Photosynthesis

• Shoot system

  Above ground
• Root system

  below ground
• Flower

  Male and female parts to make seeds
• Leaf

  Contains chloroplasts to make food by photosynthesis
• Bud

  To make new leaves or flowers
• Root

  Absorbs water and minerals from the soil
• Stem

  Holds leaves and flowers upright
• Properties of leaves

  Large surface area to catch light

  Packed with chlorophyll to trap light

  ’Skin’ has millions of pores to allow gases in and out

  Thin - materials don’t have far to travel through
• Petiole

  Attaches leaf to stem
• Blade

  Large surface area to trap light
• Midrib

  To support leaf and allow water movement
• Lateral vein

  Side branch of midrib

  Water movement
• Light is trapped by chlorophyll so

  only green parts photosynthesise
• Once light energy is trapped it is used to

  join carbon dioxide and water together to

  make food (glucose) and oxygen
• Photosynthesis word equation

  Carbon dioxide + H2O > glucose + oxygen
• Glucose made is used for

  Releasing energy

  Stored in leaf as starch

  Sent through veins to parts that cannot photosynthesise
• Parts of a plant that cannot photosynthesise

  Roots(not in light)

  Flowers/fruit(No chlorophyll)
• How is a plant prepared for leaf starch test?

  Destarching by keeping it in the dark for 48 hours so that it cannot photosynthesise and uses up all of its starch
• What colour change occurs with iodine when starch is present?

  Yellow-brown > blue-black
• Leaf starch test

  1.Create a waterbath

  2. Drop disc into water for 2 mins to remove wax

  3.Drop disc into a test tube of ethanol inside the water to remove chlorophyll

  4.Remove from ethanol and rinse it in the water to soften leaf

  5.Place disc on tile and drop iodine over it.

  The bunsen must be turned off for ethanol as it is highly flammable
• Sodium hydrogen carbonate

  Adds CO2
• Soda lime

  Removes CO2
• If a leaf has some parts with chlorophyll and some without

  it is variegated
• Limiting factors of photosynthesis

  CO2

  Water

  Light

  Temperature
• Genetically modified organisms are

  transgenic
• Genetic modification can get the plant to

  Grow bigger or faster

  Make more for people to eat

  Some plants could be made to grow in salty water

  Grow in very little water

  Resist disease

  Make vaccines against illnesses like polio or measles
• Famous examples of GE organisms

  Flavr Savr tomato

  Maize
• Genetic engineering is

  Altering the recipes for life
• Function of magnesium in soil

  Make new chlorophyll
• Function of Nitrates in soil

  Make protein for new cells
• Function of Calcium in soil

  Strengthen cell walls
• To increase mineral salts

  farmers add fertiliser
• Artificial fertiliser

  Man-made chemicals

  High cost

  They dissolve very quickly into soil

  Can be absorbed by plants immediately
• Natural fertiliser

  Animal waste (slurry) or composted plant remains

  Low cost

  Must be ploughed into soil months in advance

  Slow acting- not absorbed immediately