UV or not UV? — that is the question
Global
climate change is, quite rightly, a matter of major concern but our focus on it
means that other environmental problems may not be receiving appropriate
attention. An example of this is ozone depletion and the concomitant increase
in UV-B irradiation. This concern seems to have dropped out of public and
scientific headlines in recent years. Nevertheless, as
pointed out by Koti et al. (Mississippi State Universityand USDA/ARS, Beltsville, pp. 855–864), the problem is still very
much with us. Indeed, although measures have been taken to reduce ozone loss,
it is unlikely that we see an improvement for several years to come. It
therefore continues to be important to study the effects of increased UV-B irradiation
on plant performance. The authors exposed soybean plants to a range of UV-B
radiation intensities for 8 h per day from seedling emergence onwards. They
then measured aspects of reproductive performance, including the size of flowers
and floral organs, pollen production, pollen viability and pollen tube growth.
The results show clearly that exposure to UV-B reduced the size of flowers and
of floral organs, decreased pollen production, lowered pollen viability and
slowed pollen tube growth. Indeed, at the highest exposures, pollen grains were
shrivelled and lacked the apertures that may aid germination. The authors
comment that developing pollen grains had previously been thought to be
protected from UV-B by the perianth. But their results show clearly that UV-B
affects pollen quality, perhaps by indirect means. The authors used all their
results to construct a UV-B sensitivity index or combined response index for
each variety. Although all the varieties of soybean they used showed some
vulnerability to UV-B, some were obviously much less affected than others,
enabling them to designate some varieties as UV-B tolerant. These varieties
will be important in breeding programmes aimed at improving crop performance
under conditions of increased UV-B irradiance.
Professor J. A. Bryant
University of Exeter, UK
j.a.bryant{at}exeter.ac.uk
