O. L. LANGE, P. S. NOBEL, C. B. OSMOND, and H. ZIEGLER In the last volume of the series 'Physiological Plant Ecology' we have asked contributors to address the bases of ecosystem processes in terms of key plant physiological properties. It has often been suggested that it is not profitable to attempt analysis of complex living systems in terms of the properties of component individuals or populations, i. e. , the whole is more than the sum of its parts. Nevertheless, assessments of ecological research over the last century show that other approaches are seldom more helpful. Although it is possible to describe complex systems of living organisms in holistic terms, the most useful descriptions are found in terms of the birth, growth and death of individ uals. This allows analysis of performance of the parts of the whole considering their synergistic and antagonistic interrelationships and is the basis for a synthe sis which elucidates the specific properties of a system. Thus it seems that the description of ecosystem processes is inevitably anchored in physiological under standing. If enquiry into complex living systems is to remain a scientific exercise, it must retain tangible links with physiology. Of course, as was emphasized in Vol. 12A, not all of our physiological understanding is required to explore ecosystem processes. For pragmatic purposes, the whole may be adequantely represented as a good deal less than the sum of its parts.

"Physiology," which is the study of the function of cells, organs, and organisms, derives from the Latin physiologia, which in turn comes from the Greek physi- or physio-, a prefix meaning natural, and logos, meaning reason or thought. Thus physiology suggests natural science and is now a branch of biology dealing with processes and activities that are characteristic of living things. "Physicochemical" relates to physical and chemical properties, and "Environmental" refers to topics such as solar irradiation and wind. "Plant" indicates the main focus of this book, but the approach, equations developed, and appendices apply equalIy welI to animaIs and other organisms. We wilI specificalIy consider water relations, solute transport, photosynthesis, transpiration, respiration, and environmental interactions. A physiologist endeavors to understand such topics in physical and chemical terms; accurate models can then be constructed and responses to the internal and the external environment can be predicted. Elementary chemistry, physics, and mathematics are used to develop concepts that are key to under-standing biology -the intent is to provide a rigorous development, not a compendium of facts. References provide further details, although in some cases the enunciated principIes carry the reader to the forefront of current research. Calculations are used to indicate the physiological consequences of the various equations, and problems at the end of chapters provide further such exercises. Solutions to alI of the problems are provided, and the appendixes have a large tist of values for constants and conversion factors at various temperatures.

This richly illustrated text covers the ecophysiology of plants of all major tropical ecosystems, from tropical rain forests, epiphytic habitats, mangroves and savannas to salinas, inselbergs and paramos and their ecophysiological adaptation to these different tropical environments. The physiognomy of biotopes and characteristic life forms of plants are depicted with photographs.

This textbook is remarkable for emphasising that the mechanisms underlying plant physiological ecology can be found at the levels of biochemistry, biophysics, molecular biology and whole-plant physiology. The authors begin with the primary processes of carbon metabolism and transport, plant-water relations, and energy balance. After considering individual leaves and whole plants, these physiological processes are then scaled up to the level of the canopy. Subsequent chapters discuss mineral nutrition and the ways in which plants cope with nutrient-deficient or toxic soils. The book then looks at patterns of growth and allocation, life-history traits, and interactions between plants and other organisms. Later chapters deal with traits that affect decomposition of plant material and with plant physiological ecology at the level of ecosystems and global environmental processes.

Box 9E. 1 Continued FIGURE 2. The C–S–R triangle model (Grime 1979). The strategies at the three corners are C, competiti- winning species; S, stress-tolerating s- cies; R,ruderalspecies. Particular species can engage in any mixture of these three primary strategies, and the m- ture is described by their position within the triangle. comment briefly on some other dimensions that Grime’s (1977) triangle (Fig. 2) (see also Sects. 6. 1 are not yet so well understood. and 6. 3 of Chapter 7 on growth and allocation) is a two-dimensional scheme. A C—S axis (Com- tition-winning species to Stress-tolerating spe- Leaf Economics Spectrum cies) reflects adaptation to favorable vs. unfavorable sites for plant growth, and an R- Five traits that are coordinated across species are axis (Ruderal species) reflects adaptation to leaf mass per area (LMA), leaf life-span, leaf N disturbance. concentration, and potential photosynthesis and dark respiration on a mass basis. In the five-trait Trait-Dimensions space,79%ofallvariation worldwideliesalonga single main axis (Fig. 33 of Chapter 2A on photo- A recent trend in plant strategy thinking has synthesis; Wright et al. 2004). Species with low been trait-dimensions, that is, spectra of varia- LMA tend to have short leaf life-spans, high leaf tion with respect to measurable traits. Compared nutrient concentrations, and high potential rates of mass-based photosynthesis. These species with category schemes, such as Raunkiaer’s, trait occur at the ‘‘quick-return’’ end of the leaf e- dimensions have the merit of capturing cont- nomics spectrum.

Due to many issues related to long-term carbon dynamics, an improved understanding of the biology of C4 photosynthesis is required by more than the traditional audience of crop scientists, plant physiologists, and plant ecologists. This work synthesizes the latest developments in C4 biochemistry, physiology, systematics, and ecology. The book concludes with chapters discussing the role of C4 plants in the future development of the biosphere, particularly their interactive effects on soil, hydrological, and atmospheric processes.

Part 4=Volume 12D.

O. L. LANGE, P. S. NOBEL, C. B. OSMOND, and H. ZIEGLER In the original series of the Encyclopedia of Plant Physiology, plant water relations and photosynthesis were treated separately, and the connection between phenomena was only considered in special chapters. O. STOCKER edited Vol ume III, Pjlanze und Wasser/Water Relations of Plants in 1956, and 4 years later, Volume V, Parts I and 2, Die COrAssimilation/The Assimilation of Carbon Dioxide appeared, edited by A. PIRSON. Until recently, there has also been a tendency to cover these aspects of plant physiology separately in most text books. Without doubt, this separation is justifiable. If one is specifically inter ested, for example in photosynthetic electron transport, in details of photophos phorylation, or in carbon metabolism in the Calvin cycle, it is not necessary to ask how these processes relate to the water relations of the plant. Accordingly, this separate coverage has been maintained in the New Series of the Encyclopedia of Plant Physiology. The two volumes devoted exclusively to photosynthesis are Volume 5, Photosynthesis I, edited by A. TREBST and M. AVRON, and Volume 6, Photosynthesis II, edited by M. GIBBS and E. LATZKO. When consider ing carbon assimilation and plant water relations from an ecological point of view, however, we have to recognize that this separation is arbitrary.