Analysis of root respiration of Solanum tuberosum as related to growth, ion uptake and maintenance of biomass.

Abstract

The specific respiratory costs for growth (1/Y; mmol O 2 g -1 DW), ion uptake (1/U; mol O 2 mol -1 NO 3 - and maintenance (m; nmol O 2 s -1 g - 1 DW) of roots of potato (Solanum tuberosum L.) were determined in two experiments, and compared to process-based calculations and literature data. Both experiments yielded similar estimates for 1/Y (9.8-9.9), 1/U (0.39-0.67), and m (10.2-14.8). The range of 1/Y agreed with the literature data (6.2-10.9), but was high compared to the theoretical expectations (4.3-5.5). Our estimates of 1/U appeared affected by perturbation. It was deduced that overall costs for maintaining solute gradients correlates to 1/U (instead of m), and accounts for up to 33% of the overall costs of nitrate influx. The absence of these costs for maintaining solute gradients in present estimates of 1/U explains the good agreement with our calculation (0.43), and why these estimates are lower than most literature values (0.83-1.16). Costs of protein turnover (3.7-16 nmol O 2 s -1 g -1 DW) can fully account the experimental value of m, although m was relatively high compared to most literature data (4.0-7.0).