Species-specific differences in the assimilation of atmospheric CO2 depends upon differences in the capacities for the biochemical reactions that regulate the gas-exchange process. Quantifying these differences for more than a few species, however, has proven difficult. Therefore, to understand better how species differ in their capacity for CO2 assimilation, a widely used model, capable of partitioning limitations to the activity of ribulose-1,5-bisphosphate carboxylase-oxygenase, to the rate of ribulose 1,5-bisphosphate regeneration-via electron transport, and to the rate of triose phosphate utilization was used to analyse 164 previously published A/C(i) curves for 109 C3 plant species. Based on this analysis, the maximum rate of carboxylation, Vc(max), ranged from 6 mumol m-2 s-1 for the coniferous species Picea abies to 194 mumol m-2 s-1 for the agricultural species Beta vulgaris, and averaged 64 mumol m-2 s-1 across all species. The maximum rate of electron transport, J(max), ranged from 17 mumol m-2 s-1 again for Picea abies to 372 mumol m-2 s-1 for the desert annual Malvastrum rotundifolium, and averaged 134 mumol m-2 s-1 across all species. A strong positive correlation between V(max) and J(max) indicated that the assimilation Of CO2 was regulated in a co-ordinated manner by these two component processes. Of the A/C(i) curves analysed, 23 showed either an insensitivity or reversed-sensitivity to increasing CO2 concentration, indicating that CO2 assimilation was limited by the utilization of triose phosphates. The rate of triose phosphate utilization ranged from 4.9 mumol m-2 s-1 for the tropical perennial Tabebuia rosea to 20.1 muMol m-2 s-1 for the weedy annual Xanthium strumarium, and averaged 10.1 muMol M-2 s-1 across all species. Despite what at first glance would appear to be a wide range of estimates for the biochemical capacities that regulate CO2 assimilation, separating these species-specific results into those of broad plant categories revealed that Vc(max) and J(max) were in general higher for herbaceous annuals than they were for woody perennials. For annuals, Vc(max) and J(max) averaged 75 and 154 muMol M-2 S-1, While for perennials these same two parameters averaged only 44 and 97 mumol M-2s-1, respectively. Although these differences between groups may be coincidental, such an observation points to differences between annuals and perennials in either the availability or allocation of resources to the gas-exchange process.
