Plant Adaptations to the Environment Flashcards
all life on earth is __
carbon-based
- complex sequence of metabolic reactions
- can be separated into two processes: light dependent, light-independent reactions
photosynthesis
two process of photosynthesis
- light dependent reaction
- light independent reaction
Process of photosynthesis (formula)
6CO2 + 12H20 –> C6H1206 + 602 + 6H20
rates of photosynthesis and respiration, and therefore net photosynthesis, aer typially measured in what
mole CO2 per unit leaf area (or mass) per unit time
(µmol/m^2/s)
the harvesting of energy from the chemical breakdown of simple sugars and other carbohydrates
cellular respiration
net photosynthesis formula
photosynthesis - repiration
where does the process of cellular respiration occur
mitochondria
other term for cellular respiration
aerobic respiration
what does the cellular respiration involve
oxidation of carbohydrates to generate energy (ATP)
cellular respiration formula
C6H12O6 + 6O2 –> GCO2 + 6H20 + ATP
where does the process of photosynthessis occur
chloroplast in mesophyll cells
three main types of photosynthesis
- C3 photosynthetic pathway
- C4 photosynthetic pathway
- CAM (crassulacean acid metabolism)
other term for C3 photosynthetic pathway
Calvin cycle
products of light dependent reactions
- ATP
- NADPH
what is ATP and NADPH used for
- synthesize energy-rich sugar G3P
- regenerate RuBP (light-independent reaction)
obligatory component of energy-producing reactions including glycolysis and glycerolipid biosynthesis
Glycerol-3-phosphate (G3P)
molecule that starts the cycle, is regenerated so that the cycle can continue
ribulose 1,5-bisphosphate (RuBP)
catalyzes a reaction between CO2 and RuBP
Ribulose-1,5-bisphosphate Carboxylase-Oxygenase (RuBisCO)
- light of wavelengths 400-700 nm
- portion of light spectrum utilised by plants for photosynthesis
Photosynthetically active radiation (PAR)
provides energy required to convert co2 into simple sugars
solar radiation
what directly influence rate of photosynthesis
availability of light (PAR)
what happens at night in the absence of PAR
- respiration
- net uptake of CO2 is negative
what does rate of CO2 loss when value of PAR is zero provide
estimate of rate of respiration
what happens when the value of PAR increases
rate of photosynthesis also increases
Rate of net photosynthesis is zero
CO2 uptake in photosynthesis = CO2 loss in respiration
- light level at which rate of CO2 uptake for photosynthesis = loss of CO2 in respiration
- value of PAR at which
O2 produced by photosynthesis = O2 consumed by respiration
light compensation point
- light intensity at which a plant reaches the maximum photosynthesis rate
- about 10% of full sunlight for shade plants
- 50-70% of full sunlight for C3 sun plants
- 200% for C4 sunplants
light saturation point
value of net CO2 exchange at PAR = 0 provides an estimate of what
rate of respiration
where CO2 enters leaf in terrestrial plants
stomata
how does CO2 enter in stomata
diffusion
where does water move
region of high to low (more negative) water potential
difference between aquatic and terrestrial plants in their leaves
lack of stomata in aquatic autotrophs
examples of aquatic autotrophs
- submerged plants
- algae
- phytoplankton
difference between terrestrial and aquatic autotrophs in terms of carbon source
some aquatic species use bicarbonate
used to convert bicarbonate into CO2
carbonic anhydrase
two ways of conversion of bicarbonate into CO2
- active transport of bicarbonate into cell followed by conversion to CO2
- excretion of enzyme to adjacent waters and subsequent uptake of converted CO2 across membrane
both photosynthesis and respiration respond directly to variations in what
temperature
temperature that controls the rate of photosynthesis and respiration
temperature of leaf
where does temperature of leaf depend
exchange of thermal energy between leaf and surrounding environment
where is the relative importance of evaporation and convection to the maintenance of leaf temperature dependent
physical environment
heat dissipation in location where water is available
transpiration
heat dissipation in location with drier conditions
convection
harness energy of the SUn to fuel conversion of CO2 into glucose in process of photosynthesis
autotrophs
temperature decrease from __ to __ of leaf surface
center to edge
to survive, grow, and reproduce, what must plants maintain
positive carbon balance (photosynthesis > respiration)
examples of many features of physical environment that directly influence plant processes
- light
- temperature
- moisture
most important of trade-offs in the ability of plants to adapt to limitations
acquisition of ABOVE and BELOW ground sources
allocating carbon to production of leaves and stems
decrease allocation of carbon to production of roots
allocating carbon to production of roots
decrease allocation of carbon to production of leaves
where does the amount of solar radiation reaching the Earth’s surface vary
- diurnally
- seasonally
- geographically
major factor influencing amount of light a plant receives
shade
Two light environments where plants live
- sun
- shade
species adapted to high-light environments
- shade-intolerant species or
- sun-adapted species
species adapted to low-light environments
shade-tolerant plants
shade-tolerant plants tend to have what
- lower light saturation point
- lower maximum rate of photosynthesis
why do shade-tolerant plants have lower light saturation point and lower maximum rate of photosynthesis
lower concentrations of photosynthetic enzyme RuBisCo
low concentrations of producing rubisco and other compounds involved in photosyntheis result in what
lower rate of leaf respiration
where are the variations in photosynthesis, respiration and growth rate that characterize plant species adapted to different light environments illustrated
work of plant ecologist
Peter Reich & colleagues at University of Minnesota
Results of Peter Reicha nd colleagues about species adapted to lower light environments
lower maximum rates of net photosynthesis and leaf respiration
plants adaptation have evolved to respond variations in what
- precipitation
- soil moisture
- demand for water linked to temperature
as air temperature rises, what increases
saturation vapor pressure
amount of water required by plant to offset losses from transpiration will increase with __
temperature
what causes the decline in leaf area due to decreasing water availability
reduced allocation of carbon to production of leaves
capture light energy and transform CO2 into sugars in mesophyll cells
C3 plants
divide photosynthesis between mesohpyll and bundle sheath cells
C4 plants
C4 plants two distinct types of photosynthetic cells
- mesophyll cells
- bundle sheath cells
C4 plants are mostly what
- grasses (native to tropical and subtropical regions)
- shrubs (arid and saline environments)
pathway used by small group desert plants in hot deserts
CAM pathway
Two advantages of C4 plants over C3 plants
- PEP does not react with oxygen
- conversion of malic and aspartic acids into CO2 with bundle sheath increase efficiency of reaction
C4 plants have a __ __ __ of photosynthesis than C3 plants
higher maximum rate
PEP
Phosphoenolpyruvate
CAM plants open their stomata at night to take up CO2 and convert it to __ using __
- malic acid
- PEP
although CAM pathway is slow and inefficient, what is its advantages?
- reduce water loss through transpiration
- increase water-use efficiency
what causes the different temperature responses of different species from different thermal habitats
process of acclimation reversible phenotypic changes
- plants acquire this through the formation or addition of protective compounds in the cells, which act as antifreeze and lower the temperature at which freezing occurs
- genetically controlled characteristic
frost hardening
happens when plants shed their leaves before the colds season start
winter deciduous
amount of light reaching a plant influences what
photosynthetic rate
two key physical processes of photosynthesis
- diffusion
- transpiration
where does the amount of water loss depend
humidity
where does plant draw water, and release to
- draw from soil (highest water potential)
- release to atmosphere (lowest water potential)
what problems are created during transpiration
moisture conservation problems
how are stomata used
- open to take CO2
- closed to conserve water
affect both photosynthesis and respiration
leaf temperature
what increases with temperature
respiration
difference between the absorption and release of longwave and shortwave radiation by plants
plant’s net radiation balance
response to different light environments by plants
- adaptations
- phenotypic plasticity
have low photosynthetic, respiratory, metabolic, and growth rates
shade-adapted (shade-tolerant) plants
- have higher photosynthetic, respiratory, and growth rates
- lower survival rates under shaded conditions
sunplants (shade-intolerant)
where does C4 plants fix CO2
- malate
- aspartate
mesophyll cells
the amount of carbon fixed per unit of water transpired
water-use efficiency
CAM plants convert CO2 to what
malate
ability to tolerate high air teperatures is related to what
plant moisture balance
directly affects a plant’s survival, growth, and reproduction
availability of nutrients