Seed dormancy and germination ecology of several clover species

This research was carried out to evaluate the effect of (1) different methods of breaking seed dormancy (physical and chemical scarification, high temperature, hot water and after-ripening), and (2) environmental factors (temperature, salinity and water stress) on seed germination of Trifolium angustifolium , T. arvense , T. fragiferum , T. fucatum , T. repens , T. subterraneum and Trifolium sp. All experiments were conducted in the Seed Research Laboratory of Gorgan University of Agricultural Sciences and Natural Resources, Iran, in 2021. All the examined clover species were dormant after harvest, with little germination. Mechanical scarification with sandpaper or sulphuric acid resulted in more than 88 and 52% germination, respectively. Seeds were able to germinate between 5 and 35°C, but the highest germination (≥ 98% on average) occurred at 20°C. Fluctuating temperature regimes were more efficient in improving the germination than constant temperatures. Seeds of clover species, in addition to having a hard seed coat, have a non-deep physiological dormancy. Fresh seeds showed a high sensitivity to water stress compared with after-ripened seeds. However, relative resistance to salinity stress was observed. The results obtained in this research can be used to develop effective sowing strategies and support the successful establishment of these clover species.