Plants Flashcards
Function of waxy cuticle
Water resistant- decreases water loss from evaporation and water glides off
Function of upper epidermis
Thin, protective and transparent to allow free passage of light
Function of palisade layer
Compact cell, layer full of chloroplasts, dense packing allows the maximum amount of light energy absorbed
Function of spongy mesophyll
Gaps allow fast diffusion of gases
Function of the vein
Xylem Carrie’s minerals and water from the roots
Phloem Carrie’s nutrients (sucrose) from the leaves
Function of guard cell
Controls stomata opening and closing
Function of stoma
A gap that allows gases through CO2 and H2O and O2
Stomata control
Water entering the guard cells by osmosis causes the cells to become turgid. This results in the pushing away and there by opening the stoma. In low water conditions, the water in the guard cells leave by osmosis. Guard cells become flaccid and close the stoma.
Requirements for photosynthesis
- the availability of light
- the presence of a pigment to absorb the light
- a supply of carbon dioxide and water
- a temperature suitable for enzyme activity
Why do plants need nitrate
Plants need nitrate to be able to join with glucose to produce amino acids that are then used to form proteins . A shortage of nitrate, the plant will reduce it rate of photosynthesis because it will need fewer sugars to make amino acids. Stunted growth, yellowing leaves, poor seed development
Testing for starch
- Collect leaf samples: A) has been covered with black paper
B) has been left exposed - Dip the leaves in boiling water - kills the cells to stop metabolic activity- soften up the leaf
- Dip the boiled leaves in ethanol- chlorophyll is soluble in ethanol so it leaves the leaf - will look brown
- Dip the leaves in water again
- Add iodine to the leaf
Hypothesis- A) covered leaf: negative ( iodine remains brown)
B) exposed leaf: positive ( iodine turns starch black/ blue)
What is the use of the availability of light
Light provides the energy that drives photosynthesis by splitting water molecules
Light energy absorbed by a plant depends on what
- the intensity of the light source
-v the wavelength of the light - the length of time that the light is available
What is the use of cholorophyll
Chlorophyll is essential for the absorption of light energy. The synthesis of chlorophyll requires magnesium ions, which must be supplied from the soil
What is the use of carbon dioxide
Carbon dioxide concentration has a major influence on the rate of photosynthesis because it is the substrate that is in shortest supply there is almost always enough water
What does temperature affect
Temperature affects the rate of enzyme activity. A 10C rise in temperature can cause a doubling in the rate of enzyme activity, higher temperatures cause denaturation. This is important both on leaves, enzymes involved directly in photosynthesis and in roots involved in active transport of mineral ions
Equation of photosynthesis
6CO2 + 6H2O ——-> 6O2 + C6H12O6
Factors of photosynthesis
- temperature
- light intensity
- CO2 concentration
- surface areas of leaves
- stomatal density