Lecture #4 Photosynthesis III

Question 1

What is luminance

Answer 1

Light emitted from a source

Question 2

What is illuminance

Answer 2

Light falling on a surface

Question 3

When does the maximum incident sunlight on a leaf occur

Answer 3

When the incoming sunlight is perpendicular to the leaf surface

Question 4

What is sunlight on a leaf measured in

Answer 4

umol/m^2/s

Question 5

how much is sunlight at an angle on a leaf reduce by

Answer 5

The cosine of the angle between the sunlight and the leaf surface

Question 6

How do plants leaves track the suns trajectory

Answer 6

movement is generated by asymmetric swelling of pulvinous

Question 7

What is the spectral range of solar light that is important for photosynthesis

Answer 7

400nm - 700nm

Question 8

what is photosynthetically active radiation (PAR)

Answer 8

when electrons are captured from photons of specific wavelengths and transferred to Photosystem reaction centers

Question 9

What’s the difference between leaves grown in sun and leaves grown in shade

Answer 9

Leaves exposed to sunlight are much thicker and have much longer palisade cells (column like)

Question 10

Are chlorophyll molecules evenly distributed in leaves

Answer 10

No

Question 11

what are C3 plants

Answer 11

Plants that capture CO2 and use it to synthesize sugar directly through the Calvin cycle

Question 12

where do you c3 plants grow

Answer 12

In areas where CO2 concentration is high and temperature and light intensity are moderate and ground is water abundant

Question 13

What happened in hot areas win the stomata are close to prevent water loss

Answer 13

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

Question 14

What are C4 plants

Answer 14

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

Question 15

What environments are C4 plants best adapted to

Answer 15

Environments with high daytime temperatures, intense sunlight, or nitrogen, or CO2 limitation, i.e. tropical environments

Question 16

Do you shade plants have a lower light compensation point typically

Answer 16

Yes and bus have lower maximal photosynthetic rates than the sun plants

Question 17

how is photo inhibition of the photo synthesis reaction centers caused

Answer 17

Too much light which causes photo bleaching

Question 18

How can photo inhibition be prevented

Answer 18

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

Question 19

What are Violaxanthin, antheraxanthin, and zeaxanthin

Answer 19

special carotinoid Molecules to dissipate excess heat that are synthesized by plants under high light exposure

Question 20

How do Violaxanthin, antheraxanthin, and zeaxanthin work?

Answer 20

A and Z capture excess photons and keep them away from photosynthesis reaction centers

V -> A -> Z

Question 21

What happens when the temperature in C3 plants is increased

Answer 21

Photo respiration increases which increases the energy cost of net CO2 fixation and therefore a lower quantum yield

Question 22

What happens when the temperature of C4 plants are increased

Answer 22

Nothing changes the quantum yield is independent of temperature

Question 23

How do leaves dissipate heat when exposed to sunlight

Answer 23

By the mission of long wavelength aka infrared radiation and by the evaporative of cooling caused by transpiration

Question 24

Do you c3 plants or C4 plants have a lower optimal temperature range

Answer 24

C3 plants do

Question 25

When does the light compensation point occur

Answer 25

when photosynthetic CO2 assimilation is equal to CO2 evolved by respiration so photo synthesis is CO2 limited above the LCP

Question 26

What is the major point of resistance to CO2 diffusion

Answer 26

Stomatal pores

Question 27

what is the CO2 compensation point

Answer 27

The partial pressure at which CO2 assimilation is zero

Question 28

Which type of plants need higher CO2 concentrations for photosynthesis

Answer 28

See three plants do and therefore need to assimilate CO2 at a much higher partial pressure then C4 plants

Question 29

Increase in atmospheric CO2 concentrations and higher temperatures will likely favor which plants

Answer 29

C4 plants

Question 30

Northern latitudes becoming more temperate hire CO2 concentrations with moderately warm temperatures would favor which plants

Answer 30

C3 plants