chapter 15 plant processes. 15.1 photosynthesis & respiration

Chapter 15

Plant Processes

15.1 Photosynthesis & Respiration

Gas Exchange in Plants

• Humans:

• Plants:

INHALE EXHALE

N N

O2 CO2

CO2 H2O vapor

CO2 O2

H2O

• Plants need water and CO2 to survive• ROOTS absorb most of the water & move

it up through the plant• Stomata: small openings on leaves where

water and gases enter & leave plants (**CO2)

• Guard Cells: structures that swell & shrink to regulate the opening & closing of the stomata

Stomata

• When guard cells lose water, they shrink and close the stomata.– Less CO2 enters and less H2O leaves

• Stomata are usually closed at night or when the plant lacks water.

Open & Closed Stomata

Transpiration:

• Loss of water vapor through the stomata of a leaf

Photosynthesis:

• The process by which plants use CO2, water, and sunlight to produce food

Chlorophyll

• 6CO2 + 6H2O + light energy

C6H12O6 + 6O2

Chlorophyll:

• A pigment that traps light energy from the sun and gives leaves and stems in plants their green color

Steps of Photosynthesis

• 1. CO2 & H2O are the “ingredients”

• 2. These atoms are rearranged to form a new molecule (C6H12O6), a simple sugar called glucose

• The energy in the chemical bonds of glucose is used by the plant for growth & reproduction

Photosynthesis Table

Ingredients Products

6 CO2 (carbon dioxide)

C6H12O6 (glucose)

6 H2O (water) 6 O2 (oxygen)

Light energy

Products of Photosynthesis

• O2 most is released through stomata

• C6H12O6 main form of food for plant cells

Importance of Photosynthesis

• 1. provides food for nearly all other organisms on Earth

• 2. removes carbon dioxide from the atmosphere and replaces it with oxygen

Respiration:

• Series of chemical reactions by which all organisms break down food to release energy

• Occurs in the mitochondria of a cell

Respiration Equation

• C6H12O6 + 6O2 6CO2 + 6H2O + energy

• This equation is the exact reverse of photosynthesis!

2 Types of Respiration

• 1. Aerobic: occurs in the presence of O2

• 2. Anaerobic: occurs without O2

• Aerobic respiration combines oxygen and food to release the energy in the chemical bonds of food.

Cellular Respiration Table

Ingredients ProductsC6H12O6 (glucose) 6 CO2 (carbon

dioxide)

6 O2 (oxygen) 6 H2O (water)

Energy

Importance of Respiration

• Energy in food is in a form that CANNOT be used by cells.

• During respiration, food energy is converted into a form that all cells can use

• Aerobic respiration returns CO2 to the atmosphere where it can be used again by photosynthetic organisms

15.2 Plant Responses

• Stimulus: anything in the environment that causes a change in the behavior of an organism

• Response: change in behavior as a result of the stimulus

2 Types of Stimuli

• 1. Outside (phone ringing)

• 2. Inside (chemical reactions & hormones)

ALL living organisms, including plants, respond to stimuli.

Hormones:

• Substances made by cells for use somewhere else in the organism

Tropisms:

• Response of a plant to an outside stimulus

• Can be positive or negative (toward or away from the stimulus)

• Thigmotropism: – plant response to touch

• Gravitropism: – plant response to gravity

• Phototropism: – plant response to light