R: Plant Systems,Reproduction and Development

Autotrophs -- green plants and algae (organisms capable of making their own organic food from sunlight, water, and carbon dioxide)

** Starch is the principal plant storage material.

All respiratory gases are released through tiny holes in the plant.

(Stem Functions)

1. Support plant.

2. Translocation of materials between the roots and the leaves.

3. Storage of food and water.

4. Some help produce new plants.

meristem: growing tissue of a stem

** Bark and epidermis protect against disease and mechanical injury.

(Functions of Roots)

1. Anchor plant into the soil

2. Store food materials

3. Transport by xylem and phloem.

4. Absorb soil water and minerals by diffusion.

5. Respiratory organ in well aerated soil.

root hair: root epidermis projection that functions

in the absorption of water and minerals (increases root surface area)

** Water enters by passive transport. (osmosis)

** Minerals enter by both active and passive transport.

Transpiration pull: the loss of water through leaves helps pull water up the plant

tropism: response in which a plant moves toward or away from a stimulus

Auxins: plant growth hormones

(Functions of Leaves)

1. Photosynthesis (food making)

2. Regulate gas exchange.

3. Regulate water content of the plant.

(Leaf Cross Sectional Structures)

1. cuticle: thin wax coating on upper epidermis

helps protect against excessive water loss,

mechanical injury, and fungal attack

2. upper epidermis: aids the cuticle in its function

3. palisade layer: closely packed columnar shaped cells below the

upper epidermis

--contains many chloroplasts and carries on most plant photosynthesis

4. Spongy layer: located below the Palisade layer

-- exchange and circulation of gases and water vapor occurs here

--also carries on some plant photosynthesis

5. Veins--contain the conducting tissues

xylem: carries water and minerals to leaf cells from the stem and roots (upward)

phloem: carries food (glucose) made in the leaves to the stem and the

roots for use and storage (downward)

6. lower epidermis: assists the upper epidermis and the cuticle in its fct.

stomata --tiny openings in the lower epidermis--regulates the exchange of

gases and water between the leaf and the atmosphere

guard cell -- one on each side of the stomate to regulate its opening and closing

Stomates open during periods of high moisture -- they close during

periods of limited moisture. (help maintain plant water homeostasis)

transpiration: loss of excess water through the stomata and lenticels

LEAF DAYLIGHT oxygen & water OUT

GAS EXCHANGE: carbon dioxide IN

(photosynthesis and respiration occurs)

But usually more photosynthesis than respiration

NIGHT EXCHANGE: oxygen IN carbon dioxide and water OUT

(only respiration occurs)

Leaf Cross-Sectional Graphic below (Courtesy of the Troy HS Web Page)

Flower -- plant structure specialized for reproduction

-- carries on the processes of meiosis and fertilization

Chief Flower structures:

petals: colored parts inside the sepals -- attract insects

stamen: forms the male reproductive organ

-- consists of an anther and a filament

anther: pollen box in which pollen grains are formed -- knob shaped (produce sperm)

filament: supports the anther

pistil: female reproductive organ -- consists of three parts

stigma: at the top of the pistil -- is sticky and hairy -- thus is adapted to catch and hold pollen

style: tubelike connection between the stigma and the ovary

ovary: enlarged part of the pistil attached to the receptacle (stem tip on which the flower rests)

-- contains the ovules (makes eggs)

ovules: small white structures within the walls of the ovary -- produces the plant egg cells

** After fertilization the entire ovary will enlarge and become the fruit of the plant.

pollination: transfer of pollen grains from the anther to the stigma

** Natural pollination may be enhanced by wind, birds, and insects.

petals: visual attractant

nectar: chemical attractant

** Pollen grains have a thick protective wall. This prevents the dehydration of the

pollen grain.

[Process of Fertilization and Development in Plants]

1. Pollination

2. Pollen grain germinates on the stigma and forms a pollen tube which extends into the ovule.

(The pollen tube is an adaptation for internal fertilization.)

3. Sperm nuclei in the pollen tube form from the monoploid (haploid) nuclei in the pollen grain. (Both have the n number of chromosomes.)

4. The pollen tube grows all the way down the style to the ovule of an ovary.

The sperm nucleus travels down this tube.

5. The union of the male and female nuclei in the ovule (egg is n number also)

results in the zygote (start of a seed) being formed. (n + n = 2n)

(Embryonic Development)

1. The zygote develops into an embryo through repeated mitotic cell divisions.

2. The ripened (developing) ovary develops into a fruit -- the ripened ovule develops into a seed.

3. Differentiation of the embryo or seed begins to occur.

SUITABLE ENVIRONMENTAL CONDITIONS FOR GERMINATION

1. Sufficient moisture

2. Sufficient oxygen

3. Proper temperature

Patterns of development vary among plants. In seed bearing plants, seeds contain the stored food for early development, followed by varying patterns of growth to adult form.