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Wetland Ecology
Lectures 17-18
Wetland Adaptations
Wetlands are physiologically ‘harsh’ environments
Organisms are grouped as either:
Tolerators (resisters)
Regulators (avoiders)
Unicellular Adaptations to Anoxia
Most are metabolic
When O2 becomes limiting; most cells use internal organic compounds as electron acceptors
Pyruvate  ethyl alcohol  lactic acid
Desulfovibrio genera uses only sulfur as terminal electron acceptor
Plant Adaptations to Anoxia
Adaptation grouped into 3 main categories:
Structural (morphological) adaptations
Physiological adaptations
Whole Plant Strategies
Structural/Morphological
Arenchyma – air spaces that develop in roots & stems that allow diffusion of oxygen from aerial portions
into the roots
Characteristic of flood tolerant species NOT flood sensitive plants
Result is a honeycomb structure
Adventitious roots – [ ] of ethylene in hypoxic tissues initiates structural adaptations. Ethylene stimulates
the formation of adventitious roots in:
Flood tolerant trees (Salix & Alnus)
Flood tolerant herbs (Phragmites, Ludwigia, & Lythrum)
Also, flood intolerant plants (Solanum sp)
Stem Hypertrophy
When hypertrophy occurs in a tree its called a buttress
Taxodium & Nyssa
Fluted trunks occur in:
Quercus palustris
Ulmus americana
Stem elongation + lenticels
Grow fast to get photosynthetic organs above water-line
Shallow root systems common in wetland plants
Acer rubrum highly plastic (shallow roots in wetlands & deep roots in uplands)
Prop roots & lenticels
Pneumatophores
“Air roots” that are usually ‘studded’ with lenticels
Perceived to improve gas exchange in the root system
Black mangrove (Avicennia sp.)
Cypress (Taxodium sp.)
Height of pneumatophores indicative of water level height
Physiological Adaptations
Pressurized gas flow Rhizosphere oxidation – Believed that plants modify sediment anovia enough to allow the survival of
nearby nontolerant plants
One indicator of a wetland (hydric soils, thus wetlands are present)
Lower Water Uptake – decreased water uptake is common in saturated conditions
Response to overall reduction of root metabolism
Similar to drought condition responses
Close stomata, decreased CO2 uptake, decreased transpiration & wilting
Altered Nutrient Absorption – Anoxia modifies nutrient availability in wetland soils
O2 needed for efficient O2 uptake
Sulfide avoidance – alcohol dehydrogenase (ADH) activity is inhibited by hydrogen sulfide
Tolerance in plants includes:
Oxidation of sulfide to sulfate through root aeration
Accumulation of sulfate in the vacuole
The conversion to gaseous hydrogen sulfide, carbon disulfide & dimethylsulfide
Anaerobic Respiration
Whole Plant Strategies
Life History attributes include:
Timing of seed production
Production of buoyant seeds
Germination of seeds while the fruit is still attached to the tree (vivipary) (red mangrove)
Production of a large, persistent seed bank
Production of tubers, roots, and seeds that can survive long periods of submergence
Animal Adaptations
An organism’s ‘successful’ adaptations are often compromises; enabling it to live with competing (often
several) environmental demands
1. Special organs
Development or modification of specialized regions of the body for gaseous exchange
Gills on fish & crustacea, parapodia on polychaetes
2. Improving oxygen conditions – Mechanisms to improve oxygen gradient across a diffusible membrane
(e.g., by moving to oxygen-rich environments or by moving water across the gills by ciliary action)
3. Internal structural changes – increased vascularization, a better circulation system, or stronger pump
(the heart)
4. Respiratory pigments – modification of respiratory pigments to improve oxygen-carrying capacity
5. Physiological adaptations – shifts in metabolic pathways and heart pumping rates
6. Behavioral patterns – decreased locomotor activities or closing a shell during low oxygen stress