Plant nutrition

• photosynthesis


  the fundamental process by which plants manufacture carbohydrates from raw materials using energy from light.
• What 3 Elements do plants need?

  oxygen, carbon and hydrogen
• cuticle


  Waxy substance secreted by upper epidermal cells to reduce water evaporation from leaf surface.
• epidermis


  An outer layer of cells that form a transparent protective layer (against fungi and bacteria). *Chloroplasts are absent.
• stomata


  Pores are present on the lower epidermis.

  Allows diffusion of gases in and out of the leaf including water vapour.
• guard cells


  Pair of bean-shaped cells that open or close the stoma.

  Contain chloroplasts.
• palisade layer


  Cells are rectangular and stand on their end. They contain a large number of chloroplasts.
• spongy layer


  Cells are smaller, rounder and also contain chloroplasts.

  
  

  Intercellular air spaces allow air to diffuse to cells inside the leaf.

  
  

  Provide a large moist thin surface for gas exchange.
• xylem


  Transports water and mineral ions from roots to leaves.

  *Always on top of the phloem in the leaf.
• phloem


  Transports sucrose and amino acids produced from the leaves to other parts of the plant.
• vascular bundle


  Tubes (vessels) in the outer parts of the stem which contain the xylem and phloem.
• sucrose


  Transported in the phloem.
• What are the limiting factors affecting the rate of photosynthesis?

  light intensity

  CO2 concentration

  temperature

  chlorophyll
• What mineral nutrients do plants need and why?

  Nitrates: contain nitrogen to form amino acids to make proteins. Nitrogen deficency results in stunted growth.

  
  

  Magnesium: part of chlorophyll molecule. Results in taller plant but yellow leaves.
• How do you test for sucrose in a plant?

  Add benedicts solution and it fails to react unlike glucose so its a non-reducing sugar.
• Why do plants store glucose as starch?

  It is insoluble and has no osmotic effect so it will not diffuse out of leaf cells.
• What are the differences between phloem and xylem?

  Xylem-carry minerals/H2O, dead, no end walls, passive transport.

  
  

  Phloem-carry sucrose, amino acids, alive, active transport.
• What is sap?


  water, sucrose, amino acids
• photosynthesis word equation


  carbon dioxide + water = glucose + oxygen
• How does carbon dioxide enter a plant?

  Through stomata by diffusion and into moist gas exchange surface of the mesophyll cells and diffusion to palisade layer. (Occurs during the day).
• What is the role of chlorophyll?

  Chlorophyll absorbs light energy and converts it into chemical energy for the formation of carbohydrates.
• What is the balanced chemical equation for photosynthesis?

  6CO₂ + 6H₂O (light & chlorophyll) → C₆H₁₂O₆ + 6O₂.
• limiting factor


  something present in the environment in such short supply that it restricts life processes.
• What are the uses and dangers of nitrogen fertilisers?

  Used to increase plant growth through formation of protein form nitrates.

  
  

  Danger is eutrophication of water ways and poisoning of soil drinking water.