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