Diffusion in plant cuticles as affected by temperature and size of organic solutes: similarity and diversity among species

Abstract

Ptant, Cell and Environment (^997) 20,[982][983][984][985][986][987][988][989][990][991][992][993][994],viv In this range, solute mobilities increased up to 1000-fold, which corresponds to temperature coefficients Qio of 3 (IAA in P. armeniaca) to 14 (cholesterol in fi. hetix). For most species, Arrhenius graphs showed good linearity up to 40 °C, and up to 78 °C for some species, while for others activation energies declined with increasing temperature. However, no distinct phase transitions caused by sudden structural changes in the CM were observed. In three species we examined whether heating to 70 °C changed solute mobility irreversibly by comparing Arrhenius graphs for two successive experiments with the same CM. The two graphs were very similar for P, taurocerasus, while mobilities in the second graph were somewhat reduced for C. aurantium and greatly increased (at 25 and 35 °C) for H. helix. This indicates rearrangements of at least some wax constituents when heated to high temperatures. The activation energies of diffusion (/i|,) ranged from 75 to 189 k. F moP' depending on .species and .solute size. Size selectivity and variability between cuticles decreased witb increasing temperature, and this is caused by differences in li|,. An excellent correlation between the pre-exponential factor of the Arrhenius equation and /i,, was observed, which is evidence that organic solutes differing greatly in molecular size (130-349 cm' moP') and cuticle/water partition coefficient (25-10*") use similar diffusion paths in the CM of all 12 plant species tested. Diffusion occurs in regions with identical phy.sicochemical properties and differs only in magnitude.

Polydisperse ethoxylated fatty alcohol surfactants as accelerators of cuticular penetration. 2: Separation of effects on driving force and mobility and reversibility of surfactant action

“…17 The temperature dependence of bifenox mobility in CM of Stephanotis¯oribunda decreased drastically in the presence of the very effective accelerator tributylphosphate, as indicated by the decrease in slope (Fig 6A). At 15°C the mobility of bifenox was about 55-fold (arithmetic mean) higher in the presence of tributylphosphate.…”

“…This is possible since the effect of increasing temperature up to 35°C on solute mobility in Citrus and Pyrus CM is reversible. 17 In one experiment (Citrus/Bifenox), desorption with surfactant (C12E6) was started at 35°C followed by 25 and 15°C using the same CM. In this case and in experiments with TBP two different sets of CM were used as control (desorption with PLS) and treatment (desorption with C8E4 or C12E6).…”

“…38 The same effect was found for several species when the temperature was increased. 17 Our data for the mobility of WL 110547 in Citrus cuticles enables paired observations (the same CM were used) for both the effects of increasing temperature and of sorption of GP C-050 in CM on variability and in addition, these data can also be compared with MX with or without GP C-050. The data in Fig 7 show that both treatments successively reduced coef®cients of variation from about 92% without GP C-050 at 15°C to 26% with the surfactant at 35°C in a systematic manner.…”

Effect of the interaction between fungicide application time and rainfall simulation interval on Asian Soybean Rust control effectiveness

“…In the absorption process, the temperature is usually expressed as the diffusion activation energy. The diffusion activation energies are interpreted as the energy needed to produce free volume in a sufficiently large polymer to accommodate the diffusion molecule (BAUR et al, 1997). Therefore, temperature is an important factor because it affects the chemical reactions and physical properties of cells, organs and the whole plant (GRUDA, 2005).…”

Fate of Pesticide Residues on Raw Agricultural Crops after Postharvest Storage and Food Processing to Edible Portions

“…The systemic insecticide dimethoate with water solubility equal to 23300mg/L and quinalphos that exhibits systemic action and its water solubility is 18 mg/L, were not reduced during the washing of olives . Furthermore in many studies washing was not related with the water solubility of the pesticide residue but with Kow such reinforcing the view that partition coefficients between cuticle and washing water correlate well with pesticides Kow (Baur et al, 1997). In consequence, the use of an appropriate detergent that has the ability to solubilise waxes may dissipate the residue present in the fruit's epicuticular wax layer (Angioni et al, 2004).…”