Effects of Enhanced UV-B Radiation on Plant Chemistry: Nutritional Consequences for a Specialist and Generalist Lagomorph

Abstract

Ultraviolet-B (UV-B) radiation has been increasing in temperate latitudes in recent decades and is expected to continue rising for some time. Enhanced UV-B radiation can change plant chemistry, yet the effects of these changes on mammalian herbivores are unknown. To examine the influence of enhanced UV-B radiation on nutrition of a specialist and generalist hindgut fermenter, we measured nutritional and chemical constituents of three common North American range plants, big sagebrush (Artemisia tridentata), yarrow (Achillea millefolium), and bluebunch wheatgrass (Pseudoregneria spicata), and how these changes influenced in vitro dry matter digestibility and in vivo digestibility by pygmy rabbits (Brachylagus idahoensis) and eastern cottontails (Sylvilagus floridanus). Forages were irradiated for 3 mo with ambient (1x) or supplemental (1.6x) UV-B radiation representing a 15% ozone depletion for Pullman, WA, USA. Enhanced UV-B radiation had minimal effects on the nutritional content and the tannin-binding capacity of forages. Similarly, the terpene concentration in sagebrush and yarrow was not affected by higher UV-B irradiances. Flavonoid compounds increased in sagebrush but decreased in yarrow. Rabbit preference and intake was not affected by treatment levels for any forage species and no differences were found between treatments for dry matter, fiber, protein digestibility, and apparent digestible energy.

Shade Effects on Leaf Production and Essential Oil Content and Composition of the Novel HerbEucalyptus citriodoraHook.

“…A similar phenomenon was reported in seedlings of other plants grown under shaded conditions 22,23 . Solar radiation has been shown to reduce growth and yield of terrestrial plants 22,24,25 and to change plant morphology, including height, leaf area, leaf waxes and epidermal layers 26 . Exposure to direct sunlight probably caused the soil in the pots to dry more quickly than under shaded conditions, leading to an apparent water stress.…”

Survival and causes of mortality for pygmy rabbits (Brachylagus idahoensis) in Oregon and Nevada

“…Sagebrush A. tridentata, which is high in PSMs (including monoterpenes; Shipley et al 2006, Frye et al 2013, Ulappa et al 2014, comprises the majority of the diet of pygmy rabbits (Green and Flinders 1980, Weiss and Verts 1984, Thines et al 2007). The classes of PSMs in sagebrush (e.g.…”

Within-plant distribution of volatile compounds on the leaf surface of Flourensia cernua

“…2: camphor þ trans verbenol greater in NW quadrant, and borneol, selin-11-en-4-a-ol, and bacoradienol lower in NE quadrant). Light intensity has been shown to affect concentrations of some plant secondary metabolites (Tingey et al, 1991;Thines et al, 2007). Although we speculated light intensity may differ among quadrants and alter chemical patterns, no consistent patterns were detected.…”

“…Biotic and abiotic factors and stressors (e.g., light intensity/wavelength, soil moisture/nutrients, herbivory/mechanical damage, etc.) can alter chemical profiles and concentrations of secondary compounds (Gershenzon and Croteau, 1991;Tingey et al, 1991;Kainulainen et al, 1992;Litvak and Monson, 1998;Thines et al, 2007;Burney and Jacobs, 2011). Plant age, growth stage, and phenology of a given species (Cedarleaf et al, 1983;Sinclair et al, 1988;Bryant et al, 1991;Vourc'h et al, 2002;Fredrickson et al, 2007) are also important drivers of plant chemistry.…”