Answer to Worksheet on Nutrition in Plant (by Mr Chandra)
a. Which part(s) of the leaf would turn blue black on iodine test?
P
b. Why should we put the plant in dark cupboard before the experiment?
To destarch the plants. So that starch tested in the leaf would come from
photosynthesis.
c. Why should we use the leaf showing green and pale?
To determine whether chlorophyll is needed for photosynthesis.
d. What is the use of the tin foil in the experiment?
To prevent sunlight from reaching that part of the plant, to allow us to determine if
sunlight is needed for photosynthesis.
e. (i)
What is the use of cotton wool soaked in limewater?
To absorb carbon dioxide. To prevent carbon dioxide from the air from entering.
e. (ii)
What is X. Describe its function in the experiment.
Potassium hydroxide. To absorb carbon dioxide.
f. From the experiment, what can you conclude about the conditions necessary for
photosynthesis?
Sunlight, chlorophyll, and carbon dioxide is needed for photosynthesis.
3
a. when plotting graph. Ignore outlying points. Plot curve of best fit .
b. State the relationship between light intensity and rate of photosynthesis for both
plant at light intensities up to 40 lux.
As light intensity increases, rate of p/s increases
c. State with reason which plant would grow best in a shady condition.
Plant D. The rate of p/s is higher when light intensity is lower.
d. Explain why at a light intensity above 80 lux, the rate of photosynthesis for both
plant might increase if they were
(i)
Supplied with higher concentration of carbon dioxide.
(ii)
Exposed to higher temperature.
(i)
(ii)
Higher concentration of carbon dioxide would speed up the rate of
enzyme reaction.
Higher temperature would speed up the rate of enzyme reaction.
e. Suggest why rate of photosynthesis may fall when the plant wilt.
When plant wilts, water is lost from the plant. Water is required for
photosynthesis.
Carbon dioxide is also limiting as stomata are closed.