Transcript File - Mr. Shanks` Class

Monocot Roots
• large vascular cylinder in center
• ring pattern of xylem (large openings) and phloem
tissue surrounded by endodermis
• vascular cylinder surrounded by fairly thick cortex
• fibrous root system
Dicot Roots
• small vascular cylinder in center;
• large openings are xylem tissue surrounded by smaller
phloem cells in a ‘star’-shaped pattern
• very thick cortex
• tap root system
Stems
• support leaves
• transport materials between roots and
leaves (e.g. water, sugar)
• storage of food (e.g. sugars)
• may be photosynthetic
Herbaceous stems: green in
colour, contain chlorophyll,
undergo photosynthesis, die
back in winter
Woody stems: found in trees
and shrubs, don’t die back in
winter, annual rings used to
determine age
Monocot Stems
• vascular bundles scattered in fundamental
(ground) tissue
Dicot Stems
• vascular bundles in ring pattern in fundamental tissue
HERBACEOUS STEMS
Vascular Bundles
collection of xylem and phloem
xylem is closer to the inside
and phloem the outside
phloem
xylem
Vascular Cambium
between the xylem and the phloem
this is where new xylem and phloem are made
vascular
cambian
Woody stem
Heartwood
dead cells fill with materials that harden
Sapwood
active xylem that transports water & minerals
heartwood
sapwood
Vascular Cambium
new layers of xylem & phloem cells allow stem to grow
in width
Cork
dead phloem cells containing chemicals
Bark
outer protective layer, also dead phloem
vascular cambian
bark
cork
Annual rings
more xylem forms in wet months (light band) than
in dry months (dark band)
Dry
months
Wet
months
bark
annual rings
cambium
pith
rays
heartwood
sapwood
Both herbaceous and woody stem types are found in
monocots and dicots
However there is no secondary growth (stem diameter
increases) for woody monocot stems and thus no “tree
rings” to use to determine their age.
Palm tree crosssection showing
no annual rings
Modified Stems
Tuber: modified for food storage, grow underground (e.g. potato)
Bulb: underground stem with layers of modified leaves (e.g. onion)
Corm: enlarged, underground stem, with scaly leaves (e.g. gladioli)
Rhizome: thick, fleshy underground stems (e.g. irises)
tuber
bulb
corm
rhizome
Leaves •
main function is photosynthesis
(carbon dioxide + water --> glucose + oxygen)
• green colour due to chlorophyll pigment which
absorbs energy and reflects green
Cuticle:
waxy layer that prevents water loss
Epidermis:
Outer layer of cells
that protects the
leaf
Palisade Layer
Main site of
photosynthesis as
cells have many
chloroplasts
Spongy Layer
Some photosynthesis, but lots of
air spaces [for CO2]
Vein
Xylem & phloem
to bring water &
remove sugars
Stoma(ta)
Guard Cells
Cells that swell when filled
with water to open stoma
Small openings that allow
air in and out of leaf
Monocot Leaves
• veins (vascular bundles) are spaced evenly along leaf
• leaves tend to be long & narrow
• stomata allow exchange of gases
Dicot Leaves
• veins are large, spaced randomly through leaf
• leaves are broad, have many parts
• stomata found mostly along bottom of leaves
Leaf Adaptations
spines (e.g. cacti and pine needles) have thick waxy cuticle to
prevent water loss
thick leaves (e.g. jade plant) are used for water storage
aquatic plants (e.g. water lily) must have stomata on
upper surface of leaf only for gas exchange
Drawing some plant parts
Draw a cross section of each the following:
Monocot root and dicot root (using the ‘wedge’)
Monocot stem and dicot stem (using the ‘wedge’)
Monocot leaf and dicot leaf (drawing everything)
THE “WEDGE” METHOD:Used when specimens take up the entire field of view or to show repeating patterns in a specimen.
Name of Specimen (stain
used if known)
High detail inside wedge including stippling
“Wedge” is large enough to show detail of pattern
Wedge is in centre or on right side of field of view
“Wedge” includes centre of field of view
Low detail outside of wedge to show pattern
Magnification
Number
All plants have vascular bundles.
(VERY IMPORTANT TO SHOW!!!)