EFFECTS OF FUMIGATION ON GROWTH, PHOTOSYNTHESIS, WATER RELATIONS AND MYCORRHIZAL DEVELOPMENT OF WINTER WHEAT IN THE FIELD

Abstract

Winter wheat (Triticum aestivum L.) was grown in methyl bromide fumigated and nonfumigated soils in the field. Fumigation increased growth of wheat in the winter but depressed growth later in the spring. Growth depression of winter wheat in fumigated soils coincided with VAM-fungal colonization of wheat roots in nonfumigated soils. In the spring, wheat plants growing in fumigated soils were more chlorotic than those in nonfumigated soils. Plants grown in fumigated soils produced 18–21% less aboveground biomass during grain filling, and 42% less grain at final harvest than controls. In May, photosynthesis, stomatal conductance, and transpiration of flag leaves were reduced 40–52, 41–55, and 24–36%, respectively, in fumigated plots when compared to nonfumigated plots. Wheat was colonized by VAM only 20% of the growth period; however, VAM colonization may occur at a period critical to grain production of winter wheat.Key words: Triticum aestivum, fumigation, mycorrhizae, photosynthesis, water relations, wheat (winter)