factors that affect photosynthesis

• what is the limiting factor?

  • at any given time, photosynthesis is limited primarily by the one factor that is the least favourable in terms of value.
• for plants in the uk, what are optimum conditions?

  • hight light intensity of a certain wavelength
  • temperature around 25'C
  • carbon dioxide around 0.4 %
• explain the optimum condition of : high light intensity of a certain wavelength

  • light needed to provide energy for light dependent reaction, the higher the intensity of the light, the more energy is provides.
  • only certain wavelengths of light are used for photosynthesis. the photosynthetic pigments (eg: chlorophyll a) only absorb the red and blue light in sunlight.
• explain the optimum condition of : temperature around 25'C

  • photosynthesis involves enzymes, (ATP synthase and rubisco). if the temp falls between 10'C, the enzymes become inactive but if the temp is more than 45'C they may start to denature.
  • also, at high temps stomata close to avoid losing too much water, this causes photosynthesis to slow down because less CO2 enters the leaf.
• explain the optimum condition of : carbon dioxide at 0.4 %

  • CO2 makes up around 0.04 % of the gases in the atmosphere
  • increasing this to 0.4 % gives a higher rate of photosynthesis, but any higher and the stomata start to close.
• explain water as a factor in photosynthesis

  • plants need a constant supply of water
  • too little and photosynthesis has to stop
  • too much and the soil becomes waterlogged, this reduces uptake of minerals needed to make chlorophyll a.
• what happens when 2 factors are at perfect level but one isn't?

  • it will still limit photosynthesis, as long as one factor isn't right, the perfect conditions won't make any difference to rate.
• what is the saturation point?

  • where a factor is no longer limiting the reaction, something else has become the limiting factor.
• how does a greenhouse manage CO2 concentration?

  • CO2 is added to the air, eg: burning a small amount of propane in a CO2 generator.
• how does a greenhouse manage light intensity?

  • lamps can get in through the glass
  • lamps provide light at night-time
• how does a greenhouse manage temperature?

  • glasshouses trap heat energy from sunlight, which warms the air.
  • heaters and cooling systems can also be used to keep a constant optimum temperature.
  • air circulation systems make sure the temperature is even throughout the greenhouse.