9: Nutrition and Gas Exchange in Plants - Problems Flashcards
(18 cards)
A farmer planned to grow crops in three fields (X, Y, and Z). Each field was divided into two parts. Extra nitrate was applied to one of the parts. Then they grew crops in both parts and harvested the crops after three months. The graph below shows the crop yield in the three fields.
Explain which field contained enough nitrate fore the crops before applying extra nitrate. (3)
Field Z.
In field Z, the crop yield in both field parts was high.
Applying extra nitrate to field Z did not improve the crop yield.
A farmer planned to grow crops in three fields (X, Y, and Z). Each field was divided into two parts. Extra nitrate was applied to one of the parts. Then they grew crops in both parts and harvested the crops after three months. The graph below shows the crop yield in the three fields.
Describe and explain the results in field Y. (3)
Field Y has the lowest crop yield among the three fields.
Applying extra nitrate to field Y did not improve the crop yield.
This indicates that the growth of crops in field Y is not limited by the amount of nitrate in the field.
A farmer planned to grow crops in three fields (X, Y, and Z). Each field was divided into two parts. Extra nitrate was applied to one of the parts. Then they grew crops in both parts and harvested the crops after three months. The graph below shows the crop yield in the three fields.
Explain why the amount of nitrate in tie field decreased after harvesting the crops. (1)
Part of the nitrate in the fields was absorbed by the crops to synthesise useful materials such as proteins and nucleic acids.
A student used the set-up below to investigate the effect of light intensity on the gas exchange of leaves.
Suggest a control set-up for this experiment. (1)
A stoppered test tube containing wire gauze and hydrogencarbonate indicator only.
A student used the set-up below to investigate the effect of light intensity on the gas exchange of leaves.
Explain why the test tubes were sealed completely during the experiment. (1)
This prevents the outside air from entering the test tubes and reacting with the hydrogencarbonate indicator, ensuring that any change in gas content inside the test tube indicated by the colour of the hydrogencarbonate indicator is due to the gas exchange of the leaf inside the test tube.
A student used the set-up below to investigate the effect of light intensity on the gas exchange of leaves.
State and explain the colour of hydrogencarbonate indicator in test tube Y after 3 hours. (3)
The hydrogencarbonate indicator turned from red to yellow.
The leaf in test tube Y was in complete darkness. Only respiration and no photosynthesis occurred. Therefore, there is a net release of carbon dioxide by respiration and a net uptake of oxygen for respiration.
As a result, the carbon dioxide concentration in the test tube increased to a value higher than the atmospheric concentration, and the hydrogencarbonate indicator turned from red to yellow.
A student used the set-up below to investigate the effect of light intensity on the gas exchange of leaves.
Explain why the colour of hydrogencarbonate indicator in test tube Z remained red after 3 hours. (3)
The leaf in test tube Z was exposed to light of relatively dim intensity. The rates of photosynthesis and respiration in the leaf were similar. Therefore, the rate of carbon dioxide release by respiration is similar to the rate of carbon dioxide uptake for photosynthesis.
As a result, the carbon dioxide concentration in the test tube remained relatively constant at a value close to the atmospheric concentration, and the hydrogencarbonate indicator remained red.
The graph below shows the rate of oxygen releasee of two plants (P and Q) of the same species under different light intensities. Plant P was grown in a complete nutrient solution while plant Q was grown in a magnesium-deficient nutrient solution.
Calculate the actual rate of oxygen release of plant P at 5 units of light intensity and state the assumption in calculation. (2)
The actual rate of oxygen release of plant P
= 4 + 2 units = 6 units
Assumption: the rate of oxygen consumption in respiration remains constant throughout the experiment.
The graph below shows the rate of oxygen releasee of two plants (P and Q) of the same species under different light intensities. Plant P was grown in a complete nutrient solution while plant Q was grown in a magnesium-deficient nutrient solution.
Determine and explain the compensation point of plant P in terms of light intensity. (3)
1 unit of light intensity
At this level of light intensity, the rate of net oxygen release is 0.
This indicates that the rate of oxygen consumption in photosynthesis of the plant is equal to its rate of oxygen production in respiration, thus its rate of photosynthesis is equal to its rate of respiration at 1 unit of light intensity.
The graph below shows the rate of oxygen releasee of two plants (P and Q) of the same species under different light intensities. Plant P was grown in a complete nutrient solution while plant Q was grown in a magnesium-deficient nutrient solution.
Describe and explain the difference of rate of oxygen release of plant Q from that of plant P at 5 units of light intensity. (3)
At 5 units of light intensity, the rate of oxygen release of plant Q is lower than that of plant P.
Magnesium is essential for the synthesis of chlorophyll.
Without magnesium, plant Q cannot produce enough chlorophyll for photosynthesis and hence the rate of oxygen released by photosynthesis is lower compared to plant P.
The graph below shows the rate of oxygen releasee of two plants (P and Q) of the same species under different light intensities. Plant P was grown in a complete nutrient solution while plant Q was grown in a nutrition-deficient nutrient solution.
Name 3 possible major elements which may be deficient in the nutrient solution for plant Q. (3)
Magnesium, nitrogen, potassium
The photomicrograph below shows the cross section of a dicotyledonous leaf.
Name tissues P and Q. (2)
Tissue P: palisade mesophyll
Tissue Q: spongy mesophyll
DSE 2012 IB Q5
The graph below shows the oxygen production rate and carbon dioxide production rate of a local plant on a summer day.
State the times at which there is no net exchange of gases into or out of the leaves. (1)
7:00 and 18:00
The photomicrograph below shows the cross section of a dicotyledonous leaf.
Describe how carbon dioxide from the environment reached the cells of tissue P. (3)
Carbon dioxide from the environment diffuses into the air space in the leaf through the stomata.
The carbon dioxide dissolves in the water film on the surfaces of the cells of tissue Q.
Dissolved carbon dioxide then diffuses to the neighbouring cells down the concentration gradient until it reaches the cells of tissue P.
The photomicrograph below shows the cross section of a dicotyledonous leaf.
With reference to the photomicrograph, describe two structural features of tissue Q that enable it to carry out gas exchange efficiently. (2)
The cells of tissue Q are loosely packed. This provides a larger surface area for exchange of gases between air and cells.
There are numerous air spaces among the cells of tissue Q. This allows gases to diffuse freely.
DSE 2012 IB Q5
The graph below shows the oxygen production rate and carbon dioxide production rate of a local plant on a summer day.
State the times at which there is no net exchange of gases into or out of the leaves. (1)
7:00 and 18:00
DSE 2012 IB Q5
The graph below shows the oxygen production rate and carbon dioxide production rate of a local plant on a summer day.
The area below the line showing the oxygen production rate of usually greater than the area below the line showing the carbon dioxide production rate. Explain the importance of this observation. (4)
The area below the line showing oxygen production rate represent the food production over 24 hours.
The area below the line showing carbon dioxide production rate represent the food consumption over 24 hours.
It is important for food production to be larger than food consumption such that there is a net amount of food produced,
providing energy for the plant to survive, grow and produce fruits.
DSE 2016 IB Q11
Gas exchange in organisms relies very much on diffusion. Discuss how the structures of leaves in plants and lungs in humans are adapted to fulfil their functions. Despite these similarities, explain why the operation of a breathing system in human is more effective. (8+3)
large surface area for diffusion of gases (1)
numerous air sacs in the lungs of humans vs spongy mesophyll with numerous air spaces in leaves / numerous leaves in plants (1)
a moist surface for dissolving of gas (1)
presence of a water film on the inner surface of the air sac vs that of the surface of spongy mesophyll (1)
short diffusion distance for exchange of gas between internal and external enrivonment (1)
one-cell thick wall of air sacs and capillary versus flat and thin leaves (1)
there is active ventilation in humans, breathing movements draw in and expel air actively (1)
oxygen diffused in are transported away by the blood of the capillary network surrounding the air sacs (1)
both of the above maintain a steep concentration gradient for diffusion of gases (1)
while leaves rely on passive ventilation / diffusion only (1)
