Root hairs confer a competitive advantage under low phosphorus availability


Bates, T.R.; Lynch, J.P.


Plant and Soil, Kluwer Academic Publishers, Volume 236, Issue 2, Netherlands, p.243-250 (2001)

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Root hairs are presumably important in the acquisition of immobile soil resources such as phosphorus. The density and length of root hairs vary substantially within and between species, and are highly regulated by soil phosphorus availability, which suggests that at high nutrient availability, root hairs may have a neutral or negative impact on fitness. We used a root-hairless mutant (rhd2) of the small herbaceous dicot Arabidopsis thaliana to assess the effect of root hairs on plant competition under contrasting phosphorus regimes. Wild-type plants (WS) were grown with hairless plants in a replacement series design at high (60 micro m phosphate in soil solution) and low (1 micro m phosphate in soil solution) phosphorus availability. At high phosphorus availability, wild-type and mutant plants were equal in growth, phosphorus acquisition, fertility and relative crowding coefficient (RCC). At low phosphorus availability, hairless plants accumulated less biomass and phosphorus, and produced less seeds when planted with wild-type plants. Wild-type plants were unaffected by the presence of hairless plants in mixed genotype plantings. Wild-type plants had RCC values greater than one while hairless plants had RCC values less than one. We conclude that root hairs increase the competitiveness of plants under low phosphorus availability but do not reduce growth or competitiveness under high phosphorus availability.