Lecture 6: Light as Information

1. Lecture 6: Light as Information Photoregulation • Photosynthesis • Light Quantity • Photomorphogenesis • Light Quality • Photoperiodism • Light Duration • Phototropsim • Light Direction

2. Photomorphogenesis Maximize resource acquisition Seedling survival Shade avoidance

3. What is the adaptive advantage to a seed having information on how deeply it is “planted”? What is the adaptive advantage to a seed being dormant until it is close enough to the soil surface to germinate? How does a seed know how deeply the seed is “planted”?

4. Action Spectra for Seed Germination / Inhibition

6. Photomorphogenesis • Light Quality • Seed Germination • Release from dormancy • Weed seeds • Red Light (5 sec) Induce Germination • Far-Red (5 sec) Inhibit Germination • R + FR - Inhibit • R + FR + R - Induce

7. Seed Germination Dark 5’ Red 5’ R + 5’ FR R + FR + R

8. Etiolation / De-etiolation Now that the seed is germinated how does the seedling get to the light resource as quickly and efficiently as possible?

9. Deetiolation

10. Seedling Development Monocot Light Monocot Dark Dicot Light Dicot Dark

11. Stem elongation (inhibition)

12. Photomorphogenesis • Seedling Development • Etiolated • Dark • long, spindly, white (or yellow) • De-Etiolated • Blue response not reversible • Red Light reversible ( 5 sec pulse) • red light: short, thick, green • R + FR: etiolated

13. Photomorphogenesis • Internode Elongation • Shade Adapted Plants (Shade Tolerant) • No Response • Sun Adapted Plants (Shade Sensitive) • Low Red : Far-Red Ratio • Canopy Shade • Rapid Elongation • Escape Shade

14. Photomorphogenesis • What is the adaptive advantage to a plant to know its’ neighbors? • How does a plant know if it has neighbors?

16. Plants in Motion