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Plants can't move and get out of the way when water levels become difficult to handle. Flooding and soil saturation leads to a depletion of oxygen in the soil and reduction of light and carbon dioxide availability. So how do plants deal with the stress of being flooded?
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Plant responses to flooding and waterlogging
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Overview
Issues with too much water
Plant strategies
Root adaptations
Shoot adaptations
Signalling and hormones
Summary
Flooding of plants
Difference
– Flooding – complete inundation of the soil and above ground area
– Waterlogging – saturation of the soil with water
One of the most common and widespread stressors that plants must deal with
Important for planning and management of crops and agricultural pastures
Impacts of waterlogging and flooding
Hypoxia and anoxia of soils
Loss of nitrogen fixing bacteria
Toxic anaerobic
Submerged plants have reduced availability of:
– Light
– CO₂
Plant strategiesAvoid
Tolerate
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Only grow during dryer seasons.
Grow roots above the water table.
Grow tissue that helps to get oxygen into roots.
Grow leafs and stems that are adapted to survive under water.
Root adaptations
Aerenchyma
– Long interconnected gas-filled chambers.
– Pathway for gas to diffuse from leaves to roots.
– Allows aerobic respiration to continue in the roots.
– Allows oxygenation of the soil surrounding roots.
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Root adaptations
Adventitous roots
– Roots that grow above the soil.
Shallow roots
Pneumatophores
– root tips that stick up from the soil surface.
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Shoot adaptations
Shoot elongation
– Removes the shoots from complete submergence
– Mechanism
• loosening of cell walls
• Intake of water
• Synthesis of new polysaccharides
– Reduces the health of the plant once the water level recedes
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Shoot adaptations
Hyponastic growth
– Growing leaves and shoots more vertically.
– Helps to implement the effectiveness of shoot elongation.
Submerged leaves
– Thinner cuticles
– Longer
– Physiological changes to cells
Signalling and hormones
Regulate the responses of plants to waterlogging and flooding
Ethylene – most important
Gibberellic acid
Abscisic acid
Hormones are interdependent
– Ethlyene decreases abscisic acid concentrations which leads to an increase in gibberellic acid
SummaryMain problems of water logging and flooding
– low oxygen in soil, gas diffusion in flooding
Avoid or tolerate
Low soil O₂ - aerenchyma formation
Flooding – shoot elongation, hyponastic growth
Ethylene is main regulator response to flooding
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358.
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Voesenek, L. & Sasidharan, R. 2013, ‘Ethylene – and oxygen signalling – drive plant survival during flooding’, Plant Biology, vol. 15, no. 3, pp. 426-435.
