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A sonic anemometer-thermometer was used to measure turbulent lluxes of momentum and sensible heat and related turbulence statistics just above plant canopies in unstable conditions. The stability dependence of transport processes is presented, using observational data in a wide range of instability. The analysis of joint probability distributions of w -u, w -7', w -WU, and w -wT confirmed that just above plant canopies, downdrafts were remarkably efficient for vertical transport of momentum and scalar quantities in near neutral conditions. Furthermore, it was shown that updra.!?s became more efficient than downdrafts for vertical transport, especially of scalar quantities, in very unstable conditions.

Suspension‐cultured carrot (Daucus carota L. cv. Kintoki) cells were grown in calcium (Ca2+)‐deficient and normal liquid media. Cell growth was limited by the Ca2+ deficiency. Similar amounts of pectic fractions were extracted from the walls of control and Ca2+‐deprived cells, but the fractions from the walls of Ca2+‐deprived cells showed a substantial decrease in galacturonic acid content. However, after 15 days of culture, Ca2+‐deprived cells released galacturonic acid‐rich extracellular polysaccharides at twice the rate of control cells. The polysaccharides consisted of a mixture of several polymers containing predominantly arabinose, galactose and galacturonic acid. Ca2+‐deprived cells also secreted three times more extracellular proteins, containing many glycan‐hydrolytic enzymes, into the medium than did normal cells. SDS‐PAGE analysis revealed several distinct changes in the polypeptide pattern in the medium of control and Ca2+‐deprived cells. Activities of α‐galactosidase, β‐glucosidase and exo‐polygalacturonase increased considerably during Ca2+ deficiency, whereas α‐ l‐arabinofuranosidase and β‐galactosidase activities were much reduced.

Downward fluxes of turbulent kinetic energy have been frequently observed in the air layer just above plant canopies. In order to investigate the mechanism for such downward transport, analysis of observational data is attempted. Height-dependency of turbulent kinetic energy flux and turbulence statistics including higher order moments is represented as a function of a non-dimensional height z/H, where z is an observational height and H an average height of plant canopies. Downward fluxes and non-Gaussianity of wind velocity fluctuations are predominant just above plant canopies and decrease with increasing height. The downward flux is closely related to the high intensity of turbulence and the non-Gaussianity of wind velocity fluctuations, especially with a positive skewness in the longitudinal wind and a negative skewness in the vertical wind. The analysis method of conditional sampling and averaging is applied to the present observations. The results show that the predominance of the intermittent inrush phase over the intermittent ejection phase leads to the above-mentioned non-Gaussianity. Finally, a simple explanation is given in order to interpret the turbulent flow structure in the air layer near the plant canopies, which is associated with the downward energy transport process.