Plants & Photosynthesis

• chlorophyll absorbs light energy and is used to make glucose
• Word equation for photosynthesis:

  carbon dioxide + water --> glucose + oxygen
• enzymes control the chemical reactions of photosynthesis
• Environmental factors that affects the rate of photosynthesis are light intensity, temperature, CO2 concentration, and water availability
• glucose is used to release energy in respiration
• glucose can be changed to starch and stored
• glucose can be used to make proteins and cellulose
• order of the layers of a leaf:

  . upper epidermis

  . palisade mesophyll

  . spongy mesophyll

  . lower epidermis
• palisade layer contains cells packed with chloroplasts for photosynthesis
• spongy layer contains large air spaces to allow gaseous exchange
• cuticle is a waxy waterproof layer to reduce water loss
• xylem transports water and mineral ions
• phloem transports glucose and other nutrients
• stomata opens to allow carbon dioxide to diffuse into the leaf and oxygen to diffuse out
• when the stomata opens, the leaf will lose water which would increase the rate of transpiration
• the stomata close to prevent water loss
• a potometer measures transpiration rate
• temperature, humidity and wind can affect water loss from a plant
• transpiration is the loss of water that evaporates and diffuses from the leaves of a plant
• Three main minerals are needed for healthy plant growth: nitrates, potassium and phosphates
• Nitrogen deficiency will cause poor growth in plants
• Potassium deficiency will cause yellowing of leaves
• Phosphate deficiency will cause poor root growth
• Nitrogen deficiency will cause poor growth in plants
• Potassium deficiency will cause yellowing of leaves
• Phosphate deficiency will cause poor root growth
• the constant flow of water in a plant is called the transpiration system
• the constant flow of water in a plant is called the transpiration system
• water supports the plant by keeping the cells turgid which prevents cells becoming flaccid and plants wilting
• photosynthesis equation


  carbon dioxide + water --> oxygen + glucose
• plants make glucose during photosynthesis which is stored as starch
• if starch is present iodine turns blue black
• test leaf for starch

  1. boil leaf in water to kill cells
  2. put leaf in boiled ethanol to remove chlorophyll
  3. wash leaf in water to soften it
  4. place leaf on white tile and drop iodine: if brown then no starch, if blue black then starch is present
• before testing a plant for photosynthesis, plants are placed in the dark for 48 hours to destarch the leaves so that we know any starch present must be from the experiment
• the green parts of variegated leaves have chloroplasts while the white parts dont
• partly covered leaves are to test for use of sunlight in photosynthesis