Dawsonia (plant) lamella – chains of small cells on the upper surface of the leaves analogous to the mesophyll cells of vascular plant leaves. They increase the surface area of cell walls available for CO uptake, while at the same time maintaining layers of moist air between lamellae, reducing water loss. Lamella margins have a surface wax layer which prevents water from flooding into the interlamellar spaces. Dawsonia (plant) Dawsonia is a genus of acrocarpous mosses. "Dawsonia", along with other members of the order Polytrichales, are taller than most mosses and have thicker leaves. Their sporophytes have conducting systems analogous to those
Transmission of plant viruses but the most common route use the vascular system, otherwise known as the xylem and phloem, and the plasmodesmata, which interconnect adjacent cells. Nevertheless, the rigidity of the cell wall of plant cells, not only poses a problem for transmission of the viruses between different plant hosts, but also acts to prevent viral transmission between cells. Consequently the virus must modify the plasmodesmata as they, themselves, are too large to fit through the small and tightly regulated plant structure. There are again a variety of mechanisms used for this, which have evolved for different viruses. The main mechanisms involve expressing