Changes in UV-B radiation screening effectiveness with leaf age in Rhododendron maximum

C. T. Ruhland, T. A. Day

Research output: Contribution to journalArticle

34 Scopus citations


We examined how ultraviolet-B radiation (UV-B; 300 nm) screening effectiveness changes with leaf age in Rhododendron maximum growing in a shaded understory by measuring depth of penetration and epidermal transmittance with a fibre-optic microprobe. Depth of penetration (and epidermal transmittance) of UV-B decreased with leaf age in 1- to 4-year-old leaves, averaging 62 (32), 52 (22), 45 (16) and 48 μm (13%), respectively. Epidermal thickness increased with age in 1- to 4-year-old leaves due to a thickening of the cuticle from an average of 20 to 29 μm. Ultraviolet-B-absorbing compound concentrations increased with age from 1.3 to 1.5 A300 cm-2 leaf area. Concentrations of UV-B-absorbing compounds (area basis) were a strong predictor of depth of penetration (r2 = 0.82) and epidermal transmittance (r2 = 0.95) of UV-B in mature (1-4 year-old) foliage. Chlorophyll concentrations (area basis) increased in leaves up to 3 years of age. Current-year leaves (30 d old) were exceptional in that while they were particularly effective at screening UV-B (depth of penetration and epidermal transmittance averaged 39 μm and 5%, respectively) they had relatively low concentrations of UV-B-absorbing compounds (1.3 A300 cm-2). Our findings show that UV-B-screening effectiveness is not necessarily related to absorbing compound concentrations on a whole-leaf basis, possibly due to anatomical changes within the epidermis that occur with leaf age.

Original languageEnglish (US)
Pages (from-to)740-746
Number of pages7
JournalPlant, Cell and Environment
Issue number6
StatePublished - Jan 1 1996
Externally publishedYes



  • Chlorophyll
  • Epidermis
  • Flavonoids
  • Rhododendron maximum
  • Stratospheric ozone
  • UV-B-absorbing compounds
  • Ultraviolet-B

ASJC Scopus subject areas

  • Physiology
  • Plant Science

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