1. Leaf Reflectance & Absorption

2. Leaf Reflectance & Absorption
“Pimple” Savanna forms from termite mounds in innundated tropical grasslands

3. Beltsville winter wheat

4. True & False Color Photos
In true-color, grass and astroturf look similar; in the near-infrared, grass is more reflective
grass
True color film
grass
astroturf
astroturf
Color infrared film

5. Plant Pigments So, what absorbs in functioning leaves?
None of the key pigments absorbs green light; instead it is reflected to our eyes, which makes plants look green to us.

6. Liquid Water Absorption
Liquid water in plant leaves completes the absorption picture: leaves must be hydrated for photosynthesis

7. Green Leaf Structure

8. Dicot and Conifer Leaves
Bean leaf x420
Pine needle x370

9. Maple & Pine reflectancel
Similar in visible light, different in the near-IR
maple
pine

10. Leaf Reflectance & Absorption
Banana x1400
Cucumber x490

11. Leaf Photosynthesis Photosynthesis Determines Optical Properties
Bean leaf x4200

12. Leaf Photosynthesis Photosynthesis Determines Optical Properties
Must capture photons to drive chemical reactions (energy input)
Must be in presence of H2O
Must be in presence of CO2
Must get rid of O2 (poisonous)
Must live in hostile setting…

13. Internal Leaf Structure
Intercellular air labyrinth CO2 in & O2 out
Chloroplasts

14. Leaf Reflectance & Absorption
Photosynthesis requires CO2 from atmosphere to be in contact with the plant cell surfaces. The intercellular labyrinth allows movement of CO2 into leaves and O2 out. Part of the “deal” is H2O is lost

15. Leaf Photosynthesis
Stomata regulate gas exchange and water loss CO2 in/O2 out

16. Leaf Photosynthesis Piers Seller’s PAR Diagram

17. Photosynthesis Action Spectrum