Plants What are plants and why are they important to study?

Plants • What are plants and why are they important

to study?

Learning Objectives• What are the characteristics – evolutionary

adaptations - of plants?• What are the structures of a plant and what do

the structures do?• What are the major types of plants (how are the

classes broken down)?• What is the difference between a monocot &

dicot?• How does a plant reproduce?• Label a flowering plant and a flower and describe

the function of the parts.

Plant General Characteristics

1. Carry out photosynthesis (autotrophs)2. Produce cellulose in their cell walls3. Non-motile (don’t move around)4. Reproduce sexually and asexually5. Have specialized tissues and organs

Botany: the study of plants

Where did Plants come from?

• Plants likely evolved from plant-like Protist green algae from a watery environment.

• Likely evolved around 500-400 million years ago!

What do Plants Need to Survive?

• Sunlight• Water and Minerals• Gas Exchange• Movement of Water and

Nutrients• Not to be cut down.

Kingdom Plantae adaptations:Specialized Tissues

• Vascular tissue (like arteries and veins!)– (UP) Xylem – transports materials up from the roots to

leaves and supports the plants as “wood” after the cell dies

– (DOWN) Phloem – transports materials down from the leaves to roots and stem

• Vascular Cambium – makes more vascular tissue• Parenchyma – used for storage, surrounded by

vascular tissue• Meristematic tissue – only tissue that produces

new cells by mitosis, found on edges• Cork Cambium – outer bark of trees

Contains 4 Main Groups

• Bryophytes• Seedless Vascular Plants• Gymnosperms• Angiosperms

Evolution of Plants

PROTISTA

Bryophytes – Non Vascular Plants• Includes: mosses, liverworts, hornworts• First land plants; had to overcome obstacles

– avoid drying out (desiccation) – live in moist areas– develop a means of support (roots and stems)– develop new reproductive methods– obtaining nutrition– No vascular tissue, so they are close to the ground to

draw up water by the properties of water (adhesion & cohesion)!

– Their reproduction also relies on the use of water!

Seedless Vascular Plants

• Includes: Ferns, Club mosses, Horsetails• 3 Key Adaptations

– Vascular System = xylem/phloem = larger, roots, stems, and leaves.

– Larger Sporophyte = better distribution of spores– Drought resistant Spores = thickened spore wall

Tracheophytes – Vascular Plants• Gymnosperms – means “naked seed”, not

protected by fruit. Can reproduce through wind or other methods on land!– Class Ginkoopsida – Gingkos; one species exists

today, living fossil– Class Cycadopsida – Cycads; found in tropics– Class Pinopsida – cone bearers; 9 families contain

over 300 species, evergreens: pines, spruce, hemlocks, firs

What does Vasuclar Tissue mean? Means they have xylem (water) and phloem (sugar) to transport water up from the ground into the rest of the plant!

Tracheophytes – Vascular PlantsAngiosperms – flowering plants, produce a form of fruit! (A wall

of tissue surrounding a seed.) Gives animals a tasty treat to place their offspring elsewhere.

Can reproduce on land.• Two classes of angiosperms are based upon the number of Cotyledon: tiny seed leaves that store or absorb food for developing embryo.

• Class Monocotyledonae – Monocots (1)• Class Dicotyledonae – Dicots (2)• Have Unique life spans.

– Those who die in one season are called annuals.– Those who die in two years are called biannuals.– Those who live many years are called perennials.

Plant Structure: Roots• Roots anchor plants into the

ground, absorb water & minerals from the soil, protect the plant from bad bacteria/fungi, and transport these materials to the stem.

• Contain xylem and phloem in the center of the root.

• Root pressure – dew is an example of root pressure (forcing excess water out of the plant)

• The root cap burrows through the soil and the cells are replenished by the apical meristem.

• Meristem = areas of rapidly dividing cells

Plant Structure: Stems• Stems can be either woody or

herbaceous. • Transpiration – as water

evaporates, the energy released pulls water up the stem

• Vascular tissues are arranged differently in stems than leaves.– Monocots: scattered in stem– Dicots: circular pattern in stem

• Xylem – transports water & minerals

• Phloem – transports sugars & hormones– Portion of a plant that stores

sugar is called a sink.

Plant Structure: Leaves• Leaves are protected by a

waxy cuticle.• Petiole – vascular tissues

extending from stem to leaf (appear as veins)

• Mesophyll – contain chlorophyll

• Guard cells & Stomata – regulate water loss through the underside of the leaf (Transpiration)

• Monocots: parallel veins• Dicots: net veined

Plant Asexual Reproduction

• Vegetative Reproduction – when plants form new plants from portions of their own roots, stems, or leaves

• Spores – non-seed vascular plants (ferns) release spores

Plant Sexual Reproduction Overview• Pollination – when pollen is deposited on stigma.• Fertilization – when pollen grain reached the ovary and fuses with

the egg.• After fertilization, the seed develops food storage regions for the

embryo called fruit.• Seeds are eventually dispersed using many different methods.

(Wind, Animals, Water, Fruit, etc)• Remember, this is called the Alternation of Generations!• Can remain dormant until temperature and moisture cause the

seed to start early growth called germination. • The systematic cultivation of plants by humans is called agriculture.

How Plants Reproduce: Flowers & Flowering

• Flowers are made up of four organs: (called Perfect Flower)– Petals – colorful leaf like structure

around the stem.• They attract insects and other

pollinators of the flower.– Sepals –leaf-like structure around

the flower stem beneath the petals.

• They enclose the bud before it opens and protect the flower while it is developing.

– Stamens – male part of the flower where at their tip is the anther that rests on the filament contains pollen.

– Carpel– [Also called the Pistil] Female part of the flower, which contains sticky stigma where pollen grains land and travel down the style to the ovary and ovules.

Not all sepals are green.Alstroemeria (a lily-like monocot) have sepals the same color as the petals.

Fertilization: Seed & Fruit Production

• 2 sperm fertilize the female, one the egg (1n), the other the central cell (2n)

• The walls of the ovule become the protective seed coat, the central cell becomes the endosperm or food for the embryo, and the ovary wall the fruit.

• Because two fertilization events take place at the same time, it is called double fertilization.

• Fruits and seeds are modified for dispersal.– Shape of seed can determine type of

dispersal (wind, water, animal, etc) • Seeds can stay dormant for long

periods of time!

Maple seed. The fruit isn’t edible but designed with a wing to float away from the tree.

Plant Responses: Hormones• Hormones cause a physiological

change either in growth or development.– Auxins (IAA) – stem elongation.– Gibberellins – increase rate of

seed germination and allows the stem to grow taller.

– Cytokinins – stimulate proteins for cell division and extends the life of the plant.

– Ethylene – ripens fruits and the emergence of seeds from the soil.

– Abscisic Acid – helps leaves prevent water loss by hardening certain leaf cells.

Plant Responses: Tropisms• Plants respond to their environment as

other organisms do.• Photoperiodism affects the timing of flower

production.– Duration of light and dark periods in the day– Short-day plants, Long-day plants, day-neutral

plants

• Tropism – a plant’s response to an external stimulus that comes from a particular direction.

• Involve growth, so they are not reversible.– Phototropism (Light)– Gravitropism (Gravity)– Thigmotropism (Touch)

• Nastic movement –Does not involve growth, so are reversible.– Example: folding of a venus flytrap.