Plant Structure Adaptations and Responses - Plant Science - Lecture Slides, Slides of Biology

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Structure

of

Plants

A. Functions of Roots

1. Anchor & support plant in the ground
2. Absorb water & minerals
3. Hold soil in place

Root Hairs^ Fibrous Roots

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 Root

Root Hairs

Meristem Root Cap

Xylem

Phloem

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?Docsity.com

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 Guard Cells Surround each Stoma

Mesophyll

(Opening)

Leaf Cross-Section

Veins

Cuticle

Stoma

Stoma- singular Stomata-plural Docsity.com

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 CO 2 in & O 2 out of leaf - TRANSPIRATION: Allows excess H 2 O out of leaf

Stoma

Stoma Open Stoma Closed

Guard Cells

Function of Guard Cells

• These stomata (leaf Guard Cells 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 Docsity.com

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.

C. Plants find a use for Transpiration

1. Transpiration: loss

of excess water from plant leaves

2. Significance:

A^ B

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.

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

Filament

Anther Stigma Style Ovary

Pistil

Petal Ovule Sepal

Stamen

3.Sepals : encloses & protects flower before it blooms

4.Petals : usually colorful & scented; attracts pollinators

Structure of a Flower

Filament

Anther Stigma Style Ovary

Pistil

Petal Ovule Sepal

Stamen

Chapter 25

Plant

Responses

and

Adaptations

Hormone- producing cells

Target cells

Movement of hormone

Hormone Action on Plants

A. Plant cells can produce hormones : which are chemical messengers that travel throughout the plant causing other cells called target cells to respond.

B. In plants, hormones control:

1. Plant growth & development
2. Plant responses to environment

Cells in one blooming flower signals other blooms using hormones to open Docsity.com.

D. Ethylene causes

Fruit to Ripen

1.Fruit tissues release a small amount of ethlyene

2.Causes fruits to ripen.

3.As fruit become ripe, they produce more and more ethlyene , accelerating the ripening process.

Ethylene released by apples and tomatoes causes fruit to age quickly.

Plant Tropisms

1. Tropism : the way a plant grows in response to stimuli in the environment. a.Phototropism : growth response to light

• Plants bend towards light

a.Geotrophism : growth response to gravity -plant roots grow down with gravity, shoots (stems) grow up against gravity and out of the soil.

a.Thigmotropism : growth response to touch -vines grow up around trees, venus flytrap closes when leaves are touched