OCR A-Level Biology B H422
The Developing Cell: Cell Division and Cell Differentiation
The Developing Individual: Meiosis, Growth and Development
The Development of Species: Evolution and Classification
Cells and Microscopy
Water and Its Importance in Plants and Animals
Proteins and Enzymes
Nucleic Acids
Patterns of Inheritance
Population Genetics and Epigenetics
Gene Technologies
The Principles and Importance of Homeostasis
The Hormonal Control of Blood Glucose and the Management of Diabetes
Kidney Functions and Malfunctions
The Cellular Basis of Cancer and Treatment
Respiratory Diseases and Treatment
Cellular Respiration
Metabolism and Exercise
Pathogenic Microorganisms
The Immune System
Controlling Communicable Diseases
Photosynthesis, Food Production and Management of the Environment
The Impact of Population Increase
Planning and Implementing Practical Work
Analysing and Evaluating Practical Results
Practical Skills, Apparatus and Techniques
Fertility and Assisted Reproduction
The Effects of Ageing on the Reproductive System
Plant Reproduction
The Nervous System and the Identification and Consequences of Damage
Monitoring Visual Function
The Effect of Ageing on the Nervous System
The Heart and Monitoring Heart Function
Transport Systems in Mammals
Gas Exchange in Mammals and Plants
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.
Outline how prolonged cold makes a plant competent to flower.
How can a winter cereal variety be sown in spring?
Questions from this subtopic
Each one with the model answer underneath.
- 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
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
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
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
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
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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