Arsenic contamination of rice is widespread, but the rhizosphere processes influencing arsenic attenuation remain unresolved. In particular, the formation of Fe plaque around rice roots is thought to be an important barrier to As uptake, but the relative importance of this mechanism is not well characterized. Here we elucidate the colocalization of As species and Fe on rice roots with variable ...

In the unicellular green algae Chlamydomonas reinhardtii, high-affinity uptake of iron (Fe) requires an Fe(3+)-chelate reductase and an Fe transporter. Neither of these proteins nor their corresponding genes have been isolated. We previously identified, by analysis of differentially expressed plasma membrane proteins, an approximately 150-kD protein whose synthesis was induced under conditions ...

It has been hypothesized that nitrate (NO(3)(-)) nutrition might induce iron (Fe) deficiency chlorosis by inactivation of Fe in the leaf apoplast (H.U. Kosegarten, B. Hoffmann, K. Mengel [1999] Plant Physiol 121: 1069-1079). To test this hypothesis, sunflower (Helianthus annuus L. cv Farnkasol) plants were grown in nutrient solutions supplied with various nitrogen (N) forms (NO(3)(-), NH(4)(+) ...

Trichodesmium provides new nitrogen (N) to marine surface waters via N2 fixation, a process that requires a substantial amount of iron (Fe). Organic ligands in seawater that bind Fe could either increase or reduce the bioavailability of Fe. Electrochemical techniques indicate that these naturally occurring ligands have Fe-binding constants similar to those of siderophores and porphyrins, sugges...

This study investigated the effects of strenuous exercise on transferrin (Tf)-receptor (TfR) expression and Tf-bound iron (Tf-Fe) uptake in erythroblasts of rat bone marrow. Female Sprague-Dawley rats were randomly assigned to either an exercise or sedentary group. Animals in the exercise group swam 2 h/day for 3 mo in a glass swimming basin. Both groups received the same amount of handling. At...

to evaluate the relationships between soil inorganic phosphorus p (pi) fractions, the soil p test and plant parameters such as plant p uptake, dry matter yield, tissue p concentra-tion and relative yield, glasshouse experiments and chemical analyses were conducted on 13 calcareous soils from six agricultural and seven adjacent bushland (virgin soil) sites. four rates of p (0, 15, 30, 60 mg/kg s...

The effects of added Si and Fe on the rate of silicic acid uptake were examined during two cruises to the equatorial Pacific upwelling zone between 110uW and 140uW. Maximum uptake rates of Si (Vmax) were highly consistent with a mean of 0.026 6 0.007 h21(n 5 29), implying maximum diatom growth rates of ,0.6 d21. Halfsaturation constants for Si uptake (KS) also showed little variance, averaging ...

The acidification caused by the dissolution of anthropogenic carbon dioxide (CO2) in the ocean changes the chemistry and hence the bioavailability of iron (Fe), a limiting nutrient in large oceanic regions. Here, we show that the bioavailability of dissolved Fe may decline because of ocean acidification. Acidification of media containing various Fe compounds decreases the Fe uptake rate of diat...