A fall mystery: why do only certain leaves turn red?
Summary
Host Emily Kwong explores the mystery of why some autumn leaves turn red instead of yellow, featuring biologist Nikki Hughes. The episode discusses two leading theories: that red pigments act as chemical sunscreen to protect nutrient reabsorption, or that they serve as warning signals to deter insects. Guests also highlight the surprising lack of research in this field, noting that even scientists are unsure why specific species or individual trees display these vibrant colors.
Topics discussed
Sponsorships and show introduction
Introduction to autumn foliage and Nell Greenfield Boyce
The biology of yellow vs. red leaves
The mystery of why trees make new red pigment
Sponsor breaks and transition to scientific theories
Theory 1: Red pigments as light protection
Evidence from yellow mutant trees and nitrogen recovery
Geographic differences in leaf color and sunlight exposure
Theory 2: Red leaves as insect warning signals
Human and insect perception of red color
Experimental evidence on aphids and red leaves
The lack of research and application of leaf color science
Parking lot science: Variability in single-species trees
Ombre effects and ongoing experiments with oaks
Conclusion and call to action for listeners
Listener reviews and show credits
Sponsor segment: Medical technology in space
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