From Plant Press, Vol. 3, No. 3, July 2000.
By Robert DeFilipps
Agrostology, the botanical study of grasses, is the specialty of Paul M. Peterson, Curator of Botany. The grass family, Poaceae (or, Gramineae) comprises around 11,000 species, and is one of the few plant groups that the general public recognizes at a glance. Prairies, savannas and lawns are of worldwide occurrence. Closer to home the mention of “amber waves of grain” or Walt Whitman’s Leaves of Grass can invoke in some an unabashed glow of endearment. In the United States we consume tons of popcorn, a product of the fruit of grass, and thus we can easily relate to novelist Nicholson Baker’s description of our national snack: “…a dried bicuspid of American grain dropped into a lucid gold liquid pressed from less fortunate brother kernels…an asteroid of Styrofoam…composed of exfoliations that in bursting beyond their outer carapace…”, and so forth (D. Garrison, The New Yorker 68(3):93-96. 9 March 1992).
Paradoxically, as easy as they are to recognize as a family, grasses are among the most notoriously difficult groups (orchids are another) for botanists to contend with during identification to the species level. That is because of the huge variation in the complex morphology of the grass inflorescence and flowers, which necessitates a special terminology. For an understanding of grasses, the non-specialist must learn to navigate in the spikeleted nether world of tiny lodicules, glumes, paleas, lemmas and awns. The grass stem itself has a special name: culm, as does the fruit: caryopsis.
Many people are unfamiliar with the presumed ancestral family of the grasses, the Joinvilleaceae. But grasses themselves have certainly made up for their lackluster antecedents. They are the foundation of our entire way of life. As noted by David J. Mabberley, “Most major civilizations are based on the triploid endosperm of Gramineae”. He refers to the wheat, barley, oats and rye of Eurasia; millets of Africa; rice in East Asia; and maize (corn, Zea) in the New World. Other civilizing benefits of grasses include bamboo for building materials, sugar cane, and an occasional tumbler of rum. The only exception to the grass/civilization connection seems to have been the benighted Maori of New Zealand, a noble culture based on the sweet potato. From the realm of diversity exhibited by the grasses, Peterson has chosen to specialize in the Subfamily Chloridoideae. As curator of grasses, he has the advantage of proximity to the c.500,000 specimens of Poaceae in the United States National Herbarium (US), and has omnivorously found subjects of interest among the grass of many regions.
A native Californian, Peterson first became interested in agrostology as an undergraduate student, stimulated by Dennis Anderson. He received a B.A. degree from Humboldt State University, Arcata, California (1977); an M.S. from the University of Nevada, Las Vegas (1984); and a Ph.D. from Washington State University, Pullman in 1988. Among the positions held prior to arriving at the Smithsonian Institution in September, 1988, were four terms as a Range Technician in the 1970s and 1980s, with the Bureau of Land Management (BLM) in Wyoming, Colorado and Idaho, and with the U.S. Forest Service at Mammoth Lakes, California. He has since collected grasses during extensive field studies in Peru, Bolivia, Argentina, Australia, Ecuador, Guyana, Mexico, Panama, Venezuela, Guatemala and China.
One major focus of Peterson’s population biology studies of the Subtribe Muhlenbergiineae is research on identifying the direction of migration of amphitropical disjuncts between North and South America, as they basically originate in North America, and make their way from there to South America. As a whole, his work has involved biosystematics of grasses using a multitude of techniques including morphological, micromorphological, anatomical, cytological, molecular, cladistic, and population based genetic studies of allelic variation using soluble enzymes. For experimental studies of alliances of Muhlenbergia with M.R. Duvall and A.H. Christensen, phylogenetic analyses were made of mapped restriction sites from plastid (chloroplast) DNAs; a “restriction site” is a base pair where you cut a molecule of DNA into fragments. His revisionary studies have been in large genera such as Eragrostis, Muhlenbergia and Sporobolus, all important forage grasses.
Many scientists have collaborated with Peterson in the grass laboratory. Among them are Ed Terrell, who joined in papers on oryzoid grasses such as wild rice using scanning electron microscopy (SEM); Jacques Cayouette who jointly worked on several papers concerning the Bromus ciliatus group; and Rob Soreng, with whom he and other collaborators compiled the Catalogue of New World Grasses, Part I (2000). Peterson’s versatile presence among the grasses may also be exemplified by several papers on South American bamboo of the genus Guadua, which were done with X. Londono in 1991-1992. One of the species, Amazonian Guadua sarcocarpa, is unusual in having edible fleshy fruit, which is eaten by the local populations. The plant is a dominant bamboo in the Urubamba region of Peru, yet specimens had lain undescribed for years. The period of 1993-1994 saw him curating the Trinius Herbarium of grasses at the Komarov Botanical Institute in St. Petersburg, Russia, under an award from the James Smithson Society of the Smithsonian Institution. He has also branched out further afield from the grasses, into the family Cyperaceae, and with M.S. Gonzalez-Elizondo and I. Granzow-de la Cerda, published studies in 1996-1997 on cladistic and phenetic analyses in Eleocharis of the Pauciflorae group.
Floristic studies of grasses have also occupied a major portion of Peterson’s interests. Currently he is reviewing manuscripts of Eragrostis and Muhlenbergia, generated by Chinese authors, for the Flora of China, which is headquartered at the Missouri Botanical Garden. Contributions of treatments of various grass genera have been published in floras of the following areas: British Columbia (Canada), St. John (U.S. Virgin Islands), Ecuador, and the new Manual of Grasses for the Continental United States and Canada (in press). In addition to continuing biosystematic studies, Peterson is deeply involved with the electronic Catalogue of New World Grasses, with authors R.J. Soreng, G. Davidse, F.O. Zuloaga, E.J. Judziewicz and T.S. Filgueiras. It can be consulted at <http://mobot.org/Pick/Search/nwgc.html> and the published hardcopy version of Part I, concerning four subfamilies (Anomochlooideae, Bambusoideae, Ehrhartoideae and Pharoideae), is available as Contributions from the United States National Herbarium 39:1-128 (2000). A recently received Seidell grant of $125,000 will allow completion of the catalogue in three or four more parts.
For a major project with Mones S. Abu-Asab, Stanwyn Shetler and Sylvia Stone Orli, which was covered in The Plant Press 3(2): 5 (April-June 2000), Peterson recently participated in a study which determined that, in the Washington, D.C. area, plants have been flowering earlier in spring as a response to global warming, actually 4.5 days earlier than they did in the 1970s. With numerous botanical interests such as this, his research and explorations will be yielding source material for future decades, just by finding “splendor in the grass”, as William Wordsworth might say.
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