Germination

• Which hormone does the embryo release at germination?

  Gibberellin
• What does this hormone stimulate?

  Genes in the aleurone layer
• What is the role of the aleurone layer?

  -Production of amylase and protease
• What does amylase do?

  Hydrolyses starch stored in the endosperm to maltose then glucose
• What are the differences between a monocotyledenous and dicotyledonous plant?

  Monocotyledonous: one seed leaf, parallel veins, floral parts in multiples of three. Dicotyledonous: two seed leaves, branched veins, floral parts in multiples of four or five.
• How can you test for the presence or absence of starch?

  Iodine
• Describe the experiment that assesses amylase production in germinating seeds

  -Large quantities of starch stored in the endosperm of seeds such as Maize

  -During germination of a seed starch is broken down by the enzyme amylase into maltose

  -In the experiment, amylase digests starch in the agar plate

  -iodine solution will fail to turn blue-black in areas that lack starch
• Identify the independent variable for this investigation

  -Live or dead seeds
• Identify two variables that should be controlled in this investigation

  -Starch concentration

  -Temperature
• What is the difference between an endospermic seed and non-endospermic seed?

  Endospermic seed: contains endosperm for nourishment. Non-endospermic seed: lacks endosperm, relies on cotyledons for nourishment.
• Why is barley a fruit?

  It has a fruit/ovary wall
• What is the food store for dicotyledons and monocotyledons?

  Dicotyledons: two seed leaves (from the embryo)

  Monocotyledons: endosperm (from the primary endosperm nucleus
• For germination to take place the seed needs to:

  -Absorb water through the micropyle

  - this mobilises enzymes

  -increases cell size through formation of vacuoles causing the testa to split

  -transports materials in seeds

  -Absorb oxygen through the micropyle for aerobic respiration

  -Suitably warm temperature and some seeds need light to trigger germination
• Explain germination in a non-endospermic seed (Broad bean)

  -Begins with water entering the micropyle

  -Water enters the seed and swells the cotyledons, splitting the testa

  -The split testa allows more oxygen in for aerobic respiration

  -Starch and proteins stored in the cotyledons are mobilised through hydrolysis

  -The starch and proteins are used as sources of energy for use in respiration and the growth of radicle and plumule
• Explain germination in an endospermic seed (Maize)

  -Water enters the seed

  -The embryo releases the plant hormone gibberellin

  -Gibberellin diffuses to the protein rich aleurone layer and amylase enzymes are made to break down stored starch in the endosperm