Aperture (botany) pollen grain. Aperture (botany) Apertures are areas on the walls of a pollen grain, where the wall is thinner and/or softer. For germination it is necessary that the pollen tube can reach out from the inside of the pollen grain and transport the sperm to the egg deep down in the pistil. The apertures are the places where the pollen tube is able to break through the (elsewhere very tough) pollen wall. The number and configuration of apertures are often very exactly characteristic of different groups of plants. The biggest class of plant species, the Eudicots, usually have three apertures
Chemical Agent Resistant Coating combined to produce a cured paint film. The materials were designed for resistance to windblown dust, sand and chemical agents. An improvement to solvent-borne polyurethanes, MCU materials offered both lower levels of volatile organic compounds and elimination of hazardous air pollutants. 2) Two-component, high-performance, water-reducible polyurethane: Waterbased CARCs, most commonly used by the military, were composed of water-reducible polyurethane resins, marking the first time a water-based two-component CARC was commercially available. This formulation eliminated several solvents, including methyl isobutyl ketone, toluene and xylene. Citation Chemical Agent Resistant Coating Chemical Agent Resistant Coating is a paint commonly applied to military vehicles