plants ୨୧

• equation : 6CO2 + 6H2O >> C6H12O6+6o2
• Photosynthesis occurs at the mesophyll cells
• Photosynthesis converts light energy to chemical energy.
• Chloroplast contains chlorophyll.
• Chlorophyll absorbs light energy for photosynthesis.
• Oxygen is released as gas/bubbles.
• Plant cells store glucose as starch.
• Oxygen : During aerobic respiration to release energy
• Glucose:

  During aerobic respiration to release energy

  Excess glucose stored as starch.

  Glucose converted to fats and amino acid for synthesis of new

  protoplasm

  Glucose transported as sucrose during translocation
• Light energy ( limiting factor )

  At low light intensity, as light intensity increases,

  More light energy is absorbed by the chlorophyll for faster rate of

  photosynthesis.

  At high light intensity, as light intensity increase,

  Rate of photosynthesis remains the same.
• Carbon dioxide concentration ( Limiting factor )

  At low carbon dioxide concentration, as CO2 concentration increase,

  rate of photosynthesis is faster.

  At high carbon dioxide concentration, as CO2 concentration increase,

  rate of photosynthesis remains the same.
• Temperature ( Limiting factor )

  At low temperature, as temperature increases,

  Rate of photosynthesis increases.

  At optimal temperature, rate of photosynthesis is the highest.

  At high temperature, as temperature increases,

  Rate of photosynthesis decreases.
• Mineral salts dissolve into water and are transported together with water
• Carbon dioxide is needed by mesophyll cells for photosynthesis
• Palisade mesophyll contains the most chloroplast
• Spongy mesophyll contains lesser chloroplast than palisade mesophyll
• Lower epidermis have little chloroplast found on guard cells
• Upper epidermis has no chloroplast
• Upper epidermis has waxy & transparent cuticle: to reduce evaporation, hence reduce water loss from the leaf. Transparent for light energy to reach the mesophyll cells for photosynthesis
• Mesophyll cells contain chloroplast containing chlorophyll to absorb and trap light energy and convert light energy to chemical energy used in photosynthesis to make glucose.
• Palisade mesophyll cells are found near the surface of leaves to allow more light energy to be absorbed and trapped for photosynthesis
• Palisade mesophyll are long & cylindrical, closely packed together to maximise light energy absorbed and trapped to maximise photosynthesis rate
• More chloroplast found on palisade mesophyll cells to maximise light energy absorbed and trapped to maximise photosynthesis rate
• Spongy mesophyll cells have a thin film of moisture to allow oxygen molecules to dissolve and diffuse into spongy mesophyll cells for photosynthesis
• Spongy mesophyll cells have a thin film of moisture as water evaporates into water vapour molecules into the intercellular air spaces
• Intercellular air spaces contain oxygen, water vapour and carbon dioxide molecules
• Vascular bundle: xylem and phloem
• Xylem : water and mineral salts from roots to leaves by transpiration pull
• Sucrose and amino acids from leaves to plant parts by translocation
• Guard cells control stomata size
• Oxygen and water vapour molecules leave stomata by diffusion
• Diffusion of water vapour molecules through stomata into atmosphere = transpiration
• Carbon dioxide molecules enter stomata by diffusion
• Guard cells have chloroplast to photosynthesize
• Lower epidermis layer has a waxy and transparent cuticle to reduce evaporation hence reduce water loss from the leaf
• Lower epidermis layer are waxy and transparent for light energy to reach the mesophyll cells for photosynthesis
• Define transpiration

  Diffusion of water vapour molecules from intercellular air spaces into the atmospheric air through the stomata
• Define transpiration pull


  Transpiration pull is the suction force due to transpiration
• Define photosynthesis

  Photosynthesis is a process in which light energy is absorbed by chlorophyll to make glucose from carbon dioxide and water
• Define translocation

  Translocation is the bi-directional transport of food, mainly sucrose, in the phloem tissue from the leaves to other parts of the plant