Sexual Reproduction in Plants

Sycamore trees produce flowers in the spring.

The flowers have these characteristics:

• small and green coloured
• produce large quantities of small, light pollen grains
• contain nectar.

Explain why scientists think that the flowers can be pollinated by wind and by insects.

The flowers of the sycamore tree are cross-pollinated.

State an advantage of cross-pollination rather than self-pollination.

______

The sentences describe the processes that occur in a sycamore flower after pollination.

Complete the sentences by writing words in the gaps.

The pollen grain grows a ______ which allows the male gamete to reach the female gamete.

After fertilisation, the ovule becomes a ______ and the ______ will develop into a fruit.

Fig. 6.1 shows two sycamore fruits.

The wings on the fruits cause them to spin as they fall to the ground. This slows their fall so that they can be blown away by the wind.

Explain why this is an advantage to the parent tree and any young trees that are produced from these fruits.

Complete the table to show the name of structures P, Q and R and one function of each structure.

Describe the surface of a pollen grain from an insect-pollinated flower.

Explain how this feature is an advantage in insect-pollination.

Explain how a pollen grain from a wind-pollinated flower is adapted for pollination.

Suggest, with reference to structures shown in the diagram, how each fruit is dispersed.

P: ______

Q: ______

R: ______

Outline the importance to a plant species of fruit dispersal.

State, in the correct place on the flow chart, the name of stage 5.

Describe the role of enzymes in this stage of the plant's life cycle.

Two of the stages in the life cycle of this flowering plant may depend on the action of an animal.

Identify each of these stages and for each stage describe how the action of an animal may be required.

stage ______
action of an animal ______

stage ______
action of an animal ______

Name two factors that must be present for the seed to germinate.

1. ______
2. ______

State two substances, other than starch and sugar, that contribute to the total mass of the seed at stage 1.

1. ______
2. ______

State the stage at which the seedling starts to photosynthesise, and give your reasons.

stage = ______
reasons = ______

Explain the difference in the amount of starch and sugar between stage 2 and stage 3.

______

State the number of each of the following parts of the flower shown in the diagram.

petals = ______
filaments = ______

On the diagram of the flower label the ovary (the structure containing ovules).

its method of pollination and give reasons for your answer

method of pollination = ______
reasons = ______

its method of seed dispersal and give reasons for your answer.

method of seed dispersal = ______
reasons = ______

Suggest why this fruit is most likely to be wind-dispersed.

Describe the pattern shown by the results in the graph.

State the number of fruits in the investigation that took between 4 and 10 seconds to reach the ground.

______

Suggest and explain advantages to the plant of its fruits taking a longer time to reach the ground.

When a fruit of the plant reaches the ground, the process of germination to form a new plant may take place.

State one environmental condition that affects germination and explain the importance of this condition.

environmental condition = ______
explanation = ______

Name two structures visible in Fig. 2 that are not visible in Fig. 1.

1. ______
2. ______

Name the process represented by the arrow drawn between Fig. 1 and Fig. 2.
Describe the use of enzymes in this process.

name of process = ______
use of enzymes = ______

In an experiment, the growth of a plant from a seed is found to be faster as temperatures increase up to $35\,^\circ\text{C}$.

Explain how the development of a plant from a seed would be affected by a temperature much higher than $35\,^\circ\text{C}$.

A total of 12 pollen grains were placed in the 20% sucrose solution.

Use the information in the table to calculate the number of pollen grains that germinated to produce a pollen tube in the 20% sucrose solution.

______

Suggest why the mean pollen tube length was calculated for each sucrose concentration.

Use the information in the table to suggest the optimum (best) concentration of sucrose solution for pollen tube germination and growth.

______ %

Explain how the information in the table enabled you to reach this conclusion.

The germination of a pollen grain to form a pollen tube requires the movement of water into the pollen grain from its surroundings.

Suggest why placing a pollen grain in a solution with a higher sucrose concentration than in your answer to (a)(iii) may result in a lower percentage of germination.

Describe the route taken by a growing pollen tube in a plant and explain its importance in plant reproduction.

On Fig. 3.1, use lines labelled S and C to label a sepal (S) and a carpel (C).

The flowers are cross-pollinated by an insect. Explain why the insect must visit flower D before visiting flower E.

Suggest how flowers of this species are adapted to be pollinated by an insect such as a bee.