Phosphate uptake kinetics of Artemisia tridentata roots exposed to multiple soil enriched-nutrient patches

Abstract

Root phosphate (P) uptake capacity in a nutrient-rich soil patch (termed the Primary Patch) was assessed as the rest of the root system was exposed to different mineral nutrient conditions in the form of other nutrient-rich patches (Additional Patches) in a factorial experiment. The experimental design involved different numbers of Additional Patches with different phosphate concentrations, [P i ]. In addition to testing the effect of the total quantity of added P on root uptake capacity in the Primary Patch, the influence of the distribution of the added P was also tested. The [P i ] and number of Additonal Patches were chosen such that the total quantity of P added was the same among some treatments which afforded a test of the influence of the concentration and distribution of Additional Patches on the uptake capacity of the roots in the Primary Patch. As the number and the concentration of Additional Patches increased, the upake capacity of Primary Patch roots was expected to be reduced relative to roots from untreated Control Patches. Averaged across all treatments, roots from the Primary Patch exhibited greater uptake capacities than the Control Patch roots (i.e., roots from unamended soil). With substantial enrichment of P i in the Additional Patches, the uptake capacity of roots was reduced in both the Primary and Control Patch roots. However, the concentration and number of Additional Patches had no clear influence on P uptake capacities in the Primary Patch. The P uptake capacity of roots from the Additional Patches with low and moderate [P i ] did not differ from the uptake capacity of roots in the Control Patches. However, for roots in the Additional Patches with high [P i ] (equivalent [P i ] to that of the Primary Patch) the uptake capacities were significantly greater that those of the Control Patch roots. In an ancillary P acquisition experiment, plants procured less P from the Primay Patch if there were four Additional Patches than if there were only two Additional Patches. This suggests that P acquisition occurred in the Additional Patches and that regulation at the whole-plant level reduced the uptake of P from the Primary Patch. In contrast, the root uptake kinetics did not seem to be as responsive to added P i presented in the Additional Patches.