Plant responses to elevated CO2 levels in soils: distinct CO2 and O2-depletion effects

To investigate potential environmental effects in the context of carbon dioxide (CO2) leakage from Carbon Capture and Storage (CCS) schemes, the University of Nottingham ASGARD (Artificial Soil Gassing And Response Detection) facility, was used to inject CO2 into the soil in replicated open-air field plots over several seasons to measure the effects on UK crop species. However, this system lacked a way of distinguishing the concomitant effects of oxygen (O2)-depletion (occurring as a consequence of high CO2 levels in the soil). As plants are aerobic, they require O2 for functional integrity of root processes. Here a complementary laboratory system was used to specifically identify distinct CO2 and O2-depletion effects on two crop species, beetroot and wheat. Parameters measured (photosynthetic rate, transpiration rate, stomatal conductance and biomass) between CO2-gassed, nitrogen (N2)-gassed (O2-depletion control) and non-gassed control plants showed distinct differences in response to CO2 gassing and O2-depletion. Differences between field and laboratory studies illustrate effects of variable meteorological conditions in the field, whilst more stable laboratory conditions show differences between crop species. Results show that the interactions of these two stresses (very high soil CO2 and O2 depletion) on crop physiology are discrete and complex

Do Native Parasitic Plants Cause More Damage to Exotic Invasive Hosts Than Native Non-Invasive Hosts? An Implication for Biocontrol

Field studies have shown that native, parasitic plants grow vigorously on invasive plants and can cause more damage to invasive plants than native plants. However, no empirical test has been conducted and the mechanism is still unknown. We conducted a completely randomized greenhouse experiment using 3 congeneric pairs of exotic, invasive and native, non-invasive herbaceous plant species to quantify the damage caused by parasitic plants to hosts and its correlation with the hosts' growth rate and resource use efficiency. The biomass of the parasitic plants on exotic, invasive hosts was significantly higher than on congeneric native, non-invasive hosts. Parasites caused more damage to exotic, invasive hosts than to congeneric, native, non-invasive hosts. The damage caused by parasites to hosts was significantly positively correlated with the biomass of parasitic plants. The damage of parasites to hosts was significantly positively correlated with the relative growth rate and the resource use efficiency of its host plants. It may be the mechanism by which parasitic plants grow more vigorously on invasive hosts and cause more damage to exotic, invasive hosts than to native, non-invasive hosts. These results suggest a potential biological control effect of native, parasitic plants on invasive species by reducing the dominance of invasive species in the invaded community

Potassium : a neglected nutrient in global change

L'article inclou sis apèndixsAim: Potassium (K) is the second most abundant nutrient after nitrogen (N) in plant photosynthetic tissues. Thousands of physiological and metabolic studies in recent decades have established the fundamental role of K in plant function, especially in water use efficiency and economy, and yet macroecological studies have mostly overlooked this nutrient.- Methods: We have reviewed available studies on the contents, stoichiometries and roles of potassium in the soil-plant system and in terrestrial ecosystems. We have also reviewed the impacts of global change drivers on K contents, stoichiometries, and roles. - Conclusions: The current literature indicates that K, at a global level, is as limiting as N and phosphorus (P) for plant productivity in terrestrial ecosystems. K limitation has been seen up to some degree in 70% of all studied terrestrial ecosystems. However, atmospheric K deposition from human activities represents higher amounts than that from natural sources in some areas. We are far from understanding the K fluxes between the atmosphere and land, and the role of anthropogenic activities in these fluxes. The increasing aridity expected in wide areas of the world makes K more critical through its role in water use efficiency. N deposition exerts a strong impact on the ecosystem K-cycle, decreasing K availability and increasing K limitation. Plant invasive success is enhanced by higher soil K availability, especially in environments without strong abiotic stresses. The impacts of other global change drivers, such as increasing atmospheric CO² or changes in land use remain to be elucidated. Current models of the responses of ecosystems and carbon storage to projected global climatic and atmospheric changes are now starting to consider N and P, but they should also consider K, mostly in arid and semiarid ecosystems

Screening peach rootstocks for tolerance to iron deficiency stress: mechanisms of Fe₋p3+ ₋sreduction

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Yield and Mineral Element Concentration of Beetroot in Response to Nutrient Source in Hydroponic Solution

The yield and mineral element concentration of beetroot (Beta vulgaris ‘Bulls Blood’) was determined in a closed nutrient-recirculating ‘Nutrient Film Technique’ (NFT) hydroponic experiment. Seedlings were grown and harvested 42 days after transfer into NFT system (DAT), either with a commercial hydroponic fertilizer or a non-hydroponic soluble fertilizer containing in mg liter-1: 108 nitrogen (N) and 12 calcium (Ca) (N1Ca1), or 200 N and 66.7 Ca (N2Ca2), respectively. Nutrient source had no significant effect (p=0.05) on leaf fresh and dry weight (LFW, LDW) or root dry weight (RDW) (g/plant) of beetroot. Whereas, edible root fresh weight (RFW) was significantly (p=0.0308) increased at N2Ca2 compared with N1Ca1, root dry weight ratio (RDWR; RFW/RDW) was greater (p=0.0004) at N1Ca1 than N2Ca2. The greater RFW at N2Ca2 corresponded with significantly higher (p=0.05) leaf concentrations of Ca, magnesium (Mg), manganese (Mn), molybdenum (Mo), aluminum (Al) and sodium (Na), but not zinc (Zn). Nutrient source had no affect leaf N, phosphorus (P), potassium (K) and sulfur (S) concentration. Although leaf macro- and micronutrient concentration were variable, all the essential elements except Ca, iron (Fe) and B (at N1Ca1) were either within or above the sufficiency range for beetroot. These observations suggest that low tissue concentration of Ca and B contributed to the lower RFW at N1Ca1 compared with N2Ca2. Sufficiency in Ca and B content should be a major consideration in nutrient source selection and management in NFT hydroponic culture of beetroot

Does serum B lymphocyte chemoattractant protein13 (CXCL13) level correlate with parameters of disease activity and severity in rheumatoid arthritis? Clinical and musculoskeletal ultrasonographic assessment

Abstract Background Rheumatoid arthritis (RA) affects about 1–3% of the population making it one of the most popular autoimmune diseases. Chemokines through switching on their receptors exert a climacteric role in RA pathogenesis. The purpose of this cross-sectional study was to quantify the serum levels of serum B lymphocyte chemoattractant protein13 (CXCL13) chemokine in recent onset RA patients and to correlate its levels with clinical, laboratory, and musculoskeletal ultrasonographic parameters (MSUS) of disease activity and severity. Results The mean serum CXCL13 value showed a significant increase in the RA patients (388.86 ± 283.63 pg/ml) than in the controls (62.94 ± 31.62 pg/ml) (P < 0.001). Highly active RA patients had significantly the highest mean of CXCL13 (mean ± SD 819.13 ± 191.05) compared with the moderately active RA patients (mean ± SD 284.95 ± 137.93) (P < 0.001) and the RA patients with low disease activity (mean ± SD 129.5 ± 21.27) (P < 0.001) and its levels were positively related with clinical disease activity and musculoskeletal ultrasonographic severity parameters. Conclusion Serum CXCL13 is correlated with clinical disease activity and MSUS disease severity that encourages its use for monitoring the activity and severity of synovitis in recent onset RA patients. Future studies to detect the effect of disease activity control by medications on CXCL13 levels and the effect of the CXCL13 antagonist on controlling RA disease activity and severity are recommended