Radial Spaces Research Articles

Radial Turgor and Osmotic Pressure Profiles in Intact and Excised Roots of Aster tripolium : Pressure Probe Measurements and Nuclear Magnetic Resonance-Imaging Analysis

High-resolution nuclear magnetic resonance images (using very short spin-echo times of 3.8 milliseconds) of cross-sections of excised roots of the halophyte Aster tripolium showed radial cell strands separated by air-filled spaces. Radial insertion of the pressure probe (along the cell strands) into roots of intact plants revealed a marked increase of the turgor pressure from the outermost to the sixth cortical layer (from about 0.1-0.6 megapascals). Corresponding measurements of intracellular osmotic pressure in individual cortical cells (by means of a nanoliter osmometer) showed an osmotic pressure gradient of equal magnitude to the turgor pressure. Neither gradient changed significantly when the plants were grown in, or exposed for 1 hour to, media of high salinity. Differences were recorded in the ability of salts and nonelectrolytes to penetrate the apoplast in the root. The reflection coefficients of the cortical cells were approximately 1 for all the solutes tested. Excision of the root from the stem resulted in a collapse of the turgor and osmotic pressure gradients. After about 15 to 30 minutes, the turgor pressure throughout the cortex attained an intermediate (quasistationary) level of about 0.3 megapascals. This value agreed well with the osmotic value deduced from plasmolysis experiments on excised root segments. These and other data provided conclusions about the driving forces for water and solute transport in the roots and about the function of the air-filled radial spaces in water transport. They also showed that excised roots may be artifactual systems.

On compact embeddings of radial sobolev spaces and their applications

(1992). On compact embeddings of radial sobolev spaces and their applications. Communications in Partial Differential Equations: Vol. 17, No. 5-6, pp. 941-952.

Fracture Properties of an Anisotropic Biological Cellular Material - Apple Flesh

AbstractThe texture of apple flesh is important in assessing its eating qualities. The texture in turn is related to the structure of the parenchyma. The parenchyma cells of the fruit are arranged in radial quasi-columnar form with radial spaces in between. This anisotropy has a marked effect on the fracture properties such that it is much easier to drive a crack between the columns (radially) than to drive it across them (tangentially). The fracture tests used were simple crack-opening tests under tension or using a wedge. This difference was also detected by a taste panel. The radial spaces ease the passage of cracks travelling along them, and act as crack stoppers for cracks travelling at right angles to them. They also allow the cells to deform more in one orientation more giving the structure ductility and making the apple tougher in that orientation. It is possible to increase this effect by controlled damage such as slow freezing which causes the intercellular spaces to expand increasing the crack-stopping mechanisms and increasing the ductility, therefore increasing the fracture toughness. Toughness first increases, then decreases with increasing damage. This effect can be mimicked with brittle paper: fracture toughness of tracing paper initially increases if holes are punched randomly in it.

Relationship between density and stiffness of apple flesh

AbstractThe parenchyma of a number of varieties of apple was tested in torsion. It is necessary to use small samples (cylinders 10 mm long × 5 mm diameter) orientated to take account of the radial air spaces. Over a range of nine varieties of apple, the torsional stiffness (0.5 to 7 MPa) is largely dependent on the average density (0.6 to 0.9 g cc−1) both within and between varieties. At a given density, the outer parenchyma is stiffer than the inner. As the apple matures, density and stiffness reduce and their mutual dependence is also less. A model is presented which can convert density (or volume fraction) of packed cells into the degree of mutual cellular contact. The calculated degree of contact (never greater than 0.4 of the wall area of a cell) correlates well with stiffness, though the nature of the correlation varies with the variety of apple and its maturity. The anisotropy and density/stiffness relationship must be considered in any mechanical (and presumably, therefore, organoleptic) testing of apples.

Further investigation on the mode of entry of human rotavirus into cells.

Entry of the KUN strain of human rotavirus into MA 104 cells was studied by electron microscopy. Double-shelled rotavirus particles attached to the cell membrane, and in the presence of trypsin their nucleic acids were expelled from the virus core into the cytoplasm through radial spaces between the capsomeres and the cell membrane pores formed after their attachment. This mechanism was considered to be analogous to those of phages.