WetlandQuiz1

Hydrophyte

Plants adapted to living in water or saturated soil

Emergent

Extend above water surface

Floating-leaf

Floating leaves and roots attached or floating

Submerged

Below water surface

Stressors for wetland plants

1. Low or no oxygen

2. Low light conditions in water

3.High salt concentration

4.Reproduction

Hypoxic

Low oxygen concentration

Anoxic

No oxygen present

How Wetland Plants Deal with Anoxia?

Passive Diffusion of Gases

Aerenchyma Tissue

Pressurized Gas Flow

Passive Diffusion of Gases

Primary mechanism of gas exchange

• Occurs in air & water (& oxic soil)

• Higher O2 concentration in air than water

• Passive diffusion slow in water

Aerenchyma Tissue

Tissue with large intercellular spaces

• Throughout the plant: leaves, stem, roots

• Easy movement & exchange of gases

Pressurized Gas Flow

Gas moves into internal gas spaces of young leaves

• Gas forced down through aerenchyma from stem to roots by slight pressure caused by the heating of the leaves

• Older leaves lose their capacity to support pressure gradients so gas from the roots returns out through the old leave

Describe this

Pressurized gas flow

Describe this

Daily variation in solar energy, temperature

• Solar radiation peaks mid-day

•Air temp increases mid-day

• Leaf outer & inner temps increase

Pressure & gas flow within leaves

• Pressure builds within leaves/plant

•Gas flow in plant follows daily temperature fluctuations

Gas flow follows a 24-hr cycle

• Depends on time of year & light intensity

Stem Hypertrophy

Swelling of the lower stem

• Increased cell size, number of cells unchanged

• Is not from aerenchyma tissue

• Increases gas exchange (increased surface area)

Adventitious Roots

Roots developed on the stem above the anaerobic zone

• Better obtain O2 for respiration

What is the function and structure of root tissue found in non-root portions of plants, especially in submerged environments?

• Location: Grows from above-ground or non-root portions of the plant.

• Function:

  • Anchors into soil for extra stability.

  • Facilitates diffusion of oxygen and gases from the atmosphere into the root zone.

• Submerged Plants:

• Develop side shoots that remain underwater.

• Aim to reach soil or stay submerged to enhance gas exchange.

• Increased surface area boosts diffusion efficiency.

Pneumatophores

Root structure growing out of the water

•Gas exchange with atmosphere

Rhizosphere Oxygenation

Rhizosphere: narrow region of soil surrounding roots directly influenced by root secretions & root microbiome

Release O2 from roots into soil to create oxic root zones

• Aerenchyma tissue provides O2 to roots

Shallow Root Systems

Roots spread near soil surface to avoid anoxia in deeper soil

• Increased O2 near water column

Rapid Shoot Growth, Stem Elongation

Shoots get above water surface quickly to allow for gas exchange (& photosynthesis)

• Adjusts growth rate based on water levels

Low light levels in water cause?

Reduced photosynthesis

How wetland plants increase photosynthesis and gas exchange?

Increase leaf surface area,

ribbon-like, highly branched,

floating/emergent leaves

Heterophylly

Different leaf shapes on the same plant

•Floating/emergent leaves

•Maximize light exposure, gas exchange

•Submerged leaves

•Increased gas diffusion

•Less resistance in water: waves, currents

• Less physical damage to plant

High Salt Concentration causes plants to perform

Salt Exclusion (Some species) or salt secretion

Prevent salts from entering or accumulating

• Higher K+ ions in root cells than Na+ in soil

• Water enters roots through osmosis

Allow salts to enter roots, but

inhibit movement to stems & shoots (concentrated in roots)

Salt glands

actively move salt to outside of leaves

Salt accumulates in tissue that is shed

• Salt concentrates in older leaves

• Plant sheds these leaves once salt levels high enough

Reproduction in Water (4 types)

Produce buoyant seeds,

Delay flowering when flooded or accelerate flowering,

Large Persistent seed banks,

Seeds germinate while on parent plant

Buoyant seeds

Marine or lacustrine, always water present, allowing seeds to become bouyent, waves and currents to disperse seeds, encounter soil

Flowering time

Super unpredictable, wet and dry seasons, not predicable, they'll adaptbly achange the timing of flowering and how long based on water level, very short window, wait until water low and flower, and time of flowering changes.

Large, persistent seed bank

Seed bank - dormant seeds that exist in the soil, viable just waiting for the right conditions, wetland plants can sit dormant for years/months, etc, waiting for right conditions.

Seeds germinate while on parent plant

Sitting in condition where seed is above water, waiting for conditions, having the seed germinate and begin growing before dropping them.