Root growth and physiological responses to elevated CO2 were investigated for three important Mojave Desert grasses: the C3 perennial Achnatherum hymenoides, the C4 perennial Pleuraphis rigida and the C3 annual Bromus madritensis ssp. rubens. Seeds of each species were grown at ambient (360 \uffce\uffbcl l\uffe2\uff88\uff921) or elevated (1000 \uffce\uffbcl l\uffe2\uff88\uff921) CO2 in a glasshouse and harvested at three phenological stages: vegetative, anthesis and seed fill. Because P. rigida did not flower during the course of this study, harvests for this species represent three vegetative stages. Primary productivity was increased in both C3 grasses in response to elevated CO2 (40 and 19% for A. hymenoides and B. rubens, respectively), but root biomass increased only in the C3 perennial grass. Neither above\uffe2\uff80\uff90ground nor below\uffe2\uff80\uff90ground biomass of the C4 perennial grass was significantly affected by the CO2 treatment. Elevated CO2 did not significantly affect root surface area for any species. Total plant nitrogen was also not statistically different between CO2 treatments for any species, indicating no enhanced uptake of N under elevated CO2. Physiological uptake capacities for NO3 and NH4 were not affected by the CO2 treatment during the second harvest; measurements were not made for the first harvest. However, at the third harvest uptake capacity was significantly decreased in response to elevated CO2 for at least one N form in each species. NO3 uptake rates were lower in A. hymenoides and P. rigida, and NH4 uptake rates were lower in B. rubens at elevated CO2. Nitrogen uptake on a whole root\uffe2\uff80\uff90system basis (NO3+NH4 uptake capacity \uffc3\uff97 root biomass) was influenced positively by elevated CO2 only for A. hymenoides after anthesis. These results suggest that elevated CO2 may result in a competitive advantage for A. hymenoides relative to species that do not increase root\uffe2\uff80\uff90system N uptake capacity. Root respiration measurements normalized to 20 \uffc2\uffb0C were not significantly affected by the CO2 treatment. However, specific root respiration was significantly correlated with either root C\uffe2\uff88\uffb6N ratio or root water content when all data per species were included within a simple regression model. The results of this study provide little evidence for up\uffe2\uff80\uff90regulation of root physiology in response to elevated CO2 and indicate that root biomass responses to CO2 are species\uffe2\uff80\uff90specific.
", "keywords": ["0106 biological sciences", "2. Zero hunger", "ABSORPTION D'AZOTE", "CO2", "15. Life on land", "01 natural sciences", "[SDV.BV.PEP] Life Sciences [q-bio]/Vegetal Biology/Phytopathology and phytopharmacy", "[SDV.BV.PEP]Life Sciences [q-bio]/Vegetal Biology/Phytopathology and phytopharmacy"]}, "links": [{"href": "https://doi.org/10.1046/j.1469-8137.2000.00576.x"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/New%20Phytologist", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.1046/j.1469-8137.2000.00576.x", "name": "item", "description": "10.1046/j.1469-8137.2000.00576.x", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1046/j.1469-8137.2000.00576.x"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2000-02-01T00:00:00Z"}}, {"id": "10.3389/fpls.2022.922982", "type": "Feature", "geometry": null, "properties": {"updated": "2026-05-25T16:20:44Z", "type": "Journal Article", "created": "2022-06-23", "title": "Molecular Mechanisms of Intercellular Rhizobial Infection: Novel Findings of an Ancient Process", "description": "Establishment of the root-nodule symbiosis in legumes involves rhizobial infection of nodule primordia in the root cortex that is dependent on rhizobia crossing the root epidermal barrier. Two mechanisms have been described: either through root hair infection threads or through the intercellular passage of bacteria. Among the legume genera investigated, around 75% use root hair entry and around 25% the intercellular entry mode. Root-hair infection thread-mediated infection has been extensively studied in the model legumes Medicago truncatula and Lotus japonicus. In contrast, the molecular circuit recruited during intercellular infection, which is presumably an ancient and simpler pathway, remains poorly known. In recent years, important discoveries have been made to better understand the transcriptome response and the genetic components involved in legumes with obligate (Aeschynomene and Arachis spp.) and conditional (Lotus and Sesbania spp.) intercellular rhizobial infections. This review addresses these novel findings and briefly considers possible future research to shed light on the molecular players that orchestrate intercellular infection in legumes.Establishment of the root-nodule symbiosis in legumes involves rhizobial infection of nodule primordia in the root cortex that is dependent on rhizobia crossing the root epidermal barrier. Two mechanisms have been described: either through root hair infection threads or through the intercellular passage of bacteria. Among the legume genera investigated, around 75% use root hair entry and around 25% the intercellular entry mode. Root-hair infection thread-mediated infection has been extensively studied in the model legumes Medicago truncatula and Lotus japonicus. In contrast, the molecular circuit recruited during intercellular infection, which is presumably an ancient and simpler pathway, remains poorly known. In recent years, important discoveries have been made to better understand the transcriptome response and the genetic components involved in legumes with obligate (Aeschynomene and Arachis spp.) and conditional (Lotus and Sesbania spp.) intercellular rhizobial infections. This review addresses these novel findings and briefly considers possible future research to shed light on the molecular players that orchestrate intercellular infection in legumes.