Practicals Flashcards
What is it important to do to the leaf before the starch test?
Leave in a dark place for 48 hrs - de starching..
Method for starch test.
Leaf placed in boiling water for 30secs - kills leaf and stops reactions whilst removing waxy cuticle.
Put in ethanol in water bath for 5 minutes. - removes chlorophyll.
Briefly dipped in warm water - softens leaf
Spread on tile, add iodine
Method for light intensity experiment
Set up a boiling tube containing 45 cm3 of sodium hydrogencarbonate solution (1%). Allow the tube to stand for a few minutes and shake to disperse any air bubbles that might form.
Cut a piece of the pondweed, Cabomba. The pondweed should be 8 cm long.
Use forcepts to place the pondweed in the boiling tube carefully. Make sure that you don’t damage the pondweed, or cause the liquid to overflow.
Position the boiling tube so that the pondweed is 10 cm away from the light source. Allow the boiling tube to stand for five minutes. Count the number of bubbles emerging from the cut end of the stems in one minute. Repeat the count five times and record your results.
Calculate the average number of bubbles produced per minute. Repeat the experiment at different distances away from the light source.
Method for 3 tubes experiment
Put elodea in three test tubes with water. Add hydrogen carbon indicator each tube.
Cover one in tinfoil.
Leave one as normal
Put a water beetle in the third test tube.
Leave for a day.
Results for test tubes
Tube covered in tinfoil - yellow (more CO2)
Normal tube - purple (less CO2 - rate of photosynthesis higher than respiration)
Beetle tube - red (rate of photosynthesis = rate of plant and beetle respiring)
