plant physiology Flashcards
properties of starch
insoluble, compact, easily broken down
testing leaves for starch practical
- remove leaf from plant that has been in light for several hours prior
- place in boiling water for 30 seconds to kill it and remove the wax
- place in boiling tube containing ethanol and place this in a beaker containing boiling hot water which will boil the ethanol for a few mins until it cools, since ethanol (78) has a lower boiling point than water (100)
- this decolourises the leaf
- wash with cold water then spread out on tile and add a few drops of iodine solution
- part of the leaf with starch will turn blue-black
starch is only made in
the parts of plants that contain chlorophyll
starch production in leaves needs
- light
- carbon dioxide
- chlorophyll
how starch is produced in plants
first plants produce glucose which is then joined together in chains to form starch
photosynthesis
process carried out in organisms containing chlorophyll. light energy is used to drive reactions where carbon dioxide and water are used to make glucose and oxygen
photosynthesis equation
carbon dioxide + water –> glucose + oxygen
6CO2 + 6H20 –> C6H12O6 + 6O2
what is photosynthesis the conversion of
photosynthesis is the conversion of light energy into chemical energy
the structure of a leaf
the upper and lower epidermis contain few chloroplasts and are covered by a thin waxy material called the cuticle- which reduces water loss by evaporation and acts as a barrier against disease-causing microorganisms e.g bacteria and fungi
the lower epidermis contains many little pores called stomata, the upper epidermis contains few or none. Stomata are formed as gaps between two highly specialised cells called guard cells which change their shape to open or close the stoma.
the mesophyll is made up of two layers of cells known as the palisade mesophyll and spongy mesophyll
the palisade mesophyll consists of long, narrow-shaped cells containing hundreds of chloroplasts. These are close to the source of light and since the upper epidermis is relatively transparent, this means that the light is able to reach the chloroplasts in the cell
the spongy mesophyll consists of rounded, loosely-packed cells with air spaces between them. it has fewer chloroplasts but still photosynthesises this is the main gas exchange surface of the leaf, it absorbs CO2 and releases water vapour and oxygen. the air spaces allow gases to diffuse in and out of the mesophyll.
the xylem and phloem make up the vascular bundle. xylem supplies the leaf with water and mineral ions. phloem carries the products of photosynthesis such as sugars away from the mesophyll. It transports the products to other parts of the plant that cannot make their own food.
effect of increasing light intensity on photosynthesis and respiration
means higher rate of photosynthesis than respiration which means there is a higher uptake of carbon dioxide than released
hydrogen carbonate indicator experiment (effect of light intensity on photosynthesis)
- 4 tubes
- observe change of color
explaining how starch is needed for photosynthesis
- chlorophyll= variegated leaf experiment
- CO2= soda lime experiment
- light= plant in darkness for 48 hours
all test negative for starch, shows that starch is needed for photosynthesis
how leaves are adapted for photosynthesis
- large SA to absorbs sunlight
- upper epidermis is relatively transparent
- palisade cells which contain many chloroplasts are close to the top of the plant and therefore the light source
- stomata allow CO2 to diffuse directly into the leaf
- large network of vascular bundles
- waxy cuticles reduce water loss + act as a barrier
- spongy mesophyll has air spaces to allow diffusion
limiting factors on the rate of photosynthesis
light intensity, concentration of CO2, temperature
canadian pondweed experiment
- sodium hydrogen carbonate is added to water in the boiling tube (solution produces Co2)
- measures the oxygen produced from photosynthesis in plants
- gas syringe
- water bath
- light source
uses of glucose in plants
- sucrose for transports (phloem)
- respiration
- cellulose for cell wall
- chlorophyll
- lipids for membranes and energy
- proteins + DNA
uses of nitrate
makes amino acids, proteins, chlorophyll, DNA
deficiency: limited growth, older leaves turn yellow
uses of phosphate
contains phosphorous for making DNA and cell membranes
deficiency: poor root growth, younger leaves turn purple
uses of potassium
needed for enzymes of photosynthesis and respiration
deficiency: discoloured leaves, poor flower and fruit growth
uses of magnesium
part of chlorophyll molecule
deficiency: leaves turn yellow
osmosis
net diffusion of water molecules across a partially permeable membrane from a solution with higher water potential to a solution with a lower water potential