Crop plants

• Greenhouses help increase crop yield by:

  Light - transparent allowing light to enter. Additional artificial lighting can be provided to increase light intensity for photosynthesis

  Heat - trap heat energy but may need to be ventilated to prevent excessively high temperatures in summer that might denature enzymes
• Polytunnels help increase crop yield by:

  • They are plastic so can be used on either a very small or a very large scale
  • They are cheaper and can be used for individual allotments or commercial growers
  • Used for crops such as strawberries, tomatoes, cucumbers, lettuces etc
  • With polytunnels and greenhouses, crops can become ripe for harvest out of season, providing year round crop availability
• What can be controlled in glasshouses?

  Carbon Dioxide concentration
• How can farmers increase Carbon Dioxide levels in glasshouses?

  By burning Paraffin lamps
• What is the limiting factor that affects crop yield when Carbon Dioxide concentration is high?

  Another factor will limit the rate of Photosynthesis
• What is the relationship between Carbon Dioxide concentration and Photosynthesis?

  • Increased Carbon Dioxide concentration boosts Photosynthesis
  • Carbon Dioxide is a reactant in the Photosynthesis process
  • Beyond a certain concentration, Photosynthesis rate plateaus
• • As glasshouses are enclosed, heat from the Sun can be trapped to create a warm climate
  • As temperature increases towards optimum, the rate of Photosynthesis will increase to increase crop yield
  • This is because the increase in temperature towards optimum will allow optimum enzyme activity for Photosynthesis-related enzymes, hence increasing the rate of photosynthesis
  • However, as temperature increases above optimum, enzymes involved in Photosynthesis will denature, therefore causing the rate of Photosynthesis to decrease - crop yield will decrease
• Fertilisers contain nitrate ions for making proteins/DNA, magnesium ions for making chlorophyll, and phosphate ions to make ATP and DNA
• Organic fertilisers are natural e.g. manure or compost
• Chemical fertilisers are artificially manufactured to contain high concentrations of compounds such as ammonium nitrate
• A disadvantage of fertilisers is it can cause leaching of nutrients into rivers and lakes which leads to eutrophication
• PEST CONTROL: Use of Pesticides (chemicals such as Fungicides, Herbicides and Insecticides) to control pests from consuming or damaging Plants
• Advantages for pest control:

  • Efficient and quick
  • Immediate effect
  • Targets and kills the entire population
• Disadvantages for pest control:

  • Pests can develop resistance
  • Chemicals are non specific - could kill other organisms
  • Toxic to food chain - bioaccumilation
  • Need for continuous application
• BIOLOGICAL CONTROL: Natural method to control pests using organisms that feed on pests
• Advantages to biological control:

  • Natural method
  • No resistance
  • Ability to target specific species
  • Long-lasting
  • Efficient as minimal effort is required
• Disadvantages to biological control:

  • May kill other organisms - non specific
  • Time lag in effect
  • Cannot kill the entire population
  • Organism may be unadaptable to new environment and die
• Herbicides are chemicals that are toxic to weeds, used by farmers to help crop yield because the herbicide removes plants that would compete with the crop plants for resources such as light, water and mineral ions