Effects of ozone and acidic fog on red spruce needle epicuticular wax production, chemical composition, cuticular membrane ultrastructure and needle wettability

Abstract

SUMMARYOne-year-old red spruce {Picea rubens Sarg.) seedlings were exposed, from bud break, to ozone (O,,) and acidic fog for 14, 42 or 77 days. Ozone was more damaging than acidic fog to epicuticular wax. Wax quantity on needles exposed to charcoal-filtered air (CFA) and pH 4-2 fog (control) increased from 14 to 42 days, but decreased by 77 days. Exposure of elongating needles to 70 ppb O3 and pH 4-2 fog reduced tbe rate of de novo wax syntbesis. Red spruce wax is composed of secondary alcobols (50 °o), nonacosane diols (25%), alkyl esters (12 "0), primary alcobols (6 %), estolides (2 %), fatty acids (3 %), and bydroxy-fatty acids (2 °b)-Wax cbemical composition varied temporally. Needles exposed to O3 bad significantly less secondary alcobols, diols, alkyl esters, fatty acids, and hydroxy-fatty acids tban needles exposed to CEA. Production of secondary alcobols was significantly reduced following needle exposure to fog at pH 30. Cuticular membrane tbickness increased significantly following needle exposure to O3. The increase in tbickness at 250 ppb O3 was due to a new amorpbous layer wbicb appeared above the reticulate layer. Contact angles on needles exposed to CFA and pH 4-2 fog increased from 92° after 14 days to 96° after 42 days, tben declined to 77° after 77 days. Needle exposure to O3 for 42 or 77 days significantly decreased contact angles.

Effects of u.v.‐B radiation on epicuticular wax production and chemical composition of four Picea species

“…1), and\or the sequence of class deposition onto the needle surface would be expected to play a role in the degree of biosynthetic response, and overall sensitivity of the cuticle to u.v.-B radiation. This has been clearly shown to be the case for needle wax response to other components of the changing atmospheric environment such as acid rain (Percy & Baker, 1990), acid vapour (Bytnerowicz et al, 1997, tropospheric ozone\acid fog (Percy, Jensen & McQuattie, 1992), or general pollution climate (Turunen et al, 1997 ;Cape & Percy, 1997). Response to changes in plant growth environment such as light quantity\quality (Cape & Percy, 1993) is also known to be influenced by shoot phenology in the four species studied here.…”

“…Of particular concern would be the interaction of increased u.v.-B with co-occurring air pollutants such as ozone\acid fog (Percy et al, 1992), acid rain (Percy & Baker, 1990) or mixtures of drydeposited and wet-deposited pollutants (Cape & Percy, 1997) known to alter spruce needle wax chemical composition. Even subtle changes to needle physico-chemical characteristics might result in altered micro flora\pathogen interactions, needle water loss patterns, foliar uptake rates and early needle abscission.…”

Fogs: Physical Basis, Characteristic Properties, and Impacts on the Environment and Human Health

“…Investigations have been performed on the impacts of fog on plants, such as the red spruce [108] and beech [109], as well as on hypolithic microbial communities [101,110]. Percy et al [108] reported that red spruce exposure to pH 4.2 acid fog increased wax quantity for a certain period, but a longer exposure decreased it; reduced the rate of de novo wax synthesis; changed the composition of wax reducing production of secondary alcohols (pH 3.0 fog).…”

“…Percy et al [108] reported that red spruce exposure to pH 4.2 acid fog increased wax quantity for a certain period, but a longer exposure decreased it; reduced the rate of de novo wax synthesis; changed the composition of wax reducing production of secondary alcohols (pH 3.0 fog). Acidic fogs also influence the cuticular membrane thickness and wettability of needles.…”

Comparative investigations of cuticular permeability of conifer needles from healthy and damaged trees

“…All these studies have in common that a more or less evident alteration of ,^^^ surface wax aggregates can be observed by scanning electron microscopy (Huttunen & Laine, 1983 ;Barnes, Davison & Booth, 1988;Bermadinger, Grill & Golob, 1988;Adams, Capron & Hutchinson, 1990;Percy & Baker, 1990). As a consequetice, leaf surface wettability increased as measured by the means of contact angle determination (Cape, 1983;Percy, Jensen & McQuattie, 1992). Besides many other factors, these changes of leaf surface properties are also believed to be involved in the occurrence of novel forest decline (Elstner & Osswald, 1984;Schulze, 1989) observed during the last decade in Western Europe (Blank.…”