photosynthesis part 4 Flashcards
dehydraiton is a problem for
plants
on hot, dry days plants do what to stomata, why?
close
-conserves H2O
disadvatage of closing stomata
limits photosynthesis
closed stomata conditions favor what wasteful process
photorespiration
in most plants (C3 plants) initial fixation of what forms a 3 carbon compound
initial fixation of CO2 via rubsico forming a 3 carbon compound (3-phosphoglycerate or 3-PG)
in photorespiration, rubsico adds __ instead of __ to what
adds O2 instead of CO2 to RuBP in the calvin cycle, producing a 3-PG and a two carbon compound, CO2 is ultimately released
photorespiration occurs at _____ CO2 [] and _______ O2 []
low; elevated
photorespiration releases what
CO2 (previously fixed carbon)
does photorespiration make ATP or NADPH
no
on a hot dry day photorespiration can drain as much as what
50% of the carbon fixed by calvin cycle
what are the three types of plants based on how they fix CO2
C3, CAM, C4
what are majority of plants species
about 85% are C3 plants
example of C3 plants
wheat, barley, most trees
how do C3 make sugar from CO2
only use the C3 pathway
what is only enzyme C3 plants use to fix CO2
rubisco
C3 plants stomata
open during the day and closed at night
-exception - also close when hot + dry
-prevent water loss and desication
-leads to photorespiration
C4 and CAM plants stomata
during day to conserve water in hot temps, but they avoid doing photorespiration
C4 and CAM plants have additional waht to fix CO2
pathway
where do C4 and CAM plants concentrate CO2
near rubisco for the calvin cycle
water usage in C4 plants vs C3
C4 plants use 1/3 the water of C3 plants
example of C4 plants
corn, sugar cane, some grasses
>8000 species of plants
how many times did C4 plants evolve independently
64
in what conditions are C4 plants more efficient
at photosynthesis in conditions of high temp and light intensity
anatomical and biochemical adaptations combine to allow what
C4 plants to outperform C3 plants in their ability to perofmr photosythesis under hot, dry, bright conditions
CAM plants use what to fix carbon
crassulacean acid metabolism (CAM)
CAM plants anatomical and biochemical adaptations allows them to live
in very hot, dry (xeric conditions)
example of CAM species
> 16000 species of plants
-succulents and cacti
how much water do CAM plants use
about 1/20 the water of C3 plants
both C4 and CAM plants use what pathway
C4
the C4 pathway precedes what
the calcin (C3) cyecle - it does not replace the calcin cycel
since when has CO2 levels risen
since industrial revolution
will increase levels of CO2 impact C3 and C4 plants the same
no, perhaps changing relative abundance of these species. Changes are unpredictable and are a cause for concern
