Gas Exchange in Plants Humans: Plants: INHALEEXHALE NN O2O2 CO 2 H 2 O vapor CO 2 O2O2 H2OH2O
Plants need water and CO 2 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 (**CO 2 ) Guard Cells: structures that swell & shrink to regulate the opening & closing of the stomata
When guard cells lose water, they shrink and close the stomata. –Less CO 2 enters and less H 2 O 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 6CO 2 + 6H 2 O + light energy C 6 H 12 O 6 + 6O 2
Chlorophyll: A pigment that traps light energy from the sun and gives leaves and stems in plants their green color
Steps of Photosynthesis 1. CO 2 & H 2 O are the “ingredients” 2. These atoms are rearranged to form a new molecule (C 6 H 12 O 6 ), a simple sugar called glucose The energy in the chemical bonds of glucose is used by the plant for growth & reproduction
Photosynthesis Table IngredientsProducts 6 CO 2 (carbon dioxide) C 6 H 12 O 6 (glucose) 6 H 2 O (water)6 O 2 (oxygen) Light energy
Products of Photosynthesis O 2 most is released through stomata C 6 H 12 O 6 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 C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + 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 IngredientsProducts C 6 H 12 O 6 (glucose)6 CO 2 (carbon dioxide) 6 O 2 (oxygen)6 H 2 O (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 CO 2 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