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Tissues and the Primary Growth Stems (Internal Organization of Stems:…
Tissues and the Primary Growth Stems
Types of Cells and Tissues
Parenchyma
thin walls, makes soft parts of plants.
chlotenchyma= p cells that mess with photosynthesis
transfer cells= p cells that mediate short distance
often die when plant matures
Collenchyma
long plants need this to stay up, works with parenchyma. this stuff needs a lot of glucose! kind of like clay.
Sclerenchyma
elastic, but unlike c they go back to how they were. s cells happen when p and c cells stop growing. very strong; work alone
conducting sclerenchyma
mechanical sclerenchyma
External Organization of Stems
nodes=where leaves are attached
internodes=region between nodes
Leaf axil= stem area above point where leaf attaches
Axillary bud= miniature shoot with a dormant apical meristem
bud is covered by small corky waxy bud scales
terminal bud= at tip of each stem
phyllotaxy= arrangement of leaves on stem
alternate=just one leaf on each node
two leaves per node=opposite
three or more=whorled
distichous phyllotaxy=only two rows(corn)
decussate phyllotaxy= four rows(opposite leaves)
spiral=leaves not aligned with nearest neighbor
Internal Organization of Stems: Arrangement of Primary Tissues
Epidermis
single layer of living parenchyma cells
cutin, cuticle outer tangential wall
guard cells w stomal pore=stomata
guard cells control opening/closing of this
swell by absorbing water. stress also causes closing
some cells elongate outward and become..trichomes/hairs
Cortex
interior to epidermis
made of parenchyma / collenchyma
fit compactly. or open w large air spaces
Vascular Tissues
xylem conducts water and minerals
phloem distributes sugars and minerals
Vascular Bundles
xylem+phloem=vascular bundles
interior of cortex. all are collateral. cells of primary xylem> primary phloem
Phloem
http://img.sparknotes.com/figures/D/de8ebcc8ff4d3a7214b83f580ad855f3/phloem.gif
sieve cells
sieve tube members
controlled by companion cells
sieve element= either
only have primary walls, have to be alive to conduct. sieve pores are their modesmata
pores are called sieve pores. clustered groupa=sieve areas
xylem
http://slideplayer.com/9246677/27/images/5/Structure+of+xylem+tissue.jpg
tracheids
vessel elements
tracheary element= either or
tracheids obtain water from other tracheids below them
annular thickenings= interior face wall
helical thickening= one to three helices interior to wall
Scalariform thickening= stronger
reticulate thickening=wall is deposited in the shape of a net
Stem Growth and Differentiation
apical meristems effect growth
subapical meristem
protoxylem
metaxylem