Organic Crop Production Overview

This publication provides an overview of the key concepts and practices of certified organic crop production. It also presents perspectives on many of the notions, myths, and issues that have become associated with organic agriculture over time. A guide to useful ATTRA resources and to several non-ATTRA publications is provided

Different strategies of cadmium detoxification in the submerged macrophyte Ceratophyllum demersum L.

The heavy metal cadmium (Cd) is highly toxic to plants. To understand the mechanisms of tolerance and resistance to Cd, we treated the rootless, submerged macrophyte Ceratophyllum demersum L. with sub-micromolar concentrations of Cd under environmentally relevant conditions. X-ray fluorescence measurements revealed changing distribution patterns of Cd and Zn at non-toxic (0.2 nM, 2 nM), moderately toxic (20 nM) and highly toxic (200 nM) levels of Cd. Increasing Cd concentrations led to enhanced sequestration of Cd into non-photosynthetic tissues like epidermis and vein. At toxic Cd concentrations, Zn was redistributed and mainly found in the vein. Cd treatment induced the synthesis of phytochelatins (PCs) in the plants, with a threshold of induction already at 20 nM Cd for PC3. In comparison, in plants treated with Cu, elevated PC levels were detected only at the highest concentrations (100–200 nM Cu). Our results show that also non-accumulators like C. demersum store toxic metals in tissues where the heavy metal interferes least with metabolic pathways, but remaining toxicity interferes with micronutrient distribution. Furthermore, we found that the induction of phytochelatins is not proportional to metal concentration, but has a distinct threshold, specific for each PC species. Finally we could show that 20 nM Cd, which was previously regarded as non-toxic to most plants, already induces detoxifying mechanisms

Poster P3: Toxicity and Detoxification of Cadmium in the Aquaticmacrophyte Ceratophyllum Demersum; session "Metal homeostasis and detoxification"

The heavy metal cadmium (Cd) is an important pollutant and poisonousto many organisms. We studied the effects of Cd on C.demersum under environmentally relevant conditions. High, moderateand low concentrations of Cd had different effects. Lethally toxicconcentrations (100–200 nM) led to growth stop and the plants’ability to perform photosynthesis (measured as Fv/Fm) decreased morethan twofold, consistent with decreased pigment content. Moderatelytoxic concentrations (10–50 nM) led to reduced growth, slightlyreduced pigment content, but hardly affected photosynthesis (measuredas O2 exchange and as Fv/Fm). Lower concentrations(0.2–5 nM) even had beneficial effects, like enhanced growth rate.When applied in low concentrations, Cd was homogeneously distributedin the whole cross-section of the leaves like a nutrient.Moderate and high Cd concentrations led to sequestration of Cd in thevascular bundle and the epidermis cells, where Cd does not affectphotosynthetic molecules. At toxic Cd concentrations, Zn was redistributedand mainly found in the vein along with Cd, indicatinginhibition of Zn transporters. Consistently, by metalloproteomics(HPLC-ICP-MS) we found that during Cd toxicity concentrations of Cdincreased in fractions of the major photosynthetic complexes while Mgdecreased, suggesting the replacement of Mg by Cd in chlorophylls.Furthermore, the induction of phytochelatins was not proportionalto metal concentration, but had distinct thresholds, specific for each PCspecies. PC3 especially was switch-like induced already at 20 nM Cd,which was previously regarded as non-toxic to most plants. Phytochelatinlevels at the lowest Cd concentrations were not detectable orbelow 0.1 % of the level at sublethally toxic concentrations, suggestingthat they do not have another function than metal detoxification

Effect of percutaneous coronary interventions for in-stent restenosis in degenerated saphenous vein grafts without distal embolic protection

AbstractObjectivesThis study was designed to investigate the impact of percutaneous coronary interventions (PCIs) in degenerated saphenous vein grafts (SVGs) without distal embolic protection.BackgroundDistal embolic protection devices have been shown to reduce the incidence of no reflow/slow flow during PCI of de novo lesions in degenerated SVGs. It is unclear whether PCI of in-stent restenosis (ISR) lesions in degenerated SVGs is associated with no reflow/slow flow and whether distal embolic protection is beneficial in these cases as well.MethodsWe studied 54 consecutive patients with treated ISR lesions in degenerated SVGs who underwent PCI without distal embolic protection in a single center. Procedural and in-hospital outcomes were examined.ResultsThe average age was 71 ± 8 years; 32% of the patients had diabetes. The mean lesion length was 13 ± 6 mm and the procedural success rate was 98% (53/54). Cutting balloon angioplasty was used in 46% (25/54) of cases, and a new stent was inserted in 46% (25/54) of patients. Gamma brachytherapy was performed in 19% (10/54) of patients. During the procedure there were no episodes of no reflow/slow flow, and there were no patients with in-hospital Q-wave or non–Q-wave myocardial infarction. There was one in-hospital noncardiac death.ConclusionsIn this consecutive series of patients with ISR of degenerated SVGs undergoing PCI without distal protection, there were no episodes of slow flow/no reflow and no procedure-related myocardial infarctions. It appears that distal embolic protection may not be necessary during PCI of ISR lesions in degenerated SVGs

A star-shaped molecule of MnII4O6 core with an St = 10 high spin state : a theoretical and experimental study with XPS, XMCD, and other magnetic methods

We report a comprehensive study of the electronic and magnetic properties of a star-shaped molecule comprising a MnII 4O6 core. One feature of this compound is weak magnetic coupling constants compared to other similar polyoxo compounds. This leads to complicated low-lying magnetic states in which the ground state is not well separated from the upper-lying states, yielding a high-spin molecule with a giant magnetic moment of up to 20 μB/formula unit. We apply X-ray diffraction and magnetometry as well as other X-ray spectroscopic techniques, namely, X-ray photoelectron spectroscopy, X-ray magnetic circular dichroism, and X-ray emission spectroscopy. We compare our experimental results with ab initio electronic band structure calculations as well as the localized electronic structure around the Mn2+ ions with charge-transfer multiplet calculations

A Star-Shaped Heteronuclear (CrMn3II)-Mn-III Species and Its Precise Electronic and Magnetic Structure: Spin Frustration Studied by X-Ray Spectroscopic, Magnetic, and Theoretical Methods

Prinz M, Kuepper K, Taubitz C, et al. A Star-Shaped Heteronuclear (CrMn3II)-Mn-III Species and Its Precise Electronic and Magnetic Structure: Spin Frustration Studied by X-Ray Spectroscopic, Magnetic, and Theoretical Methods. Inorganic Chemistry. 2010;49(5):2093-2102.Molecular magnets incorporate transition-metal ions with organic groups providing a bridge to mediate magnetic exchange interactions between the ions. Among them are star-shaped molecules in which antiferromagnetic couplings between the central and peripheral atoms are predominantly present. Those configurations lead to an appreciable spin moment in the nonfrustrated ground state. In spite of its topologically simple magnetic structure, the [(CrMn3II)-Mn-III(PyA)(6)Cl-3] (CrMn3) molecule, in which PyA represents the monoanion of syn-pyridine-2-aldoxime, exhibits nontrivial magnetic properties, which emerge from the combined action of single-ion anisotropy and frustration. In the present work, we elucidate the underlying electronic and magnetic properties of the heteronuclear, spin-frustrated CrMn3 molecule by applying X-ray magnetic circular dichroism (XMCD), as well as magnetization measurements in high magnetic fields, density functional theory, and ligand-field multiplet calculations. Quantum-model calculations based on a Heisenberg Hamiltonian augmented with local anisotropic terms enable us not only to improve the accuracy of the exchange interactions but also to determine the dominant local anisotropies. A discussion of the various spin Hamiltonian parameters not only leads to a validation of our element selective transition metal L edge XMCD spin moments at a magnetic field of 5 T and a temperature of 5 K but also allows us to monitor an interesting effect of anisotropy and frustration of the manganese and chromium ions