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 drought or nondrought conditions, on leaf water potential and sugar and phosphorus status was examined in a greenhouse study. Seeds of selection-cycles 0 (GO, drought sensitive) and 8 (C8, drought resistant) of the tropical maize cultivar Tuxpeno sequia were used for this experiment. 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 stage. Daily midday leaf water potential during drought and recovery periods and daily soil moisture content and weekly leaf relative water content during drought were measured. Sugar concentrations, phosphorus contents, and dry masses of roots and shoots were determined at the end of drought and recovery periods. Mycorrhizal plants of CO and C8 maintained 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 water potential comparable with well-watered plants. The AM plants had higher phosphorus contents at the end of drought and recovery periods. Drought 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 shoot masses were higher in AM than non-AM plants under well-watered and drought-stressed conditions. Overall results suggest that AM colonization helped the host plant to sustain moderate drought stress and recover rapidly when the irrigation was restored.