Most cells of the epidermis are relatively unspecialized.
Also includes guard cells (which contain chloroplasts) that surround pores, called stomata. Guard cells are often associated with subsidiary cells and control transpiration and carbon dioxide intake.
Trichomes—hair-like structures that fill a variety of roles
prevention of water loss
defense
Periderm replaces the epidermis in stems and roots having secondary growth.
Cork (non-living); also called phellem
Cork cambium; also called phellogen
Phelloderm (living parenchyma tissue)
Phloem-Food conducting Tissue in vascular plants
primary cells are called sieve elements (because there are clusters of pores at the ends of cells through which adjacent protoplasts are connected)
cells are living at maturity, but the nucleus and tonoplast are broken down
sieve cells have sieve areas with uniform, narrow pores
sieve-tube elements may have larger pores on some walls than on othersà sieve plate
companion cells are specialized parenchyma cells associated with sieve-tube elements; may play a role in delivery of substances to sieve-tube elements
albuminous cells—found in gymnosperms
Think of xylem and phloem as long pipes or tubes that extend from the roots all the way throughout the plant to the top leaves, even in tall trees! In order for tall trees to prevent wilting, water must be moved continuously from the roots to replace water being lost through transpiration.
cells are living at maturity, but the nucleus and tonoplast are broken down
sieve cells have sieve areas with uniform, narrow pores
sieve-tube elements may have larger pores on some walls than on othersà sieve plate
companion cells are specialized parenchyma cells associated with sieve-tube elements; may play a role in delivery of substances to sieve-tube elements
albuminous cells—found in gymnosperms
Think of xylem and phloem as long pipes or tubes that extend from the roots all the way throughout the plant to the top leaves, even in tall trees! In order for tall trees to prevent wilting, water must be moved continuously from the roots to replace water being lost through transpiration.
Xylem-Water conducting Tissue
continuous system throughout the plant, made of up tracheary elements
have secondary cell wall thickenings that may appear as rings or spirals
tracheids—elongated cells (dead at maturity); usually only type of xylem cell in most gymnosperms and seedless vascular plants
vessel elements—may be wider than tracheids; contain perforations (areas lacking in cell walls), usually on the end walls; more specialized cell type
xylem also has parenchyma associated with it, often found in rays (long strands) & called ray parenchyma
have secondary cell wall thickenings that may appear as rings or spirals
tracheids—elongated cells (dead at maturity); usually only type of xylem cell in most gymnosperms and seedless vascular plants
vessel elements—may be wider than tracheids; contain perforations (areas lacking in cell walls), usually on the end walls; more specialized cell type
xylem also has parenchyma associated with it, often found in rays (long strands) & called ray parenchyma
Plant cell and Tissue Types
Simple tissues are composed of one cell type.
A) Parenchyma:
living cells with thin cell walls
functions: storage, photosynthesis, secretion
make up the bulk of the cortex and pith of stems and roots
B) Collenchyma:
living cells with unevenly thickened cell walls
most often found beneath the epidermis
main function is support
C) Sclerenchyma:
2 cell types:
i. Fibers: long, slender cells that occur in strands or bundles. ii. Sclereids: variable in shape, but much shorter than fibers.
cells are not living at maturity
very thick cell walls
primary function is support
A) Parenchyma:
living cells with thin cell walls
functions: storage, photosynthesis, secretion
make up the bulk of the cortex and pith of stems and roots
B) Collenchyma:
living cells with unevenly thickened cell walls
most often found beneath the epidermis
main function is support
C) Sclerenchyma:
2 cell types:
i. Fibers: long, slender cells that occur in strands or bundles. ii. Sclereids: variable in shape, but much shorter than fibers.
cells are not living at maturity
very thick cell walls
primary function is support
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