Ecology - Abiotic Factors: CO2 Availability/Temperature Flashcards
What is the definition of ecology?
study of organisms’ relationship to environment
What are the examination of ecological factors?
abiotic and biotic
What does abiotic and biotic provide clues to?
how plants adapted to different environmental conditions on land
What are the key abiotic factors that determine plant distribution?
temperature
water (precipitation)
what is the definition of adaptation?
characteristic that promotes plant’s survival and reproduction in the environment that it has
what does adaptation includes?
- external morphological modifications
- histological changes in tissues/cells
-physiological specializations (photosynthetic pathways)
True or False
any plant that is able to survive and reproduce in that environment has adapted to that environment?
True
What is photosynthesis?
involves light captures, electron transport, carbohydrate biosynthesis
What are the environmental factors that affect photosynthetic rates directly?
- light
-temperature
-CO2 concentrations
What are the environmental factors that affect photosynthetic rates indirectly?
-water (humidity/ soil moisture)
- nutrients
what does environmental stress led to for plants?
unique adaptations to permit survival in less than ideal conditions
what are the 5 key environmental factors affect photosynthesis?
- effect of CO2 concentration/fluxes
- effect of temperature changes
- effect of light availability/ quality
- effect of water availability
- effect of soil conditions (nutrient levels)
what is photosynthesis controlled by?
“supply” and “demand” of photosynthetic palisade/spongy mesophyll cells for CO2 or by CO2 inside leaf cells
Where is photosynthesis happening in leaf?
inside leaf cells
where is supply of CO2 thru gas exchange controlled by?
stomata that are controlled by guard cells
what do guard cells respond to?
water levels that are impacted by temperature
what does photosynthesis require?
coordination of all cell activity within leaf
what is the ancestoral pathway?
C3 photosynthetic pathways
what plants are considered C3 plants?
most plants
What does the C3 plants do?
maintain CO2 in leaves above the CO2
What is the CO2 compensation point?
intracellular CO2 concentrations in leaf cells that support photosynthetic balance of cellular respiration rates
what is the photosynthetic CO2 consumption?
respiratory CO2 production
what does leaves in C3 plants regulate?
internal [CO2] between limits imposed by Calvin Cycle
What does the Calvin Cycle do?
- capacity to re-generate RuBP
- carboxylation capacity of Rubisco
What are the certain conditions that with Rubisco -oxygenase function favoured in C3 plants?
- high temperatures
- low CO2 concentrations
- high O2 concentrations
What happens when hot and dry to plants?
- stomata close to reduce water loss
- reduces gas exchange
CO2 levels drop, O2 accumulates
how is balance between two Cycles determined?
- kinetic properties of plant’s Rubisco
- relative concentration of substrates (CO2 and O2)
- temperature (affects stomatal opening/closing)
What does increasing in external temperature do to plants?
1) modifies kinetic constants of Rubisco
- favours oxygenation over carboxylation
2)lowers CO2 concentration in a solution more than for O2
- favours oxygenation over carboxylation
what does increasing temperature favours?
photorespiration over the Calvin Cycle C3 pathway
True or False
many photosynthetic organisms do photorespire?
False
what happens when plants do not show photorespiration?
normal Rubisco
how are alternative pathways evolve?
through modifications of photosynthetic pathways
what are the alternative pathways with CO2 concentrating mechanisms?
- C4 photosynthetic Carbon Fixation Pathway
- CAM (Crassulacean Acid Metabolism) Pathway
what oxygenase activity of Rubisco limit?
photosynthesis especially under warmer temperatures and water stress
What does C4 photosynthesis evolve?
compensate for low atmospheric [CO2} using spatial separation
What is C4 pathway?
spatial separation
where does evolved C4 pathway live?
terrestrial habitats where temperature was high
what happens to plants with older C3 pathway?
could not compete with plants with the new C4 pathway
what happens to C4 plants with CO2 concentrating mechanisms?
at carboxylation sites in chloroplasts is saturating for Rubisco activity
What are C4 plants require?
less Rubisco than C3 plants for similar rates of photosynthesis
What does C4 plants use more efficiently than C3 plants?
water and nitrogen
What does C4 plants use less efficiently than C3 plants?
light - have higher energy requirement
what are the shade plants classified?
C3 plants because of lower energy requirements under low light conditions
what is CAM pathway and for what?
Crassulacean Acid Metabolic Pathway
for temporal separation
What does CAM pathway occur in?
cacti, orchids, bromeliads, other succulents
What happens during CAM pathway to plants?
opposite to C3 and C4 plants
stomata open at night (during cooler conditions) and closed at day
where are plants that are lowest transpiration ratio in?
desert-adapted plants with CAM photosynthesis
What is the transpiration ratio?
water lost (g) : CO2 uptake (g)
what is the transpiration Ratio for C3 plants?
500 : 1
What is the transpiration ratio for C4 plants?
250 : 1
What is the transpiration ratio for CAM plants?
50 : 1
what is the range ratio of water loss?
greater than 250 to 500 molecules of H2O : 1 molecule CO2
why is water loss a problem?
dehydration, wilting
what is the benefit of water loss?
leaf cooling
what is the problem of high temperatures on leaves?
