Somatic embryogenesis from immature seeds of yellow poplar
Liriodendron tulipifera L. (yellow poplar, tulip poplar, tuliptree) is one of the most distinctive and valuable hardwoods in the eastern US. Large volumes of yellow poplar wood are used for furniture, plywood, corestock, millwork, siding, and other light construction lumber. Traditionally, woody plants, in general, and forest trees, in particular, have been challenging subjects for in vitro propagation compared to agronomic and other herbaceous species, due to a number of properties intrinsic to their biology. This chapter illustrates some of these problems and how they can be handled. In addition, yellow poplar embryogenic cultures have the rare property among forest tree embryogenic cultures of proliferating as proembryogenic masses (PEMs). Like many embryogenic systems yellow poplar PEMs are maintained in a proliferative state by some minimal level of exogenous auxin, and once the concentration of auxin is reduced below this level or removed entirely, clusters of cells on the surface of the PEMs are "released" to develop into somatic embryos.