Leaves: anatomically similar to terrestrial bottom of leaves have stomata cuticle present Cell walls...
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Transcript of Leaves: anatomically similar to terrestrial bottom of leaves have stomata cuticle present Cell walls...
•Leaves: anatomically similar to terrestrial
bottom of leaves have stomatacuticle present
•Cell walls heavily thickened by cellulose (rigidity)
•New growth must respire anaerobically until leaves reach surface, then lacunae increase in size
Structural Support Emergents
Structural Support Floating Leaf•Leaf shape:
circular with entire margins - resistance to tearing
large surface area yet reduced resistance to current
support tissues drastically reduced or absentlack of rigidity prevents mechanical
damage
•Leaf texturetough and leathery - withstand wind, rain, hailwaxy cuticle on upper surface only
•Petioles long and thin - rapid elongation when necessary
Structural Support Submersed
•Leaf shape: ribbon-like
large surface area yet reduced resistance to current
support tissues drastically reduced or absentlack of rigidity prevents mechanical
damage
•Vascular elements generally lacking in lignin support provided by water that surrounds the
leaf and aerenchyma within the blade
Heterophylly
•A form of polymorphism where more than one kind of leaf on the same plant
•Occurs among aquatic plants that grow in shallow, submersed habitats that undergo fluctuations in water levels
Figure from Reimer, Donald N. 1993. Introduction to Freshwater Vegetation, Krieger Publ. Co. p. 106.
Myriophyllum humile
AA
BB
Part IIIMacrophytes effects on the wetland
environment:
1. Productivity
2. Habitat Structure
3. Water column
4. Sediment composition & chemistry
Primary Productivity
Among the highest of any community
Emergents 1500 to 4500 g C m-2 yr-1
Submersed 50 to 1000 g C m-2 yr-1
Phytoplankton 50 to 450 g C m-2 yr-1
Below ground Biomass
Below ground biomass can be more than half of total
Portion of biomass in roots and rhizomes by plant type:
Emergents 30-95 % Floating Leaved 30-70 % Submersed 1-40 % Image from Whitley et al. Water Plants for Missouri Ponds
Litter
Emergents tend to have more cellulose and more lignins and other refractory components than submersed plant tissues. Water transparency and pH is also affected by humic and fulvic DOC (dissolved organic carbon).
Combined with higher biomass, greater contribution to the litter and peat accretion.
Floating leaved tissues intermediate in refractory component.
Oxidized
Rhizosphere
•Loss of oxygen from the roots varies with plant species
•Oxygen leakage is primarily from root tips, although some leak along whole length of root, others (e.g. water lilies) leak only from 1 cm apex
•Young root tissue release more oxygen than old (more cuticularized tissue)
Fe
Oxidized Rhizosphere
• Oxygen leakage serves to oxidize and detoxify potentially harmful reducing substances in the rhizosphere (Fe, Mn, S).
• Species with convective through flow significantly increase the root length that can be aerated compared to diffusion onlyOxidizin
gConditions
ReducingConditions
Water Quality Changes
•pH and alkalinity
•DO
•humic acids
Dense stands of Ceratophyllum
pH
alkalinity
Water Quality Changes
•Nutrient cycling - 108 mg P/m2/day from sediment pore water, 45 to plant and 62 excreted to water. •(Eelgrass, McRoy, et al. 1972)
water20 ug/L 2000 ug/L
leavesroots &rhizomes
interstitialwater
Effects on Nutrient Cycling
On at least a seasonal basis, rooted macrophytes act as nutrient pumps, translocating nutrients from the sediments to the water column.
Studies indicate that between 30 and 70% of nutrients taken up from the sediments are releasedto the water column during scenescence. The balance is tied up in DOM (detritus).
Water Quality Changes, cont.
• Aquatic macrophytes reduce bio-turbidity -
through competition with phytoplankton
• Macrophytes reduce the action of current on
waves against the sediment water interface,
thereby reducing resuspension.
Water Quality Changes, cont.
• Aquatic macrophytes (living and dead) provide
a surface area for growth of periphyton
(bacteria, algae, fungi, invertebrates living
attached or associated with surfaces).
• The primary producers in this biofilm obtain
their nutrients from the water column.
Habitat Structure
• Effects on fish:
protection from
predation
• Effects on
macroinvertebrates:
higher biomass and
species richness
Habitat Structure
•PERIPHYTON - usually
primary source of fixed
edible carbon
•Macrophytes - not heavily
grazed, more nutritious as
detritus (covered with
bacteria and other
decomposers: peanut butter)
Habitat Structure
•Effects on birds:
more herbivorous
species
Habitat Structure
•Effects on
zooplankton: refugia,
particularly during the
day
Macrophytes: Conclusions
• Evolved a variety of adaptations to life in the
water
• Have specialized tissue that transport and store
oxygen
• Accessory pigments allow utilization of low light
levels
• Rooted plants act as nutrient pumps, w/
moderate net sink
• Food web based on periphyton and detritus
(with detritus contributing bulk of organic carbon)
• Macrophytes provide physical refugia and
surface area