Please enable JavaScript.
Coggle requires JavaScript to display documents.
Tissues and the Primary Growth and Stems, angiosperms have sieve tubes,…
Tissues and the Primary Growth and Stems
Concepts
(Herb) three basic parts: leaves, stems, and roots
highly modified by natural selection
angiosperms
#
monocots
eudicots
basal angiosperms
Basic Types of Cells and Tissues
Parenchyma
most common, all soft parts of plants
chlorenchyma cells
involved in photosynthesis
many chloroplasts
transfer cells
short distance transfer
sometimes die to benefit plant
Sclerenchyma
primary wall and a thick secondary wall
conducting sclenrenchyma
transports water; type of vascular cell
mechanical sclerenchyma
Collenchyma
primary wall thin in some areas; thicker in areas like corners
wall has plasticity
in shoot tips and young petioles
External Organization of Stems
nodes: leaves are attached
leaves attach at leaf axil
axillary bud, mini shoot with a dormant apical meristem
end of each stem is terminal bud
phyllotaxy
positioning leaves so they don't shade each other
stolons (runners)
bulbs
short shoots that have thick, fleshy leaves
corms
vertical, thick stems that have thin, papery leaves
rhizomes
fleshy horizontal stems allow spreading
tubers
horizontal grow short period
Internal Organization of Stems
Epidermis
outermost surface of a herbaceous stem
single layer of parenchyma cells
#
thin walled parenchyma cells
incrusted with cutin
fatty substance makes wall impermeable to water
guard cells
with a hole (stomatal pore)
guard cells and stomatal pore together forms a stoma
trichomes also called hairs
Cortex
interior to the epidermis
Vascular tissues
xylem
conducts water and minerals
two types of conducting cells
tracheids
much occur in groups
has pit membrane
all plants with vascular tissue has tracheids
vessel elements
a way to move more water less friction
entire stack of vessel elements is a vessel
have perforations (complete holes)
occur almost exclusevily in flowering plants
tracheary element
annular thickenings
large surface area for movement of water into and out of cell
helical thickenings
scalariform thickening
reticulate thickening
circular bordered pits
most derived and strongest
phloem
distributes sugars and minerals
two types of conducting cells
sieve cells
long and spindle shaped and sieve areas all over
nuclei degenerate but cell stays alive
associated with albuminous cells
sieve tube members
both types are parenchyma cells and have only primary walls
sieve pores
clusters sieve areas
sieve tubes
shorter than plant
important for transport of phloem sap
all angiosperms have
controlled by companion cells
companion cells load sugar into and out of sieve tube members
Vascular bundles
xylem and phloem
collateral xylem and phloem run parallel
pith region of parenchyma similar to cortex
#
Stem Growth and Differentiation
apical meristems
cells divide producing progenitor cells
pushes meristem upward
subapical meristem
just below apical region
constitute the first xylem to appear
called protoxylem
metaxylem
largest tracheary element of all
provascular tissue
young cells of xylem and phloem
protoderm
cells in early stages of differentation
ground meristem
pith and cortex
protophloem
exterior cells mature as protophloem
metaphloem
smaller cells
angiosperms have sieve tubes
parenchyma makes up vascular bundles
epidermis is made up of parenchyma cells
