Lecture 9: Photosynthetic Pathways Flashcards
1
Q
Photorespirations
A
Positively correlated with: -Light -Temperature (and water) Negatively correlated with -CO2
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
3
Q
Morphology
A
- Kranz anatomy: wreath-like arrangement of bundle sheath cells
- Oxygenase activity of rubisco effectively eliminated in c4 bundle sheath cells
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
5
Q
Nitrogen and Photosynthetic Machinery
A
Relationships between nitrogen content and
- (a) chlorophyll content
- (b) Rubisco aciticity in Triticum aestivum
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
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)