Plant adaptions Flashcards
Lecture 5 & 6 (35 cards)
What is the consequence of diverse plants?
Diversity of plants consequence of different
evolutionary solutions to common problems of
acquiring the resources which support photosynthesis.
What is photosynthesis?
Light (PAR*) + Nutrients + CO2 + H2O → C6H12O6 +
O2 + H2O
▪ Availability of light directly influences the rate of photosynthesis
▪ An increase in PAR leads to increase in rate of photosynthesis
What is respiration?
C6H12O6 + O2 → CO2 + H2O + ATP
▪ In the dark only respiration occurs, and CO2 is lost.
O2 from photosynthesis is used for respiration.
How does photosynthesis involve exchanges between
the plant and atmosphere?
▪ Photosynthesis takes place in mesophyll cells in the leaf.
▪ CO2 moves from the atmosphere into the leaf via stomata.
▪ the flow rate of CO2 through the stomata is determined by.
▪ stomatal density.
▪ aperture.
▪ Stomata are not always open.
How does Water Move from the Soil, through the
Plant, to the Atmosphere?
▪ Plants function best when their cells are fully hydrated.
▪ The rate of transpiration varies daily.
▪ Controlling the stomata is a plant’s most important way to regulate water loss
▪ Trade-off: taking in CO2 for photosynthesis vs losing water needed to live.
▪ Directly influences the productivity of different ecosystems with different environmental conditions.
How does The Process of Carbon Uptake Differ for
Aquatic and Terrestrial Autotrophs?
▪ Aquatic autotrophs don’t have stomata
▪ CO2 diffuses from the water across the cell membrane directly into the cell
▪ Why is this different to terrestrial plants?
▪ Susceptible to CO2 depletion.
▪ Why?
How does Plant Temperatures Reflect Their Energy Balance with the Surrounding Environment?
▪ Both photosynthesis and cellular respiration increase as temperature increases.
▪ Internal leaf temperature may sometimes be much higher than air temperature and may reach critical levels.
▪ Plants must therefore lose heat:
- Evaporation
- Convection
- Heat loss
Evaporation
How does Plant Temperatures Reflect Their Energy Balance with the Surrounding Environment?
part of transpiration
* Evaporative cooling increases with increase in the rate of transpiration.
* Terrestrial plants.
Convection
How does Plant Temperatures Reflect Their Energy Balance with the Surrounding Environment?
Transfer of heat energy through the circulation of air (wind) or water (currents)
▪ Terrestrial & aquatic plants.
▪ Prevents the boundary layer from getting too thick.
* this prevents the transfer of heat, water and CO2 between the leaf and the environment.
Heat Loss
How does Plant Temperatures Reflect Their Energy Balance with the Surrounding Environment?
Increased by
interrupting the boundary
layer by modifying leaf
size and shape.
▪ The physical environment affects how plants lose heat:
▪ Areas of high water-availability.
- most heat is lost through transpiration.
▪ Areas of lower water availability.
- transpiration is limited
- other stuff not on slide
What is a boundary layer?
the layer of still air (or
water) next to the leaf surface.
It doesn’t move.
inhibits the loss of water through transpiration.
What is trade-off?
Plants must balance water loss vs heat gain.
What Constraints Imposed by the Physical Environment Have led to a Wide Array of Plant Adaptations?
▪ To survive, plants must acquire essential resources while tolerating environmental conditions.
▪ Features of physical environment often interdependent
▪ In dry, sunny environments
▪ greater PAR
▪ lower humidity
How would plants adapt structurally to a dry & sunny environment or a cool & wet environment?
How would plants deal with conflicting needs above- and below ground?
What is The Link between Water Demand and
Temperature Influences Plant Adaptations?
- Modifications to stomata
- Modifications to root: leaves
- Modification to photosynthetic pathways
- Changes in leaf size and shape.
- Curling or wilting leaves
- Chlorophyll production is inhibited and leaves turn yellow if water stress is prolonged
- Plants may be drought deciduous
Modifications to stomata
What is The Link between Water Demand and
Temperature Influences Plant Adaptations?
▪ The demand for water is related to temperature
▪ air temperature rises → rate of transpiration (& water-loss) rises.
▪ Plants modify open/close cycle of stomata.
- closed or partially closed
- when atm and soil is dry
- during the hottest part of the day
- open only during early morning or at night.
- cooler or more humid conditions
▪ Plants modify size & density of stomata.
What are the consequences to the plant?
Modifications to energy put into the development of root: leaves
ratio of roots to leaves
What is The Link between Water Demand and
Temperature Influences Plant Adaptations?
▪ Proportionate allocation of carbon to roots & leaves depends on prevailing conditions during early development. (when it is very dry)
▪ Plant compensates to maximise acquisition of scarce resource or to take advantage of abundant resource.
- More roots and less leaves allows plants to explore more soil for extracting water.
- Reducing leaf area decreases the amount of solar radiation striking the plant and decrease the surface are across which is lost through transpiration.
[ shrubs and grasslands have more roots than shoots than forest and woodlands ]
Modifications to photosynthetic pathways.
What is The Link between Water Demand and
Temperature Influences Plant Adaptations?
▪ C3 plants – in areas without water limitation
▪ C4 plants– increased efficiency of water use in warmer and drier environments.
[ different photosynthetic plants use a different water pathway ]
Changes in leaf size and shape.
What is The Link between Water Demand and
Temperature Influences Plant Adaptations?
▪ In dry environments leaves tend to be
- smaller and thicker (more cells in the same unit area)
- covered in hairs that scatter solar radiation
- coated with waxes and resins that reflect light and reduce absorption.
Curling or wilting leaves
What is The Link between Water Demand and
Temperature Influences Plant Adaptations?
- reduces leaf area exposed to the sun.
- reduces water loss and heat gain.
Chlorophyll production is inhibited and leaves turn
yellow if water stress is prolonged
What is The Link between Water Demand and
Temperature Influences Plant Adaptations?
- Deciduous trees prematurely shed leaves
Plants may be drought deciduous
What is The Link between Water Demand and
Temperature Influences Plant Adaptations?
- Drop their leaves at start of dry season.
- New leaves grow just before the rainy season begins.
how do Plants Exhibit Both Acclimation and Adaptation in Response to Variations in Environmental Temperatures?
▪ Plants are exposed to wide variations in temperature on many spatial and time scales
▪ All plants experience daily & seasonal changes in
temperature.
