16.2 Plant Responses To Abiotic Stress Flashcards
What are seven examples of abiotic stress?
Changes in day length
Cold and heat
Lack of water / excess water
High winds
Changes in salinity
What are some physiological adaptations of plants to respond to HOT, DRY or extremely WINDY conditions?
Thicker cuticles
Hairy leaves
Sunken stomata
Wilting response
What are some physiological adaptations of plants in an aquatic environment?
Aerenchyma
What is aerenchyma?
Intercellular spaces containing gas which provides plant roots with oxygen in an aquatic environment
Why do deciduous trees in temperate climates lose all of their leaves in winters and remain DORMANT until spring?
Amount of glucose required for respiration to maintain leaves + produce chemicals to protect against freezing
GREATER THAN
amount of glucose produced by photosynthesis
Tree with leaves MORE LIKELY to be blown over by WINTER GALES
What do plants express regarding daylight?
Photoperiodism
What is photoperiodism?
Sensitivity of plants to a LACK of light in environment
What does the sensitivity of plants to dark length result from?
Phytochrome
What is phytochrome?
Light-sensitive pigment
In what two forms does phytochrome exist?
Pr and Pfr
What, regarding phytochrome, changes depending on the LEVELS OF LIGHT?
Ratio of Pr to Pfr
What does the lengthening of the dark period during winter trigger?
Abscission and a period of dormancy
What is abscission?
Leaf fall
Can you describe the responses of the plant leaves to falling levels of light?
- Concentration of AUXIN DECREASES
- Leaves produce ethene in response
- Ethene initiates GENE SWITCHING of cells in ABSCISSION ZOME
- Production of new enzymes
- Enzymes digest and weaken cell walls in SEPARATION LAYER
- Vascular bundles sealed off
- AND fatty material is deposited in cells on STEM SIDE of separation layer
- Cells deep in separation respond to hormonal cues by RETAINING WATER and SWELLING
- Puts more strain on weakened outer layer
- Further abiotic factors finish process
E.g. strong autumn winds or low temperatures - Neat, waterproof scar left behind
Where I St he abscission zone found?
Base of leaf stalk
What is the abscission zone made up of?
TWO layers of cells sensitive to ETHENE
What are the cell walls in the OUTER LAYER of the abscission zone known as?
Separation layer
What does the protective scar left behind after the leaf falls do?
Prevents entry of pathogens
How plants prevent their cells from freezing?
CYTOPLASM and SAP IN VACUOLES of plant cells contain SOLUTES which LOWER freezing point
What things act as antifreeze in plants?
Sugars
Polysaccharides
Amino acids
Proteins
How does a plant cool down?
Stomata opens
Water evaporates from cells in TRANSPIRATION
What is the opening and closing of the stomata in repose to abiotic stresses under the control of?
Hormone ABA
How does a plant respond to ABA tofalling soil water levels?
- Soil water levels falls
- Plant ROOTS produce ABA
- Transported to leaves
- Binds to receptors on plasma membrane of STOMATAL GUARD CELLS
- ABA activates changes in IONIC CONCENTRATION of guard cells
- Water potential reduced
- Turgor of cells reduced
- Guard cells close stomata
- Water loss by transpiration is greatly reduced