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Interspecific correlates of plasticity in relative growth rate following a decrease in nitrogen availability

Antonio Useche and Bill Shipley
Annals of Botany
Vol. 105, No. 2 (February 2010), pp. 333-339
Published by: Oxford University Press
Stable URL: http://www.jstor.org/stable/43576479
Page Count: 7
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Interspecific correlates of plasticity in relative growth rate following a decrease in nitrogen availability
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Abstract

• Background and Aims Nitrogen availability varies greatly over short time scales. This requires that a welladapted plant modify its phenotype by an appropriate amount and at a certain speed in order to maximize growth and fitness. To determine how plastic ontogenetic changes in each trait interact and whether or not these changes are likely to maximize growth, ontogenetic changes in relative growth rate (RGR), net assimilation rate (NAR), specific leaf area (SLA) and root weight ratio (RWR), before and after a decrease in nitrogen supply, were studied in 14 herbaceous species. • Methods Forty-four plants of each species were grown in hydroponic culture under controlled conditions in a control treatment where the supply of nitrogen remained constant at 1 ITIM, and in a stress treatment where the nitrogen supply was abruptly decreased from 1 to 0·01 mM during the growth period. • Key Results and Conclusions In the treatment series, and in comparison with the control, NAR and RGR decreased, RWR increased, and SLA did not change except for the timing of ontogenetic change. Species having greater increases in the maximum rate of change in RWR also had smaller reductions in RGR; plasticity in RWR is therefore adaptive. In contrast, species which showed a greater decrease in NAR showed stronger reductions in RGR; plasticity in NAR is therefore not adaptive. Plasticity in RGR was not related to plasticity in SLA. There were no significant relationships among the plasticities in NAR, RWR or SLA. Potentially fast-growing species experienced larger reductions in RGR following the nitrogen reduction. These results suggest that competitive responses to interspecific competition for nitrogen might be positively correlated with the plasticity in the maximum rate of change in RWR in response to a reduction in nitrogen supply.

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