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.

1. Plant responses to flooding and
waterlogging
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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.
Blom, C., Voesenek, L., Banga, M., Engelaar, W., et al. 1994, ‘Physiological ecology of riverside species: adaptive responses of plants to
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
the hyponastic growth of submerged Rumex palustris petioles. Plant Physiology, vol. 136, pp. 2948-2960.
Groeneveld, H. W., Voesenek, L. 2003, ‘Submergence induced petiole elongation in Rumex palustris is controlled by developmental stage
and storage compounds’. Plant and Soil, vol. 253, pp. 115-123.
Jackson, M. B. 1990, Hormones and developmental change in plants subjected to submergence or soil waterlogging, Aquatic Botany, vol.
38, pp. 49-72.
Koch, M. S. & Mendelssohn, J. A. 1989, ‘Sulphide as a soil phytotoxin: differential responses in two marsh species’, Journal of Ecology,
vol. 77, pp.565-578.
Mommer, L., de Kroon, H., Pierik, R., Bogemann, G. M. & Visser, E. 2005, ‘A functional comparison of acclimation to shade and
submergence of two terrestrial plant species’, New Phytologist, vol. 167, no. 1, pp. 197-206.
Setter, T. L., Laureles, E. V. 1996, ‘The beneficial effect of reduced elongation growth on submergence tolerance of rice’, Journal of
Experimental Botany, vol. 47, pp. 1551-1559.
Voesenek, L. & Sasidharan, R. 2013, ‘Ethylene – and oxygen signalling – drive plant survival during flooding’, Plant Biology, vol. 15, no. 3,
pp. 426-435.