Plant cell the major classes of cells and tissues of roots, stems, leaves, flowers, and reproductive structures, each of which may be composed of several cell types. Parenchyma cells are living cells that have functions ranging from storage and support to photosynthesis (mesophyll cells) and phloem loading (transfer cells). Apart from the xylem and phloem in their vascular bundles, leaves are composed mainly of parenchyma cells. Some parenchyma cells, as in the epidermis, are specialized for light penetration and focusing or regulation of gas exchange, but others are among the least specialized cells in plant tissue, and may remain totipotent, capable of
Tobacco BY-2 cells Tobacco BY-2 cells Tobacco BY-2 cells is a cell line of plant cells, which was established from a callus induced on a seedling of "Nicotiana tabacum cv. BY-2" (cultivar Bright Yellow - 2 of the tobacco plant). Tobacco BY-2 cells are nongreen, fast growing plant cells which can multiply their numbers up to 100-fold within one week in adequate culture medium and good culture conditions. This cultivar of tobacco is kept as a cell culture and more specifically as cell suspension culture (a specialized population of cells growing in liquid medium, they are raised by scientists in order to study