Plant structures and their functions

• Why are photosynthetic organisms important for all living things?

  They are the main producers of food and therefore biomass.
• What type of reaction is photosynthesis?

  Endothermic
• State the word equation for photosynthesis?

  Carbon dioxide+water -> Glucose+Oxygen
• What other reactants are required for photosynthesis besides carbon dioxide and water?

  Light and chlorophyll
• Describe how temperature can affect the rate of photosynthesis?

  The higher the temperature, the higher the rate of photosynthesis because the enzymes needed for photosynthesis are working closer to their optimum temperature
• State how temperature can be a limiting factor of photosynthesis?

  If the temperature is too low, the enzymes needed for photosynthesis work too slow, therefore a slower rate of photosynthesis. If temperature is too high, enzymes denature
• Explain the effect of light intensity on the rate of photosynthesis?


  The higher the light intensity, the faster the rate of photosynthesis because chloroplasts are getting more sunlight, therefore more chemical energy to turn to energy stores like glucose
• Describe how light can be a limiting factor of photosynthesis?

  When the distance between plant and light source increases, the light intensity decreases, making light intensity and distance inversely proportional.
• Explain how carbon dioxide can be a limiting factor of photosynthesis?

  Carbon dioxide is a reactant of photosynthesis, therefore if there is not enough of it, the rate of photosynthesis decreases
• Describe how light intensity affects the rate of transpiration?

  The higher the light intensity, the higher the rate of transpiration because stomata remain open for longer, so water vapour can diffuse out
• Describe how temperature can affect the rate of transpiration?

  The higher the temperature, the higher the rate of transpiration because the water particles have more energy to evaporate and diffuse out of the stomata.
• Describe how air flow can affect the rate of transipration?

  The better the air flow, the faster transpiration happens, because if air flow is good, water vapour around the surface of the leaf is spread out, therefore maintaining a low concentration of water particles outside the leaf compared to the inside, allowing diffusion to occur.
• Explain how small leaves and spines help cacti survive in extreme conditions?

  Reduces the surface area for water loss by evaporation; Spines stop animals from eating the plant to get water
• Describe how curled leaves and hairs on the surface of leaves help plants survive in extreme conditions?

  Reduces air flow close to the leaf, trapping water vapour near the air, therefore reducing diffusion from the leaf to the air
• How does a thick waxy cuticle allow plants to survive in extreme conditions?

  Reduces water loss by evaporation
• What is the purpose of a thick, fleshy stem in cacti?

  Stores water
• Why do fewer stomata help certain plants survive in extreme conditions?

  Because they reduce water loss by evaporation
• Why would it be advantageous to a plant living in extreme conditions have stomata sunken in pits?

  Stomata are lower than the surface of the leaf, which reduces air flow close to the stomata, reduces water loss.
• What is a tropism?

  The response of an organism to a stimuli which causes growth
• What is phototropism?

  The growth of a plant in response to light
• Which hormone causes growth in a plant?

  Auxins
• Are shoots positively or negatively phototropic?

  Positively
• What is gravitropism?

  The growth of a plant in response to gravity.
• What do auxins cause in shoots?

  Cell elongation on the shaded side, causing the shoot to bend towards the light
• How do auxins affect the growth of roots?

  Inhibit cell elongation, so roots grow downwards, so they are positively gravitropic
• State how auxins can be commercially used?

  As selective weedkillers; Rooting powders
• Describe how selective weedkillers only affect certain plants?

  Auxins target broad leaved weeds, whilst not affecting grass and narrow leaved plants. Auxins disrupt the growth pattern of broad-leaved weeds, which kills them.
• Descrobe how rooting powder allows growers to clone plants?

  Rooting powder contains auxins, which allow the cutting to grow roots rapidly, so it can grow as a new plant
• State how gibberellins can be used commercially?

  Controlling flower and fruit formation; They can cause a plant to flower at any time+

  Stimulate seed germination+

  Reducing flower formation can improve fruit quality
• Explain another commercial use of gibberellins?


  Producing seedless fruit; Gibberellins applied to unpollinated plants causes the fruit to grow but not the seeds
• What plant hormone is used for fruit ripening?

  Ethene
• What plant hormone can be used to control seed germination?

  Gibberellins; They can cause many seeds to germinate at times of the year when they wouldn't normally. They can cause them to germinate all at the same time