Symptom differential
Bleaching & High-Light Injury
Very pale or bleached upper-canopy tissue can result from excessive light/radiant exposure, heat, chemical injury, or other stress. Location relative to the light source is important evidence.
Pattern questions
- Is bleaching strongest at the highest or most exposed sites?
- What are PPFD and leaf temperature at those points?
- Is there a sharp exposure boundary?
- Did fixture height, power, or environment change recently?
Plausible cause categories
- Excess light exposure
- Radiant or heat stress
- Chemical injury
- Root stress affecting pigment maintenance
- Genetic variegation or unusual pigmentation
Discriminating checks
- Map PPFD
- Measure leaf temperature
- Compare shaded leaves
- Review fixture and environmental changes
- Inspect for residue or spray history
Red flags
- Rapid necrosis
- Bleaching unrelated to exposure pattern
- Concurrent systemic decline
Visual study guide
- High-light bleaching gradient
- PPFD heat map
- Exposure-boundary example
- Chemical-injury comparison