Vascular transport in plants
Holbrook NM, Zwieniecki MA. eds. 2005.
Amsterdam: Elsvier,
Academic Press. £62.99
(hardback). 564 pp.
E-mail: jfisher{at}fairchildgarden.org
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But how to review 26 papers? Some are extensive literature reviews and place the topic in a broader context. Many others emphasize new data and observations, such as hydraulic functional differences related to photosynthetic pathways or hydraulic features related to species distribution. Most are new and interesting. Repeatedly, I found myself saying ‘I didn't know that’ or thinking that this chapter would be perfect as the basis for a lecture or student seminar topic. But such reactions speak more about my own research interests and ignorance. I'm confident that this volume will be referred to frequently in my research and teaching.
The first two chapters succinctly summarize the present state of knowledge about xylem and phloem transport and how they are closely integrated with structure. Every general botany/biology instructor should read them. The vascular system is far more complex and interesting than just a pathway between source and sink as simplified in some textbooks. As one would expect, all chapters emphasize the inseparable connection between physiological mechanisms and structure, whether at the scale of whole plant, tissue or sub-cellular. The complexities of studying transport in roots, leaves and developing fruits are the focus of some papers. Local transport in rays and sapwood, as well as long distance transport in tall trees, are covered in others. Ecological adaptations related to draught and freezing are also surveyed. In some, evolutionary concepts are presented but not developed in great detail. A neglect of tropical plants and phenomena, such as all sapwood trees, is a weakness but a consequence of temperate bias that continues in most of plant biology.
Some long-accepted models involving mass flow of sugars in the phloem and the continuous meta-stable water columns in the xylem have been challenged in the last ten years. This has led to a flurry of innovative research and new hypotheses that use freeze-SEM, MRI, Arabadopsis genomics and ingenious whole-plant experiments. Most of the major players in this dynamic area are contributors to this volume.
In conclusion, the book both reviews our present knowledge and points out the many areas that are still in doubt or in need of new technologies to understand vascular transport fully. However, the emphasis on an integrated view of xylem and phloem and the research vitality displayed in these papers bode well for continued clarification of how vascular tissues accomplished their role in higher plants.
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