Plant Reproduction

Distinguish between self-pollination and cross-pollination

• self-pollination: transfer of pollen from an anther to a stigma of the same plant

• cross-pollination: transfer of pollen from an anther to a stigma of a different plant of the same species

Adaptations of a wind-pollinated flower

• stigma is large and feathery

• petals are small and not coloured brightly

• anthers outside

Describe the main events of pollen grain development

• begins with a diploid microspore mother cell in the anther

• Meiosis produces four haploid microspores

• Each microspore undergoes mitosis, forming:

  • 1 generative cell (later makes 2 sperm cells)

  • 1 tube cell (forms the pollen tube)

• Together, they make a mature pollen grain (male gametophyte)

• Generative cell later divides again to form two sperm cells during pollen tube growth

Two fertilisations occur during the sexual reproduction of flowering plants.

Describe what happens during both of these fertilisations

• First fertilisation:
  1 sperm cell fuses with the egg cell → forms a diploid zygote (future embryo)

• Second fertilisation:
  1 sperm cell fuses with the 2 polar nuclei → forms a triploid cell (develops into endosperm to nourish the embryo)

1. what is a cotyledon

2. give one function of a cotyledon

1. A seed leaf

2. stores food/supplies nutrients to embryo/absorbs food from endosperm

Give one function of the testa, the plumule and the radicle

• testa - seed coat

• radicle - forms young root

• plumule - forms young shoot

Give any two methods of seed dispersal

• animal

• water

Give one reason why fruit and seed dispersal are of benefit to plants

• avoids overcrowding

• colonises new areas

• increases chnaces of survival

Water, oxygen and temperature are all required for the germination of seeds.

In the case of any two factors, describe their effect of the process of germination

Water:

• activates enzymes

• transport medium for digested products

Oxygen:

• Needed for aerobic respiration

Suitable temperature:

• allows maximum enzyme activity

Give one example of an endospermic seed and a non-endospermic seed

Endospermic seed: Maize

Non-endospermic seed: Broad bean

1. Give two advantages of a plant that reproduces by seed

2. Give two advantages of a plant that reproduces by vegetative propogation

1. Sexually: cross-pollination ensures variation/more resistant to disease

2. Asexually: no variation/rapid growth

Explain the term vegetative propagation

Plant asexual reproduction- production of a new identical plant from the root, stem or leaf of the parent plant

Give two methods of artificial vegetative propagation

1. Cutting:

   • Cut a shoot from the plant

   • Root it in water, compost, or with rooting powder

   • Grows new roots and leaves

2. Grafting:

   • Scion (top part) is cut from one plant

   • Attached to rootstock (bottom part) of another plant

   • Combines useful traits from both plants