Lecture 9: Photosynthetic Pathways Flashcards

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1
Q

Photorespirations

A
Positively correlated with:
-Light 
-Temperature (and water)
Negatively correlated with
-CO2
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2
Q

C4 pathway

A
  • Spatial separation of C-fixation steps, includes additional steps
  • CO2 concentrated at site of carboxylation in bundle sheath
  • Phosphenolpyruvate
  • PEP carbocylase only fixes CO2
  • 1st product is 4C oxaloacetate
  • Decraboxylations malate in bundle sheath cell
  • CO2 is 10 times higher in bundle sheath than in atmosphere
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3
Q

Morphology

A
  • Kranz anatomy: wreath-like arrangement of bundle sheath cells
  • Oxygenase activity of rubisco effectively eliminated in c4 bundle sheath cells
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4
Q

Daily Fluctuations in CO2 exchange as a function of available radiation

A
  • C4 plants can use even the most intense radiaiton for photosynthesis
  • C3 plants reach light saturation at lower light intensity
  • Sciophytes (shade-loving) adapted to dim light rake up more CO2 than heliophytes (sun-loving) in early morning and late evening
  • Heliophytes utilize full sunlight more efficiently than sciophytes
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5
Q

Nitrogen and Photosynthetic Machinery

A

Relationships between nitrogen content and

  • (a) chlorophyll content
  • (b) Rubisco aciticity in Triticum aestivum
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6
Q

Nitrogen Use Efficiency

A

-Overall C4 plants have low N rewuirements contain 1/3-1/6 amount of N found in C3 plants, yet maintain same or greater photosynthetic rates
-High NUE, maximum photosynthetic rate per gram if nitrogen in the leaf
-Relationship between photosynthetic capacity and N content in leaves:
A) C3 crip plnats (wheat and rice)
C) C3 grasses and herbs
D)Deciduous trees and shrubs
E) evergreen trees and schlerophyllous shrubs

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7
Q

Geographical Distributions

A
  • C4 taxa are found in warm to temperate environments and are uncommon in cool th cold climate
  • Mainly inhabit warm, grassland eosystem (maize, Millet, sorghum, sugarcane)
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