Sexual Reproduction in Plants (Cambridge O Level Biology)

Some students investigated the conditions needed for the germination of maize seeds. They used maize seeds from a packet of seeds they had purchased in a shop.

Three dishes were used, each containing cotton wool and the same number of maize seeds, as shown in Fig. 1.

Fig. 1

Table 1 shows the conditions provided for each dish. 

Table 1

The seeds were left for five days and then observed.

The results are shown in Table 2

Table 2

[2]

In a second investigation, maize seeds were placed in a dish containing damp cotton wool.

This dish was left in the dark for five days at 20°C.

[2]

A student gathered 70 maize seeds from plants growing in a field. The seeds were placed in dishes containing damp cotton wool.

After five days, only 64 seeds had germinated. 

Calculate the percentage of seeds that germinated.

Show your working.

Give your answer to the nearest whole number. 

[2]

Suggest a reason why some of the seeds did not germinate.

[1]

Fig.1 shows a photomicrograph of a pollen grain with a pollen tube growing from it.

Fig. 1

A student placed pollen grains from the same type of plant in sucrose solutions of different concentrations for a fixed amount of time. After this time, the student used a microscope to examine the grains and tubes.

Table 1 shows the results of the investigation.

Table 1

[1]

 [1]

 [1]

[2]

[3] 

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

Fig. 1 shows a section through a flower.

Fig. 1

Write one letter from Fig. 1 to identify each of the following.

You may use each letter once, more than once, or not at all.

[6]

Fig. 2 shows pollen grains from the flowers of several different species, labelled with the letters K–Q.

Fig. 2

State the letters of the pollen grains that come from insect-pollinated flowers.

Fig. 1 shows sections of two flowers, K and L, from the same species.

Fig. 1

[2]

State the names of the parts in Fig. 1 that: 

• produce ovules
• protect the bud of the flower

On Fig. 1, draw an arrow to represent the transfer of pollen from flower K to flower L during pollination.

A student said, “Flowers K and L are pollinated by insects.”

Describe two structures in flowers K and L that support this statement. 

Use features that are visible in Fig. 1. 

Describe the pathway water takes in a plant, as it moves from the soil to a leaf.

Fig. 1 is a half-flower drawing of pride of Barbados, Caesalpinia pulcherrima.

Fig. 1

Complete Table 1 by stating the letter from Fig. 1 that indicates the organ where each function occurs and the name of the organ.

Table 1

Extended Only

Fig. 2 is a scanning electron micrograph of some pollen grains from wind-pollinated flowers and insect-pollinated flowers.

Fig. 2

Write the formula that would be used to calculate the actual diameter of pollen grain H.

[1]

The actual diameter of pollen grain H is 0.082mm.

Convert this value to micrometres (μm).

Explain how the pollen grain labelled J is adapted for insect pollination.

Extended Only

Pollen grains grow tubes, which contain haploid male gamete nuclei.

One of these male gamete nuclei fuses with the female gamete. State the part of the flower that contains the female gamete

[1]

Define the term haploid nucleus.

Explain why it is important for gametes to be haploid.