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Ecology of Photosynthesis. Photosynthetically Active Radiation (PAR). The Light Compensation Point. PPFD = Photosynthetic Photon Flux Density. Three Forest Understory Herbs. Summer-green: Viola pubescens. Spring ephemeral: Allium tricoccum. Semi-evergreen: Tiarella cordifolia.
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Photosynthetically Active Radiation (PAR)
The Light Compensation Point PPFD = Photosynthetic Photon Flux Density
Three Forest Understory Herbs Summer-green: Viola pubescens Spring ephemeral: Allium tricoccum Semi-evergreen: Tiarella cordifolia
Light Compensation Points
Maximum Photosynthetic Rates
Photorespiration: A curious bottleneck in C3 Photosynthesis
Key enzyme 3-carbon compound Catalysis of carbon fixation in Photosynthesis
Photosynthesis • Photorespiration Photorespiration: An alternate pathway Rubisco catalyzes two competing reactions: Rubisco
Ecological Factors Increasing Photorespiration Rates High temperatures Rubisco Low CO2 concentrations
C4 Photosynthesis: A Solution in Space C4 Grass C3 reactions in bundle sheath C3 Grass C3 reactions throughout
C4 Intermediates produced in low CO2 environment of mesophyll (1000 02 : 1 CO2 ) C4 Photosynthesis: A Solution in Space • CO2 concentrated in bundle sheath (100 02 : 1 CO2 )
Differential Response of C4 and C3 Plants Light response Temperature response
CAM Photosynthesis: A Solution in Time CO2 Capture by Night Photosynthesis by Day
Distribution Patterns of the Three Photosynthesis Types
Geographic Patterns in the Distribution of the Proportion of C4 Grasses
C3 – Cool Season Grasses C4 – Warm Season Grasses • Lower temperatures • Lower total rainfall • Higher winter rains • Higher temperatures • Higher total rainfall • Higher summer rains
Habitats Favoring CAM Plants Epiphytes – Plants using other plants for support Arid habitats – deserts and semi-deserts that aren’t too extremely dry
Ecology of Photosythesis Part II
Sun and Shade Leaves Shade Sun
Anatomy of Sun and Shade Leaves (Thermopsis montana): a general view Sun Leaf Shade Leaf • Smaller • Thicker • More rubisco • More chlorophyll • Bigger • Thinner • Less rubisco • Less chlorophyll
Sun and Shade Leaves: Response to Light (Fagus sylvaticus)