Plant nutrition

• Photosynthesis is the process by which green plants manufacture carbohydrates from carbon dioxide and water using energy from light
• Glucose is made and oxygen is released as a waste product during photosynthesis
• Chlorophyll is a green pigment found in chloroplasts within plant cells that absorbs light energy to transfer it into energy in chemicals for the synthesis of carbohydrates
• Carbohydrates produced during photosynthesis can be used in various ways:

  • Converted into starch molecules for energy storage
  • Converted into cellulose for building cell walls
  • Used in respiration to provide energy
  • Converted to sucrose for transport in the phloem
  • Used as nectar to attract insects for pollination
  • Converted into lipids for energy source in seeds
  • Converted into amino acids for protein synthesis when combined with nitrogen and other mineral ions absorbed by roots
• Plants obtain mineral ions actively absorbed from the soil by root hair cells to produce various biological molecules
• Leaves can be tested for starch to indicate which parts are photosynthesizing, as starch is stored in chloroplasts where photosynthesis occurs
• Light is necessary for photosynthesis, as proven by testing destarched leaves partially covered with aluminum foil that did not receive sunlight
• Carbon dioxide is necessary for photosynthesis, as shown by testing plants placed in environments with and without carbon dioxide absorption
• The rate of photosynthesis can be investigated by counting bubbles produced by pondweed over a minute or by measuring the volume of oxygen collected over time
• Factors affecting the rate of photosynthesis can be investigated by changing light intensity, temperature, or carbon dioxide concentration
• Plants are respiring all the time
• Plant cells take in oxygen and release carbon dioxide as a result of aerobic respiration
• Plants photosynthesise during daylight hours, taking in carbon dioxide and releasing oxygen
• At night, plants do not photosynthesise but continue to respire, taking in oxygen and giving out carbon dioxide
• During the day, especially when the sun is bright, plants are photosynthesising at a faster rate than they are respiring
• Net intake of carbon dioxide and net output of oxygen during photosynthesis
• Factors limiting the rate of photosynthesis: Temperature, Light intensity, Carbon dioxide concentration
• Temperature:

  • Rate of photosynthesis increases with temperature until enzymes denature and the rate decreases
• Light intensity:

  • More light leads to a faster rate of photosynthesis until another factor limits the rate
• Carbon dioxide concentration:

  • More carbon dioxide present leads to a faster reaction until another factor limits the rate
• Leaf structure adaptations for photosynthesis
• Pathway of carbon dioxide from the atmosphere to chloroplasts by diffusion: atmosphere → air spaces around spongy mesophyll tissue → leaf mesophyll cells → chloroplast
• Identifying leaf structures in a dicotyledonous plant: Chloroplasts, Cuticle, Guard cells, Stomata, Upper and lower epidermis, Palisade mesophyll, Spongy mesophyll, Air spaces, Vascular bundles (xylem and phloem)
• EXPLAIN WHY A WOMAN'S DIETARY REQUIREMENT WILL CHANGE WHEN SHE IS PREGNANT?

  • Women will require more energy
  • For the growth/development of foetus
  • More carbohydrates / proteins / fats / named vitamin / named mineral (need to be consumed)
  • Role of named nutrient (must be linked to named nutrient), e.g. carbohydrates for energy / protein for growth