Pollination and fertilisation in plants

Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow. Pollination in fruit trees Plants need to be pollinated to produce fruits and seeds. Some plants are self‑pollinated and others are cross‑pollinated. Self‑pollination is usually the transfer of pollen from flowers on the same tree. In fruit trees, self‑pollination also includes the transfer of pollen from another tree of the same cultivar. A cultivar is a genetically identical group of trees produced by selective breeding. Self‑pollinating plants need bees or other insects to transfer pollen. Examples of self‑pollinated fruit trees are plum, apricot and peach that have sweet‑tasting, soft fruits.

(Source: © freya‑photographer/Shutterstock) (Source: © Leena Robinson/Shutterstock) Other fruit trees require cross‑pollination and can only produce fruit by fertilisation from a different cultivar. Cross‑pollination is the transfer of pollen from one cultivar to the flower of a different cultivar. Self‑incompatibility prevents the same plant or cultivar from fertilising its own flowers. For example, the pollen from one cultivar of an apple tree will not fertilise trees of the same cultivar. Most hard fruit trees such as pear and apple require the presence of two different compatible cultivars for pollination to result in fruit production. Pollen can be transferred by wind, insects or birds. Many fruit trees are pollinated by insects. Nut trees are usually pollinated by wind. After pollination the pollen grain must germinate to lead to fertilisation. The success of pollination and fertilisation depends on favourable environmental conditions. It also requires the right pollen grain reaching the right flower, as pollen can only fertilise specific, compatible flowers. For example, pollen from a peach flower will not pollinate apple flowers.

Cross-pollinating fruit trees should be planted no more than 60 m apart. This will ensure that bees visit the trees often enough to ensure pollination. Nut trees need to be planted no more than 15 m apart. A further complication is that a few apple and pear cultivars, known as triploids, produce sterile pollen. Triploid cultivars have three sets of chromosomes within their cells. A triploid cultivar will require another cultivar for pollination, and the trees must flower at the same time.

Explain the differences between self-pollination and cross‑pollination. (lines 3 to 5 and 9 to 11)

Describe the sequence of events from pollen landing on a flower to fruit production.

Fruit trees often produce sweet-tasting fruit containing sugars.

Sugars are carbohydrates. Name the three elements in carbohydrates.

Suggest how production of sweet-tasting fruit may help spread the seeds of fruit trees. (lines 7 to 8)

Explain how self-incompatibility prevents self-fertilisation. (lines 11 to 13)

Describe how the structure of insect‑pollinated flowers helps to achieve pollination. (line 16)

Give a reason why nut trees need to be planted closer together than fruit trees. (lines 23 to 25)

Explain why triploid cultivars produce sterile pollen. (lines 26 to 29)

The diagram shows an insect-pollinated flower with some structures labelled.

Which structures are the male parts of the flower?

On which structure does the pollen grain germinate?

Which structure becomes the seed after fertilisation?

The picture shows a strawberry plant. This plant can reproduce sexually using its flowers, or asexually.

(Source: © Havryliuk-Kharzhevska / Shutterstock)

Describe how a strawberry plant reproduces asexually.

A farmer wants to produce a plant that has strawberries with a different flavour. He then wants to produce large numbers of these plants. Discuss how he can use sexual and asexual reproduction to achieve this.

The diagram shows a flower with some structures labelled.

Which structure is the style?

Which structure releases pollen?

On which structure do the pollen grains germinate?

This flower is insect-pollinated. Describe how structures P, R and T would be different in a wind-pollinated flower.

Flowering plants can reproduce asexually.

Give an example of a natural method of asexual reproduction in plants.

Give an example of an artificial method of asexual reproduction in plants.

Give three differences between asexual and sexual reproduction.

A farmer has two varieties of a plant species. One variety has a red flower colour and no scent. The other variety has a white flower colour and a perfumed scent. The farmer wants to produce a variety that has the red flower colour and the perfumed scent. Explain how the farmer could achieve this.

The diagram shows the structure of an insect pollinated flower.

Which part of the flower produces pollen?

Which part of the flower becomes a fruit?

The image shows a pollen grain produced by the plant.

(Source: © STEVE GSCHMEISSNER / SCIENCE PHOTO LIBRARY)

The diameter of the pollen grain in the image is 30 mm. The pollen grain has an actual diameter of 313 µm. Calculate the magnification of the pollen grain in the image. Give your answer to the nearest whole number. [1 mm = 1000 µm]

magnification = ×_........

State how the structure of the pollen grain is adapted to ensure insect pollination.

Gardeners often reproduce plants by taking cuttings. Explain why gardeners often reproduce plants by taking cuttings instead of growing the plants from seeds.

The diagram shows a flower from an apple tree, with some structures labelled.

This apple tree is able to self-pollinate. Which is the correct transfer of pollen during pollination?

Which structure does the pollen tube grow down?

Which structure develops into the seed?

The flower from an apple tree is insect‑pollinated.

Give three differences between the structure of this apple flower and the structure of a wind‑pollinated flower such as grass.

The seeds of many plants are surrounded by sweet‑tasting fruit.

Suggest how this enables the plants to spread their seeds.

A species of grass has a diploid chromosome number of 12.

Which row in the table shows the number of chromosomes in the nucleus of a pollen grain, and in the nucleus of a root cell, of this grass?

The diagram shows a flower from the grass plant.

Explain two ways this flower is adapted for wind pollination.

Scientists use this method to investigate self-pollination and cross-pollination in a species of grass plant.

• take pollen grains from the anther of a flower

• place some of the pollen grains on the stigma of the same flower

• after one day, count how many of the pollen grains grow a pollen tube

Repeat the method but place the pollen grains on the stigma of a flower of a different plant.

The table shows the scientists’ results.

State the dependent variable in this investigation.

Explain how the results of the investigation show that this species of grass plant is able to survive in a changing environment.

Use the information in the table to support your answer.

Grass plants can also be produced by asexual reproduction.

New plants are produced from the roots of a parent plant.

State the name of the type of cell division used to produce new plants by asexual reproduction.

Describe why it is an advantage for commercial growers to produce plants by asexual reproduction.

The diagram shows a wind-pollinated flower with some structures labelled W, X and Y.

Describe how structures W, X and Y are adapted for wind pollination.

Structures W, X and Y are adapted for wind pollination.

Give two other differences between wind-pollinated flowers and insect-pollinated flowers.

Wind-pollinated flowers often cause an allergic response in people. This is known as hay fever.

Most people in the United Kingdom who get hay fever have the symptoms from April to September.

The graph shows the changes in total pollen count for three different plant types from March to September during one year in the United Kingdom.

1 Mar 1 Apr 1 May 1 Jun 1 Jul 1 Aug 1 Sep

As part of an investigation into pollen allergy, five people keep a diary of their hay fever symptoms. They do this for the same year as the pollen count.

The table gives their results.

Using the data in the table and the information from the graph, discuss the likely causes of the allergic responses in each person.

The allergic response to pollen is part of the body’s immune response.

Explain what is meant by the term immune response.

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.

There is a relationship between the colour of a flower and pollination by insects.

Design an investigation to find out if the colour of a flower affects how attractive it is to pollinators.

Include experimental details in your answer and write in full sentences.

The diagram shows an insect-pollinated flower called a lily.

Which of these is the name of structure P?

Which of these is the name of structure Q?

On which structure do pollen grains germinate?

Describe how the structures of P, Q and S would differ in a wind-pollinated flower.

Plants can also reproduce by asexual reproduction.

Give one natural method that plants use to reproduce asexually.

Give one artificial method that a plant grower may use to reproduce a plant asexually.

Suggest why a plant grower may choose to reproduce a plant asexually rather than allowing the plant to reproduce sexually.

The passage describes reproduction in flowering plants.

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

Flowers are organs that allow plants to carry out_........ reproduction.

The male gamete is contained within the_........ grains. These grains

are released from the_........ , which is found on top of the filament.

These grains need to land on the_........ , the female part of the flower.

Grains can be transferred by wind or by animals. These animals are often insects such as

_........ or butterflies. The petals of insect-pollinated plants are often

_........ and brightly coloured. After pollination, the grains

germinate and a tube grows down the_........ to reach the ovary.

In the ovary, the gametes fuse. This process is known as_........ .

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.