Environmental Factors Influencing Gardner Saltbush Seed Dormancy Alleviation

Pregermination treatments applied to seed of Gardner saltbush, [ALriplexgar&cri(Moq.) D. Dietr.] were evahtated for alleviation of seed dormancy. Treatments selected simulated conditions the seed might be exposed to in its natural environment, including dry afterripening, scarification, leaching, and cold stratification. Germination response to individual treatments was equal to or higher than nontreated seed. Germination percentage of afterripened seed was increased from 17% for nontreated filled seed to an average of 86% of filled seed by the combined treatments of scarification, leaching, and 4-week stratification. This combination of treatments allowed optimum germination. Response to treatments provided evidence as to the type of dormancy in Gardner saltbush seeds. The levels of germination response to specific treatments appears to be an adaptation to ensure a temporal dispersal of dormancy release and seedling emergence. Pregermination treatments used in this study were relatively easy to apply to the seeds and stimulated germination without potentially damaging the embryo. Thus, they would be useful in revegetation by direct seeding efforts. Gardner saltbush [Atriplexgurdneri (Moq.) D. Dietr.] is a lowgrowing perennial half-shrub, 20 to 50 cm tall, which occurs in cold desert regions of Montana and Wyoming. It is particularly adapted to saline, alkaline, and clayey soil conditions, extreme temperatures, high winds, and aridity (Stubbendieck et al. 1981). It is a Authors are postdoctoral research associate, Texas A & M Agricultural Experiment Station, Vernon 76348; and assistant professor, Plant Science Division, University of Wyoming, Laramie 8207 I. At the time of the research? the senior author was a graduate research assistant, Plant Science Division, University of Wyoming. Research was funded in part by the University of Wyoming Agricultural Exp. Sta. and the High Plains Grassland Res. Sta., through USDA-ARS Coop. Agreement No. 58: 9AHZ-9-467. Published as Wyoming Agricultural Exp. Sta. Journal Article 1286. Manuscript accepted October I, 1984. JOURNAL OF RANGE MANAGEMENT 38(4), July 1985 valuable winter forage and aids in stabilization in areas where grasses are not predominant. Seed dormancy can be considerable in Gardner sahbush and closely related Atriplex spp. (Foiles 1974, Vories 1981), and this may explain why previous efforts to establish these species via direct seeding have largely been unsuccessful (Bleak et al. 1965, Nord et al. 1971, McKell 1979). Beadle (1952), Twitchell (1955), Cornelius and Hylton (1969), and others found that the presence of salts in the utricle imposed dormancy in seeds of many Atriplex spp. and that leaching with water partially alleviated dormancy. Most of these species, unlike Gardner saltbush, occur in Mediterranean climates and dormancy breaking mechanisms may be somewhat different (Chatterton and McKell 1969, Osmond et al. 1980). Atripfex spp. occurring in colder climates, including Gardner saltbush, reportedly have cold stratification requirements ranging from 2 weeks to 10 months at 2 to 5°C (McLean 19531, Foiles 1974, Eddleman 19782). It is not known whether stratification affects embryo or seedcoat dormancy in Atriplex spp. A better understanding of processes involved in alleviation of Gardner saltbush seed dormancy may aid future revegetation efforts. In some species a correlation exists between requirements for dormancy alleviation and conditions necessary for seedling establishment (Mayer and Poljakoff-Mayber 1975, Thompson 1973). We hypothesized that because Gardner saltbush evolved in an extremely variable desert environment which offers infrequent opportunities for successful seedling establishment, maximum ‘McLean, A. 1953. The autecology of Arriplex nudli S. Wats. in southwestern Saskatchewan. MS. Thesis, Utah State Agr. COIL, Logan. ‘EddIeman, L.E. 1978. Survey of viability of indigenous grasses, forbs, and shrubs. Annu. Prog. Rep. prepared for U.S. Energy Res. and Devel. Admin. Missoula. Mont.. p 160-161.