Quantity, chemistry, and wettability of epicuticular waxes on needles of red spruce along a fog-acidity gradient

Percy, K.E.; Jagels, R.; Marden, S.; McLaughlin, C.K.; Carlisle, J.

Two sites on Isle au Haut and three other sites in Maine were chosen for collection of red spruce needles for assessment of needle wettability and wax chemistry. 'Needle wettability and epicuticular was physicochemical characteristics were examined for red spruce (Picea rubens Sarg.) trees growing along a gradient of fog quantity and acidity. Trees at four coastal and one inland site were sampled in November 1988 for three needle age-classes. Needle wettability was assessed by measuring needle - water droplet contact angles. Mean angles per site and age-class ranged from 73 to 42o and decreased significantly with increasing needle age. Needle contact angles were highly correlated with fog acidity (R=0.99), decreasing with increasing acidity. Angles were lower on needles from declining trees than on needles from visually healthy trees. Epicuticular wax amount was highly correlated with quantity of fog collected at the sites (R=0.99). Needles from trees at the inland site located outside the coastal fog zone had the smallest wax deposit, while needles from trees exposed to the greatest amount of fog had the largest wax deposits. Epicuticular wax was comprised of secondary alcohols (42%), diols (19%), alkyl esters (16%), primary alcohols (6%), hydroxy fatty acids (2%), and fatty acids (1%). Estolides (14%) in the wax were tentatively identified but not confirmed by mass spectrometry. Needles from trees exposed the most fog had the greatest amounts of secondary alcohols and alkyl esters. Needles from trees not exposed to fog had greater amounts of diols. There was no obvious relationship between fog acidity and wax chemistry composition.' /STUDY LOCATIONS:/ /ISLE AU HAUT/Head Harbor/Eastern Head/

Quantity, chemistry, and wettability of epicuticular waxes on needles of red spruce along a fog-acidity gradient

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