Chapter Introduction

Lesson 1 Energy Processing in Plants

Lesson 2 Plant Responses

Chapter Wrap-Up

What processes enable plants to survive?

What do you think?

Before you begin, decide if you agree or disagree with each of these statements. As you view this presentation, see if you change your mind about any of the statements.

1. Plants do not carry on cellular respiration.

2. Plants are the only organisms that carry on photosynthesis.

3. Plants make food in their underground roots.

Do you agree or disagree?

4. Plants do not produce hormones.

5. Plants can respond to their environments.

6. All plants flower when nights are 10–12 hours long.

Do you agree or disagree?

• How do materials move inside plants?

• How do plants perform photosynthesis?

• What is cellular respiration?

• How are photosynthesis and cellular respiration alike, and how are they different?

Energy Processing in Plants

• photosynthesis

• cellular respiration

Energy Processing in Plants

• Xylem and phloem—the vascular tissue in most plants—transport materials throughout a plant.

• Water flows inside xylem to all parts of a plant.

• Most plants make their own food; a liquid sugar that moves out of food-making cells, enters phloem, and flows to all plant cells.

Materials for Plant Processes

Carbon dioxide, oxygen, and water vapor pass into and out of a plant through tiny openings in leaves.

Materials for Plant Processes (cont.)

How do materials move through plants?

Photosynthesis is a series of chemical reactions that convert light energy, water, and carbon dioxide into the food-energy molecule glucose and give off oxygen.

Photosynthesis

photosynthesis

from Greek photo–, means “light”; and synthesis, means “composition”

• Two types of mesophyll cells inside a leaf contain chloroplasts, the organelles where photosynthesis occurs.

• Near the top surface of the leaf are palisade mesophyll cells, which are packed together.

• Spongy mesophyll cells have open spaces between them, and gases needed for photosynthesis flow through the spaces.

Photosynthesis (cont.)

• In the first step of photosynthesis, plants capture the energy in light.

• This occurs in chloroplasts, which contain plant pigments.

• Chlorophyll, the most common plant pigment, is necessary for photosynthesis.

Photosynthesis (cont.)

• Sugars are made in the second step of photosynthesis.

• In chloroplasts, carbon dioxide and water are broken down and, using energy stored in chlorophyll, form sugar molecules.

Photosynthesis (cont.)

Photosynthesis (cont.)

What are the two steps of photosynthesis?

• Cellular respiration is a series of chemical reactions that convert the energy in food molecules into a usable form of energy called ATP.

• Glucose molecules break down during cellular respiration.

• Plants produce sugar, but without cellular respiration, plants could not grow, reproduce, or repair tissues.

Cellular Respiration

Cellular Respiration (cont.)

What is cellular respiration?

• Most plants, some protists, and some bacteria carry on photosynthesis.

• Most organisms carry on cellular respiration.

• Life on Earth depends on a balance of these two processes.

Cellular Respiration (cont.)

Cellular Respiration (cont.)

How are photosynthesis and cellular respiration alike, and how are they different?

• Materials that a plant requires to survive move through the plant in the vascular tissue, xylem and phloem.

• Plants can make their own food by using light energy, water, and carbon dioxide.

• The products of photosynthesis are the reactants for cellular respiration.

A. palisade mesophyll cells

B. chlorophyll

C. chloroplasts

D. spongy mesophyll cells

Which term refers to the organelles where photosynthesis occurs?

A. cellular respiration

B. light energy capture

C. first step of photosynthesis

D. second step of photosynthesis

Which process breaks down glucose molecules?

A. spongy mesophyll cells

B. palisade mesophyll cells

C. chloroplasts

D. chlorophyll

Which have open spaces between them that gases flow through?

1. Plants do not carry on cellular respiration.

2. Plants are the only organisms that carry on photosynthesis.

3. Plants make food in their underground roots.

Do you agree or disagree?

• How do plants respond to environmental stimuli?

• How do plants respond to chemical stimuli?

Plant Responses

• stimulus

• tropism

• photoperiodism

• plant hormone

Plant Responses

• Stimuli are any changes in an organism’s environment that cause a response.

• A plant responds to light by growing toward it.

Stimuli and Plant Responses

• A tropism is a response that results in plant growth toward or away from a stimulus.

• When the growth is toward a stimulus, the tropism is called positive.

• Growth away from a stimulus is considered negative.

Environmental Stimuli

The growth of a plant toward or away from light is a tropism called phototropism

Environmental Stimuli (cont.)

tropism

from Greek tropos, means “turn” or “turning”

• The response of a plant to touch is called a thigmotropism.

• Special structures that respond to touch, called tendrils, can wrap around or cling to objects.

Environmental Stimuli (cont.)

• The response of a plant to gravity is called gravitropism.

• Stems grow away from gravity, while roots grow toward gravity.

Environmental Stimuli (cont.)

Environmental Stimuli (cont.)

What types of environmental stimuli do plants respond to? Give three examples.

• Photoperiodism is a plant’s response to the number of hours of darkness in its environment.

• Plants that flower when exposed to less than 10-12 hours of darkness are called long-day plants.

Environmental Stimuli (cont.)

• Short-day plants require 12 or more hours of darkness for flowering to begin.

• Day-neutral plants flower when they reach maturity and the environmental conditions are right.

Environmental Stimuli (cont.)

The number of hours of darkness controls flowering in many plants.

• Plant hormones are substances that act as chemical messengers within plants.

• Auxins are hormones responsible for phototropism.

• They cause the cells on the dark side of the plant’s stem to grow longer.

Chemical Stimuli

• The plant hormone ethylene helps stimulate the ripening of fruit.

• Ethylene is a gas that can be produced by fruits, seeds, flowers, and leaves.

Chemical Stimuli (cont.)

How do plants respond to the chemical stimuli, or hormones, auxin and ethylene?

• Rapidly growing areas of a plant, such as roots and stems, produce gibberellins, which increase the rate of cell division and cell elongation.

• Root tips produce cytokinins, a hormone that increases the rate of cell division and, in some plants, slows the aging process of flowers and fruits.

Chemical Stimuli (cont.)

• Humans make plants more productive by using plant hormones.

• Some crops now are easier to grow because humans understand how plants respond to hormones.

Humans and Plant Responses

• Plants respond to stimuli in their environments in many ways.

• Photoperiodism occurs in long-day plants and short-day plants. Day- neutral plants are not affected by the number of hours of darkness.

• Plant hormones are internal chemical stimuli that produce different responses in plants.

A. phototropism

B. photoperiodism

C. gravitropism

D. thigmotropism

Which term refers to the growth of a plant toward or away from light?

A. auxins

B. cytokinins

C. ethylene

D. tendrils

Which of the following helps stimulate the ripening of fruit?

A. roots

B. stems

C. leaves

D. tendrils

Which refers to special plant structures that respond to touch?

Do you agree or disagree?

4. Plants do not produce hormones.

5. Plants can respond to their environments.

6. All plants flower when nights are 10–12 hours long.

Key Concept Summary

Interactive Concept Map

Chapter Review

Standardized Test Practice

Plants survive by maintaining homeostasis and responding to stimuli. In addition, they acquire the energy they need for life processes through photosynthesis and cellular respiration.

• The vascular tissues in most plants, xylem and phloem, move materials throughout plants.

• In photosynthesis, plants convert light energy, water, and carbon dioxide into the food-energy molecule glucose through a series of chemical reactions. The process gives off oxygen.

• Cellular respiration is a series of chemical reactions that convert the energy in food molecules into a usable form of energy called ATP.

• Photosynthesis and cellular respiration can be considered opposite processes of each other.

Lesson 1: Energy Processing in Plants

Lesson 2: Plant Responses• Although plants cannot move from one place to

another, they do respond to stimuli, or changes in their environments. Plants respond to stimuli in different ways. Tropisms are growth responses toward or away from stimuli such as light, touch, and gravity. Photoperiodism is a plant’s response to the number of hours of darkness in its environment.

• Plants respond to chemical stimuli, or plant hormones, such as auxins, ethylene, gibberellins, and cytokinins. Different hormones have different effects on plants.

A. leaves

B. phloem

C. roots

D. xylem

Carbon dioxide, oxygen, and water vapor pass into and out of a plant through which part of a plant?

A. xylem

B. phloem

C. chloroplasts

D. chlorophyll

Water flows to all parts of a plant in which of these?

A. photoperiodism

B. photosynthesis

C. stimuli

D. tropism

Which term refers to a response that results in plant growth toward or away from a stimulus?

A. negative

B. photoperiodism

C. photosynthesis

D. positive

When the growth is toward a stimulus, what is the tropism referred to as?

A. hormones

B. stoma

C. tendrils

D. xylem

Which acts as chemical messengers in plants?

A. cellular respiration

B. photosynthesis

C. xylem

D. phloem

Which term refers to a series of chemical reactions that convert light energy, water, and carbon dioxide into the food-energy molecule glucose?

A. xylem

B. phloem

C. mesophyll cells

D. chloroplasts

Where does the first step of photosynthesis occur?

A. tropism

B. gravitropism

C. phototropism

D. stimuli

Which term describes any changes in an organism’s environment that cause a response?

A. 12 or more

B. 10 to 12

C. 8 to 10

D. less than 8

Short-day plants require how many hours of darkness for flowering to begin?

A. gravitropism

B. photoperiodism

C. phototropism

D. thigmotropism

A growing ivy plant comes into contact with a brick building and begins to grow up the building. What is this response?