Download Plant Processes: Photosynthesis

Plant Processes: Gas Exchange
and Photosynthesis
What is gas exchange in plants?
• When we inhale, we breathe in a mixture of gases we
need for survival
• When we exhale, we breathe out the waste products
• In plants, CO₂ and H₂O are two substances needed for
survival
– CO₂ enters through the stomata
– H₂O is absorbed through roots of
the plant and released as water
vapor through the stomata
Gas Exchange
• Light, H₂O and CO₂ all
affect the opening and
closing of stomata
• Stomata are usually open
during the day and close
at night
– When stomata closes, less
CO₂ can enter and less H₂O
can escape
• When plants lose water
vapor through stomata,
this is called transpiration
Photosynthesis
• Photosynthesis is the process in
which plants use light energy to make food
– Chlorophyll is a chemical in plants that helps to
capture this light energy
• Other than light, plants also need H₂O and CO₂
• These molecules combine to form an organic
compound, a carbohydrate (sugar) called glucose
Process of Photosynthesis
6CO₂ + 6H₂O + light energy  C₆H₁₂O₆ + 6O₂
Carbon dioxide + water +
light
(and chlorophyll) produces glucose and oxygen
• A plant needs 6 molecules of carbon dioxide (CO₂) and 6 molecules
of water (H₂O) to make one molecule of glucose (C₆H₁₂O₆)
• The chemical bonds in glucose contain the energy the plant needs
for growth and survival and is the main source of food for plants
• Oxygen is produced as a waste product during photosynthesis and
released through plant stomata