ch. 2 light and photosynthesis (ps). light radiant energy (electromagnetic radiation) –particle +...
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Light Wave: has Wavelength inverselyTRANSCRIPT
Ch. 2 Light and Photosynthesis (Ps)
Light• Radiant energy (electromagnetic radiation)
– Particle + wave• Particle:
torp
Light• Wave: has • Wavelength inversely
Light• Visible light: 380-750 nanometers (nm) (nano=10-9)
Electromagnetic spectrum• T/F: Plants green because chlorophyll absorbs green
light
Electromagnetic spectrum• 400-700 nm: Photosynthetically Active Radiation (PAR)
– Drives Ps– Green least (why leaves green)
Action spectrum for photosynthesis (Ps)
Radiation• Helps determine • IR: 750-106 nm. • Objects > absolute 0 emit • Gain energy from IR too
Pred
IR• “Infrared (IR) window” of leaves• Transmit near IR (beyond visible): little • Most visible
IR window
IR• Near IR transmitted through leaves (dashed
line)
IR• Use IR window (sense overstory)??
• First: phytochrome
Phytochrome• 2 forms (interconvertible)• Pr absorbs R: converted to Pfr• Pfr absorbs FR (near IR): converted to Pr
• Pfr active
IR• 1) Ratio Pr:Pfr depends on ratio R:FR light• 2) R:FR influenced by leaves
– Leaves remove R, let FR through “IR window”
IR• Ex, red alder (Alnus rubra)• Germination sensitive to Pfr
– Pfr high: – Pfr low:
IR• Ex, red alder (Alnus rubra)• In open: lots R light, lots Pfr
IR• Ex, red alder (Alnus rubra)• Under canopy: lots FR light, less Pfr
IR• Plants may use phytochrome
– 1) shaded: stimulate etiolation (spindly, less chlorophyll)
– 2) info on canopy (deciduous forest)
Trillium
Electromagnetic spectrum• UV radiation: < 350 nm (to 1 nm)
UV• Danger: Damage DNA (skin
cancer!)• Pigments (ex, flavonoids) absorb• +DNA repair mechanisms
Diamorpha smallii
Units (Intensity)• ?
Units
Units• PAR: Photosynthetic Photon Flux Density (PPFD)• moles photons/sq. m/sec
National Mole Day??
Units PPFD• 1 mole photons = 1 Einstein• So, Einsteins/sq. m/sec
National Mole Day??
Light intensity variation• Canopies patchy in
Light intensity variation• Phenoseason: seasonal light change + canopy change
Max. lite ground level
Max. litecanopytop
Phenoseasons• Ex, Eastern Deciduous Forest understory plants• 4 strategies:• 1) Spring herbs (“Ea”): emerge early
Canopy leaf dropCanopy leaf expansion
Spring herbsEx, Trillium
Spring herbsEx, Erythronium (trout lily)
2. Summer green herbs• Emerge late spring, green summer, dormant fall• “Us”
Canopy leaf expansionCanopy leaf drop
Summer green herbs• Ex, Uvularia sessilifolia (bellwort)
Uvula??
Summer green herbs• Ex, Uvularia sessilifolia (bellwort)
3. Late-summer herbs• Emerge summer, get early fall sun (Aa)• Ex, Aster acuminatus (sharp-leaved aster)
Canopy leaf expansion
Canopy leaf drop
4. Semievergreens• Emerge late spring, green late: “Om”• Ex, Oxalis montana (wood sorrel)
Canopy leaf expansionCanopy leaf drop
Light variation• Canopies patchy• Question: Technical name for beam sunlight on
forest floor?
Light variation• Canopies patchy in space• ______: beam sunlight on forest floor
Sunflecks: Good• Useful (forest floor plants)
– Some: 70% energy sunflecks
Sunflecks: Good• Useful (forest floor plants)
– Some: 70% energy sunflecks• Ability to use:
– Spring herbs (Trillium) respond – Summer green herbs (Uvularia) exploit
Sunflecks: Bad– Ex: shade-adapted Oxalis. Redwood
forest (Oxalis oregana-redwood sorrel)
– Coast redwood (Sequoia sempervirens)
• Tallest tree: 368 ft. DBH 23 ft.!
Sunflecks: Bad• O. oregana: Sunflecks
damage Ps machinery
Sunflecks: Bad• Sunflecks & drought stress• Ex, regeneration Abies magnifica (CA
red fir)
Sunflecks• Ex, regeneration Abies magnifica (CA red fir)• Seedling pattern from sunfleck pattern