2019HSCShort answer

Q29

3 marks

Question

Describe ONE mechanism by which plants maintain internal water homeostasis.

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Solution

Criteria	Marks
Describes a mechanism by which plants detect and respond to internal water levels to maintain homeostasis	3
Outlines features of a mechanism by which plants maintain water balance	2
Provides some relevant information	1

Sample answer:

Plants can control movement of water out of the leaf to keep a stable internal environment with respect to water, by altering the size of the opening of the stomates. The opening and closing is under hormonal control, for example abscisic acid is a stress hormone produced by plants when internal water is low, causing stomata to close thus reducing water loss.

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Syllabus alignment

Module 8 · Non-infectious Disease and Disorders

HomeostasisInvestigate behavioural, structural, physiological, hormonal, neural and plant water-balance mechanisms.

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