NON-DAMAGING AND POSITIVE EFFECTS OF UV RADIATION ON HIGHER PLANTS - Environmental UV Radiation: Impact on Ecosystems and Human Health and Predictive Models - page 163

using filters above plants increases insect herbivory. Ballaré et al 84 found that reducing
ambient UV-B radiation by covering Datura ferox L. plants with UV-B opaque
polyester filters resulted in increased insect herbivory compared to plants which had
grown under UV-B transmitting cellulose diacetate filters.
Mazza et al 85 used similar filters to study thrips ( Caliothrips phaseoli ) predation
on soybean grown both in controlled environment and field conditions (Fig. 5). They
observed that not only did the thrips prefer plants which had not been exposed to UV-B
radiation, but that they also appeared to detect UV-B radiation and deliberately avoid it.
In addition, they also reported that the soybean worm preferred leaves which had not
been attacked previously by the thrips. Clearly, the non-damaging effects of UV-B
radiation on plants are not straightforward: complex interactions between radiation,
plant and predator exist.
Figure 5 . Effects of solar UV-B radiation on thrips density. Redrawn after Mazza et al 85 .
Following an earlier study 86,87 examined the effects of excluding natural UV-B
radiation from an ecosystem of plants growing in Tierra del Fuego in Argentina which
is an area which receives enhanced UV-B as a result of ozone depletion over Antarctica.
The authors were therefore studying the growth and herbivory of plants which either
received enhanced UV-B (10 - 13% ozone depletion) with plants receiving only 15-20%
of ambient UV-B levels. Over three complete growing seasons they found negligible
differences in the growth of the dominant evergreen shrub Chiliotrichum diffusum .
Marginal negative effects of ambient UV-B radiation on vegetative growth (about 12%)
were found on the interspersed hebaceous species Gunnera magellanica and Blechnum
penna-marina . The most striking observation was that insect herbivory (measured as
leaf area consumed) was increased by between 25 and 75% in G. magellanica when it
received reduced UV-B radiation.
Gwynn-Jones et al 88 studied the effects of supplementary UV-B radiation
simulating a 15% reduction in the ozone column on a sub-arctic forest heath ecosystem