Coupling Short‐Term Changes in Ambient UV‐B levels with Induction of UV‐Screening Compounds^†

Abstract

A substantial number of studies have been conducted over the last several decades to assess the potential impacts of long-term increases in ultraviolet-B radiation (UV-B between 280 and 320 nm) that will result from continued depletion of stratospheric ozone. However, seasonal changes, tropospheric chemistry and cloudiness are the dominant factors controlling ambient UV-B levels on a short-term or daily basis. The effects of short-term changes in UV-B on plant growth, phytochemistry and physiological processes have received relatively little attention. The USDA UV-B Monitoring and Research Program provides an excellent network of stations that provide an opportunity to monitor long-term changes in solar UV-B radiation and evaluate the responses of plants to short-term variation in UV-B levels on a near-real-time basis. In this study barley (Hordeum vulgare L.) and soybean (Glycine max [L] Merr.) were used as model systems. Emerging seedlings of these species were grown under either near-ambient levels of UV-B or under reduced levels (ca 90% reduction) in the field. Periodic measurements of foliar UV-screening compounds were made on separate groups of seedlings planted at intervals over the growing season during contrasting periods of ambient levels of UV radiation. The levels of UV-screening compounds correlated with UV-B levels in both species and with UV-A in soybean but the sensitivity of the response differed between the two species and among the soybean cultivars. Response differences among species may be related to unique secondary chemistry of each species, so one response estimate or action spectrum may not be appropriate for all species.

Adequate phenylalanine synthesis mediated by G protein is critical for protection from UV radiation damage in young etiolated Arabidopsis thaliana seedlings

“…However, there is a wide variation in sensitivity to UV between species and even among varieties of the same species (Sato, Kang & Kumagai 1994;Torabinejad & Caldwell 2000;Cartwright et al 2001;Li et al 2003;Koti et al 2005Koti et al , 2007Rozema, Boelen & Blokker 2005;Sullivan et al 2007). The mechanisms of perception and signal transduction that determine the level of sensitivity to UV-B and invoke 'protective' responses remain largely unstudied and undetermined (Ulm & Nagy 2005;Sullivan et al 2007).…”

“…The United States Department of Agriculture (USDA) UV-B Monitoring and Research Network (UVBMRN) monitors the actual UV exposure at the earth's surface. Projects such as the UVBMRN allow for collaborative studies between physicists and plant biologists on understanding the effects of UV-B on plants (Sullivan et al 2007). The question we hope to address with our research with young seedlings is, 'What are the mechanisms for sensing and responding to UV-B radiation?…”

“…It is not clear what controls (i.e. the rate-limiting step) the synthesis of UV-screening molecules or stress responses associated with UV-B radiation in developing plants (Ulm & Nagy 2005;Sullivan et al 2007). It is known that exposure to UV-B can result in the induction of genes encoding enzymes active in the phenylpropanoid pathway [e.g.…”

Study of suitability of AvaSpec array spectrometer for solar UV field measurements

“…It is related to the deepened research of the health effects of UV radiation (Berwick and Kesler, 2005;Lehmann, 2005;Grant et al, 2005) as well as of its environmental effects in the atmosphere (Brönnimann et al, 2001), in plants and microorganisms (Neale et al, 2007;Sullivan et al, 2007). International collaboration has widened in the recent decades.…”

Advances in Crop Responses to Enhanced Uv-B Radiation

“…Rutin concentration was higher in top leaves than in lower ones regardless of the UV-B level, top leaves typically receive more radiation than lower leaves. Sullivan et al (2007) did not find that even though UV-B absorbing compounds accumulated with an imposed stress, but these compounds were not directly related to sensitivity/tolerance of soybean genotypes.…”