Micropropagation

Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow.

Tissue culture and plants

In micropropagation, plant tissues are grown in vitro on plant tissue culture media, under aseptic conditions in a controlled environment. This technique is possible because plant cells can differentiate and become specialised cells. This allows them to change their metabolism, growth and development to form a whole plant.

Plant tissue culture media contain substances to support the normal growth and development of plants. The media are mainly composed of minerals, vitamins, and plant hormones. The pH of the media is kept constant.

Plant hormones play an essential role in determining how cells and tissues develop in culture media. Plant cells can differentiate into different tissues and cell types. The concentration of hormones can determine the tissue that develops. Auxins and cytokinins are the most widely used. A balance of both auxin and cytokinin leads to the development of a mass of undifferentiated cells known as a callus.

In vitro cell culture offers an alternative method for conserving endangered species and varieties. Tissue culture can be used when the plant species produce seeds that do not germinate or have seeds that cannot be stored for a long period of time. These can be successfully preserved using in vitro techniques for the maintenance of gene banks.

Embryo culture is a type of plant tissue culture that is used to grow embryos from seeds in nutrient media. In embryo culture, the plant develops directly from the embryo or indirectly through the formation of a callus and then subsequent formation of shoots and roots. The technique has been developed to break dormancy in seeds, and to reproduce rare species and haploid plants.

Scientists are also using cell suspension culture systems from which products can be extracted. A suspension culture is developed by transferring a portion of the callus into liquid media. The media are maintained under suitable conditions of agitation, light and temperature. This system can provide a continuous, reliable source of natural products independent of climate and soil conditions. The first commercial application of large‑scale suspension cultivation of plant cells was carried out to produce shikonin. Shikonin is used in traditional Chinese medicine and is a potential anti‑cancer treatment.

State what is meant by the term in vitro. (line 1)

Explain how plant cells differ from human cells in their ability to differentiate and specialise. (lines 2 and 3)

Give the function of two named minerals included in the culture media. (line 6)

Explain why the pH of the media needs to be kept constant. (line 7)

Auxin also controls the response of plants to light.

Describe a simple experiment you could do to show the phototropic response of plant stems to light.

Explain why scientists want to conserve endangered plant species and varieties. (lines 13 and 14)

Explain why plant cell suspension culture media are maintained under suitable conditions of agitation, light and temperature. (lines 24 and 25)

The photograph shows a plant called a snapdragon.

(Source: © BRIAN GADSBY/SCIENCE PHOTO LIBRARY) Selective breeding has been used to produce snapdragons with brightly coloured flowers.

Describe how selective breeding can produce snapdragon plants with brightly coloured flowers.

Micropropagation is often used to make copies of a snapdragon plant. Describe the process of micropropagation.

Scientists investigate the effect of exposing snapdragon explants to increasing amounts of ionising radiation. This is the scientists’ method.

• take a snapdragon plant and use micropropagation to produce many explants

• expose groups of explants to different amounts of ionising radiation

• grow the explants into plants and record the number of differences in their phenotypes compared with the original plant

• take samples of each of the plants and measure the number of differences in DNA nucleotides of each plant compared with the original plant

Give the reason why micropropagation is used to produce the plants to be tested.

What term is given to all the DNA in an organism?

The graph shows the scientists’ results.

Number of changes Number of in DNA different

Discuss the effects that increasing the amount of ionising radiation has on the snapdragons.

Scientists have genetically modified soya plants so that the soya beans they produce contain less saturated fat.

The scientists produced one transgenic soya plant. Micropropagation was then used to make multiple copies of this transgenic soya plant.

Explain why micropropagation was used to produce copies of the transgenic soya plant.

A student uses this equipment to compare the energy content of transgenic soya beans with the energy content of non‑transgenic soya beans.

Describe how the student could use the equipment to make a valid comparison of the energy content of the two types of soya bean.

Give one safety precaution that the student should take when using the apparatus.

The diagram shows a different type of apparatus that can be used for the investigation.

Explain two reasons why this apparatus will give a more accurate energy value than the apparatus used by the student.

The following passage contains information about using micropropagation to produce plants.

Complete the passage by writing a suitable word in each blank space.

Micropropagation uses small fragments of plants which are regrown into whole

plants. These fragments of plants are known as_........ .

The surface of each fragment is sterilised to prevent growth of

_........ . The fragments are placed in a growth medium. The growth

medium contains agar and a source of energy such as_........ .

This method is able to produce large quantities of genetically identical plants called

One advantage is that micropropagation is quicker than_........

reproduction, which involves flower and seed production. Another advantage of

micropropagation is that plants can be produced_........ the year.

Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow.

Supercharging plants to reduce global warming

The proportion of carbon dioxide in the atmosphere has increased in the last 100 years. In 2020, a mass of 727 gigatonnes of carbon dioxide was released into the atmosphere from natural processes, along with a mass of 37 gigatonnes from human activities. Scientists have estimated that plants naturally remove a mass of 746 gigatonnes of carbon dioxide from the atmosphere every year. The difference between what is removed and what is released causes atmospheric carbon dioxide to rise every year. Carbon dioxide is a greenhouse gas, and a significant rise will cause global warming.

To help solve the problem of rising concentrations of atmospheric carbon dioxide, scientists are planning to produce transgenic, supercharged plants that can remove atmospheric carbon dioxide and store it in their roots. The scientists estimate that if these plants can be developed, the plants could remove a mass of carbon dioxide equivalent to 50% of the emissions from human activities.

Coastal plants that have their roots in seawater contain a substance called suberin in the cell walls of the outer layer of the roots. Suberin is a waterproof substance that contains a high proportion of carbon atoms. Suberin is decomposed very slowly so remains in the soil for a long time.

The photograph shows a coastal plant called a mangrove.

To produce the supercharged plants, scientists intend to take the gene that codes for high suberin production from a coastal plant and insert it into crop plants. The crop plants used are perennial plants. Perennial plants live for many years rather than dying each winter. The transgenic crops would take in large amounts of carbon dioxide and use the carbon atoms to make suberin. The carbon would then be locked up and stored as suberin in the roots. After successfully producing one plant, they will use micropropagation rather than pollination to produce others.

These supercharged crop plants may have other uses. Suberin in roots helps to make them tolerant to soil with a high salt concentration, helping to produce higher crop yields in areas that have difficult growing conditions.

Carbon dioxide is a greenhouse gas.

State the name of another greenhouse gas (line 7).

Calculate the increase in mass, in kg, of atmospheric carbon dioxide in 2020 (lines 2 to 7).

Give your answer in standard form.

[1 gigatonne = 1 000 000 000 000 kg]

State two consequences of global warming for the environment.

Explain why producing genetically engineered plants with additional suberin in their roots could reduce atmospheric carbon dioxide (lines 14 to 17 and lines 19 to 24).

Which enzyme is used to remove a gene from a section of DNA?

Explain why the additional suberin in the cell walls of the roots will make the transgenic plants tolerant to soil with a high salt concentration (lines 26 to 28).

Give three reasons why the scientists use micropropagation to reproduce the transgenic crop plants (lines 24 to 25).

Micropropagation is used to produce plant clones.

The process involves growing explants in vitro.

State what is meant by the term in vitro.

The explants grow new roots and shoots.

A student investigates the effect of pH on the growth of new shoots.

The table shows the student’s results.

Explain the relationship between pH and the mean number of shoots per explant.

Describe a procedure the student could use to obtain explants and produce these results.

Give two benefits of using micropropagation to produce new plants rather than using seeds.