Identification of physical dormancy and dormancy release patterns in several species (Fabaceae) of the cold desert, north-west China

Abstract

AbstractA clear understanding of the mechanisms involved in releasing seed dormancy is important for effective plant conservation and regeneration of desert species. The dormancy types and dormancy release mechanisms of 19 Fabaceae species from four cold deserts in Xinjiang province, China, were studied. An imbibition experiment was performed to determine the presence or absence of physical dormancy. Other treatments included mechanical scarification, sulphuric acid scarification and simulation of summer temperatures typically encountered in the field. High summer temperature treatments included a maximum soil temperature of 80°C, 65°C and 40°C, conducted under dry and wet conditions. The results showed that all the species had orthodox seeds.Caragana korshinskii,Caragana intermedia,Caragana microphyllaandOnobrychis taneiticaseeds were not dormant.Glycyrrhiza uralensis,Ammodendron bifolium,Vicia costataandEremosparton songoricumseeds had combinational dormancy (PY+PD) whereas the other 11 species had physical dormancy. The mechanical scarification and sulphuric acid scarification treatments were significant to break dormancy (>80%).Melilotus suaveolensandOxytropissp. seeds were temperature-insensitive.Sophora alopecuroides,S. salsula,E. songoricum,A. bifoliumandCassia toraseeds were wet-heat sensitive.Glycyrrhiza glabraseeds were dry-heat sensitive, while those ofHalimodendron halodendronandAstragalus lehmannianuswere sensitive to both dry and wet heat. Although high temperatures, typical of summer, promoted the breaking of physical dormancy, the proportion of seeds of which dormancy was broken differed among species. These differences were indicative of the conditions in which the species are found naturally. Species may have different adaptations that promote favourable regeneration. Given suitable temperature and moisture conditions similar to those in their natural environment, most species were capable of regeneration.