Pollen are the tectum and the foot layer, which is just above the intine. The tectum and foot layer are separated by a region called the columella, which is composed of strengthening rods. The outer wall is constructed with a resistant biopolymer called sporopollenin. Pollen apertures are regions of the pollen wall that may involve exine thinning or a significant reduction in exine thickness. They allow shrinking and swelling of the grain caused by changes in moisture content. Elongated apertures or furrows in the pollen grain are called colpi (singular: colpus) or sulci (singular: sulcus). Apertures that are more circular are
Compartmentalization of decay in trees compartmentalization. According to CODIT, when a tree is wounded cells undergo changes to form "walls" around the wound, slowing or preventing the spread of disease and decay to the rest of the tree. By increasing understanding of how trees respond to decay, CODIT has had many applications. For example, arborists are frequently called upon to analyze the danger posed to people or property by a damaged or decaying tree. By knowing how decay is likely to spread, such hazard tree analyses may be more accurate, thereby preventing unnecessary tree removal, property damage, or injury. For another example, in the production