Light, Energy and Heat - Principles of Ecology - Lecture Slides, Slides of Ecology and Environment

Download Light, Energy and Heat - Principles of Ecology - Lecture Slides and more Slides Ecology and Environment in PDF only on Docsity!

Lecture 3: Adaptation to Physical

Environment: Light, Energy and Heat

3.4 Plant adaptation to control water loss

In addition to photosynthetic pathway

differences, heat and drought-adapted plants

have anatomic and physiological modifications

that reduce transpiration, heat load and enable

plants to tolerate high temperature.

Oxygen concentration in aquatic

environment

O2 is dissolved in water

O

concentration in water is determined by solubility and diffusion.

Anaerobic conditions in the deep water

High O2 in the surface due to diffusion

3.6 Carbon gained in photosynthesis is allocated to

production of plant tissues

Carbon allocation is an important issue and has not been well studied. Difficult to measure, especially below ground.

Allocation to different parts has major influences on survival, growth, and reproduction. Leaf: photosynthesis Stem: support Root: uptake of nutrient and water Flower and seed: reproduc.

Constraints Imposed by the Physical Environment Have

Resulted in a Wide Array of Plant Adaptations

• Plants must maintain a positive carbon balance to survive, grow, and reproduce
• Essential plant resources and conditions are interdependent - Light (PAR) - CO 2 - H 2 O and Minerals - Temperature

3.7 Species of Plants are adapted to light

conditions

• Plants adapted to a shady

environment

• Lower levels of rubisco
• Higher levels of chlorophyll (increase ability to capture light, as light is limiting)
• low light compensation and saturation lights
• Plants adapted to a full sun

environment

• Higher levels of rubisco
• Lower levels of chlorophyll
• High compensation and saturation lights

Red oak • Changes in leaf structure evolve

leaves at top and bottom of canopy

• Shade tolerant (shade-adapted)

species

• Plant species adapted to low- light environments
• Shade intolerant (sun-adapted)

species

• Plant species adapted to high- light environments

Change of allocation to leaf of broadleaved peppermint (Reich et al.).

Light also affects whether a plant allocates to

leaves or to roots

Shade tolerance and intolerance

Shade tolerance

Shade intolerance

Seedling survival and growth of two tree species over a year Augspurger 1982

Plants need to make serious evolutionary

adaptations to temperature

 Topt: C 3: <30oC; C4: 30 oC to 40 oC; CAM, >40 oC

Neuropogon: Arctic lichen (C3)

Ambrosia: cool coastal dune plant (C3)

Tidestromia: summer-active desert C4 perennial

Atriplx: everygreen desert C4 plant

C

C

C

Photosyn. rate and Topt

Plants Vary in Their Response to Environmental

Temperatures

• Temperature responses are not fixed
• When individuals of the same species are grown under

different thermal conditions, a divergence in temperature response of net photosynthesis is often

observed

• The T opt shifts in the direction of the thermal

conditions under which the plant is grown

• A similar pattern is seen in individual plants in

response to seasonal shifts in temperature (acclimation)

 Uptake of a nutrient through the roots depends on its concentration

 However there is a maximum uptake rate

 Effect of nutrient availability can also reach a maximum

Plants exhibit adaptations to variations

in nutrient availability

Photosynthesis and nutrient

• Nitrogen can limit photosynthesis
• N in enzyme rubisco

and pigment chlorophyll.

Illustration of

tradeoffs of C4, C3 plants

with CO 2

concentration

Increase in CO2 will influence the competition of C3 and C

CO 2 influence on photosynthesis