Plants

Classification Timeline

500 million years ago: Algae• Example: Blue-green algae

425 million years ago: Land plants (bryophytes)• Example: Mosses

375 million years ago: Vascular seedless plants (pterophytes)• Example: Ferns

200 million years ago: Vascular seeded plants (gymnosperms)• Example: Pine Trees

130 million years ago: Flowering plants (angiosperms)• Example: Daffodils

Non-vascular plants: Algae

• Non-vascular- no tubes to transport water & nutrients or provide support– All movement occurs through osmosis

• Aquatic• Can photosynthesize- use sunlight to

produce its own energy– Essential source of oxygen in aquatic

ecosystems (70-80% oxygen comes from algae)

Non-vascular plants: Bryophytes

• Bryophytes- non-vascular plants– No tubes to transport water & nutrients or

provide support to the plant– All movement occurs through osmosis

• No true stems, leaves, or roots• Rhizoids act as roots- absorb water &

minerals• Need water to reproduce

– Less likely to survive harsh conditions because of need for water

Vascular Plants: Pterophytes, Gymnosperms, & Angiosperms

• Contain vascular tissue– Xylem & Phloem

• Xylem transports water• Phloem transports

sugars

Pterophyte Gymnosperm Angiosperm

Angiosperm Classification: Monocot vs. Dicot

Angiosperm Classification: Alternate vs. Opposite Leaves

Roots

• Purpose– Increase surface area to absorb more water &

minerals– Anchor plant– Store water & minerals

Types of Roots

• Tap- one main root that goes straight down– I.e. Carrot

• Fibrous- has root hairs or lateral roots

• Aerial- roots exposed to air

aerial

Parts of the Root• Root hair- increase surface area

to absorb more water & minerals• Epidermis- protection &

absorption• Cortex- Movement of water &

minerals to center of root– Storage of food

• Endodermis- assists in movement of water & minerals to center of root

• Xylem- movement of water• Phloem- deliver food to root• Apical meristem- area of growth• Root cap- protection & helps

root elongate farther into soil

Cross section

Longitudinal

Herbaceous Stem

• Contains vascular bundles– Xylem & phloem

• Xylem (inside of vascular bundle)– Dead cells – Main purpose to move water

through the stem• Phloem (outside of vascular

bundle)– Alive at maturity– Main purpose to move sugars

down through stem• Cortex

– Water & minerals transported• Epidermis

– Protection

Monocot- vascular bundles spread throughout

Dicot- vascular bundles in a ring

• Consists of sapwood & heartwood– Heartwood- xylem that

no longer transports water, provides support

– Sapwood- xylem that still transports water

Woody Stems

Woody Stems: How Tree Rings Form

• Vascular cambium– Layer outside of wood– Create new xylem

every year in the spring & the summer (tree rings!)

– Indicator of weather• Good season, wider

ring• Bad season, narrower

ring

Woody Stems: Bark

• Bark- includes cork & phloem– Vascular cambium

creates new phloem

– Cork cambium produces new cork (bark that we see)

Leaves• Cuticle- waxy covering;

prevents drying out and provides support

• Stomata- opening for gas exchange

• Guard cells- open & close stomata

• Vein– Contains xylem & phloem

• Xylem- transport water• Phloem- transport sugar

• Palisade- packed closely together- photosynthesis

• Sponge- open spaces- allow gas exchange within leaf

Leaf Cross Section

Stomata

• Opens to allow gas exchange between plant and atmosphere

• Open- photosynthesis, at risk to dry out

• Closed- no photosynthesis, maintains moisture

Water Movement in Plants

• Root pressure– Moves water through osmosis– Works up to 1 meter

• Capillary Action– Movement due to small area– Cohesion & adhesion

• Cohesion- water sticks to itself• Adhesion- water sticks to walls of xylem

Water Movement in Plants

• Transpirational Pull– Main source of

upward water movement in plants

• Water evaporates from stomata in leaves

• Water moves up plant to replace lost water

• Occurs through cohesion & adhesion

• If guard cells open longer, greater transpirational pull

Food Movement in Plants

• Food (glucose) moves downward starting from the leaves

• _________: vessel that transports glucose

Plant Hormones

• Have specific receptors that enable specific responses

1. Auxins• Stimulate cell

elongation & suppresses

growth of lateral (side) buds• Enables plants to

bend toward light

Plant Hormones

2. Gibberellin• Stimulate stem

elongation by stimulating cell division & elongation

Plant Hormones

3. Cytokinin– Stimulates growth of lateral (side) buds and

release apical dominance (more growth on sides of plant rather than at the top)

– Stimulate flowering

Plant Hormones

4. Abscisic acid (ABA)

• Inhibits plant growth (short)

Plant Hormones

5. Ethylene

• Promotes fruit ripening and flower opening