The document discusses plant responses and adaptations to flooding and waterlogging. It describes the main problems plants face with too much water like low oxygen levels. It outlines strategies plants use to tolerate flooding, including root adaptations like aerenchyma tissue to transport oxygen and shoot adaptations like elongation to grow above water. Hormones like ethylene play an important regulatory role in triggering responses to help plants survive flooding and waterlogging.
2. Overview
Issues with too much water
Plant strategies
Root adaptations
Shoot adaptations
Signalling and hormones
Summary
3. 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
4. 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
5. Plant strategies
Avoid
Only grow
during
dryer
seasons.
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Tolerate
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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.
6. 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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7. 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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8. 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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9. 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
10. 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
11. Summary
Main 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
12. References
Armstrong, W., Brandle, R. & Jackson M. B. 1994, ‘Mechanisms of flood tolerances in plants’, Acta Botanica Neerlandica, vol. 43, pp. 307-
358.
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submergence’, Annals of Botany, vol. 74, pp. 253-263.
Blom, C. & Voesenek, L. 1996, ‘Flooding: the survival strategies of plants’, Trends in ecology and evolution, vol. 11, no. 7, pp. 290-295.
Cosgrove, D. J. 1999, ‘Enzymes and other agents that enhance cell wall extensibility’, Annual Review of Plant Physiology and Plant
Molecular Biology, vol. 50, pp. 391-417.
Cox, M., Benchop, J. J., Vreeburg, R., Wagemaker, C., Moritz, T. et al. 2004, ‘The roles of ethylene, auxin, abscisic acid and gibberellin in
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38, pp. 49-72.
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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.