Structure of Woody Plants
Vascular Cambium
vascular cambium - one of the meristems that produce secondary plant body.
fascicular cambium - cells located between the metaxylem and metaphloem, in woody plants these cells do not stop dividing
interfascicular cambium - parenchyma cells between fascicular cambium
fusiform initials
fusiform initials - one of 2 types of cells in vascular meristem; long and tapered
periclinal wall - parallel wall formed when fusiform undergo longitudinal cell division
anticlinal walls - perpendicular walls formed during longitudinal division
ray initials
ray initials - similar to fusiform initials except that they are short and more or less cuboidal
mostly produce short cells, storage parenchyma, in gymniosperms, albuminous cells
Secondary Xylem
secondary xylem - all cells formed to the interior of the vascular cambium, aka wood
Hardwoods - trees with very strong wood consisting of a lot of fibers
softwoods - trees with wood containing less fiber, making them softer
rays - parenchyma cells arranged as uniseriate, biseriate, or multiseriate masses
ray tracheids - horizontal, rectangular cells that look somewhat like parenchyma cells but have secondary walls, circular bordered pits, and protoplasts that degenerate once secondary wall is complete.
Growth Rings
early wood - (spring wood) first wood formed, high proportion of wide vessels
Late wood - (summer wood) thicker wood with less vessels
annual ring (growth ring) - the ring formed by early wood and late wood together
diffuse porous - wood with of a growth ring with vessels located throughout
ring porous - species with vessels restricted mainly to early wood
heartwood - dark wood in a tree
sapwood - lighter moister outer region of tree
Secondary Phloem
secondary phloem - formed from vascular cambium. has axial and radial systems
axial system - responsible for conduction up and down the stem or root
Outer Bark
cork and cork cambium
cork cambium (phellogen) - similar to the activation of parenchyma cells during the interfascicular vascular cambium, but occurring in secondary phloem.
cork cell (phellem) - outer cells of cork cambium
phelloderm - inner cells of cork cambium that mature (rare 1-2)
periderm - the cork cambium, layers of cork cells, and the phelloderm combined
outer bark - all tissues outside the innermost cork cambium
innerbark - all secondary phloem between the vascular cambium and the innermost cork cambium
lenticels - intercellular spaces that penetrate the cork layer, creating diffusion pathways