Abiotic Stress Flashcards
Why do plants need to respond to their environment?
-cope with changing conditions
-maximise photosynthesis
-obtain more light
-avoid biotic stress
-ensure germination in suitable conditions
What is photoperiodism?
-sensitivity to a lack of light in their environment
-results from light pigment called phytochrome
How is abscission triggered?
- phytochrome detect falling light levels
- decreased auxin production
- increased ethene production
- ethene activates genes in cells in A zone to produce digestive enzymes
- enzymes digest cell wall in separation zone
How are vascular bundles sealed off?
-fatty material deposited at stem side to protect plant
How does a lack of water affect the plant?
- root hairs detect low levels of water in soil
- starts to produce ABA and travel up plant
- ions move out of guard cells - decreases WP
- water leaves by osmosis
- guard cells become flaccid and close stomata
= low levels of transpiration
What is herbivory?
-process by which herbivores eat plants
What are the types of plant defence traits?
-mechanical, chemical, developmental and phenological
What are some examples of physical defences?
-thorns, stings and spikes
What are some examples of chemical defences?
-tannins, alkaloids and terpenoids
What are tannins?
-bitter chemical compounds
What are alkaloids?
-nitrogenous bitter chemicals
-affects metabolism of herbivore
What are terpenoids?
-essential oils that can be toxic to insects and fungi
-eg. citronella
State 2 responses that some plants use to defend themselves from herbivory
-foldings
-stings
How do plants prevent freezing?
-cytoplasm and cell sap contain solutes that lower the freezing point
-become frost resistant
-only during winter-spell of warm weather reverses the process
How is the stomata controlled in plants?
-controlled by ABA
-release it under abiotic stress
-closes stomata
-ABA activates changes in ionic conc of guard cells
-reducing WP = closure of stomata
