Effects of elevated ultraviolet-B radiation on a plant–herbivore interaction

Abstract

Enhanced ultraviolet-B (UV-B) radiation may have multiple effects on both plants and animals and affect plant-herbivore interactions directly and indirectly by inducing changes in host plant quality. In this study, we examined combined effects of UV-B and herbivory on the defence of the mountain birch (Betula pubescens ssp. czerepanovii) and also the effects of enhanced UV-B radiation on a geometrid with an outbreak cycle: the autumnal moth (Epirrita autumnata). We established an experiment mimicking ozone depletion of 30% (a relevant level when simulating ozone depletion above Northern Lapland). Both arctic species responded only slightly to the enhanced level of UV-B radiation, which may indicate that these species are already adapted to a broader range of UV-B radiation. UV-B exposure slightly induced the accumulation of myricetin glycosides but had no significant effect on the contents of quercetin or kaempferol derivatives. Mountain birch seedlings responded more efficiently to herbivory wounding than to enhanced UV-B exposure. Herbivory induced the activities of foliar oxidases that had earlier been shown to impair both feeding and growth of moth larvae. In contrast, the contents of foliar phenolics did not show the same response in different clones, except for a decrease in the contents of tannin precursors. The induction of foliar phenoloxidase activities is a specific defence response of mountain birches against insect herbivory. To conclude, our results do not support the hypothesis that the outbreak cycle of the autumnal moth can be explained by the cycles of solar activity and UV-B.

Genetic and Environmental Factors Behind Foliar Chemistry of the Mature Mountain Birch

“…Ruohomäki et al (1996) showed that birch families differed in their foliage chemistry, and Suomela et al (1995) found that most of the variation in phenolics occurred between trees, as compared to withintree variation. Anttila et al (2010) found that birch clones differed in their foliar chemistry. Despite the huge dynamic changes occurring in foliar chemistry during a season, individual birch trees show some consistence in phenolic composition (Riipi et al, 2004).…”

Boron Fertilization Enhances the Induced Defense of Silver Birch

“…The light:dark -cycle was set to 20:4 h, to mimic the light conditions of spring at the same latitude (N 62°36.059′ E 029°45.813′). Seedlings were placed into eight large cages (70×120×125 cm) that were divided into two crosswise parts separated by a voile fabric wall (Anttila et al, 2010). The wooden framed sides of the cages were covered with light permeable voile fabric, and the tops with a polyethene filter that transmitted photosynthetically active radiation (PAR).…”

“…czerepanovii) to its major defoliator, Epirrita autumnata Borkhausen, autumnal moth Anttila et al, 2010). Both quinones and ROS are harmful to plant eating animals, decreasing the assimilation of nutrients and producing, for example, mid gut lesions (Bi and Felton, 1995).…”

“…Interestingly, B deficiency causes effects on phenol metabolism similar to those of herbivory. Both stresses trigger the activity of polyphenol oxidases (PPO) and the accumulation of quinones (Cakmak and Römheld, 1997;Anttila et al, 2010). Additionally, the level of reduced ascorbic acid decreases in response to B deficiency (Lukaszewski and Blevins, 1996) and herbivory (Bi and Felton, 1995), which also contribute to the enhancement of quinone formation and reactive oxygen species (ROS) production.…”

Immunomodulation in insects post-treatment with abiotic agents: A review

“…This is because the haemocytes are damaged by the irradiation. Whereas, exposing larvae of E. autumnata to ultraviolet-B (UV-B) radiation, mediated by UV-B-exposed birch, did not significantly affect the rate at which they encapsulated sterile nylon filaments (Anttila et al, 2010). Nation et al (1995) suggest that ionizing radiation inhibits the production of one or more enzymes involved in melanization, including PO.…”