Investigation of limiting factors

The rate of photosynthesis is influenced by several environmental factors. Fig. 1.1 shows how light intensity changes the rate of photosynthesis.

Feb/March 2016

An experiment was done to find the photosynthesis rate at a range of carbon dioxide concentrations. The two plants, barley and sugar cane, were investigated at two temperatures, $10^\circ\text{C}$ and $25^\circ\text{C}$. The results are presented in Fig. 4.1.

Feb/March 2017

The influence of light intensity on the rate of photosynthesis may be studied using a cut shoot of a pond plant. Fig. 1.1 shows the apparatus used in the investigation. Light intensity can be altered by moving the lamp to different distances from the pond plant.

Feb/March 2019

The banana plant, Musa acuminata, is a tall herbaceous species with very large leaves. An investigation was carried out to find the net carbon dioxide uptake of a banana plant at different light intensities. Fig. 6.1 shows a banana plant. Fig. 6.2 presents the investigation results, with mean net carbon dioxide uptake measured in $\mu\text{mol m}^{-2}\text{s}^{-1}$ plotted against light intensity in lux.

Feb/March 2022

Leaves of tobacco plants, Nicotiana sp., contain chlorophyll a and chlorophyll b in their chloroplasts.

Feb/March 2025

Maize, Zea mays, is an important cereal food crop. In contrast with most crop plants, maize seed is formed by hybridisation between two distinct inbred parental strains.

May/June 2011

Maize, Zea mays, is an important cereal crop used as food. Unlike most crop plants, maize seed is formed by hybridisation between two separate inbred parental strains.

May/June 2011

Fig. 8.1 illustrates how temperature changes the rate of photosynthesis in a plant when light intensity is kept constant and the carbon dioxide concentration is 0.03%.

May/June 2012

Fig. 8.1 illustrates the effect of temperature on the photosynthesis rate of a plant while light intensity remains constant and the carbon dioxide concentration is $0.03\%$.

May/June 2012

A student carried out an investigation into how temperature and light intensity affected the rate of photosynthesis in an aquatic plant. Fig. 1.1 shows the outcomes of the investigation.

May/June 2013

The unicellular green alga Chlorella, which is a photosynthetic protoctist, was first investigated as a possible food source. Large-scale cultivation turned out not to be economical, but because Chlorella provides many health benefits it is now produced on a mass scale and collected for use as a health food supplement. In a study of Chlorella productivity, the concentration of carbon dioxide was varied to see how this affected the light-independent stage of photosynthesis. A cell suspension of Chlorella was exposed to a bench lamp. For $200\ \text{s}$ the suspension received carbon dioxide at $1\%$. The carbon dioxide concentration was then lowered to $0.03\%$ for another $200\ \text{s}$. The concentrations of RuBP and GP (PGA) were recorded at regular intervals. The temperature of the suspension was kept at $25\,^{\circ}\text{C}$ throughout. The findings are shown in Fig. 1.2.

May/June 2014

The unicellular green alga Chlorella, which is a photosynthetic protoctist, was first examined for its possible use as a food source. Although producing it on a large scale turned out not to be economical, the many health benefits of Chlorella mean that it is now mass-produced and collected for use as a health food supplement. Fig. 1.1 shows cells of Chlorella. In one investigation of Chlorella productivity, the carbon dioxide concentration was changed to find out how it affected the light-independent stage of photosynthesis. A suspension of Chlorella cells was illuminated with a bench lamp. For $200$ seconds, the suspension was given carbon dioxide at a concentration of $1\%$. The carbon dioxide concentration was then lowered to $0.03\%$ for a further $200$ seconds. The concentrations of RuBP and GP (PGA) were recorded at regular intervals. Throughout the investigation, the temperature of the suspension was kept at $25\,^{\circ}\text{C}$. The results are shown in Fig. 1.2.

May/June 2014

The rate of photosynthesis is often restricted by the carbon dioxide concentration in the atmosphere and by light intensity.

May/June 2016

The amount of carbon dioxide in the atmosphere and the light intensity frequently limit the rate of photosynthesis.

May/June 2016

Section B. Choose one question and answer it.

May/June 2019

Photosynthesis is a complicated process in which light energy is changed into chemical energy.

May/June 2021

Photosynthesis is a complicated process with a light dependent stage and a light independent stage.

May/June 2021

Photosynthesis is influenced by several environmental factors.

May/June 2022

A student carried out an investigation into how temperature affected the rate of photosynthesis at two different light intensities. The rate of photosynthesis was found by measuring how quickly oxygen was produced by the plant. Fig. 7.1 presents the results of the investigation.

May/June 2024

Experiments were performed to investigate how light intensity affects the rate of photosynthesis in a species of the unicellular protoctist, $\textit{Chlorella}$. A suspension of $\textit{Chlorella}$ cells was used. Carbon dioxide uptake was taken as a measure of the rate of photosynthesis. • The $\textit{Chlorella}$ suspension was illuminated at a light intensity of 3 lux for 20 seconds. • At the end of the 20 second illumination period, the carbon dioxide uptake by $\textit{Chlorella}$ was measured. • The experiment was then repeated at 6 lux, 9 lux, 12 lux and in a dark room. • Throughout the experiment, the suspension was kept at a temperature of $20\,^\circ\text{C}$. Table 7.1 presents the experimental results.

May/June 2024

A lichen is a symbiotic partnership in which a fungus lives with an organism called a photobiont, to the advantage of both partners. One photobiont is the green alga Trebouxia sp., a photosynthetic protist. Fig. 8.1 illustrates lichen growing on a tree.

May/June 2025

Fig. 4.1 presents the male and female flowers of maize.

Oct/Nov 2011

Fig. 8.1 shows a palisade cell taken from a leaf. With label lines and the letters X, Y and Z, identify in Fig. 8.1 a structure that: • contains RuBP - X • is fully permeable - Y • is made mainly of phospholipids - Z

Oct/Nov 2014

One method for estimating the rate of photosynthesis is to measure how quickly carbon dioxide is taken up. Fig. 7.1 shows how light intensity is related to relative carbon dioxide uptake and production in a dicotyledonous plant.

Oct/Nov 2015

One way to estimate the photosynthesis rate is to measure how fast carbon dioxide is taken up. Fig. 7.1 shows how light intensity is related to relative carbon dioxide uptake and carbon dioxide production in a dicotyledonous plant.

Oct/Nov 2015

Fig. 5.1 depicts the seaweed Laminaria hyperborea. This photosynthetic protoctist is found in coastal waters around Norway. It is commercially cultivated to obtain the glucose polysaccharide alginate, which is used in some food products. A rise in carbon dioxide concentration in the atmosphere has led to higher carbon dioxide levels in the ocean. This has reduced the pH of the ocean and caused ocean acidification. Scientists are investigating seaweeds such as L. hyperborea because they take in a large amount of carbon dioxide during photosynthesis. This could help to raise the pH of the ocean and reverse ocean acidification.

Oct/Nov 2019

Cotton, Gossypium hirsutum, and false flax, Camelina sativa, are cultivated in different regions of the world. Rubisco activase is a chloroplast stroma enzyme that is required to keep a second enzyme, rubisco, functioning. Scientists investigated rubisco activase activity in cotton and false flax across a range of temperatures. Fig. 2.1 presents the findings.

Oct/Nov 2021

Cotton, Gossypium hirsutum, and false flax, Camelina sativa, are crop species cultivated in different parts of the world. Rubisco activase is an enzyme in the chloroplast stroma that is required to keep a second enzyme, rubisco, active. Scientists investigated rubisco activase activity in cotton and false flax across a range of temperatures. Fig. 2.1 presents the results.

Oct/Nov 2021