Amino acid transport in plants is mediated by at least two large families of plasma membrane transporters. Arabidopsis thaliana, a nonmycorrhizal species, is able to grow on media containing amino acids as the sole nitrogen source. Arabidopsis amino acid permease (AAP) subfamily genes are preferentially expressed in the vascular tissue, suggesting roles in long-distance transport between organs...

Climate change in the Arctic is altering delivery of nutrients from terrestrial to aquatic ecosystems. The impact these changes on downstream lakes and rivers influenced by capacity small streams retain such inputs. Given potential for nutrient limitation oligotrophic streams, biotic demand should be high, unless harsh environmental conditions maintain low biomass standing stocks that limit upt...

• In nitrogen (N)-limited systems, the response of symbiotic N fixation to elevated atmospheric [CO 2 ] may be an important determinant of ecosystem responses to this global change. Experimental tests of the effects of elevated [CO 2 ] have not been consistent. Although rarely tested, differences among legume species and N supply may be important. • In a field free-air CO 2 enrichment (FACE) ex...

Sustainable agriculture demands reduced input of man-made nitrogen (N) fertilizer, yet N2 fixation limits the productivity of crops with heterotrophic diazotrophic bacterial symbionts. We investigated floating ferns from the genus Azolla that host phototrophic diazotrophic Nostoc azollae in leaf pockets and belong to the fastest growing plants. Experimental production reported here demonstrated...

Cucumber plants (Cucumis sativus L. cv. Brunex) were grown under controlled conditions in an experimental greenhouse and treated with four rates of N in the form of KNO3 (N1, 5 g/m ; N2, 10 g/m; N3, 20 g/m; and N4, 40 g/m). The intermediate N rates (N2 and N3) gave higher utilization of NO3 ÿ in the leaves (highest NR activities) than treatment N1 (inadequate) and N4 (excessive). This latter ra...

There is growing evidence that the altered production and/or spatiotemporal distribution of reactive oxygen and nitrogen species creates oxidative and/or nitrosative stresses in the failing heart and vascular tree, which contribute to the abnormal cardiac and vascular phenotypes that characterize the failing cardiovascular system. These derangements at the integrated system level can be interpr...

In Brazil, grain crops in no-till soybean–maize succession have reduced biodiversity and carbon input into soil. Intercropping is a promising approach to address these problems. This study aimed evaluate the microbiological quality of soil conventional intercropping systems succession, depending on tropical grass nitrogen fertilizer uses. The treatments were arranged randomized complete block d...

In nitrogen (N)-limited systems, the response of symbiotic N fixation to elevated atmospheric [CO2] may be an important determinant of ecosystem responses to this global change. Experimental tests of the effects of elevated [CO2] have not been consistent. Although rarely tested, differences among legume species and N supply may be important. In a field free-air CO2 enrichment (FACE) experiment,...

Across US Great Plains grasslands, a gradient of increasing mean annual precipitation from west to east corresponds to increasing aboveground net primary productivity (ANPP) and increasing N-limitation. Previous work has shown that there is no increase in net N mineralization rates across this gradient, leading to the question of where eastern prairie grasses obtain the nitrogen to support prod...