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STRUCTURE OF WOODY PLANTS (SECONDARY XYLEM (TYPES OF WOOD CELLS (AXIAL…
STRUCTURE OF WOODY PLANTS
VASCULAR CAMBIUM
meristem that produce secondary plant body
FASCICULAR CAMBIUM
Cambium that develops within the vascular bundles in the stem of a plant.
INTERFASCICULAR CAMBIUM
The cambium arising between the vascular bundles in the stem of a plant
TYPES OF CELLS
FUSIFORM INITIALS
elongated tapering cells that give rise to all cells of the vertical system of the secondary phloem and xylem (secondary tracheary elements, fibres, and sieve cells and the associated companion cells) (tall, axially oriented)
RAY INITIALS
these formations of primarily parenchyma cells allow the radial transport of sap and are essential in the process of tylosis.smaller and round to angular in shape
SECONDARY XYLEM
REACTION WOOD
wood that forms in place of normal wood as a response to gravity, where the cambial cells are oriented other than vertically. It is typically found on branches and leaning stems.
HEART WOOD AND SAP WOOD
Sapwood is the living, outermost portion of a woody stem or branch, while heartwood is the dead, inner wood, which often comprises the majority of a stem’s cross-section.All wood starts as sapwood.
GROWTH RINGS
a concentric layer of wood, shell, or bone developed during an annual or other regular period of growth.
TYPES OF WOOD CELLS
AXIAL SYSTEM
derived from fusiform initials; tracheids, vessels, fibres, parenchyma are found
RADIAL SYSTEM
derived from ray initials; ray parenchyma, ray tracheids are present
SECONDARY PHLOEM
part the cambium vascular growth of a tree or woody plant. It is the food-conducting tissue and is sometimes referred to as the tree’s inner bark, which is where it is located, lies towards the outside of the cambium layer and is actually produced by the tree’s cambium.
OUTER BARK
LENTICELS AND OXYGEN DIFFUSION
rounded cells cannot fit tightly together, intercellular space penetrate the cork layer, creating a diffusion pathway for oxygen. these regions of aerenchymatous cork are lenticels.
CORK AND CORK CAMBIUM
As growth proceeds, the cork cambium forms in living cells of the epidermis, cortex, or, in some plants, phloem and produces a secondary protective tissue, the periderm
.
INITIATION OF CORK CAMBIUM
in some species arises before a twig or root, on stem it is dected by the surface color change, may arrise in number of tissues like epidermis, cortex, primary phloem or secondary phloem.
ANOMALOUS FORMS OF GROWTH
ANOMALOUS SECONDARY GROWTH
the term under which have been grouped cambial conformations, cambial products, and cambial numbers which differ from the most common “normal” condition, namely, a single cylindrical cambium that produces phloem externally and xylem internally
.
UNUSUAL PRIMARY GROWTH
palm trees have unusual primary growth because their trunks donot taper at the tip, vascular cambium never develops, true wood and secondary phloem donot occur, trunk doesnot grow radially.
