Book Review: Physiological

The book deals primarily with physiology, but functions are never left "hanging." They are almost always related to or buttressed by details about structure (I do not know if Haberlandt ever visited Singapore, but his lesson was learned well there). For example, information of photosynthesis (in chapter 3) becomes clearer after reading pp. 22, 23 and 25. Structural details about roots (pp 23, 24, 26-29) facilitate understanding of their functions as photosynthetic and uptake organs. This is important when dealing with orchids because some species are leafless and have stems that are reduced to almost nothing. Species like Taeniophillum in Asia, the African Microcoelia and American Polyrrhiza. depend on their roots for most, perhaps all, physiological functions. Structure, function and physiology of flowers and other parts of orchid plant are covered similarly.

One of the more interesting details to emerge from the structure-function approach is a discussion of stomata on floral segments (including sepals and petals) of Arachnis, Aranda, Arundina, and Oncidium. But these stomata are "probably vestigial and practically nonfunctional." Until not very long ago the conventional wisdom was that there are no stomata on petals and sepals (I recall interesting discussions on the subject with Prof. Klaus Raschke who was at Michigan State University at the time) . Photosynthesis, the subject of chapter 3, was studied extensively at the Botany Department, National University of Singapore by the authors of TO, former head of the department (now retired) Prof. A. N. Rao, Prof. P. N. Avadhani (retired), Dr. Paul Clifford (now at the Queens University in Belfast, Ireland), several students and visitors to the Department as well as myself. Therefore it is not surprising to find a highly informative, well illustrated and extensively referenced chapter on the subject.

As correctly pointed out by the authors, a review of orchid physiology published in 1959 (but probably written several years earlier) listed only two publications on respiration by orchids (there may have been 2-3 additional reports published as well as dissertations which are nearly impossible to find). Chapter 4 (Respiration) in this book lists about 30 references which deal specifically with respiration. Remarkably most of them are by the authors (primarily Hew) and their associates. The reasons for this is simple: most of the research in this area during the last 10-12 years is by this group. These papers and some by others have greatly enhanced our understanding of orchid respiration. To be useful the information had to be not only summarized but synthesized into a coherent body. The chapter on respiration does that admirably. It also provides just enough background information (as does the chapter on photosynthesis) to place orchids in the general context of plants.

There are endless discussions on "how to feed your orchids" in the horticultural literature, on-line news groups and orchid meetings. Many of these discussions depend on anecdotal information for lack of a proper crop physiology review-synthesis. TO provides just such a review and should be welcomed b all those who are interested in orchids.

It is no secret that orchids are grown for their flowers, except for Vanilla (to produce vanilla; just try to imagine life without "plain vanilla" ice cream!) and some of the so-called jewel orchids whose main attribute are their leaves. Orchid flowers are a major crop is Singapore (but "are" is changing to "was" as the government is de-emphasizing agriculture), Malaysia (which has always had an orchid industry of its own and is benefiting from the Singapore downsizing because many growers from Singapore move their farms across the causeway to Johor) and Thailand (which started the orchid cut flower business in South East Asia). Therefore, control of flowering is very important as a means of adjusting production to market demand. Literature on the subject is substantial, but not easily available to the general public. Furthermore, the most recent review are getting old and is oriented only toward basic science. This chapter updates the basic information and also deals with practical aspects.

In addition to flowering by mature plants TO deals with flowering in vitro, but unfortunately in chapter 9 (one of the few shortcomings of TO is this separation; all discussions of flowering should have been placed in one chapter). This coverage is very important scientifically (because orchids provide a not very well known and certainly underused system for: 1) in vitro research on flower induction and development), 2) practically ("bottle baby" orchids in full bloom should attract many buyers especially in Changi Airport in Singapore, the present Subang, and 3) historically (to set the record straight after a tragicomic boast and/or claim of priority in last year’s Malayan Orchid Review).

Also related to flowers is chapter 8 which deals with senescence and post harvest. Again, the latest extensive reviews are either getting old and/or are not oriented practically. Chapter 8 in TO updates the information and adds usable facts (much of the new information is a result of research by C. S. Hew and his associates in Singapore, H. Nair and her group at the University of Malaya in Kuala Lumpur, S. D. O’Neill and her laboratory at the University of California, Davis, and A. H. Halevy and his co-workers in Rehovoth, Israel and University of California, Davis). The coverage includes several aqueous solutions which can be used to extend the life of flowers and facilitate shipping.

Chapter 7 deals with partitioning of assimilates in orchid plants, a field created almost entirely by Hew and his associates, the most notable among them being Paul Clifford who was in Singapore for a while. This chapter is primarily basic in nature.

Orchids were the first plants to be propagated in vitro from seeds (almost a century ago) with a fungus (i.e., symbiotically) or axenically (about 75 years ago) and through tissue culture (for the first time in 1949 by Gavino Rotor at Cornell University and definitely not by Georges Morel in 1960 in France). Since orchids are slow growing plants, tissue culture propagation is (also known as micropropagation or mericloning) is a topic of great interest to growers. Again previous reviews are old (1974, 1977 and 1993), brief (1984; authors’ names omitted on purpose) and/or simply devoid of content (1986; omission of author’s name is intentional). This chapter discusses the subject in general terms and updates information.

Every chapter has a list of general and specific references. The book also has a subject index which is its only serious drawback because listings may not be detailed enough. Organism name and persons indexes would be welcome.