Topic 6

• Photosynthesis is an endothermic reaction
• 6CO2 + 6H2O ——-> C6H12O6 + 6O2
• Rate of photosynthesis slows down when lamp is moved further away
• Control factor is the time, type of bulb, same volume of sodium hydrogen carbonate
• Independent variable : distance of plant from lamp, temperature using water
• dependent variable


  Amount of bubbles released in a certain time
• photosynthesis takes place in the Chloroplast of plant cells
• Light intensity = 1/d^2
• high light intensity slows down rate of photosynthesis
• concentration gradient - difference between 2 concentrations
• Active transport requires lots of energy so there should be lots of mitochondria
• Rate of photosynthesis directly proportional to the light intensity
• limiting factors : temperature (denature or reduce speed), concentration of CO2, pH
• Plants transpire : cools leave down, keeps cells rigid, water for photosynthesis and dissolved minerals for plant
• Wind = moves water molecules away from stomata
• Humidity = how much water vapour is in the air
• Temperature = faster diffusion of particles
• light intensity = stomata are wider in greater light intensity
• Factors affecting rate of transpiration : 1. Temperature 2. Wind 3. Light intensity 4. Humidity
• Translocation


  taken where it is needed , active transport
• Transpiration

  1. passive 2. Transports water in plants
• stomata open to let CO2 into leaf and let oxygen out
• Stomata are tiny pores on underside which are controlled by guard cells
• Speed of bubble gives a measure of the rate of transpiration in potometer
• Xylem

  1. water transported up only 2. dead cells 3. Lignin withstand high water pressure 4. Hollow
• Phloem

  1. transports sugar and amino acids 2. Living cells 3. Sucrose goes in both directions
• Cuticle is waterproof and waxy (prevents water loss)
• Meristem is the tip of roots and shoots, cells differentiate here
• Epidermal is transparent and forms outer layer of the leaf
• Spongy mesophyll is a large air space for gas exchange and photosynthesis occurs here
• Vascular bundle contains xylem and phloem
• Root hair cells

  1. Long hair extension 2. Large surface area for quicker absorption 3. Mitochondria provide energy for Active transport
• Auxins control growth rate at root (geotropism) and shoot (phototropism)
• auxins used as weed killer and rooting powder
• Giberellins regulate plant growth and help plants germinate/flower
• Ethene speeds up ripening of fruits
• benefits of plant hormones

  economically beneficial, cheap to get plant hormones, gets rid of weeds
• Cacti have needles not leaves, the stem photosynthesises and are hairy for insulation in night
• Plants in Cold places have needles so snow doesn’t stay and have thick waxy cuticle for snow to slide off