Hydration regulation in Cupressus pollen
A hemispheric outgrowth external to the exine has been observed on Cupressus pollen grains before hydration, rupture and exine opening. Danti et al. confirm the presence of this temporary structure over the pore of taxoid-type pollen grains in Cupressus sempervirens and C. glabra and study its structure. It is layered and consists of polysaccharides and proteins, with the latter confined to its inner part. Its presence seems to regulate the entrance of water into the grains at the beginning of pollen hydration.
