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

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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

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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