Progress in Botany

Volume 70 of the series Progress in Botany pp 257-276

Water Relations in the Mycorrhizosphere

  • M. F. AllenAffiliated withCenter for Conservation Biology, Department of Plant Pathology, University of California Email author 

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The role of mycorrhizae in plant water relations has been controversial since it was proposed over a century ago. Improvements in plant water throughput and associated carbon fixation by mycorrhizal plants have been demonstrated since the early 1970s, but the mechanisms remain poorly understood. Mechanism studies have concentrated in greenhouse pot studies. These studies are limited because roots readily become pot-bound, in contrast to the distinct spatial stratification in the field. Water transport studies also focused on symplastic water flow rates. Recent data from hyphal structure and using models suggest that apoplastic transport may be the focal mechanism under drought conditions. Hydraulic redistribution along mycorrhizal fungal hyphae indicates that apoplastic transport and water potential gradients, especially in arid lands, regulate water flow patterns along hyphae. New sensor technologies may open the possibility of greater study of water and nutrient dynamics in situ where these mechanisms can be studied in detail.