TAKS Objective 3

Plants: Structures

and Adaptations

Structure of

Plants

Slide 1

Plants are...

Multicellular

Have cell walls

Photosynthetic

Growth occurs in modules or “pieces”

Reproduction

– Asexually

– Sexual via spores or seeds

Plants arePrimary source of food for people and animals

Produce oxygen

help to keep us cool

renew the air

Photosynthesis

Process by which CO2 and H2O in the presence of light are converted into sugar and oxygen

Chemical formula

6CO2 + 6H2O+sunlight ---->C6H12O6 + 6O2

Dermal tissue

Vascular tissue

Ground tissue

Stem

Root

Leaf

The basic structure of a plant: Root, Stem, and Leaf Tissues

THE LEAVES

THE LEAVES

A. Functions of Leaves1. Main photosynthetic organ

2. Broad, flat surface increases surface area for light absorption

3. Have systems to prevent water loss• Stomata open in day but

close at night or when hot to conserve water

• waxy cuticle on surface

4. System of gas exchange

• Allow CO2 in and O2 out of

leaf Elephant Ear Plant

B. Leaf Structures

1.Cuticle: waxy layer; covers upper surface • Protects leaf against

water loss

2.Veins: transports water, nutrients and food• Made of xylem and

phloem

3.Mesophyll: contains cells that perform photosynthesis b/c they contain Chloroplasts.

2 GuardCells

Surround each Stoma

Mes

op

hyl

l

(Opening)

Leaf Cross-Section

Veins

Cuticle

Stoma

Stoma- singular

Stomata-plural

More Plant Parts…

Guard Cells

4. Guard cells: • cells that open

and close the stoma

5. Stomata: openings in leaf’s surface; when open: • GAS EXCHANGE:

Allows CO2 in & O2

out of leaf • TRANSPIRATION:

Allows excess H2O

out of leaf

Stoma

Stoma Open Stoma Closed

Guard Cells

Stoma

Function of Stomata

Guard Cells

CO2

O2 H2O

What goes in?

What goes out?

•What process involves using CO2 and H2O releasing

O2 as a waste product?

•Photosynthesis

•What is the plant using this process to make?

•Carbohydrates-glucose

•If the plant needs water for photosynthesis, why is water coming out of the stoma?

Stoma Open Stoma Closed

Guard Cells

Function of Guard Cells

Guard Cells•These stomata (leaf openings) naturally allow water to evaporate out.

•Why would the plant close stomata with guard cells?

•Prevent excess water loss through transpiration. (conserve water)

•So what is the point of having stomata?

•Allow gas exchange for photosynthesis

THE REPRODUCTIVE ORGAN OF THE PLANT

THE FLOWER

1.Pistil:female reproductive structure

a.Stigma: sticky tip; traps pollen

b.Style: slender tube; transports pollen from stigma to ovary

c.Ovary: contains ovules; ovary develops into fruit

d.Ovule: contains egg cell which develops into a seed when fertilized

FilamentAnther

StigmaStyle

Ovary

Pistil

PetalSepalOvule

Stamen

Structure of a Flower

2.Stamen: male reproductive structure

a.Filament: thin stalk; supports anther

b.Anther: knob-like structure; produces pollen

c.Pollen: contains microscopic cells that become sperm cells

Structure of a Flower

FilamentAnther

StigmaStyle

Ovary

Pistil

PetalSepalOvule

Stamen

3.Sepals: encloses & protects flower before it blooms

4.Petals: usually colorful & scented; attracts pollinators

 Structure of a Flower

FilamentAnther

StigmaStyle

Ovary

Pistil

PetalSepalOvule

Stamen

Cross Pollination• How does pollination

happen?

• Pollen from an anther is caught by the stigma, travels through style to the ovules in the ovary.

• What is the result of pollination?

• A Fruit: An ovary containing seeds.

THE STEM

A. Functions of Stems

1.Support system for plant body

2.Transport system carries water & nutrients

3.Holds leaves & branches upright

Each light and dark tree ring equals one year of annual growth. Light rings for fast spring growth, dark for slow summer growth.

Smaller rings tell of past droughts that have occurred.

Looking at the picture to the left:

What years had the most rain?

What years experienced the worst drought?

THE ROOTS

A. Functions of Roots

1. Anchor & support plant in the ground

2. Absorb water & minerals

3. Hold soil in place

Fibrous RootsRoot Hairs

B. Root Types

2. Tap Roots –larger central root reaches deep water sources underground

Ex. Trees, Carrots, & Dandelions

1. Fibrous Roots: branching roots hold soil in place to prevent soil erosion

Ex. Grasses

Tap Root

1. Root Hairs: increase surface area for water & mineral absorption

2. Meristem: region where new cells are produced

3. Root Cap: protects tip of growing root

C. The Structure of a RootRoot Hairs

MeristemRoot Cap

Xylem

Phloem

A average size maple tree can transpire 200 liters of water per hour during the summer.

Transpiration is the #1 driving force for pulling water up

stems from roots.

Plants find a use for Transpiration

1. Transpiration: loss of excess water from plant leaves

2. Significance:

BA

a. Transpiration causes enough pressure to help pull water (& required nutrients) up stem from roots.

b. As part of the water cycle, trees transpire water back into the atmosphere.

c. Transpiration provides much of the daily rain in rainforest.