Plant Physiological Ecology Second Edition
In the decade that has passed since the first edition of this book, the global environment has changed rapidly. Even the most steadfast ‘‘deny-ers’’ have come to accept that atmospheric CO2 enrichment and global warming pose serious challenges to life on Earth. Regrettably, this acceptance has been forced by calamitous events rather than by the long-standing, sober warnings of the scientific community. There seems to be growing belief that ‘‘technology’’ will save us from the worst consequences of a warmer planet and its wayward weather. This hope, that may in the end prove to be no more than wishful thinking, relates principally to the built environment and human affairs. Alternative sources of energy, utilized with greater efficiency, are at the heart of such hopes; even alternative ways of producing food or obtaining water may be possible. For plants, however, there is no alternative but to utilize sunlight and fix carbon and to draw water from the soil. (Under a given range of environmental conditions, these processes are already remarkably efficient by industrial standards.) Can we ‘‘technologize’’ our way out of the problems that plants may encounter in capricious, stormier, hotter, drier, or more saline environments? Climate change will not alter the basic nature of the stresses that plants must endure, but it will result in their occurrence in places where formerly their impact was small, thus exposing species and vegetation types to more intense episodes of stress than they are able to handle. The timescale on which the climate is changing is too fast to wait for evolution to come up with solutions to the problems. For a variety of reasons, the prospects for managing change seem better in agriculture than in forests or in wild plant communities. It is possible to intervene dramatically in the normal process of evolutionary change by genetic manipulation. Extensive screening of random mutations in a target species such as Arabidopsis thaliana can reveal genes that allow plants to survive rather simplified stress tests. This is but the first of many steps, but eventually these will have their impact, primarily on agricultural and industrial crops. There is a huge research effort in this area and much optimism about what can be achieved. Much of it is done with little reference to plant physiology or biochemistry and has a curiously empirical character. One can sense that there is impatience with plant physiology that has been too slow in defining stress tolerance, and a belief that if a gene can be found that confers tolerance, and it can be transferred to a species of interest, it is not of primeimportance to know exactly what it does to the workings of the plant. Such a strategy is more directed toward outcomes than understanding, even though the technology involved is sophisticated. Is there a place for physiological ecology in the new order of things? The answer is perhaps a philosophical one. Progress over the centuries has depended on the gradual evolution of our understanding of fundamental truths about the universe and our world. Scientific discovery has always relished its serendipitous side but had we been satisfied simply with the outcomes of trial and error we would not be where we are today. It is legitimate to ask what factors set the limits on stress tolerance of a given species. To answer this one must know first how the plant ‘‘works’’; in general, most of this knowledge is to hand but is based on a relatively few model species that are usually chosen because of the ease with which they can be handled in laboratory conditions or because they are economically important. As well as describing the basic physiology of plants the authors of this book set out to answer more difficult questions about the differences between species with respect to environmental variables. The authors would be the first to admit that comprehensive studies of comparative physiology and biochemistry are relatively few. Only in a few instances do we really understand how a species, or in agriculture, a genotype, pulls off the trick of surviving or flourishing in conditions where other plants fail. Of course, the above has more than half an eye on feeding the increasing world population in the difficult times that lie ahead. This has to be every thinking person’s concern. There is, however, more to it than that. Large ecosystems interact with climate, the one affecting the other. It would be as rash, for example, to ignore the effects of climate change on forests as it would be to ignore its effects on crops. There is more to the successful exploitation of a given environment than can be explained exclusively in terms of a plant’s physiology. An important thrust in this book is the interaction, often crucial, between plants and beneficial, pathogenic or predatory organisms that share that environment. Manipulation of these interactions is the perennial concern of agriculture either directly or unintentionally. Changes in temperature and seasonality alter established relations between organisms, sometimes catastrophically when, for example, a pathogen or predator expands its area of influence into plant and animal populations that have not been exposed to it previously. Understanding such interactions may not necessarily allow us to avoid the worst consequences of change but it may increase our preparedness and our chances of coming up with mitigating strategies.
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