Semi-volatile organic compounds at the leaf/atmosphere interface: numerical simulation of dispersal and foliar uptake

Abstract

The behaviour of (semi-)volatile organic compounds at the interface between the leaf surface and the atmosphere was investigated by finite-element numerical simulation. Three model systems with increasing complexity and closeness to the real situation were studied. The three-dimensional model systems were translated into appropriate grid structures and diffusive and convective transport in the leaf/atmosphere interface was simulated. Fenpropimorph (cis-4-[3-(4-tert-butylphenyl)-2-methylpropyl]-2,6-dimethylmorpholine) and Kresoxim-methyl ((E)-methyl-2-methoxyimino-2-[2-(o-tolyloxy-methyl)phenyl] acetate) were used as model compounds. The simulation showed that under still and convective conditions the vapours emitted by a point source rapidly form stationary envelopes around the leaves. Vapour concentrations within these unstirred layers depend on the vapour pressure of the compound in question and on its affinity to the lipoid surface layers of the leaf (cuticular waxes, cutin). The rules deduced from the numerical simulation of organic vapour behaviour in the leaf/atmosphere interface are expected to help in assessing how (semi-)volatile plant products (e.g. hormones, pheromones, secondary metabolites) and xenobiotics (e.g. pesticides, pollutants) perform on plant surfaces.

Birch (Betula spp.) leaves adsorb and re‐release volatiles specific to neighbouring plants – a mechanism for associational herbivore resistance?

“…Leaf properties such as the thickness of the cuticular wax layer, as well as volatility and polarity (Riederer et al, 2002) of the volatile compound in question, and environmental conditions such as wind, light, humidity and temperature (Niinemets et al, 2004) affect the adsorption of volatiles from surrounding air to leaves. The volatility and lipophilicity of plant-emitted volatile compounds vary substantially (Noe et al, 2006(Noe et al, , 2008.…”

Organic Pollutant Penetration through Fruit Polyester Skin: A Modified Three-compartment Diffusion Model

“…Thus, the barrier function of the cuticles seems to be very limited. Riederer and his colleagues 21 proposed a two-compartment sorption model in which the cuticle was divided into wax and cuticular matrix and was believed to have no significant effect on the sorption capacities after dewaxing. The fundamental principles of the two models were compared, and an obvious contradiction emerged in terms of the contributions of the cuticle components to accumulation.…”

A Framework to Predict Uptake of Trace Organic Compounds by Plants

“…Kumar et al (2005a) showed that a macrolide antibiotic (tylosin, MW = 916) was not taken up by plants, compared with tetracycline‐class antibiotics (MW <500) that were taken up by plants. A similar relationship exists between skin permeability and the MW of pharmaceutical compounds, i.e., the higher the MW the lower the permeability (Potts and Guy, 1995; Sartorelli et al, 1998). In addition to octanol–water partitioning, Bunge and Cleek (1995) also highlighted the importance of MW in controlling the permeability of the stratum corneum and the epidermis in human skin.…”

“…Similar to solute uptake by plants, human drug absorption is also a passive diffusion mechanism, and thus both the physicochemical properties of the drug and the permeation barrier of membranes are the major rate determinants for its transport (Potts and Guy, 1995). In general, the structure of plant and mammalian cell membranes is similar and composed of a lipid bilayer and shown in Fig.…”

“…This evaluation does not cover foliar uptake; however, TOrCs that may come into contact with plant leaves through wet or dry deposition, or direct foliar applications may permeate into the inner volume element of the leaf cuticle and can pass through the epidermis into the leaf interior (Collins et al, 2006). Because the permeability of plant cuticles to TOrCs in solution has been found to be dependent on logK ow and molecular volume (Riederer et al, 2002), this framework may be applicable to foliar uptake of TOrCs also. The uptake of TOrCs in aboveground plant parts was considered only for developing this framework.…”