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.