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Structure of Woody Plants (Growth Rings (Early wood (wide tracheids in…
Structure of Woody Plants
Primary tissue
Meristem derived sets of tissues- epidermis, cortex, vascular bundles, pith and leaves.
How do they respond to the bottleneck of the limited conducting capacity of the first year stem?
first year leaves die during the winter
the plant produces only as many leaves it had during the first year
Secondary tissue-
constitutes the plant's secondary body- vascular cambium and cork cambium
Important consequences:
its conducting capacity is set
needs of the leaves and roots are fulfilled
water loss is prevented in a way that it produces less leaves as compare to the Xylems conducting capacity.
Growth Rings
Early wood
wide tracheids in conifers
high proportions of wide vessels
first formed wood
Late wood
lower proportions of vessels compared to early wood
thick cuticle and less transpiration
summer wood
Annual ring
age factor
early wood
late wood
Reaction wood- forms in substitute to normal woodin response to stress
-usually the upper side of branch
-tesional wood
Types of wood cells
Secondary Xylem
wood
developed from cells which are interior to vascular cambium
all primary xylem cells present
contains fibres, tracheids,vessel elements, sclereids and parenchyma
Secondary Phloem
it is also formed from vascular cambium
It contains companion cells and sieve cells
Sapwood
Outer region
lighter in color
moister
Heartwood
inner portion
dark wood
drier
Types of cell
Fusiform Initials
Axial Xylem
Axial phloem
long tappered cells
longitudinal cell division with a periclinal wall
Ray Initials
Phloem rays
Xylem rays
Cork Cambium
Phellogen
cork cell (phellem)
cuboidal cell
inner cell remains cork cambium
layer of parenchyma
Periderm
cork cell
cork cambium
phelloderm
vascular cambium
Example: herbs
