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Plant Reproduction

The control of flowering

  • 3 things to know
  • Components 01, 02 and 03

Overview

Recall questions on vernalisation and the crops needing it, the pigment that measures day length and its two forms, night interruption experiments, and how growers exploit photoperiodism.

What you need to know

Answer each one before you reveal it.

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Evaluation

Name a crop that requires vernalisation and explain the advantage of the requirement.

Key term

Outline how prolonged cold makes a plant competent to flower.

Key term

How can a winter cereal variety be sown in spring?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is vernalisation?

    Model answer

    It is the requirement for a prolonged period of low temperature before a plant becomes able to flower.

  2. 2

    Name a crop that requires vernalisation and explain the advantage of the requirement.

    Model answer

    Winter wheat requires it; because it will not flower until it has been through a cold winter, it cannot flower in the autumn when the seedlings emerge, and instead flowers and sets seed in the favourable conditions of the following summer.

  3. 3

    Outline how prolonged cold makes a plant competent to flower.

    Model answer

    Weeks of low temperature sensed at the shoot apical meristem progressively switch off a gene whose product represses flowering, and that switched-off state is inherited by the cells produced as the meristem divides, so after the winter the plant is able to respond to the flowering signal.

  4. 4

    How can a winter cereal variety be sown in spring?

    Model answer

    The moistened seed is chilled artificially for several weeks before sowing, which supplies the cold requirement so the plant will flower that year.

  5. 5

    What is photoperiodism?

    Model answer

    It is the response of a plant, such as the timing of its flowering, to the relative lengths of day and night.

  6. 6

    Which pigment do plants use to measure day length, and what are its two interconvertible forms?

    Model answer

    Phytochrome, which exists as Pr and Pfr.

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