Plants and Nutrition - chpt 6

• Photosynthesis is the process by which plants synthesize carbohydrates from raw materials using energy from light
• The raw materials for photosynthesis comes from the air and soil
• Photosynthesis takes place in plant cells with chloropasts
• Chloropasts contain the green chemical called chlorophyll
• Chlorophyll transfers energy from light into energy in chemicals, for the synthesis of carbohydtares
• The products of photosynthesis are glucose and oxygen
• Glucose is the useful product for plants. Some glucose are used straightaway by plant cells, some are converted to starch for storage and later used for food.
• Oxygen is the waste product. This gas is transported out of the leaf into the air
• Plant cells use carbon dioxide as raw material for making glucose during photosynthesis
• Plants use the glucose they make as a source of energy in respiration
• Plants can also use glucose to :

  • produce starch as an energy store
  • form cellulose to build cell walls
  • transport sucrose to phloem
  • produce nectar to attract insects for pollination
• Plants need nitrogen and magnesium to make chlorophyll
• Nitrogen is made up of nitrates of ammonium ions and is needed to make proteins. Without it, the plants will have weak growth and yellow leafs
• Magnesium is made up of magnesium ions and is needed to make chlorophyll. Without it, there would be yellowing between the veins of leaves
• Leaves are wide and flat to create a large surface area and absorb as much light as possible
• Leaves are thin so gases can reach cells easily
• Leaves have lots of veins to carry water to the cells and carry glucose away
• Leaves have holes called stomata, on their underside through which gases move in and out
• Waxy cuticle: Protective layer on top of the leaf, prevents water from evaporating
• Upper epidermis: thin and transparent to allow light to enter palisade mesophyll layer underneath it
• Palisade mesophyll: column shaped cells tightly packed with chloroplast to absorb more light, maximizing photosynthesis.
• Spongy mesophyll: contains internal air spaces that increases the surface area to volume ration for the diffusion of gases
• lower epidermis contains guard cells and stomata
• Guard cell absorbs and loses water to open and close the stomata to allow carbon dioxide to diffuse in and oxygen diffuse out
• Stomata is where gas exchange takes place, opens during the day and closes at night. It is where evaporation of water also takes place.
• Vascular bundle contains xylem and phloem to transport substances to and from the leaf
• Xylem transports water onto the leaf for mesophyll cells to use in photosynthesis for transpiration (evaporation) from stomata
• Magnesium ions are an essential part of a chlorophyll molecule
• Chlorophyll molecules have a green color as they absorb red and blue light wavelengths, reflecting green light
• Leaves deficient in chlorophyll appear yellow
• Nitrate ions are needed by plants to synthesize amino acids and proteins
• Without nitrate ions, a plant cannot grow correctly
• Green plants make the carbohydrate glucose from carbon dioxide and water
• Oxygen is made and released as a waste product during this process
• The reaction of making glucose and releasing oxygen requires energy
• Energy is obtained by the pigment chlorophyll trapping light from the Sun
• Photosynthesis is the process by which plants manufacture carbohydrates from raw materials using energy from light
• Photosynthesis is the process by which plants synthesise carbohydrates from raw materials using energy from light
• Word equation for photosynthesis: carbon dioxide + water → glucose + oxygen in the presence of light and chlorophyll
• Chlorophyll is a green pigment found in chloroplasts