Mendel had his peas, Morgan his fruit flies, Emons, Ketelaar and fellow contributors to Root hairs have their … root hairs. All these entities have established themselves as model systems for various biological studies: and why not? When you read that root hairs are ‘easy to observe through differential interference contrast microscopy because there are no other cells around them to disturb the image … cytoplasmic streaming is exceptionally clear … mitochondria and endoplasmic reticulum can be seen without reporter labelling … and root hair mutants are easy to distinguish and catalogue … ’ (Ridge and Emons, 2000; p. vii), the allure of these microscopic surface projections is clear.
Furthermore, despite their seeming insignificance from an individual perspective, collectively root hairs are of major relevance. As cytoplasmic extensions into the surrounding soil they are important for individual plants in facilitating uptake of water and essential nutrients; at the frontline in establishment of symbiotic nitrogen-fixing relationships with soil microbes they assume an even greater – global! – significance in the nitrogen economy of crop plants and entire agricultural systems. So although they may be largely out of sight in their subterranean hideaway they are definitely not out of mind, as Emons and Ketelaar's Root hairs – which is devoted to many aspects of the biology of these fascinating protuberances – ably testifies.
Interestingly, although not explicitly stated, the book looks very much like a second edition – albeit much enlarged and revised – of Springer's 2000 tome edited by Ridge and Emons. It is therefore useful to compare the present volume with its ‘predecessor’. The 2009 volume has 16 chapters (cf. 2000's 18), but there are several ‘winners’ and ‘losers’ behind the arithmetic. Some topics – although occasionally merged into a single chapter in 2009 – are retained: e.g. genetics, root-hair electrophysiology (previously electrobiology), calcium, actin and microtubules, Nod factor, and mycorrhizal fungi and root hair colonization. Others seem to have fallen by the wayside: e.g. root-hair–Frankia interactions, pH regulation and ion uptake. Intriguingly, 2000's hormones chapter has been replaced by one devoted to auxin alone. Such changes no doubt reflect the shifts in research interests and directions over the intervening eight years. The topicality of Root hairs (2009) is clearly reflected in those revised chapters in terms of post-2000 references: 112 in the root-hair genetics chapter, 60 regarding calcium, 89 in the Nod contribution, and 73 in the editors' actin chapter. Up-to-datedness is also evident in the presence of new chapters in the 2009 volume dealing with phospholipid signalling and ROP GTPases, areas that have increased dramatically in root hair relevance and research interest since 2000. Whilst 33 authors contributed to the 2000 volume, 28 feature in the present volume of whom 18 are unique to this 2009 tome. What this may mean in terms of the individuals' careers in the intervening years is debatable; what it certainly implies is that research interest in root hairs is alive and well.
The editors' chapter on intracellular organization (curiously placed after Grierson and Schiefelbein's opening contribution on the genetics of root-hair formation) is a useful scene-setter for the subsequent more molecular contributions, and reminds us that it is the cellular stage upon which the molecular players act out their dramas that is important in giving context to those studies. Root hairs is well-illustrated throughout with images, some in colour.
Although each chapter is as self-contained as it can be, there is a good deal of cross-reference among the chapters, which makes for a satisfyingly integrated text. However, it is odd that these cross-chapter references are to a 2008 text entitled Root hairs: excellent tools for the study of plant molecular cell biology. When one searches on the internet for that text the present 2009 volume comes up. Quite why this sub-title is not used by Root hairs is unclear; it would seem to add extra information, which helps to make an even more compelling case for the present tome.
One of Root hairs' nicest features is that it does not just deal with the up-to-date literature aspects of the topics, but many of the chapters also include quite detailed how-to-do-it protocols. Whilst these are probably no substitute for a detailed methodological handbook, it is hoped that they might help to inspire the next generation of scientists to take up the challenge of root-hair biology.