Other components of forest ecosystems

Pathogens are major determinants of plant fitness (Burdon, 1987). Therefore, any effects of UV-B radiation on pathogenic organisms have the potential to influence the responses of plants to increased UV-B. The impacts of UV-B on pathogens can take two forms either directly, by effects on the pathogen itself, or indirectly, through effects on the host which then influence interactions with the pathogen (Manning & Tiedemann, 1995 Paul, this volume). For example, increased leaf thickness (Fig....

Introductionozone

Penetration of harmful ultraviolet-B (UV-B) radiation (280-320 nm) to the earth's surface is limited by stratospheric ozone. However, ozone depletion, caused by the emission of synthetic chlorofluorocarbons and related compounds, is currently estimated at 4-5 per decade at UK latitudes (Stolarski et al., 1992 Herman, McPeters & Larko, 1993). If the Montreal Protocol continues to be implemented, a possibility that remains uncertain (Greene, 1995 Jordan, 1995), concentrations of chlorine and...

UVB distribution in forest canopies

Experimental exposures of plants have usually measured UV-B at the top of the canopy in terms of irradiance (the UV-B per unit time and area falling on a horizontal plane) even though fluence rate (the UV-B passing through a sphere of unit surface area) may be a more appropriate measure of UV-B exposure for three-dimensional objects and the many orientations of leaves in a tree canopy (Bj rn & Teramura, 1993). Plant orientation relative to the angle of incidence of UV-B is important in...

Enhanced UVB radiation and crop plants

To give some indication of the type of experimental approach used, the following section gives details of a typical 'indoor' type of UV-B experiment, carried out with bean plants, followed by a more general review of effects on a range of crop species. Cultivation and UV-B treatment of bean plants Seedlings of Phaseolus vulgaris were precultured for 6 days before the UV-B treatment started. Plants were grown in a glasshouse, temperature Fig. 2. Outdoor UV-B filtration system, using solid...

Ultraviolet radiation as a stress factor and the role of protective pigments

Ozone-depleting substances as well as global climatic changes (for example, increasing 'greenhouse' gases) may alter ozone chemistry by creating conditions that facilitate an increased ozone degradation. It is also of concern that ozone reductions are not confined to the Antarctic, but extend to mid-latitudes in both hemispheres (see chapter by Pyle, this volume). A reduced stratospheric ozone layer will result in a selective increase at the earth's surface of ultraviolet radiation in the...

Effects of UVB on phenology and physiology

Johanson et al. (1995a) reported that a UV-B treatment simulating a 15 ozone reduction over a subarctic heath did not have any effects on the phenology of leaf-bud break, flowering, ripening of fruit, or onset of senescence in several heathland species. By contrast, earlier flowering in plants grown at elevated C02 is well documented (Garbutt & Bazzaz, 1984 Slack, 1986 Krupa & Kickert, 1989) and Woodin et al. (1992) found that elevated C02 greatly advanced flowering in C. vulgaris. The...

UVB effects on plant disease a study in diversity

The effects of UV-B on the interaction between cultivated wheat (Triticum aestivum) and fungal pathogens of the imperfect genus Septo-ria have been studied in detail at Lancaster. Septoria tritici (perfect stage Mycosphaerella graminicola), and S. nodorum (perfect stage Leptosphaeria nodorum) are the causal agents of, respectively, leaf blotch and glume blotch, both diseases causing significant yield loss in commercial wheat crops. The wheat-S. tritici system appears to be a relatively...

Edited by Peter Lumsden

SOCIETY FOR EXPERIMENTAL BIOLOGY SEMINAR SERIES 64 One of the predicted consequences of the depletion of stratospheric ozone is an increase in the amount of ultra-violet light reaching the surface of the earth, in particular, UV-B (320-280 nm). Although the real effects are as yet unknown, this change in radiation could have profound consequences for plant growth and productivity. The need for information concerning the relationship between plants and UV-B is therefore pressing. This volume...

UVB perception and signal transduction

Plant growth and development are regulated by aspects of the environment throughout the life cycle. Plants continually gather information about a wide range of environmental variables which elicit particular responses. Such environmental factors function as cues to initiate developmental transitions, for instance, in the photoperiodic induction of flowering observed in many plant species. However, environmental signals may also be potentially harmful and the plant's response is then to minimise...