Seed dormancy and germination characteristics of several species of the Caragana genus

The majority of legumes in the temperate zone have water-impermeable seeds; however, little is known about seed dormancy and the response of seed germination to environmental factors, such as temperature and water potential. Thus, the seed dormancy and germination in response to temperature and water potential in 15 Caragana species were studied. The results showed that: 1) the percentage of hard seeds in Caragana roborovskyi and C. acanthophylla was 63% and 14%, respectively, while this was lower than 10% or absent in the other species. 2) Dry storage significantly decreased the percentage of hard seeds of the tested species to various degrees (P < 0.05). For example, the hard seed percentage of C. roborovskyi decreased from 63% to 37%. 3) With an increase in temperature, the germination percentage and germination index increased and then decreased. The germination range and temperature threshold varied according to the species. 4) The germination percentage and germination index of all species decreased with a decrease in water potential, while their sensitivity to water stress varied according to the species. Thus, the seeds of most Caragana species were permeable to water, and dry storage at room conditions significantly decreased the number of hard seeds, which should be considered during future studies.