plants

• photosynthesis = the process of making glucose from sunlight

  it changes light energy from sun to chemical energy for plant to 'eat'
• photosynthesis equation: 6CO2 + 6H2O = C6H12O6 + 6O2
• minerals are used to grow and be healthy
• magnesium = produces chlorophyll for photsynthesis - turns yellow
• nitrogen = produces amino acids and proteins to grow - stunted growth
• structure of leaf = waxy cuticle - upper epidermis - palisade mesophyll layer - spongey mesophyll layer - phloem and xylem - lower epidermis - waxy cuticle
• waxy cuticle = stops water loss via evaporation
• upper epidermis = transparent - allows light through to reach palisade mesophyll layer, protects against pathogens
• palisade mesophyll layer = lots of chloroplasts - lots of photosynthesis
• spongey mesophyll layer = many air pockets - gases diffuse easily
• xylem = carries water and minerals up plant via stem - keeps cells turgid
• phloem = transports sucrose and amino acids from leaves to plant
• stomata = opens in light - allows diffusion of CO2 into cell and O2 out cell, closes when too much water is lost via transpiration
• guard cells = water filled cells that control the stomata - turgid = filled with water and opens stomata, flaccid = lacks water and sag to close stomata
• limiting factors?

  holds back a rate
• CO2 concentration: increase in CO2 = more photosynthesis
• light intensity: increase in light = more photosynthesis
• temperature: increase in temp - reaches optimum temp - increase after = denatures and less photosynthesis
• xylem: tissue that transports water and minerals up stem of plant to the leaves - made of dead cells and a hollow lumen = waterproof by lignin - provides stem with structure
• xylem structure: cells lose end walls to create one long hollow tube - uses no energy
• phloem: move sucrose and amino acids up and down plant, from leaves to where it is needed for - used in growth, storage and development of seeds, process called translocation = active transport - against concentration gradient and uses energy
• sieve tubes (phloem) = no nucleus, specialised and has a perforated end - allows cytoplasm to connect them together
• companion cells (phloem) = attaches one or more to each end of sieve tube to provide energy - sieve tubes are dependant, has less cytoplasm and organelles = more room for energy
• plants exchange gases via diffusion - use up CO2 and produce O2 as waste product
• photosynthesising plants use lots of CO2 so not much in leaf = more CO2 moves into leaf via diffusion, lots of O2 = diffuses out cell by stoma
• adapted for gas exchange?

  • broad leaves = large surface area
  • thin = short diffusion pathway
  • air inside leaf = gases move easily between cells - larger SA
  • lots of stomata = allow movement of gases, let water escape
• stomata close at night, photosynthesis cannot happen at night = dont need to let CO2 in and stops water from escaping
• stomata also close up when there is less water = stops plant from drying out
• guard cells:

  • decrease in volume = close stomata
  • increase in volume = open stomata
• root hair cells:

  • absorbs water
  • increase surface area of roots = can take more water by osmosis and minerals by active transport
• transpiration?

  the evapouration of water from the surface of plants - water evapourates out of spongey mesophyll layer
• rate of transpiration effected by sunlight: stomata is open = more water loss
• rate of transpiration effected by temperature: warmer = more evaporation of water - faster transpiration (have more kinetic energy)
• rate of transpiration effected by wind speed: higher wind = greater transpiration (increases concentration so more diffusion)
• rate of transpiration effected by humidity: low humidity = less water in atmosphere = higher concentration gradient = faster
• measure transpiration:

  • potometer = cut shoot underwater to stop air getting in the xylem, make apparatus air tight, measure bubble at start and the distance it travels in certain length of time = amount of water lost