Changes in leaf expansion and epidermal screening effectiveness in Liquidambar styraciflua and Pinus taeda in response to UV-B radiation

J. H. Sullivan, B. W. Howells, C. T. Ruhland, Thomas Day

Research output: Contribution to journalArticle

78 Citations (Scopus)

Abstract

Absorption or screening of ultraviolet-B (UV-B) radiation by the epidermis may be an important protective method by which plants avoid damage upon exposure to potentially harmful UV-B radiation. In the present study we examined the relationships among epidermal screening effectiveness, concentration of UV-absorbing compounds, epidermal anatomy and growth responses in seedlings of loblolly pine (Pinus taeda L.) and sweetgum (Liquidambar styraciflua L.). Seedlings of each species were grown in a greenhouse at the University of Maryland under either no UV-B radiation or daily supplemental UV-B radiation levels of 4, 8 or 11 kJ m-2 of biologically effective UV-B (UV-B(BE)) radiation. Loblolly pine seedlings were subsequently grown in the field under either ambient or supplemental levels of UV-B radiation. At the conclusion of the growing season, measurements of epidermal UV-B screening effectiveness were made with a fiber-optic microprobe. In loblolly pine, less than 0.5% of incident UV-B radiation was transmitted through the epidermis of fascicle needles and about 1% was transmitted in primary needles. In contrast, epidermal transmittance in sweetgum ranged from about 20% in leaves not preconditioned to UV-B exposure, to about 10% in leaves brown under UV-B radiation. The concentration of UV-absorbing compounds was unaffected by UV-B exposure, but generally increased with leaf age. Increases in epidermal thickness were observed in response to UV-B treatment in loblolly pine, and this accounted for over half of the variability in UV-B screening effectiveness. In spite of the low levels of UV-B penetration into the mesophyll, delays in leaf development (both species) and final needle size (loblolly pine) were observed. Seedling biomass was reduced by supplemental UV-B radiation in loblolly pine. We hypothesize that the UV-induced growth reductions were manifested by changes in either epidermal anatomy or epidermal secondary chemistry that might negatively impact cell elongation.

Original languageEnglish (US)
Pages (from-to)349-357
Number of pages9
JournalPhysiologia Plantarum
Volume98
Issue number2
DOIs
StatePublished - 1996

Fingerprint

Liquidambar
Pinus taeda
Liquidambar styraciflua
leaf development
ultraviolet radiation
Radiation
screening
Seedlings
Needles
Epidermis
Anatomy
seedlings
epidermis (plant)
Growth
Biomass

Keywords

  • Epidermal transmittance
  • leaf elongation
  • Liquidambar styraciflua
  • loblolly pine
  • Pinus taeda
  • sweetgum
  • UV-B radiation

ASJC Scopus subject areas

  • Plant Science

Cite this

Changes in leaf expansion and epidermal screening effectiveness in Liquidambar styraciflua and Pinus taeda in response to UV-B radiation. / Sullivan, J. H.; Howells, B. W.; Ruhland, C. T.; Day, Thomas.

In: Physiologia Plantarum, Vol. 98, No. 2, 1996, p. 349-357.

Research output: Contribution to journalArticle

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abstract = "Absorption or screening of ultraviolet-B (UV-B) radiation by the epidermis may be an important protective method by which plants avoid damage upon exposure to potentially harmful UV-B radiation. In the present study we examined the relationships among epidermal screening effectiveness, concentration of UV-absorbing compounds, epidermal anatomy and growth responses in seedlings of loblolly pine (Pinus taeda L.) and sweetgum (Liquidambar styraciflua L.). Seedlings of each species were grown in a greenhouse at the University of Maryland under either no UV-B radiation or daily supplemental UV-B radiation levels of 4, 8 or 11 kJ m-2 of biologically effective UV-B (UV-B(BE)) radiation. Loblolly pine seedlings were subsequently grown in the field under either ambient or supplemental levels of UV-B radiation. At the conclusion of the growing season, measurements of epidermal UV-B screening effectiveness were made with a fiber-optic microprobe. In loblolly pine, less than 0.5{\%} of incident UV-B radiation was transmitted through the epidermis of fascicle needles and about 1{\%} was transmitted in primary needles. In contrast, epidermal transmittance in sweetgum ranged from about 20{\%} in leaves not preconditioned to UV-B exposure, to about 10{\%} in leaves brown under UV-B radiation. The concentration of UV-absorbing compounds was unaffected by UV-B exposure, but generally increased with leaf age. Increases in epidermal thickness were observed in response to UV-B treatment in loblolly pine, and this accounted for over half of the variability in UV-B screening effectiveness. In spite of the low levels of UV-B penetration into the mesophyll, delays in leaf development (both species) and final needle size (loblolly pine) were observed. Seedling biomass was reduced by supplemental UV-B radiation in loblolly pine. We hypothesize that the UV-induced growth reductions were manifested by changes in either epidermal anatomy or epidermal secondary chemistry that might negatively impact cell elongation.",
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