.,y^Ç Seed Characteristics of ^ 42 Economically Important Spejpies .^\ of Solanaceae in the United Sfötes l'y Technical Bulletin No. 1471 Agricultural Research Service in cooperation with Soil Conservation Service UNITED STATES DEPARTMENT OF AGRICULTURE ACKNOWLEDGMENTS We express our appreciation to the following correspondents or associates who supplied information or seeds and plants: L. Butler, Texas State Seed Laboratory, Stephenville ; A. G. Davis, Soil Conservation Service, Temple, Tex. ; Director, Hortus Botanicus Universitates Nijmegen, Netherlands; W. H. Eshbaugh, Miami University, Oxford, Ohio; H. W. Everett, Soil Conservation Service, Lexington, Ky.; L. E. Ever- son, Iowa State University Seed Laboratory, Ames ; J. C. Garrison, Soil Conservation Service, Knox City, Tex.; C. B. Heiser, Indiana University, Bloomington; P. Koostra, Ferry-Morse Seed Co., Mountain View, Calif.; D. Krizek, Plant Stress Labora- tory, Agricultural Research Service, Beltsville, Md. ; W. R. Langford, South Regional Plant Introduction Station, Experiment, Ga. ; W. F. Mahler, Herbarium, Southern Methodist University, Dallas, Tex.; M. P. Mauldin, Southwestern Seed Service Lab- oratory, Waco, Tex.; D. N. Palmer, Soil Conservation Service, Honolulu, Hawaii; C. W. Renney, Soil Conservation Service, Tucson, Ariz.; G. V. Schultz, Soil Conser- vation Service, Beltsville, Md. ; R. W. Schumacher, W. Atlee Burpee Co., Philadelphia, Pa.; K. C. Sink, Michigan State University, East Lansing ; W. H. Skrdla, North Central Regional Plant Introduction Station, Ames, Iowa; H. L. Smith, Virginia State Seed Laboratory, Richmond; J. Stevens, Germain's Inc., Fresno, Calif.; D. Ugent, Southern Illinois University, Carbondale; U.S. National Herbarium, Smithsonian Institution, Washington, D.C.; G. C. Vreebury, University of Washington, Seattle; R. D. Walters, California State Polytechnic College, San Luis Obispo; L. Warkentin, Geo. J. Ball, Inc., West Chicago, 111. Drawings were prepared by Regina 0. Hughes, botanical illustrator and artist. Botany Department, Smithsonian Institution, Washington, D.C. CONTENTS Page Materials and methods 1 General seed morphology 2 Fruit notes ^ Seed key to solanaceous species 8 Synopses of seed characteristics 10 Literature cited 31 Common name index 32 Trade names are used in this publication solely for the purpose of providing specific information. Mention of a trade name does not constitute a guarantee or warranty of the product by the U.S. De- partment of Agriculture or an endorsement by the Department over other products not mentioned. Seed Characteristics of 42 Economically Important Species of Solanaceae in the United States By CHARLES R. GUNN, botanist, Plant Taxonomy Laboratory, Northeastern Region, Agricultural Research Service, and FREDERICK B. GAFFNEY, manager, Cape May Plant Materials Center, Soil Conservation Service This study constitutes an investigation of and poisonous plants. Heiser {20) gave an ex- external and internal seed characters of 42 cellent summary of economically important economically important species of Solanaceae species in the Solanaceae. (nightshade family) found in temperate North Seed characteristics of the family have been America. The Solanaceae is composed of 85 summarized by Gunn {17), Isely {25), LeMaout to 90 genera and more than 2,000 species (three- and Decaisne {29), Lubbock {30), and Martin fourths belong to the genus Solanum), The {31). Seed identification at the species level family had its origin in Central and South generally has been restricted to a few crops or America, where about 40 genera are endemic. weedy species {3, 7,13, 28, 33, 36), Usually seed The number of native genera and species characteristics have been omitted or only men- diminishes from south to north in the New tioned superficially in the literature on State World, decreasing sharply in the central United or regional floras. With this study it is possible States. For example, in a manual on the Texas to identify isolated seeds of economically im- flora (ii),^ 17 genera and 68 species are listed. portant species found in American agriculture More than half of the genera and over two- either by using the key or by comparing un- thirds of the species are endemic. New Eng- knowns to photographs and drawings. land has 10 genera and 31 species, with four Both internal and external seed characters native genera and seven native species (35). were used in preparing the key, descriptions, Alaska has only one species, which was intro- and illustrations, because external seed topog- duced, viz Solanum nigrum (including S. amer- raphy was not always sufficiently discrete to icanum) {2^), identify seeds. Collateral data presented with The nightshade family, which is of great seed descriptions include notes about origin, economic importance, contains many food, drug, distribution, and economic value of the plant, and ornamental plants, as well as noxious weeds as well as a brief description of its fruit. MATERIALS AND METHODS At least one seed sample of each of the 42 Additional seed samples, many identified by species is documented by a voucher herbarium comparison, were used to complete the survey specimen. A complete set of specimens is de- for each species. posited in the U.S. National Herbarium, Smith- Thirty-five of the forty-two vouchered seed sonian Institution (US), and a partial set is samples were harvested from field- and green- deposited in the U.S. National Arboretum Her- house-grown plants planted in a mixture of barium (NA). These authenticated seed sam- sandy loam, peat, and per lite (3:2:1) with a pH ples were used in preparing the photographs of 6 to 6.5. In the greenhouse, night tempera- and drawings and in constructing the key. tures of 18° to 21° C. and day temperatures of 24° to 30° coupled with a day length of 14 to 'Italic numbers in parentheses refer to Literature 16 hours were used. Blossom Set {beta- Cited, p. 31. naphthoxyacetic acid—0.0042 percent) was TECHNICAL BULLETIN 1471, U.S. DEPT. OF AGRICULTURE sprayed on some flowering plants to insure and 1 percent dioctyl sodium sulfosuccinate fruit production. (aerosol OT). The seeds were kept in solution External seed topography was observed at 10 for one-half to 3 hours depending on the perme- to 20 magniñcations with a dissecting stereo- ability and consistency of the seedcoat. scopic microscope equipped with an ocular The seedcoat was peeled, leaving the intact micrometer. Measurements used in the key endosperm around the embryo. In most seeds and descriptions are average values. At least the embryo was opaque and the well-developed 50 seeds from four to 20 samples were exam- endosperm was sufficiently translucent to trans- ined for each studied species. mit an embryonic image. The dark-brown Photographs were taken on a 5- by 7-inch endosperm of Datura stramonmm was partially Ektapan ñlm. The camera was equipped with cleared with lactophenol. A drop of lactophenol a bellows and a Microtessar lens. A black or was used to keep some small seeds in place white background was used depending on the during seedcoat peeling or cross sectioning. color of the seed samples. Cross sections of moderate size, flattened In the legends for the photographs, the num- seeds were made along the long axis usually bers after the collector's name refer to the parallel to the hilum. Cross sections of minute voucher herbarium specimens. seeds were made at right angles to the length Embryo sketches and seed cross sections were of the seed and often at right angles to the made with a camera lucida fitted on a stereo- scopic microscope and a below-stage fluorescent hilum (fig. 1). light. In preparing seeds for dissection, sound Fruit notes were prepared from live plants mature specimens of average size and shape as well as herbarium specimens. Additional data were placed in a softening solution of 74 per- on fruits are included in the section Fruit cent distilled water, 25 percent methyl alcohol, Notes. GENERAL SEED MORPHOLOGY Externally the seeds of the Solanaceae may Oestrum diurnum seeds is also present in other be placed in two categories: (1) Moderate size genera in the tribe Cestraeae. (usually over 1.5 mm. in length), rather circular The seed characters discussed here are pre- in outline, and strongly compressed or (2) sented in the order of their appearance in the minute (usually less than 1.5 mm. in length), seed description section of Synopses of Seed angular and not compressed, or oblong and Characteristics. The terminology in figures 1-3 terete. is used in the seed descriptions. Internally the embryos may be categorized Dimensions of seeds are length (long axis of as (1) linear, strongly curved, with well- seed without regard to hilum position), width developed cotyledons, (2) stocky, bent, with (at right angles to length and in same plane), poorly developed cotyledons, and (3) spatulate, and thickness (short axis of seed). Seeds larger straight, with well-developed cotyledons. than 1.5 mm. are classified as moderate size Correlations of internal and external seed and those smaller as minute. characters with phylogenetic studies result in Seed outlines are categorized for moderate placing flattened seeds with linear, strongly size, flattened seeds (tribes Datureae, Nican- curved embryos and well-developed cotyledons dreae, and Solaneae) as C-shaped, D-shaped, in tribes Datureae, Nicandreae, and Solaneae obovate, ovate, oblong, or irregularly circular. fide Wettstein {ÍO) or tribes Atropeae, Hyoscy- These seeds are usually smooth in outline ameae, and Solaneae fide Bentham and Hooker though some may be moderately to definitely {Jf). Minute, cuboidal to elongate seeds, with angular or lumpy. Seed outlines of minute seeds stocky, bent embryos and poorly developed coty- (tribes Cestraeae and Salpiglossideae) are cate- ledons are found in tribes Cestraeae and Sal- gorized as cuboidal, linear-angular, oblong to piglossideae (^, W). The spatulate embryo in spheroidal-angular and terete in cross section. SEED CHARACTERISTICS OF ECONOMICALLY IMPORTANT SPECIES OF SOLANACEAE 3 or reniform. Most of these seed outlines are yellow. Seedcoat color may be affected by aging shown in figure 1.