Department of Botany, Oxford
New Phytologist (Impact Factor: 6.55). 03/1959; 58(1):1 - 4. DOI: 10.1111/j.1469-8137.1959.tb05328.x

ABSTRACT Peas were sown in sand, which was treated with varying concentrations of trichloracetic acid. The behaviour of water droplets on the leaves of peas was observed, and it was found that the angle made by the droplet on the surface falls with increasing concentration of T.C.A. No changes in leaf structure, which could account for these changes in behaviour, were revealed by ordinary light microscopy. Investigation of the sub-microscopic anatomy of the surface by the carbon replica technique under the electron microscope did reveal significant differences in the leaf surfaces. A reduction in the number and a change in form of the minute wax structures occurs with an increased concentration of T.C.A. in the soil. These changes correlate well with an increase in the wettability of the leaf surface as determined by the contact angle of water droplets.

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    ABSTRACT: Surface properties of barley straw (Hordeum vulgare) play a crucial role in some industrial applications such as sorption in oil spills and soil clean-up. In this paper, the chemical and morphological heterogeneities of barley straw leaf and stem surfaces were investigated by water and oil contact angle measurements, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The differences in the contact angles for internal versus external stem and leaf surfaces are explained by the presence of a complex wax layer at the external surface as revealed by FTIR external reflection spectroscopy. Wax composition was determined by transmission FTIR spectroscopy. SEM images confirmed the heterogeneity and complexity of the wax crystal structure of the outer stem surface. AFM measurements complemented the SEM analysis by providing additional structural details including a measure of surface roughness.
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    ABSTRACT: The uptake of trichloroacetic acid (TCA) and structural changes induced in the needles of Scots pine (Pinus sylvestris L.) seedlings were studied. Two exposure set-ups, a root route and an atmospheric route through the surfaces simulating the wet deposition of fog, were used, Both set-ups included two dose levels and corresponding control treatments. The temperature and the relative humidity in the climate chambers were adjusted to represent the conditions of June-July in a subarctic area in central Finland. The seedlings were exposed three times a week for two months. The results showed that the uptake of TCA in needles occurred both via roots and via needle surface, However, most of the TCA via the atmospheric route was absorbed on the surface of the needles. The structural responses in pine needles depended partly on the treatment method: TCA applied via the atmospheric route disintegrated the structures of the epicuticular waxes and that of the stomatal cells, which was not seen in the exposures via roots. A common feature was the decrease in size of the chloroplasts in concert with the increasing TCA concentrations inside the needles.
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    ABSTRACT: Applications of plant-derived organic essential oils (EOs) as antimicrobials for post-harvest produce operations are limited by their low water solubility. To dissolve EOs in water, microemulsions were studied using two surfactants permitted for organic production, sucrose octanoate ester (SOE) and soy lecithin that were mixed at various mass ratios before dilution with water to 40% w/w. EOs were then mixed with the surfactant solution by hand shaking. Based on visual transparency, intermediate lecithin:SOE mass ratios favoured the formation of microemulsions, e.g., up to 4.0% clove bud oil at ratios of 2:8 and 3:7, and 4.0% cinnamon bark oil and 3.0% thyme oil at ratios of 2:8 and 1:9, respectively. Microemulsions with intermediate lecithin:SOE mass ratios had a relatively low viscosity and better ability to wet fresh produce surfaces. The microemulsions established in this work may be used as washing solutions to enhance the microbial safety of organic fresh produce.
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