Growth and phosphorus inflows of Trifolium repens L. with a range of indigenous vesicular-arbuscular mycorrhizal infection levels under field conditions.

Since vesicular-arbuscular mycorrhizas (VAM) are believed to play a fundamental role in phosphorus (P) uptake for many plant species, an experiment was performed to test the hypothesis that rates of P uptake per unit root length (P inflow) should be proportional to the extent of infection. Plants of Trifolium repens L. were grown in pots containing different proportions of sterile and non-sterile soil in radially arranged rooting compartments and transplanted with a consequent range of mycorrhizal infection into the field at a hay meadow of moderate P fertility. Even though plant growth in the field was exponential, plants with greater proportions of their root systems infected did not have higher P inflows or dry matter production. For much of the experiment P inflows were below the levels at which it would be necessary to invoke mycorrhizally assisted uptake. It is suggested that for Trifolium repens, even while the plant is growing actively in the field, VAM do not always function mutualistically.

A new method which gives an objective measure of colonization of roots by vesicular-arbuscular mycorrhizal fungi.

Previously described methods to quantify the proportion of root length colonized by vesicular-arbuscular (VA) mycorrhizal fungi are reviewed. It is argued that these methods give observer-dependent measures of colonization which cannot be used to compare, quantitatively, roots examined by different researchers. A modified method is described here to estimate VA mycorrhizal colonization on an objective scale of measurement, involving inspection of intersections between the microscope eyepiece crosshair and roots at magnification × 200; it is referred to as the magnified intersections method. Whether the vertical eyepiece crosshair crosses one or more arbuscules is noted at each intersection. The estimate of colonization is the proportion of root length containing arbuscules, called the arbuscular colonization (AC). The magnified intersections method also determines the proportion of root length containing vesicles, the vesicular colonization (VC), and the proportion of root length containing hyphae, the hyphal colonization (HC). However, VC and HC should be interpreted with caution because vesicles and hyphae, unlike arbuscules, can be produced in roots by non-mycorrhizal fungi.

Reduction in erythrocyte complement receptor 1 (CR1, CD35) and decay accelerating factor (DAF, CD55) during normal pregnancy.

RBC-membrane CR1 has been assayed in pregnancy and at 48 h postpartum. It has been shown that RBC CR1 is reduced as pregnancy progress, reaching a nadir in the third trimester and that it returns to levels approaching normal within 48 h postpartum. Further, there is a reduced expression of RBC decay accelerating factor (DAF) during pregnancy but no change in expression of RBC CD59. We suggest that the reduction in RBC CR1 and DAF may reflect increased levels of circulating immune complexes and consequent increased complement activation in pregnancy.