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Structure of Woody Plants (Wood ( Secondary Xylem) New-14 (Growth rings…
Structure of Woody Plants
Wood ( Secondary Xylem)
Types of Wood cells
Ray parenchyma cells
Upright cells
Procumbent cells
It contains tracheids, vessel elements, fibers, sclereids, and parenchyma.
Axial system ( derived from the fusiform initials
Radial system ( develops from the ray initials )
Growth rings
Early wood , is the first wood formed.
Late wood is produced when cuticle is thickened, transpiration is less, and large numbers of newly formed vessels are conducting rapidly.
Annual ring forms together with early and late wood making 1 year's growth.
Diffuse porous ( It has vessels located throughout it).
Ring porous ( species with vessels restricted mainly to early wood)
Heart wood ( It is the dark wood)
Sapwood, has moister and the lighter outer region.
Reaction wood ( Growth rings are eccentric, special gelatinous fibers )
Bark ( Seondary Phloem and Cork)
Vascular Cambium
Initiation of the Vascular Cambium
It produces the secondary plant body.
Fascicular Cambium
Interfascicular cambium ( it connects with fascicular cambia).
Types of Cells
Fusiform initials
These are long tapered cells, it produces two elongate cells.
Ray initials
These are short and more or less cuboidal, They undergo periclinal cell divisions, with one of the daughters remaining a cambial ray initial and the other differentiating into either xylem parenchyma ( inner) or phloem parenchyma ( outer)
Arrangement of Cambial cells
Ray initials are typically grouped together in short vertical rows, Fusiform initials may occur in horizontal rows.
Secondary Phloem ( formed from the vascular cambium)
Outer Bark
Cork and the Cork cambium
Cork cambium is also called phellogen, its cells are like ray initials.
The inner cell remains cork cambium after division whereas the outer cell differentiates into a cork cell also known as Phellem cell.
Phelloderm ( A layer of Parenchyma cells ) is produced by the cork cambium.
The cork cambium, the layers of cork cells, and the phelloderm are known as periderm.
Anomalous secondary growth ( Alternative cambia produce secondary bodies that differ from the common type, their growth is called Anomalous secondary Growth ).
