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Effect of phosphorus availability on basal root shallowness in common bean

Authors:

Hong, L.; Rubio, G.; Yan, X.; AiQin, C.; Brown, K.M.; Lynch, J.P.

Source:

Interactions in the root environment: an integrated approach. Proceedings of the Millennium Conference on Rhizosphere Interactions, IACR-Rothamsted, UK, 10-12 April 2001, p.69-79 (2002)

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Abstract:

Root gravitropism may be an important element of plant response to phosphorus availability because it determines root foraging in fertile topsoil horizons, and thereby phosphorus acquisition. In this study we seek to test this hypothesis in both two-dimensional paper growth pouch and three-dimensional solid media of sand and soil cultures. Five common bean ( Phaseolus vulgaris ) genotypes with contrasting adaptation to low phosphorus availability were evaluated in growth pouches over 6 days of growth, and in sand culture and soil culture over 4 weeks of growth. In all three media, phosphorus availability regulated the gravitropic response of basal roots in a genotype-dependent manner. In pouches, sand, and soil, the phosphorus-inefficient genotype DOR 364 had deeper roots with phosphorus stress, whereas the phosphorus-efficient genotype G19833 responded to phosphorus stress by producing shallower roots. Genotypes were most responsive to phosphorus stress in sand culture, where relativeroot allocation to the 0-3- and 3-6-cm horizons increased by 50% with phosphorus stress, and varied from 300 (3-6 cm) to 500% (0-3 cm) among genotypes. Our results indicate that (1) phosphorus availability regulates root gravitropic growth in both paper and solid media, (2) the responses observed in young seedlings continue throughout vegetative growth, (3) the response of root gravitropism to phosphorus availability varies among genotypes, and (4) the genotypic adaptation to low phosphorus availability is correlated with the ability to allocate roots to shallow soil horizons under phosphorus stress.