Respiratory energy requirements of roots vary with the potential growth rate of a plant species

Abstract

The rates of growth, net rate of nitrate uptake and root respiration of 24 wild species were compared under conditions of optimum nutrient supply. The relative growth rate (RGR)of the roots of these species varied between 110 and 370 mg g‐1 day‐1 and the net rate of nitrate uptake between 1 and 7 mmol (g root dry weight)‐1 day‐1. The rate of root respiration was positively correlated with the RGR of the roots. Root respiration was also calculated from the measured rate of growth and nitrate uptake, using previously determined values for the costs of maintenance, growth and ion uptake of two slow‐growing species. The calculated rate of respiration was slightly lower than the measured one for slow‐growing species, but twice as high as measured rates for rapid‐growing species. This discrepancy was not due to a relatively smaller electron flow through the alternative pathway and, consequently, a more efficient ATP production in the fast‐growing species. Neither could variation in specific costs for root growth or maintenance explain these differences. Therefore, we conclude that fast‐growing species have lower specific respiratory costs for ion uptake than slow‐growing ones. Due partly to these lower specific costs of nutrient uptake, the fraction of respiration that rapid‐growing species spend on anion uptake is lower than that of slow‐growing species, in spite of the much higher rate of ion uptake of the fast‐growing ones.

Linking root traits to potential growth rate in six temperate tree species

“…Maintenance respiration should be higher in roots with higher uptake capacity due to these roots maintaining more proteins (Bouma et al 1994). However, fast-growing species in this study that had greater P uptake capacity had relatively small increases in respiratory costs, which is similar to comparisons of nitrogen uptake and respiration across fast-and slowgrowing species (Poorter et al 1991;Scheurwater et al 1998). Like respiration, nitrogen concentration has also been found to be higher in root tissue with higher nutrient absorption capacity (sugar maple roots of different orders, Pregitzer et al 1998; grape roots of different ages, Volder and Eissenstat, unpublished data).…”

“…Greater root efficiency has previously been found in species with fast relative growth rate (Poorter et al 1991) but these studies also did not include mycorrhizae. Thicker roots may be less efficient for P acquisition than thinner roots when non-mycorrhizal but thicker roots may support more mycorrhizae per unit root length.…”

Grass strategies and grassland community responses to environmental drivers: a review

“…The positive correlation between root uptake capacity and leaf nitrogen content has been also evidenced in other studies (Poorter et al 1991;Wright and Westoby 2000). Further, high leaf nitrogen content conferred low leaf N use efficiency, leading to low biomass production per unit N ).…”

Below-ground carbon distribution in barley (Hordeum vulgare L.) with and without nitrogen fertilization

“…This supports our results indicating a somewhat greater release of C from the roots at the low N-level. However, a slow growth rate also indicates a slow rate of ion uptake and thereby a lower respiratory demand compared to at faster growth rates (Poorter et al, 1991;Van der Werf et al, 1988). This should imply a lower release of C as CO z originating from root respiration at low N-level.…”