Hydrological assessment for wetland conservation at Wicken Fen

Wicken Fen in East Anglia, UK is a unique habitat and a wetland of international importance. A comparison of water table measurements made between 1928 and 1931 with contemporary observations indicates that summer minimum water table elevations are between 0.20 m and 0.45 m lower than in the past. The disparity cannot be attributed to differences in rainfall. There are a number of reasons why the Fen may be 'drying', but it was not possible to identify a single dominant cause. A simple water balance model that simulates groundwater levels in different areas of the Fen has been developed. This indicates that although locally important, in most years flows of water from ditches into the Fen comprise less than 10% of total summer inputs and in wet summers there is a net outflow from the Fen into the ditches. Based on an assessment of the water requirements of desired vegetation communities, a more active water management strategy than is presently implemented is proposed. This paper highlights how a better quantitative understanding of ecosystem functioning and the impact of human interventions are a pre-requisite for the development and implementation of sustainable wetland conservation strategies.     

Developmental and regional quantitation of glycerophosphorylcholine phosphodiesterase activities in rat brain

The activity of glycerophosphorylcholine cholinephosphodiesterase was quantified in the diencephalon, mesencephalon, cerebral hemispheres, olfactory bulb and cerebellum postnatally for P5 until P70 of rat brain. The initially low activities gradually increase to adult levels by P30. The patterns of regional development are reminescent of those previously described for choline acetyltransferase activity. It is suggested that these may be functionally linked in neuronal cells. The activity of glycerophosphorylcholine phosphocholine phosphodiesterase was also determined and found to be similar although only one half as active as the enzyme liberating choline. The present experiments show that both the GPC phosphocholine phosphodiesterase and the GPC choline phosphodiesterase are regionally and developmentally regulated in rat brain.     

An unusual phosphodiesterase activity towardsP-nitrophenylphosphorylcholine present in rat brain membranes

A phosphodiesterase activity present in rat brain membranes has been examined utilizing p-nitrophenylphosphorylcholine as the substrate. This enzyme activity has a pH optimum of 8.5, is stimulated by a variety of free fatty acids, requires either Zn⁺² or Ca⁺² and is relatively stable to heating at 75°C for 7.5 minutes. These properties appear to distinguish this particular activity from those previously reported for alkaline phosphatase, nonspecific phosphodiesterase, phosphodiesterases I and II, lecithinase, and sphingomyelinase.     

Deposition of Erysiphe graminis Conidia on a Barley Crop II. Consequences for Spore Dispersal

Measured deposition rates of Erysiphe graminis conidia are often greater than those calculated from spore fall speed, v^s, and mean wind speed. The predictions of two gradient transfer models of spore dispersal in crops, in which sedimentation and inertial impaction were calculated from v^s and local wind speed or estimated from measured values (Mc Cartney and Bainbridge 1987), were compared. Comparisons of the models suggest that deposition rates close to the source may be underestimated by a factor of two and deposition half distances may be doubled when deposition is calculated conventionally. The results illustrate the importance of accurately describing deposition processes when constructing spore dispersal models.