After fertilization, the ovule and ovary subsequently develop to form

Correct — A, seed and fruit respectively. After fertilisation the ovule, which contains the fertilised egg, matures into the seed, and the ovary that enclosed the ovules ripens into the fruit around them. The correspondence is one of containment: what held the ovules becomes what holds the seeds. Everything else in the flower — petals, sepals, stamens and style — usually withers away.

• (b)fruit and seed respectively — This reverses the pair. The ovary cannot become the seed, since a single ovary commonly holds many ovules and yields a single fruit with many seeds.
• (c)seed and flower respectively — The flower is the structure that existed before fertilisation. Nothing in a fertilised flower develops back into another flower.
• (d)degenerated ovule and seedless fruit respectively — Degeneration is what happens when fertilisation fails. Seedless fruits do occur through parthenocarpy, as in the banana, but that is development without fertilisation, which is the opposite of what the stem describes.

Flowering plants use double fertilisation. One male gamete fuses with the egg to give the diploid zygote, which grows into the embryo; the other fuses with the two polar nuclei to give the triploid primary endosperm nucleus, which becomes the food store. The ovule as a whole then hardens into the seed with its coat, while the ovary wall thickens into the pericarp of the fruit.

The sequence is pollination, then fertilisation, then the zygote dividing, then the embryo forming and finally the seedling — and getting that order right disposes of most questions from this area. A fruit that develops from the ovary alone is called a true fruit, as in mango and tomato; where another floral part swells and contributes, as the thalamus does in the apple, the result is a false fruit. Parthenocarpy is the third case, in which a fruit forms without fertilisation and so carries no seeds.

• After fertilisation the ovule develops into the seed and the ovary into the fruit.
• The zygote grows into the embryo and the primary endosperm nucleus into the nutritive endosperm.
• Double fertilisation, involving two male gametes, is characteristic of flowering plants.
• A fruit developing from the ovary alone is a true fruit; one to which another floral part contributes, as in the apple, is a false fruit.
• Parthenocarpic fruits such as the banana form without fertilisation and are therefore seedless.

• Reversing the pair and letting the ovary become the seed.
• Assuming every fruit must contain seeds, when parthenocarpic fruits do not.
• Forgetting that some familiar fruits are false fruits, with the edible part not derived from the ovary.

A one-to-one correspondence item. It is nearly always set with the reversed pairing sitting immediately below the correct one.

• practice — not a real PYQ

  The edible part of an apple develops mainly from the

  • (a)ovary wall
  • (b)thalamus
  • (c)seed coat
  • (d)endosperm

  Answer(b) thalamus — which is why the apple is classed as a false fruit rather than a true one.

• practice — not a real PYQ

  In flowering plants, the triploid endosperm is formed by the fusion of a male gamete with

  • (a)the egg cell
  • (b)the two polar nuclei
  • (c)the synergids
  • (d)the antipodal cells

  Answer(b) the two polar nuclei — the second fusion of double fertilisation, which is what makes the endosperm triploid.