Search

The soil water release characteristic is controlled by the soil pores and so alteration of the pore system will have an effect. We sought to examine the effects of various pore deformations in a range of arabic and grassland soils from the UK. Sieved topsoil materials were compressed to 50 or 200 kPa, or remolded to simulate shear deformation at the plastic limit. They were then subjected to matric potentials from 0 to -1500 kPa using conventional tension and pressure plate apparatus. Volume changes were monitored to assess shrinkage. Further samples in the compressed state were subjected to x-ray computed tomography scanning to nondestructively characterize the soil pore system. Increasing the compression from 50 to 200 kPa mainly affected the >30μm pores, changing a dual porous system of inter and ineraaggregate pores to one mainly dominated by intraaggregate pores, as confirmed by gravimetric water release characteristic data and the scans. Shear-deformed soils retained more water than the compressed soil and shrank more, such that they remained tension saturated at low (negative) matric potentials. We developed a function to predict the soil saturation state as a function of matric potential and porosity. This explained 28 to 63% of the variance, irrespective of the initial structural state, but up to 94% of the variation when one of the fitted parameters was allowed to vary for the different initial states. This was sufficiently systematic to suggest that a general model of the effects of soil deformation and shrinkage on the water release characteristic may be possible. [ABSTRACT FROM AUTHOR]

The mechanical properties of the axial muscles vary along the length of a fish's body. This variation in performance correlates with the expression of certain muscle proteins. Parvalbumin (PARV) is an important calcium binding protein that helps modulate intracellular calcium levels which set the size and shape of the muscle calcium transient. It therefore has a central role in determining the functional properties of the muscle. Transcript data revealed eight specific isoforms of PARV in common carp (Cyprinus carpio) skeletal muscle which we classified as α and β1-7. This study is the first to show expression of all eight skeletal muscle PARV isoforms in carp at the protein level and relate regional differences in expression to performance. All of the PARV isoforms were characterised at the protein level using 2D-PAGE and tandem mass spectrometry. Comparison of carp muscle from different regions of the fish revealed a higher level of expression of PARV isoforms β4 and β5 in the anterior region, which was accompanied by an increase in the rate of relaxation. We postulate that changes in specific PARV isoform expression are an important part of the adaptive change in muscle mechanical properties in response to varying functional demands and environmental change. [ABSTRACT FROM AUTHOR]