Seed germination

The diagram shows a pea flower with structures labelled X and Y.

Give the names of structures X and Y.

Explain how two structures, present in the diagram, show how the flower is pollinated.

A scientist uses this method to compare the carbohydrates present in ungerminated and germinating pea seeds.

• carry out an iodine test and a Benedict’s test on ungerminated seeds

• soak another set of seeds in water and allow them to germinate in unsealed jars

• after three days, carry out an iodine test and a Benedict’s test on the germinating seeds

The table shows the scientist’s results.

State which carbohydrates the scientist identified in the ungerminated seeds and the germinating seeds.

ungerminated seeds

germinating seeds

Explain the difference in the carbohydrate composition of the ungerminated seeds and the germinating seeds.

Explain why the jars used in the investigation are not sealed.

Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow. Moving plants Flowering plants reproduce using different methods to transfer the pollen from plant to plant. This cross‑pollination enables plants to produce offspring that show genetic variation. The transfer can be done by animals such as insects or by wind. The reliance on animals and wind for reproduction does not end with pollination. Flowering plants also need a mechanism to disperse their fruits or the seeds they contain. This seed dispersal means that seeds producing new young plants will germinate away from the parent plant.

wings on a sycamore fluff on a dandelion spines on burdock (Source: © joanna wnuk/Shutterstock) (Source: © Viktorija Reuta/Shutterstock) (Source: © Paulpixs/Shutterstock) The simplest method of seed dispersal uses gravity. The seeds are within heavy fruit, which fall from the tree when they are ripe. Although some of the fruit may roll away from the parent plant, most remain close to the parent plant. Animal dispersal is when plants rely on animals to transport their seeds to a different area. This may be because the seeds are surrounded by a brightly‑coloured and sweet‑tasting fruit. Examples of this are soft fruits such as raspberry and hard fruits such as apple. Animals may also carry seeds in a different way. Many plants produce fruits or individual seeds covered in hooks or spines that attach the seeds to the animals’ fur. The seeds are then carried away from the parent plant. Eventually, the seeds may fall off, or be rubbed off by the animal. Examples of plants using this form of dispersal are burdock and sea holly. Some plants provide seed pods with a mechanism that ejects the seeds from the pod by force. All of these rely on the effect of evaporation of water in the seed pod, so this method of seed dispersal usually takes place in sunlight. Examples of plants using this form of dispersal are gorse bushes and lupins.

Wind is one of the main methods of seed dispersal. Some tall trees produce seed pods that have wings, which allow the seeds to travel long distances. Some seed pods have two wings such as the sycamore while others have one wing such as the ash. There are also lightweight adaptations that help seeds to be blown by the wind. These include various sorts of fluff that increase the surface area of the seed, so that it can be picked up by the slightest breeze. Examples of plants using this form of dispersal are thistle and dandelion. The last method uses water. Trees found on tropical beaches often have their seeds carried away by the sea. The seeds have woody, waterproof coverings enabling them to float in the water for long periods. Coconuts are a well‑known example.

Explain how cross‑pollination can lead to an increase in genetic variation. (Lines 2–3)

Explain the advantages of the seeds germinating away from the parent plant. (Line 8)

Give one advantage of a seed germinating close to the parent plant. (Line 11)

Explain the conditions needed for seed germination.

Explain why some seeds are surrounded by a brightly‑coloured and sweet‑tasting fruit. (Lines 13–14)

Large numbers of tomato plants are often found growing along the sides of drains and settling beds on sewage farms. Suggest a reason for this observation.

Give the reason why sunlight is required for lupin seeds to be dispersed. (Lines 21–24)

Describe an experiment you could carry out to investigate how the presence of fluff on dandelion seeds affects how fast they fall. (Lines 30–31)

Scientists investigate the effect of salt (NaC l) concentration on the germination of maize seeds.

Batches of seeds are watered with different concentrations of salt solution.

They count the number of seeds that germinate in each batch 12 days after sowing. They then determined the percentage germination.

Describe how the scientists could tell if a maize seed had germinated.

The scientists measured the germination after 12 days.

State two other abiotic variables that the scientists need to control in their investigation.

The table shows the scientists’ results.

Plot a line graph to show the effect of concentration of salt solution on germination.

Use a ruler to join your points with straight lines.

Explain the effect of increasing the concentration of salt solution on germination.

As plants grow, they produce roots and stems.

Compare the responses of roots and stems to gravity.

Compare the responses of roots and stems to light.

The diagram shows some of the structures involved in fertilisation in a flowering plant.

Name the parts labelled A, B and C.

On the diagram, draw the path the pollen tube takes after the pollen grain has germinated.

Describe what happens to the structures in part C after fertilisation.

A scientist investigates the effect of four different storage conditions on the germination of grass seeds.

She stores 500 seeds in each storage condition for two months.

She then counts the number of seeds that germinate when planted.

The table shows her results.

Calculate the percentage increase in the number of seeds that germinate in wet and cold conditions compared to the number of seeds that germinate in wet and warm conditions.

Suggest why fewer seeds germinate when they are stored in wet and warm conditions than in the other conditions.

Give one observation that shows a seed has germinated.

Scientists investigate the effect of pollution on the growth of plant shoots. This is their method.

• expose a sample of 500 seeds to pollution

• leave another sample of 500 seeds free from pollution

• allow the seeds to germinate and produce shoots

• after one day, squash 100 shoots from each sample

• using a microscope, count the number of cells in each shoot

The scientists squash 100 shoots from each sample every day for five days. The table shows their results.

Plot a line graph of this data on the grid. Use a ruler to join the points with straight lines.

What is the dependent variable in this investigation?

The scientists conclude that pollution reduces the growth of shoots by affecting cell division.

Name the type of cell division affected by pollution in this investigation.

To make sure their conclusion is valid, the scientists control abiotic variables while the seeds are germinating. Discuss two abiotic variables that the scientists control.

State one biotic factor that the scientists should control.

Wheat seeds contain stores of a large insoluble molecule. This molecule is digested by amylase as the seeds germinate.

What is the name of this large insoluble molecule?

A student investigates the oxygen absorbed by germinating seeds at different temperatures. The diagram shows some of the student’s apparatus.

Suggest why the student opens the tap after obtaining one set of results.

What is the function of the soda lime?

The student measures the distance moved by the coloured liquid and converts this to volume of oxygen absorbed. The volume of oxygen absorbed can be calculated using the formula volume = π × radius² × distance Calculate the volume of oxygen absorbed when the coloured liquid moves a distance of 6.0 mm. [diameter of tube = 1.0 mm]

volume =_........ cm³

The graph shows the results of the student’s investigation.

time in minutes

Calculate the percentage increase in the rate of oxygen absorption at 22 °C compared to the rate of oxygen absorption at 12 °C.

Suggest why the rate of oxygen absorption is greater at 22 °C than at 12 °C.