daily midday leaf water potential during drought and recovery pe riods and daily soil moisture content and weekly leaf relative water c ontent during drought were measured. Sugar concentrations, phosphorus contents, and dry masses of roots and shoots were determined at the en d of drought and recovery periods. Mycorrhizal plants of CO and C8 mai ntained higher (less negative) leaf water potential during 3 weeks of drought. During recovery, AM plants took less time (GO, 7 days; C8, 4 days) than non-AM plants (GO, 15 days; C8, 8 days) to attain leaf wate r potential comparable with well-watered plants. The AM plants had hig her phosphorus contents at the end of drought and recovery periods. Dr ought reduced the sugars in shoots by 66 and 50% in non-AM plants and by only 30 and 32% in AM plants of CO and C8, respectively. Root and s hoot masses were higher in AM than non-AM plants under well-watered an d drought-stressed conditions. Overall results suggest that AM coloniz ation helped the host plant to sustain moderate drought stress and rec over rapidly when the irrigation was restored.