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Temperature Requirements for Seed Germination of Several Forage Legumes¹

Species that germinate readily over a relatively wide range of temperatures should be easier to establish in the field than those with highly specific temperature requirements. This study compared the temperature requirements for seed germination of several native and introduced legume species with those of commonly used species.

Seed germination of 17 legumes species was studied under dark conditions at alternating temperatures of 5 C – 20 C, 15 – 25 C, 20 – 35 C, and constant 20 C. Duration of the alternating temperatures was 12 hr. Seedling counts were taken on the 7th, 14th, 21st, and 28th days of germination.

Species differed significantly in germination response to temperature. Medicago sativa L. var ‘Ladak 65,’ Onobrychis viciaefolia Scop. vat. ‘Eski,’ Oxytropis riparia Litv., an unidentified Astragalus sp., A. canadensis L., A. galegiformis L., and A. falcatus Lam. were considered to be temperature-insensitive for total germination because there was very little difference in percentage germination within each of these species on the 28th day at the four temperature treatments. Half of these species, however, were at least moderately sensitive to temperature for rate of germination.

There was considerable interaction among some species and temperatures for both total germination and rate of germination. Astragalus glycyphyllos L., A. globiceps Bge., A. dahuricus (Pall.) DC., and A. chinensis L. required relatively high temperatures (15 – 25 C or 20 – 35 C) for good germination. These temperatures, however, markedly reduced germination of Desmanthus illinoensis (Michx.) MacMill. The 20 – 35 C treatment also seriously reduced germination of Coronilla varia L. var. ‘Chemung’ and slightly reduced germinatiou of Astragalus striatus Nutt., A. flexuosus (Dougl.) G. Don, and Vicia tenuifolia Roth. In comparison to other treatments, rate of germination at constant 20 C was especially high for V. tenuifolia, D. illinoensis, and C. varia. Germination response of Astragalus cicer L. differed from other species. Rate of germination and total germination increased with increase in temperature through 15 – 25 C. At 20 – 35 C, total germination dropped substantially, but rate of germination remained high.

Temperature requirements for seed germination of some species suggest why they are relatively easy or difficult to establish in the field. The species that germinated well at most temperatures but are difficult to establish are very small seeded.

Key Words: Alternating temperature • Range seeding

² Research Geneticist and Range Scientist, respectively, PSRD, ARS, USDA, and Faculty Affiliates, Departments of Agronomy and Range Science, Colorado State University.

Received for publication April 7, 1972.