Nielsen, K.L.; Eshel, A.; Lynch, J.P.


Journal of Experimental Botany, Oxford University Press, Volume 52, Issue 355, UK, p.329-339 (2001)

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Carbon budgets were constructed for 4 common bean genotypes with constrasting adaptation to low P availability (Porillo Sintetico and DOR 364 (P-inefficient) and G19839 and G1937 (P-efficient)) to assess the importance of increased carbon allocation in the roots for the adaptation of plants to low P availability. The plants were grown in plastic pots filled with acid-rinsed solid-phase-buffered silica sand providing a constant availability of low, medium and high P concentration (1, 10 and 30 micro M, respectively) in the soil solution. Compared with the high phosphorus treatment, plant growth decreased by 20% with medium P concentration and by more than 90% with low P concentration. Plants grown in low P utilized a larger fraction of daytime net carbon assimilation on root respiration (40%) compared to medium and high P containing plants (20%). No significant difference was found among the genotypes in this respect. The genotypes had similar rates of P absorption per unit root weight and plant growth per unit of P absorbed. However, P efficient genotypes allocated a larger fraction of their biomass to root growth, especially under low P conditions. The P efficient genotypes had lower rates of respiration than inefficient genotypes, enabling them to maintain greater root biomass allocation without increasing overall root carbon costs.