Laboratory studies on dry deposition of submicron-size particles on coniferous foliage

Boundary-Layer Meteorol

1984

Self Cite

Convective deposition of submicron-size aerosol to porous surface vegetation was studied by electrochemical simulation, under Reynolds and Schmidt similarity, to a rectangular array of closely-packed lichen and artificial wire roughness layers. Results, showing an approximate tenfold increase in deposition velocity over that of a flat plate placed at the same position, were compared with predictions made on the basis of various rough-surface transfer models, including those based on statistical eddy renewal, as well as with numerical solutions of the diffusion equation in statistically-renewed surface cavities.Most analytical models could be made to fit the observed data, at least for a limited range of flow velocities, but poorly known and poorly defined parameters limit their usefulness for predictive purposes; and their validity across a large variation in molecular diffusivity (or Schmidt number SC) is generally not assured. Numerical models also depend on poorly substantiated physical assumptions but the effect of such assumptions on transfer can be calculated for a wider range of conditions than those permitting an analytical solution. This allows more direct feedback between model assumptions and calculated or observed transfer.Numerically calculated values for deposition velocity in air for SC from 0.7 to 7000 and flow velocities from 0.2 to 5 m s-' are presented for different model assumptions, with values ranging from ~0.01 to >lcms-I.

Section: Experimental Methodsmentioning

confidence: 99%

Observations on the use of analytical and numerical models for the description of transfer to porous surface vegetation such as lichen

Boundary-Layer Meteorol

1984

Self Cite

“…Figure Test leaf sections were inserted as cathodes into the 0.3 X 0.3 m measuring section of the electrolyte-filled, variable speed, closed circuit tunnel used for previous simulations of leaf transfer (e.g. Schuepp, 1972Schuepp, , 1982Schuepp, , 1984. The dimension of the measuring section and total volume (300 dm^) have been enlarged compared to previous studies.…”

Section: Tl 20mentioning

confidence: 99%

“…The methodology was initially developed for engineering applications (Lin cl al, 1951;Tobias, Eisenberg & Wilkc, 1952). More recently, it has been used for the investigation of transfer properties of leaves, coniferous shoots and lichens (Schuepp, 1972(Schuepp, , 1982(Schuepp, , 1984. Modifications of the technique were necessary to preserve the detailed structure of the leaves used in the present study.…”

Section: Introductionmentioning

confidence: 99%

Boundary layer properties of highly dissected leaves: an investigation using an electrochemical fluid tunnel

Gurevitch

Plant Cell & Environment

1990

A method for modelling heat and mass ttansfer by diffusion-controlled electrode reactions in a fluid tunnel is described. In this procedure, a nickelplated leaf functions as a test electrode, and the convective transfer of ions to the leaf cathode in an electrolyte-filled flow tunnel is measured as a function of flow rate. The method permits the simulation of water vapour and heat transfer, and in particular, the determination of boundary layer conductances, by analogy with observed ion transfer. The approach is applicable to tnany problems in modelling heat and mass transfer between leaves and their surroundings, and is especially useful in examining the properties of leaves in which surface characteristics or overall shape are complex. Using this method, the properties of the highly dissected leaves of Achilica lanulosa with regard to forced convection were investigated. The leaves showed high transfer conductances, indicating that the effective unit of heat transfer was probably the individual leaf subelements. Conductances tended to be greater and effective characteristic dimensions smaller for the larger, more open leaves of a lower altitude population in contrast with leaves from high altitude plants. While the results provide insight into the properties of these cotnplex leaf shapes, difficulties in interpreting the findings are discussed, and a number of exploratory approaches are suggested for data analysis and interpretation.

On the ecological and evolutionary significance OF BRANCH AND LEAF MORPHOLOGY IN aquaticSphagnum(Sphagnaceae)

Rice

1995

American J of Botany

In aquatic environments difiusivity is low and CO2availability can limit plant growth. The hypothesis that natural selection has favored morphological features that reduce resistance to diffusion of CO2was tested using three phylogenetically independent species pairs from the genusSphagnum(S. macrophyllumand 5.strictum;S. portoricenseandS. papillosum;andS. trinitenseand S.recurvum). The aquatic (former) and the nonaquatic (latter) species were grown submerged and emerged in a common garden and used for studies of form and function. Aquatic taxa all had similar morphological features that included larger, thinner branch leaves arranged at lower densities and photosynthetic cells more greatly exposed at the leaf surface. The relationship between observed branch and leaf morphology and boundary layer resistance in the S.trinitense–S. recurvumspecies pair was assessed by measuring diffusion and convection of ions onto nickel‐plated models in a variable‐speed electrochemical fluid tunnel. For all flow speeds and orientations, the aquaticS. trinitensemodel had thinner boundary layers than the nonaquaticS. recurvummodel. Analysis of stable isotopes of carbon from the growth experiment corroborated results from the fluid‐tunnel experiments. The aquatic taxa all had lower δ13C values when grown submerged compared to their nonaquatic pair with the exception of the nonaquaticS. strictum, which was removed due to low growth rates. These results indicate that aquatic species did experience lower overall resistance to CO2uptake than nonaquatic taxa. Our observations suggest that aquatic habitats do select for morphological features that lower resistance to gas exchange.