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Structure and Function in Plants
An introduction to plant life
1. A Macroscopic View
Terminal bud
Leaves:
Flower
•Site of
photosynthesis
Flower:
Leaf
Internode
Node
•Produce fruit
with seeds
Stem:
•Supports plant
Vascular Tissues
•Gives plant
height
•Contains vessels
that transports
materials from
the roots to the
leaves
•Reproductive
structure
Seeds
Fruit
Stem
•Contains vessels
Primary root
that transports
materials from
Lateral root
the leaves to the
rest of the plant
Roots:
•Secure plant to the ground
•Take up mineral nutrients
from the soil
Root hairs
Root tip
Root cap
http://www.uic.edu/classes/bios/bios100/labs/plantanatomy.htm
•Take up water from the
soil
The Roots - Macroscopic
Root Hairs:
•Young roots grow very fine roots hairs to
help the plant gain maximum amount of
water when they are still very small and
can’t reach so far into the surrounding soil
•The root hairs increase the amount of
surface area the root has and can therefore
gather more water, this is more effective
than growing large too quickly
•Root hairs are made up of only one cell
Root hairs
http://www.sirinet.net/~jgjohnso/plants.html
The Roots - Macroscopic
http://www2.mcdaniel.edu/Biology/botf99/rootuse/2roottypes.html
Other plants have a
fine network of
fibrous roots as
seen here in this
violet plant.
http://www.cspinet.org/cspi/images/
Roots than sit
above the surface
of the soil and
help support the
plant are known
as adventitious
roots.
Plants can consist of
one main root known
as a tap root. The
carrot is an example
of this, can you give
other examples?
http://www.agry.purdue.edu/turf/weeds/violet/violet%20root.htm
The Roots – Microscopic View
What our eyes can’t see:
The Roots
Root Hairs
Xylem – transports water from the roots to the leaves
Phloem – transports water and sugars around the plant
Xylem and phloem together are known as the vascular
tissue or vascular bundle
Endodermis - tissue that makes up the bulk of the root is the
endodermis
Apical meristem – where all new growth of the root occurs
Root cap – protects the new cells (produced in the
meristem) as the root pushes forward
http://www.sirinet.net/~jgjohnso/plants.html
The Stem - Macroscopic
Modified stems include
tubers such as potatoes and
bulbs such a onions, garlic,
and daffodils. The plant
stores nutrients in these
vegetables until it needs it
later. You can see the roots
on the underside of this
onion.
http://csdl.tamu.edu/FLORA/fa02/fa02080.jpg
Tendrils are also modified
stems. In this case they are not
used as storage, but help
support the plant by attaching
to nearby structures.
http://aggie-horticulture.tamu.edu/syllabi/201h/ediblebotany/onionyellow.html
An Internal Microscopic View
What our eyes can’t see:
The Stem
Cross section of a stem:
•The cambium marks the boundary
between the xylem and phloem
•The phloem is located in a circle
around the outside of the cambium
•The xylem is located in a circle on the
inside of the cambium
•Each year the xylem leaves behind a
ring of growth – shown by the numbers
1, 2 and 3. Trees can be aged using this
method
http://faculty.uca.edu/~benw/biol1400/pictures/tilliastem.jpg
The Stem – Microscopic View
Xylem – longitudinal section:
What our eyes can’t see:
The Stem
•Xylem vessels are long, thin,
hollow and stacked end to end
•They do not have a nucleus
and are actually dead
•They are lined by lignin that
helps them keep their strength
•Xylem cells transport
dissolved mineral ions and
water from the roots to the
leaves
•Transport is unidirectional, in
an upwards direction only
http://biology.ucok.edu/personalpages/bidlack/Botany/botanypics/default.htm
The Stem – Microscopic View
Phloem – longitudinal section:
What our eyes can’t see:
The Stem
•Cells are long and thin and
stacked on top of each other
•They contain a nucleus and are
alive
•Phloem cells transport water
and sugars (sucrose) around
the plant
•Transport it is bi-directional,
both up and down the plant
•Movement of materials in the
phloem is called translocation
http://biology.ucok.edu/personalpages/bidlack/Botany/botanypics/default.htm
The Leaf - Macroscopic
Leaves can
sit opposite
each other
on the stem.
Leaves are
attached to
the stem via
the petiole
These leaves
have virtually no
petiole and are
arranged in a
whirl around the
stem.
This leaf is divided
into many small
sections. It is known
as a pinnate leaf.
Leaves can
also
alternate on
the stem.
http://csdl.tamu.edu/FLORA/fa02/fa02080.jpg
The Leaf - Macroscopic
Cabbage, lettuce, spinach
and bok choy are all leafy
structures of plants.
Celery is actually a
modified petiole rather
than a stem. Celery does
not have a true stem.
http://www.csdl.tamu.edu/FLORA/328Fall98/328VegLab/veglablist.htm
An Internal Microscopic View
Leaf cross section:
•If we cut across a leaf, turn it on its side
and magnify it, we can see several distinct
layers of cells
Cuticle – protect
upper leaf surface
from moisture loss
What our eyes can’t see:
The Leaf
Upper epidermis
Palisade cells (palisade means ‘a
fence like structure’ in Latin). You
can see their dark stained nucleus.
These cells contain lots of
chloroplasts for photosynthesis.
Spongy mesophyll is given its name
due to the air spaces between all the
cells
Lower epidermis
Stoma
http://biology.ucok.edu/personalpages/bidlack/Botany/botanypics/default.htm
An Internal Microscopic View
http://www.borg.com/~lubehawk/photosyn.htm#ans%20matching
Cuticle
What our eyes can’t see:
The Leaf
Upper epidermis
Mesophyll –
all the dark
green dots
represent
chloroplasts
Palisade cells
Spongy
mesophyll
Lower
epidermis
Cell nucleus
Vascular bundle
Large central
vacuole
Phloem cells
Guard cell
Guard cell
Stoma
Xylem cells
An Internal Microscopic View
Stomates:
• Allow the gasses involved in photosynthesis in and out of the leaf.
•They must also control the amount of water lost from the leaf. In a dry environment they need
to stay closed most of the day.
For the stoma to close the guard
cells must remove water
For the stoma to open the guard
cells must fill with water
H2 O
H2O
H2O
H 2O
Stoma
Thick inner
walls of
guard cells
H 2O
H2O
H 2O
H2O
Guard cells
http://www.sirinet.net/~jgjohnso/plants.html
Guard cells
The Flower - Macroscopic
Petal
Anther - male
Stigma - female
Style - female
Nectar site
Ovary - female
Filament - male
Ovules
Sepal – protects bud
http://bee.airoot.com/beeculture/book/chap5/quince.html
References
•Johnson, Jerry [no date] The World of Biology. Retrieved from the site http://www.sirinet.net/~jgjohnso/plants.html January 2004.
•[No authour] [no date]. Retrieved from site http://www.cspinet.org/cspi/images/ January 2004.
•[No author] [no date]. Retrieved from site http://www.agry.purdue.edu/turf/weeds/violet/violet%20root.htm January 2004.
•[No author] [no date]. Retrieved from site http://www2.mcdaniel.edu/Biology/botf99/rootuse/2roottypes.html January 2004.
•Waggoner, Ben [no date] Biology 1400. Retrieved from the site http://faculty.uca.edu/~benw/biol1400/pictures/tilliastem.jpg
January 2004.
•[No author] [no date]. Retrieved from site http://aggie-horticulture.tamu.edu/syllabi/201h/ediblebotany/onionyellow.html January
2004.
• [No author] (2004) Botany 301. Retrieved fro the site http://www.csdl.tamu.edu/FLORA/tfplab/vegchar.htm January 2004.
• [No author] (2003) Plants and People – Botany 328. Retrieved from site
http://www.csdl.tamu.edu/FLORA/328Fall98/328VegLab/veglablist.htm January 2004.
•[No author] [no date] Plant Structure and Function. Retrieved from the site
http://www.uic.edu/classes/bios/bios100/labs/plantanatomy.htm January 2004.
•Bidlack, Jim & Hinnger, Justin (2003) Plant Biology (Bio 1304) Lab Pictures. Retrieved from the site
http://biology.ucok.edu/personalpages/bidlack/Botany/botanypics/default.htm January 2004.
•Lubey, Steve (2002) Lubey’s Biohelp – Photosynthesis (the big picture). Retrieved from site
http://www.borg.com/~lubehawk/photosyn.htm#ans%20matching January 2004.
•[No author] [no date] Chapter 5: Tree Fruits and Nuts and Exotic Tree Fruits and Nuts. Retrieved from site
http://bee.airoot.com/beeculture/book/chap5/quince.html January 2004.