Responses to ultraviolet-B radiation (280–315 nm) of pea (Pisum sativum) lines differing in leaf surface wax |
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Authors: | R. Gonzalez N. D. Paul K. Percy M. Ambrose C. K. McLaughlin J. D. Barnes M. Areses A. R. Wellburn |
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Affiliation: | Biological Sciences Div., Inst. of Environmental and Biological Sciences, Lancaster Univ., Lancaster, LA1 4YQ, UK.;John Innes Inst., Colney Lane, Norwich, NR4 7UH, UK.;Dept de Fisologia Vegetal, Univ. de Santiago, E-15706 Santiago de Compostela, Spain.;Dept of Agricultural and Environmental Science, Univ. of Newcastle, Newcastle-upon-Tyne NE1 7RU, UK.;Natural Resources Canada, Hugh John Flemming Forestry Complex, Regent Street South, Canadian Forest Service –Maritimes Region, Fredericton, New Brunswick, Canada E3B 5P7. |
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Abstract: | To test the hypothesis that leaf surface wax influences plant responses to UV-B, 6 lines of cultivated pea (Pisum sativum L.), selected as having more or less wax, were grown at 0 or 6.5 kJ m-2 day-1 plant-weighted UV-B against a background of 850–950 μmol m-2 s-1 photosynthetically active radiation. In the 4 lines with least leaf surface wax the amount of wax on adaxial and abaxial leaf surfaces was increased following exposure to 6.5 kJ m-2 day-1 UV-B, but UV-B decreased surface wax in Scout, which had the greatest wax deposits. On the adaxial leaf surface, UV-B radiation caused a shift in wax composition from alcohols to esters and hydrocarbons and the ratio of short to long chain length alkyl ester homologues was increased. There was no evidence of a shortening in carbon chain length of hydrocarbons, primary alcohols or fatty acids due to UV-B and no significant correlation between wax amount and UV reflectance from leaves. UV-B induced significant increases in UV-absorbing compounds in the expanded leaves and buds of most lines. UV-B reduced the growth of all lines. Foliage area (leaves plus stipules) declined by 5–30%, plant dry weight by 12–30%, and plant height by 24–38%. Reductions in growth occurred in the absence of any changes in chlorophyll fluorescence or photosynthetic rate. UV-B also had no major effect on carbon allocation patterns. The effects of UV-B on growth appeared to be due to changes in tissue extension and expansion. Indeed, many of the responses to UV-B observed in this study of pea appear more consistent with indirect effects being expressed in developing tissues rather than through the direct action of UV-B on mature tissues. There was no evidence that wax amount or biochemistry was associated with the sensitivity of the lines to UV-B radiation. Furthermore, induction of pigments was not correlated with changes in growth. However, lines with the greatest constitutive amounts of pigments in unexpanded bud tissues were most tolerant of elevated UV-B. |
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Keywords: | Chlorophyll fluorescence cuticle growth leaf surface wax photosynthesis Pisum sativum reflectance UV-B UV-B absorption |
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