Lecture #4 Photosynthesis III Flashcards
What is luminance
Light emitted from a source
What is illuminance
Light falling on a surface
When does the maximum incident sunlight on a leaf occur
When the incoming sunlight is perpendicular to the leaf surface
What is sunlight on a leaf measured in
umol/m^2/s
how much is sunlight at an angle on a leaf reduce by
The cosine of the angle between the sunlight and the leaf surface
How do plants leaves track the suns trajectory
movement is generated by asymmetric swelling of pulvinous
What is the spectral range of solar light that is important for photosynthesis
400nm - 700nm
what is photosynthetically active radiation (PAR)
when electrons are captured from photons of specific wavelengths and transferred to Photosystem reaction centers
What’s the difference between leaves grown in sun and leaves grown in shade
Leaves exposed to sunlight are much thicker and have much longer palisade cells (column like)
Are chlorophyll molecules evenly distributed in leaves
No
what are C3 plants
Plants that capture CO2 and use it to synthesize sugar directly through the Calvin cycle
where do you c3 plants grow
In areas where CO2 concentration is high and temperature and light intensity are moderate and ground is water abundant
What happened in hot areas win the stomata are close to prevent water loss
O2 concentration in leaves is increased and RuBisCO reacts with O2 instead of CO2 and leads to photo respiration which in turn causes a reduction in CO2 fixation
What are C4 plants
CO2 is first bound to phosphoenolpyruvate (PEP) in mesophyll cells resulting in the formation of a four carbon compound that is shuttled to bundle sheath cells where it is decarboxylated and releases the CO2 to enter the calvin cycle
What environments are C4 plants best adapted to
Environments with high daytime temperatures, intense sunlight, or nitrogen, or CO2 limitation, i.e. tropical environments
Do you shade plants have a lower light compensation point typically
Yes and bus have lower maximal photosynthetic rates than the sun plants
how is photo inhibition of the photo synthesis reaction centers caused
Too much light which causes photo bleaching
How can photo inhibition be prevented
Chloroplasts removing and re-distributing them selves in photosynthesizing cells. The position themselves in the upper surface of the cells to absorb maximum light in darkness and they move to the side walls when it is bright outside to minimize absorption of excess light
What are Violaxanthin, antheraxanthin, and zeaxanthin
special carotinoid Molecules to dissipate excess heat that are synthesized by plants under high light exposure
How do Violaxanthin, antheraxanthin, and zeaxanthin work?
A and Z capture excess photons and keep them away from photosynthesis reaction centers
V -> A -> Z
What happens when the temperature in C3 plants is increased
Photo respiration increases which increases the energy cost of net CO2 fixation and therefore a lower quantum yield
What happens when the temperature of C4 plants are increased
Nothing changes the quantum yield is independent of temperature
How do leaves dissipate heat when exposed to sunlight
By the mission of long wavelength aka infrared radiation and by the evaporative of cooling caused by transpiration
Do you c3 plants or C4 plants have a lower optimal temperature range
C3 plants do
When does the light compensation point occur
when photosynthetic CO2 assimilation is equal to CO2 evolved by respiration so photo synthesis is CO2 limited above the LCP
What is the major point of resistance to CO2 diffusion
Stomatal pores
what is the CO2 compensation point
The partial pressure at which CO2 assimilation is zero
Which type of plants need higher CO2 concentrations for photosynthesis
See three plants do and therefore need to assimilate CO2 at a much higher partial pressure then C4 plants
Increase in atmospheric CO2 concentrations and higher temperatures will likely favor which plants
C4 plants
Northern latitudes becoming more temperate hire CO2 concentrations with moderately warm temperatures would favor which plants
C3 plants
