Pollen (microsporocyte, pollen mother cell or meiocyte), after meiotic division. After the formation of the four microspores, which are contained by callose walls, the development of the pollen grain walls begins. The callose wall is broken down by an enzyme called callase and the freed pollen grains grow in size and develop their characteristic shape and form a resistant outer wall called the exine and an inner wall called the intine. The exine is what is preserved in the fossil record. Two basic types of microsporogenesis are recognised, simultaneous and successive. In simultaneous microsporogenesis meiotic steps I and II are completed
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