Chapter 5- Nutrition in plants Flashcards
What is photosynthesis?
Photosynthesis is the process in which light energy is absorbed by chlorophyll and converted to chemical energy for the subsequent formation of carbohydrates.
What are the conditions necessary for photosynthesis?
- Sunlight
- Chlorophyll
- Carbon dioxide
- Optimum temperature
- Water (H2O)
What happens in the light stage?
- Absorption of light energy by chlorophyll.
- Conversion of light energy to chemical energy.
- Photolysis of water to produce 6O2 and 24H+ ions.
What happens in the dark stage?
- Products of photolysis used.
2. Hydrogen used to reduce carbon dioxide to carbohydrates, with the aid of enzymes and chemical energy.
What is the overall chemical equation of photosynthesis?
12H2O + 6CO2 –> C6H12O6 + 6H2O + 6O2
What is the importance of photosynthesis?
- It makes chemical energy available to other organisms.
- It purifies air by removing CO2 and providing O2.
- Energy is stored in fossil fuels via photosynthesis.
What is the fate of glucose in the leaves?
- Used immediately (respiration | cellulose to build cell walls).
- Converted to starch in the day and back at night.
- Converted to sucrose (storage organs | converted back).
- React with nitrates / mineral salts to form amino acids. (New protoplasm | storage as proteins)
- Converted to fats (storage | cell membrane | respiration).
What are the limiting factors for photosynthesis?
- Temperature
- Carbon dioxide concentration
- Light intensity
How are the external features of a leaf adapted for optimizing photosynthesis?
- Lamina (large flat area | increase surface area to volume ratio | maximize light absorption | thin for rapid diffusion of CO2 into leaf)
- Petiole (holds leaf away from stem | maximum absorption)
- Network of veins (carries H2O and mineral salts to the leaf)
- Leaf arrangement (regular pattern | optimum light received)
How are the internal features of a leaf adapted for optimizing photosynthesis?
- Cuticle (reduce water loss | transparent)
- Palisade mesophyll (contains lots of chlorophyll)
- Spongy mesophyll (also contains chlorophyll | not as much)
- Interconnecting system of air spaces in spiny mesophyll (rapid diffusion of O2 and CO2)
- Veins containing xylem and phloem close to mesophyll (distribute)
How do the guard cells control the size of the stomata?
In the day, the guard cells are turgid as water diffuses into the cells rapidly. The cell thus curves open and the stomata is pulled open. At night, however, potassium ions that have accumulated in the cells will diffuse out of the cells, causing water to flow out as well due to an decrease in water potential. Hence, cells become flaccid and stomata closes.
