The development of pollen grains and ovules

Overview

Produced when a pollen mother cell divides by meiosis, division that gives a pollen grain its two nuclei and two layers of the wall of a pollen grain.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   A drawing of an anther was made at a magnification of ×40 and measures 96 mm across. Calculate the actual width of the anther.

   Model answer

   96 mm divided by 40 gives an actual width of 2.4 mm.

2. 2

   Describe the arrangement of pollen sacs in a typical anther and name the layer that nourishes the developing pollen.

   Model answer

   A typical anther contains four pollen sacs, and each is lined by a nutritive layer called the tapetum.

3. 3

   Which cells inside a pollen sac divide by meiosis?

   Model answer

   The pollen mother cells, also known as the microspore mother cells.

4. 4

   What is produced when a pollen mother cell divides by meiosis?

   Model answer

   A tetrad of four haploid cells, each of which goes on to become a pollen grain.

5. 5

   Describe the division that gives a pollen grain its two nuclei.

   Model answer

   The single haploid nucleus divides by mitosis to give a tube nucleus and a generative nucleus.

6. 6

   Name the two layers of the wall of a pollen grain.

   Model answer

   The tough sculptured outer exine and the thin inner intine.

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