Plants and photosynthesis
Connect plant structures with photosynthesis, respiration, water movement, and ecosystem roles.
Photosynthesis#
Plants use light energy to convert carbon dioxide and water into glucose, releasing oxygen. The process occurs mainly in chloroplasts containing chlorophyll.
Glucose can support respiration, be stored as starch, or become cellulose and other substances.
Plant transport#
Roots absorb water and mineral ions. Xylem transports water upward, while phloem distributes sugars and other organic compounds. Water loss through leaves helps drive movement but must be regulated.
Stomata#
Small openings called stomata allow carbon dioxide to enter and oxygen and water vapour to leave. Guard cells adjust opening in response to conditions.
Respiration#
Plants respire day and night. Photosynthesis requires light; respiration releases usable energy from stored molecules. These are related but not opposite switches.
Common mistakes#
Plants do not obtain all food from soil. Minerals come from soil, while the carbon in sugars comes primarily from carbon dioxide. Oxygen production does not mean plants never use oxygen.
Ecosystem connection#
Plants form the base of many food webs, create habitats, influence water cycles, and store carbon in biomass.
Key points
- Photosynthesis uses light energy to build sugars from carbon dioxide and water.
- Chlorophyll absorbs light in chloroplasts.
- Stomata regulate gas exchange and water loss.
- Plants also perform cellular respiration.