Plant Response to Air Pollution. - book reviews

Ecology, Sept, 1997 by Howard S. Neufeld

This edited volume of papers attempts to synthesize recent developments on the responses of plants to a variety of air pollutants. To some extent it achieves its goal, whereas like all edited volumes, it suffers from the twin problems of redundancy and overlap. Nonetheless, readers will find well-written syntheses on a variety of plant responses to air pollutants, and for those not currently in the field, a good introduction to some of these topics. Chapter authorship reflects the European connections of the editors - 18 are from England and Europe, 6 from India, with 5 from North America. Only three are from the United States, two of them being biochemists. Thus coverage is decidedly biased towards topics of interest in Europe, although individual chapters are often less parochial.

The book is divided into four main divisions: atmospheric pollution patterns; uptake and metabolism of pollutants; cellular resistance and visible injury; and finally whole-plant and/or community decline. In actuality, most of the book concentrates on cellular and plant level responses, with the chapters dealing with community level phenomena making up only three of the 20 chapters. Another book on air pollution is due out this year (Sandermann, H., A. R. Wellburn, and R. L. Heath teds]. 1997. Forest decline and ozone: a comparison of controlled chamber and field experiments. Ecological studies. Volume 127. Springer-Verlag, New York) and given its emphasis on stand level factors, these two books may turn out to complement each other quite well.

Chapter organization is a bit eclectic. For example, Oren's chapter (Chapter 3) on nutritional disharmony in spruce stands would more logically be located next to Freer-Smith's chapter on forest decline (Chapter 18), while Mudd's chapter on biochemical responses to ozone (Chapter 10) should have been linked to Heath's chapter on lipid metabolism (Chapter 14).

The first chapter, by Yunus, Singh, and Iqbal, presents a broad overview of global trends in pollution. Although chockfull of statistics, pie charts and graphs, it tries to cover too much in too little space, the result being a somewhat superficial treatment of all subjects. Much of the chapter is poorly organized, jumping from topic to topic and then back again. As most of the rest of the chapters in the book are devoted to gaseous pollutants, it would have sufficed to leave out particulates and heavy metals from the introduction. The second chapter, by Krupa, is a concise view of the complexities of atmospheric chemistry, and the implications this has for assessing plant responses. Again, a great number of topics are addressed, none in great detail, but one is left with a clear impression for why it is often difficult to attribute specific responses to particular pollutants. Krupa suggests three main limitations to our current interpretations of plant responses to air pollutants as resulting from "(a) our continued view of air pollutant effects on crop growth and productivity under ambient conditions as univariate . . . systems; (b) our hesitancy to accept the rule that under ambient conditions control for one variable generally does not serve as a control for another variable; and (c) our continued reliance on retrospective numerical analyses of previously collected field data." This chapter gets the reader primed for the rest of the book, as many of the chapters emphasize both the multivariate aspects of air pollutant responses and the difficulty of making cause and effect statements when most of the data are only correlative in nature.

Many of the chapters in this book deal with interactions of air pollutants with rising atmospheric carbon dioxide levels. This is a logical extension of the work of air pollution scientists because of the physiological alterations brought about by elevated C[O.sub.2], many of which have the potential to modify or ameliorate pollutant response. In fact, C[O.sub.2] issues are rapidly assuming a primary focus with air pollution scientists, as witnessed by the growing number of such papers at recent air pollution workshops. Thus Chris Atkinson's review (Chapter 3) summarizing the effects of elevated C[O.sub.2] on terrestrial vegetation serves as a good focal point for these chapters, giving the reader a balanced and up-to-date treatment of the subject. While most experimenters have been preoccupied with the co-occurrence of high C[O.sub.2] and high temperatures, Barnes, Hull and Davison (Chapter 5) point out that few studies have looked at C[O.sub.2]/low temperature interactions. These responses may be critical for evergreens, which can carry out photosynthesis during colder months. They also show that exposure to gaseous pollutants such as S[O.sub.2] and [O.sub.3] can increase susceptibility to cold damage, even months after cessation of exposure, presumably because of long-term biochemical changes caused by these gases. They further distinguish between the effects of nitrate and ammonium as predisposing factors for winter injury, ascribing most of the reduced cold hardiness to inputs of ammonium and perhaps sulfate, and not nitrate. However, as they point out, experiments to distinguish effects among these ions are few, and this area needs more investigation.