Controlled traffic farming increases root growth, crop and soil nitrogen in vegetable cropping systems

Results from field trials on sandy and sandy loam of controlled traffic farmin

Annual CO2 fluxes from a cultivated fen with perennial grasses during two initial years of rewetting

Rewetting combined with biomass crop cultivation (paludiculture) has been proposed as a method for reducing carbon dioxide (CO2) emissions from drained peatlands. This field experiment compared CO2 fluxes from drained (control) and rewetted experimental plots in a temperate fen under reed canary grass cultivation over two successive years. The annual weighted mean water table depth from soil surface (WTD) during the study period was 9, 3 and 1 cm in control, semi-flooded and flooded plots, respectively. There were no significant effects of WTD treatment on biomass yields. The choice of response model for CO2 fluxes influenced annual estimates of ecosystem respiration (ER) and gross primary production (GPP), but all models showed that ER and GPP decreased in response to rewetting. The resulting net ecosystem exchange (NEE) of CO2, derived by combining eight ER and eight GPP models, varied widely. For example, NEE (expressed as CO2-C) ranged from 935 to -208 g m 2 yr-1 for the flooded plots. One set of ER and GPP models was selected on the basis of statistical criteria and showed insignificant differences in NEE between the three water table treatments ( 537 to -341 g CO2-C m-2 yr 1). Treatment effects on CO2 emission factors, calculated as the sum of NEE and C export in harvested biomass (58–242 g CO2-C m-2 yr-1), were similarly insignificant. Thus, the results indicated that varying WTD within this narrow range could influence both ER and GPP without altering the net emissions of CO2

Barium effect on germination, plant growth, and antioxidant enzymes in Cucumis sativus L. plants

Barium (Ba) is a nonessential element that can cause several deleterious effects in most organisms. Elevated Ba concentrations can be toxic for plants and may affect growth and disturbances in homeostasis. This study aimed to evaluate the Ba stress, the plant-tolerance limits, and the detoxification strategy adopted by Cucumis sativus L. The effect of Ba on seed's germination and vegetative development of this species was evaluated. For germination test, different Ba concentrations were used (0, 200, 500, 1,000, and 2,000 μM). Results showed that germination was stimulated with 500 and 2,000 µM of Ba. The toxicity effect on plant development was studied by treating the plants with increasing doses of Ba (100, 200, 300, and 500 μM) during 45 days. Shoot and root dry biomass production decreased significantly with elevated Ba concentrations, although water content enhanced in the roots. The concentration of Ba, 500 µM, induced high Ba accumulation in shoots and roots (9 times higher than in the control plants). Moreover, results showed that catalase, guaiacol peroxidase, and ascorbate peroxidase activities were stimulated in the different tissues of cucumber plants which highlight the occurring of an oxidative damage through Ba treatments and the involvement of the plant enzymatic antioxidant defense system

Three-dimensional coherent X-ray diffraction imaging of a ceramic nanofoam: determination of structural deformation mechanisms

Ultra-low density polymers, metals, and ceramic nanofoams are valued for their high strength-to-weight ratio, high surface area and insulating properties ascribed to their structural geometry. We obtain the labrynthine internal structure of a tantalum oxide nanofoam by X-ray diffractive imaging. Finite element analysis from the structure reveals mechanical properties consistent with bulk samples and with a diffusion limited cluster aggregation model, while excess mass on the nodes discounts the dangling fragments hypothesis of percolation theory.Comment: 8 pages, 5 figures, 30 reference

Partial symmetry breaking and heteroclinic tangencies

We study some global aspects of the bifurcation of an equivariant family of volume-contracting vector fields on the three-dimensional sphere. When part of the symmetry is broken, the vector fields exhibit Bykov cycles. Close to the symmetry, we investigate the mechanism of the emergence of heteroclinic tangencies coexisting with transverse connections. We find persistent suspended horseshoes accompanied by attracting periodic trajectories with long periods