Component 2.4 - Plant Sexual Reproduction

Question 1

Why does a seed need to be dispersed away from the parent plant?

Answer 1

1) Reduces competition following germination
2) Does not cast shade over smaller plant
3) increases the chance of growth into a mature plant

Question 2

Conditions for germination and why ?

Answer 2

Suitable temperature - optimum for enzymes and speeds up rate of diffusion
Water - causes the swelling of cotyledons and acts as a fluid medium, mobilising enzymes
Oxygen - required for aerobic respiration, ATP for metabolism

Question 3

Germination in a non-endospermic seed e.g a broad bean

Answer 3

1) Water is taken up through micropyle, the cotyledons swell and testa splits to allow entry of more oxygen for aerobic respiration
2) Enzymes are mobilised. Amylase digests starch in cotyledons to maltose. Proteins broken down into amino acids.
3) Nutrients moves to plumule and radicle for growth

Question 4

Germination in endospermic seeds e.g maize including the role of gibberellin

Answer 4

1) Following the absorption of water into the micropyle gibberellic acid is released by the embryo and diffuses into the aleurone layer
2) Gibberellic acid induces the production of enzymes that break down proteins into amino acids
3) Amino acids which are used to synthesis amylase
4) Amylase breaks down nutrients e.g starch into maltose which diffuse to the embryo where they are used for growth

Question 5

Give advantages of plant asexual reproduction

Answer 5

Only one parent needed - saves time
Rapid colonisation
Genetically identical offspring to retain useful genes

Question 6

Describe advantages of plant sexual reproduction

Answer 6

Produces genetically varied offspring to adapt to a changing environment