How do plants deal with flooding?
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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
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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
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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
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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.
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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
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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
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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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ReferencesArmstrong, 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.