Conservationists often propagate rare species to improve their long-term population viability. However, seed dormancy can make propagation efforts challenging by substantially lowering seed germination. Here I statistically compare several pretreatment options for seeds of Astragalus cicer L.: unscarified controls and scarification via physical damage, hot water, acid, and hydrogen peroxide. Although only 30% of unscarified seeds germinated, just physical scarification significantly improved germination, whereas one treatment, hot water, resulted in no germination at all. I recommend that rare species of Astragalus, as well as other hard-seeded legumes, be pretreated using physical scarification. Other methods may require considerable optimization, wasting precious time and seeds.

A greater diversity of native legumes and forbs is desirable for rangeland restoration practice in the Intermountain Region of the western United States. But for such diversity to materialize in the seed marketplace and to be effective in restoration practice, seeds that germinate reliably in seed fields and on restoration sites are needed. We measured germination response of two native legumes, basalt milkvetch (Astragalus filipes Torr. ex A. Gray) and western prairie clover (Dalea ornata [Douglas] Eaton & Wright), after eight germination treatments. Treatments were a factorial combination of 1) seed scarification with sandpaper (or unscarified), 2) a substrate of moist sand (or blotter paper), and 3) a 3-wk prechill at 5° (or nonprechilled). Cumulative germination increased linearly throughout the 10-wk course of the experiment for all treatment combinations in both species. Scarification increased germination of western prairie clover, but prechilling and substrate had no effect. In contrast, prechilling, scarification, and a sand substrate all increased germination of basalt milkvetch. Hence, for this species the prechilled/scarified/sand treatment combination displayed the numerically highest germination for all 10 wk (30−43%), and the nonprechilled/unscarified/blotter paper treatment combination always germinated lowest (1−3%). Results were consistent with physical dormancy (hard-seededness) limiting germination of western prairie clover and combinational dormancy (i.e., co-occurrence of physical and physiological dormancy) limiting germination of basalt milkvetch. Of the two species, we have found basalt milkvetch to be the more difficult to establish from seed. By prechilling acid-scarified seed in moist sand, basalt milkvetch was successfully established in two field trials seeded in mid-April. Nonprechilled mechanically (sandpaper) scarified seed germinated as high as prechilled acid-scarified seed. By scarifying and prechilling basalt milkvetch seed to address physical and physiological dormancy mechanisms, respectively, this seed-treatment protocol may be “scaled up” to produce large quantities of germinable seed.

A greater diversity of native legumes and forbs is desirable for rangeland restoration practice in the Intermountain Region of the western United States. But for such diversity to materialize in the seed marketplace and to be effective in restoration practice, seeds that germinate reliably in seed fields and on restoration sites are needed. We measured germination response of two native legumes, basalt milkvetch (Astragalus filipes Torr. ex A. Gray) and western prairie clover (Dalea ornata [Douglas] Eaton & Wright), after eight germination treatments. Treatments were a factorial combination of 1) seed scarification with sandpaper (or unscarified), 2) a substrate of moist sand (or blotter paper), and 3) a 3-wk prechill at 5° (or nonprechilled). Cumulative germination increased linearly throughout the 10-wk course of the experiment for all treatment combinations in both species. Scarification increased germination of western prairie clover, but prechilling and substrate had no effect. In contrast, prechilling, scarification, and a sand substrate all increased germination of basalt milkvetch. Hence, for this species the prechilled/scarified/sand treatment combination displayed the numerically highest germination for all 10 wk (30–43%), and the nonprechilled/unscarified/blotter paper treatment combination always germinated lowest (1–3%). Results were consistent with physical dormancy (hard-seededness) limiting germination of western prairie clover and combinational dormancy (i.e., co-occurrence of physical and physiological dormancy) limiting germination of basalt milkvetch. Of the two species, we have found basalt milkvetch to be the more difficult to establish from seed. By prechilling acid-scarified seed in moist sand, basalt milkvetch was successfully established in two field trials seeded in mid-April. Nonprechilled mechanically (sandpaper) scarified seed germinated as high as prechilled acid-scarified seed. By scarifying and prechilling basalt milkvetch seed to address physical and physiological dormancy mechanisms, respectively, this seed-treatment protocol may be “scaled up” to produce large quantities of germinable seed.

Abelmoschus moschatus Medik. subsp. moschatus is a wild uncultivated variety of common lady’s finger (Abelmoschus esculentus) possessing a high degree of seed dormancy. Methods of dormancy breaking in the seed of the plant were investigated through different physical and chemical methods. Different preconditioning treatments including hot water, dry heat, physical scarification and chemical treatments including exogenous GA₃ were applied to explore the initiation in germination. Seeds were germinated under the controlled photoperiod and temperature. The viability of the test seeds was estimated by topographical 2, 3, 5-Triphenyltetrazolium chloride (TTC) solution test. Highest germination percentage was obtained in the seeds treated with the exothermic reaction of H₂SO₄ and H₂O, followed by exposure to gibberellic acid (GA₃). The exposure time of exogenously applied GA₃ had a significant influence on the germination response. The optimum germination temperature was found to be 30 ± 0.5°C. Treatment with 0.75% of 2, 3, 5-Triphenyltetrazolium chloride solution for 4 h at 35 ± 0.5°C enabled to correlate the viability of the seeds with the germinative values. Maximum germination was induced through this technique and dormancy of the seed can be attributed due to hard impermeable seed coat and endogenous physiological factor.

Fire plays an important role in several grassland ecosystems in the world. Fire can trigger germination in several species, by breaking the physical dormancy of their seeds. Thus, we hypothesized that exposure to high temperatures during fire would break seed dormancy and enhance germination. We tested the effect of high temperatures on the germination of six species of legumes from Brazilian subtropical grasslands. We used heat shock experiments with the following treatments: 60, 90, 120 and 150ºC for one minute. Seeds were then placed to germinate for 60 days in 12/12 hours light/dark and 20/30ºC. Germination was generally low for all study species. Most species was not affected by heat shock treatments. However, Stylosanthes montevidensis was the only species that had its physical dormancy broken when exposed to 120ºC. The seeds of all the other species were neither stimulated nor killed by high temperatures. Although the exposure to high temperatures did not affect the germination of the study species (except for one), it also did not kill seeds, thereby showing that seeds are resistant to fire. Therefore, the rapid passage of fire in these grasslands is not sufficient to break the dormancy of most of the studied species of legumes.

In the context of seed technology, the use of physical methods for increasing plant production offers advantages over conventional treatments based on chemical substances. The effects of physical vigourization treatments in seeds can be now addressed at multiple levels, ranging from morpho-structural aspects to changes in gene expression and protein or metabolite accumulation. Among the physical methods available, magneto-priming and irradiation with microwaves or ionizing radiations are the most promissory pre-sowing seed treatments. Magneto-priming is based on the application of magnetic fields and described as an eco-friendly, cheap, non-invasive technique with proved beneficial effects on seed germination, vigour and crop yield. Ionizing radiations, as gamma-rays and X-rays, have been widely regarded as a powerful tool in agricultural sciences and food technology. Gamma-rays delivered at low dose have showed to enhance germination percentage and seedling establishment, acting as an actual ‘priming’ treatment. Different biological effects have been observed in seeds subjected to microwaves and X-rays but knowledge about their impact as seed vigourization agent or stimulatory effects on germination need to be further extended. Ultraviolet (UV) radiations, namely UV-A and UV-C have shown to stimulate positive impacts on seed health, germination and seedling vigour. For all mentioned physical treatments, extensive fundamental and applied research is still needed to define the optimal dose, exposition time, genotype- and environment-dependent irradiation conditions. Electron paramagnetic resonance (EPR) has an enormous potential in seed technology not fully explored to monitor seed vigourization treatments and/or identifying the best suitable irradiation dose or time-point to stop the treatment. The present manuscript describes the use of physical methods for seed vigourization, while providing a critical discussion on the constraints and advantages. The future perspectives related to the use of these approaches to address the need of seed technologists, producers and trade markers will be also highlighted.

The in vitro culture of zygotic embryos can be a useful tool to reduce the germination time and provide higher rates of embryos developed into plants (Lima 2013), as the in vitro culture allows the removal of physical barriers such as hard endocarp and facilitates the supply of nutrients to the developing embryo (Pádua et al. 2014). In vitro germination can overcome this problem by embryo rescue. In this study we optimized the in vitro germination of zygotic embryos of BRS Manicoré hybrid palm comparing various culture media and various seed lots.

Studies have been conducted to develop seed germination and suitable agri-silvi practices for Cassia angustifolia in arid areas under rainfed and irrigated conditions. Seeds were found dormant due to physical reasons and gave poor germination without any pre-treatment. The germination can be enhanced (>80%) by mechanical scarification, hot water and acid pre-treatments. Green seeds in the lot showed slightly poor germination as compared to yellow seeds. Seeds of tested seedlots without treatment gave 22% to 41% germination and average mean germination time was from 4.1 to 5.1 days. However, pre-treatments enhanced the germination percentage and reduced the mean germination time in almost all the lots. Various experiments were initiated with different spacing (30 x 30 cm, 30 x 45 cm and 45 x 45 cm), date of sowing (July, August and September) and irrigation trials. In another experiment various agroforestry tree species namely Acacia nilotica, Prosopis cineraria, Azadirachta indica and Eucalyptus camaldulensis have been selected for experimental trial with a single frequency of irrigation (after 1st plucking) in 3 replication and RBD design.

Poor seed germination is a main hindrance to the commercial cultivation of Zinnia (Zinnia elegans Jacq.). Seed enhancement is a useful strategy to improve germina-tion of major agronomic and horticultural crops. A lab study was conducted to investigate the potential of magnetic seed stimulation as a seed enhancement tool and its influence on germination and emergence capacity of zinnia. Magnetic seed treatment with 50, 100 and 150 mT strength each for 5, 10 and 15 min was compared with control (untreated). Mag-netic seed stimulation reduced time to 50% germination and mean germination time and increased final germination percentage, germination energy and germination index. Root length, shoot length, seedling fresh and dry weight was also increased as a result of mag-netic seed stimulation. Furthermore, magnetic field treatment also enhanced α-amylase activity, total soluble sugars and reducing sugars levels. Among all seed treatments, mag-netic field with strength of 100 mT for 15 min was the most effective physical treatment for improving seed germination and seedling growth of zinnia.