Structure and Function in Plants
An introduction to plant life
1. A Macroscopic View
http://www.uic.edu/classes/bios/bios100/labs/plantanatomy.htm
Primary rootLateral root
Root tipRoot cap
Root hairs
Stem
Vascular Tissues
Leaf
Node
Internode
Flower
Fruit
Seeds
Terminal bud
Roots:
•Secure plant to the ground
•Take up mineral nutrients from the soil
•Take up water from the soil
Stem:
•Supports plant
•Gives plant height
•Contains vessels that transports materials from the roots to the leaves
•Contains vessels that transports materials from the leaves to the rest of the plant
Leaves:
•Site of photosynthesis
Flower:
•Reproductive structure
•Produce fruit with seeds
The Roots - Macroscopic
http://www.sirinet.net/~jgjohnso/plants.html
Root hairs
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
The Roots - Macroscopic
http://www.cspinet.org/cspi/images/
http://www.agry.purdue.edu/turf/weeds/violet/violet%20root.htm
http://www2.mcdaniel.edu/Biology/botf99/rootuse/2roottypes.html
Plants can consist of one main root known as a tap
root. The carrot is an example of this, can you give other
examples?
Other plants have a fine network of fibrous roots as seen here in this
violet plant.
Roots than sit above the
surface of the soil and help support the
plant are known as adventitious
roots.
The Roots – Microscopic ViewWhat our eyes can’t see: The Roots
http://www.sirinet.net/~jgjohnso/plants.html
Root Hairs
Xylem – transports water from the roots to the leavesPhloem – transports water and sugars around the plantXylem 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
The Stem - Macroscopic
http://aggie-horticulture.tamu.edu/syllabi/201h/ediblebotany/onionyellow.html
http://csdl.tamu.edu/FLORA/fa02/fa02080.jpg
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.
Tendrils are also modified stems. In this case they are
not used as storage, but help support the plant by
attaching to nearby structures.
An Internal Microscopic View
What our eyes can’t see: The Stem
http://faculty.uca.edu/~benw/biol1400/pictures/tilliastem.jpg
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
The Stem – Microscopic ViewWhat our eyes can’t see: The Stem
http://biology.ucok.edu/personalpages/bidlack/Botany/botanypics/default.htm
Xylem – longitudinal section:
•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
The Stem – Microscopic ViewWhat our eyes can’t see: The Stem
http://biology.ucok.edu/personalpages/bidlack/Botany/botanypics/default.htm
Phloem – longitudinal section:
•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
The Leaf - Macroscopic
http://csdl.tamu.edu/FLORA/fa02/fa02080.jpg
Leaves can sit
opposite each other
on the stem.
Leaves can also
alternate 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.
The Leaf - Macroscopic
http://www.csdl.tamu.edu/FLORA/328Fall98/328VegLab/veglablist.htm
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.
An Internal Microscopic View
What our eyes can’t see: The Leaf
http://biology.ucok.edu/personalpages/bidlack/Botany/botanypics/default.htm
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
Upper epidermis
Lower 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
Cuticle – protect upper leaf surface from moisture loss
Stoma
An Internal Microscopic View
What our eyes can’t see: The Leaf
http://www.borg.com/~lubehawk/photosyn.htm#ans%20matching
CuticleUpper
epidermis
Mesophyll – all the dark green dots represent chloroplasts
Palisade cells
Spongy mesophyll
Vascular bundle
Phloem cells Xylem cells
Stoma
Guard cellGuard
cell
Lower epiderm
is
Large central vacuole
Cell nucleus
An Internal Microscopic View
http://www.sirinet.net/~jgjohnso/plants.html
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.
Guard cells
Guard cells
Stoma
Thick inner walls of guard
cells
For the stoma to open the guard cells must fill with
waterH2O
H2O
H2O
H2O
For the stoma to close the guard cells must remove
water
H2OH2O
H2O
H2O
The Flower - Macroscopic
http://bee.airoot.com/beeculture/book/chap5/quince.html
Petal
Sepal – protects bud
Anther - male
Filament - male
Stigma - female
Style - female
Ovary - female Ovules
Nectar site
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.