Pollen tube by recognition and hydration of the pollen that allows for germination of the tube and ultimate growth. In the pollen grain, the generative cell gives rise to the sperm, whereas the vegetative cells have a tube cell that grows the pollen tube. There is competition in this step as many pollen grains may compete to reach the egg. The stigma plays a role in guiding the sperm to a receptive ovule, in the case of many ovules. Only compatible pollen grains are allowed to grow as determined by signaling with the stigma. Some plants have mechanisms in place to prevent
Coil coating Coil coating Coil coating is the continuous and highly automated industrial process for efficiently coating coils of metal. Because the metal is treated before it is cut and formed, the entire surface is cleaned and treated, providing tightly-bonded finishes. (Formed parts can have many holes, recessed areas, valleys, and hidden areas that make it difficult to clean and uniformly paint.) Coil coated metal (often called prepainted metal) is often considered more durable and more corrosion-resistant than most post painted metal. Annually, 4.5 million tons of coil coated steel and aluminum are produced and shipped in North America, and 5 million