7 pages, 4 figures, 1 table.-- Available online Aug 12, 2008. | Erica andevalensis Cabezudo & Rivera is a threatened edaphic endemic species of Andalusia (SW Spain). Under natural conditions, the plants produce a very large number of small seeds (0.3–0.4 mm) but very few seedlings survive. Different treatments (high temperature, cold pre-treatment, nitrogen salts, and gibberellic acid applications) were tested to assess germination patterns in different populations and to determinate the most favorable conditions for germination. Gibberellic acid was provided in five different concentrations from 0 to 400 ppm GA3, while nitrogen was applied as 10 mM of either KNO3 or NH4NO3. The effect of pH on germination was also tested. The species always showed a low germination rate (6.50–22%) that was not stimulated either by 1 or 4 months in dry cold pre-treatment, nitrogen application, acid pH medium, or by high temperature (80°C for 10 min); although gibberellic acid application (100–400 ppm) significantly enhanced germination. The highest percentage of germination (41.6%) was achieved with a mean germination time to start germination (t-0) of 7.6 ± 0.54 days when the seeds were subjected to 400 ppm gibberellic acid treatment. The population origin did not have a significant effect on germination percentage. | The present research was supported in part by the Spanish Ministry of Science and Education (CGL2006/02860) and in part by Fundación Areces (Proyect title: Mecanismos de resistencia a metales pesados en especies significativas de la cuenca minera de Riotinto). | Peer reviewed

The Norway spruce seed germination is often weak (in some years, the germination rate is less than 50%). It is already known that some physical agents had a simulative influence on the germination process. For improving the spruce seed germination, the influence of the ultrasound treatment on seed germination was tested. The tests have shown that the length of plant rootlet and hypocotyl and the germination rate of seeds depended on the frequency and duration of the ultrasound treatment. For the frequency of 35 kHz, the best results, represented by the improvement of germination and an increased length of rootlets and hypocotyls for the germinated seeds, were obtained for the treatment duration longer than 40 seconds. Thus, for the treatment duration of 50 and 60 seconds, we have obtained a germination improvement by over 40%, an augmentation of the rootlet length by 32% and of the hypocotyls by 5-8%, compared to the untreated control. Because these data are only preliminary, the testing conditions and the tested species must be diversified, in order to establish regularities with practical applicability.

Delayed and inconsistent seed germination often hampers commercial production of palms (Arecaceae). Such sporadic germination is commonly due to seed dormancy. Mature, freshly shed seeds of palms typically display a combination of underdeveloped embryos (morphological dormancy) and the inability of developing embryos to rupture covering structures (physiological dormancy). Fruit and seedcoats are capable of imbibing water. Therefore, dormancy due to water-impermeable fruit or seedcoats (physical dormancy) does not occur. Removal of embryo covering structures, such as the pericarp and operculum, followed by incubation under moist, warm (25–35 °C) conditions promotes rapid and complete germination. Complete burial in soil promotes germination of seeds in intact fruit of loulu palm (Pritchardia remota).

Understanding the germination traits of plants is important not only for understanding natural regeneration processes but also for developing seedling production techniques for planting. Sabina vulgaris Ant. is a common species used for reforestation in semi-arid areas of the Mu-Us Desert, in Inner Mongolia, China, but its extremely low germination rate, both in situ and in vivo, is a bottleneck for seedling production. Sulfuric acid pretreatment was applied to improve germination, and the germination rate was compared for different soaking time (10, 30, 60, 90, and 120 min), different temperatures (10, 15, 20, 30, and 35°C) and under different lighting conditions (dark and light). Sulfuric acid treatment gave a high germination rate, reaching 60% at 30 days after sowing. However, the non-treated seeds produced no germination. The optimal treatment time in sulfuric acid was 120 min. Germination after sulfuric acid treatment increased at incubation temperatures from 10 to 30°C, but decreased at 35°C. Incubation at 25–30°C gave maximum germination of more than 50%. Light treatment had little effect on germination. Pretreatment with sulfuric acid improved water absorption by the embryo by creating cracks and cavities in the seed coat tissue. These results indicated that S. vulgaris seeds have physical dormancy caused by their hard seed coats, which prevents absorption of water into the embryo. A combination of pretreatment with sulfuric acid and incubation at 25–30°C was most effective in improving the germination of S. vulgaris seeds.

Formation and germination of somatic embryo (SE) are affected by the concentration of plant growth regulators; MS medium strength, sucrose concentration, and the photosynthetic photon flux (PPF) level. The MS medium strength and sucrose concentration for an optimal condition of the SE formation and germination of Pimpinella brachycarpa were x0.5, sucrose 30 g L-¹ and x0.25, sucrose 30 g L-¹, respectively. When 0.05 mg L-¹ of kinetin was treated, the percentage of normal somatic embryo (NSE) formation was the greatest and the percentage of hyperhydric somatic embryo (HSE) formation was the lowest. SE germination rate was greater in treatment of IAA 0.05 mg L-¹ or BA 0.01 mg L-¹ than those of other treatments. Moreover, better SE formation and germination were found at dimmer lighting (20 μmol m-² s-¹ of PPF) than that of higher PPFs. SE formation and germination were also retarded at higher PPFs. Optimum PPF for SE formation and germination was 20 μmol m-² s-¹. After forming SE from EC 0.1 g for 4 weeks, EC 0.1 g resulted in 700 total SE formation. Culturing four SEs for four weeks resulted in a secondary SE formation, germination and eventually 52 plantlets. These results indicate that a huge proliferation rate was achieved at up to 8 weeks of EC at liquid medium suspension culture and SE at solid medium culture. Through the experiment, after inducing EC from EC, the mass of EC was increased by 25 times (from 0.05 to 1.30 g) when each of the nutritional and chemical factors was controlled at the optimized condition.

Crataegus from Rosaceae family is a tree that has medical and ornamental applications. Seeds of this genus have germination problem and may not germinate for 2 to 3 years. There are limited information about germination of different species. Therefore, study on germination of three native species of Iran, Crataegus aminii,C. persica and C. babakhanloui is conducted and the most effective treatment was determined. To evaluate the germination and breaking seed dormancy of three species, an experiment was carried out as a completely randomized design with four treatments and three replications. Seeds were imposed under physical stimulator treatment, including, scarification and warmth followed by cold stratification. Results indicated that in all treatments, scarification is effective for permeability to water of seed coat and breakage of seed dormancy. Germination rate in treatment 4 (impose to running water for 24h, then 3 month warmth, followed by 4.5 month cold stratification) had the highest rate. The highest percentage of germination and vigor were in treatment 3 (sowing the seeds outdoors at the beginning of summer). The number of the seeds that have embryo in each fruit is determined. More than 80% of fruits have only one embryo.

Sawgrass (Cladium jamaicense) is the predominant plant and vegetation community in the Florida Everglades. Germination of sawgrass seeds in the laboratory or nursery has been difficult and problematic, yet little is known about the physiological mechanistic regulation of the sawgrass seed germination process. In the present study, we examined the factors and mechanisms that influence sawgrass seed germination. We found that removal of seed husk and bracts, pre-soaking with bleach (hypochlorite), breaking the seed coat, or combinations of these treatments promoted the rate and success of germination, whereas presence of seed-encasing structures or treatment with husk/bract extract inhibited germination. We further detected the presence of abscisic acid (ABA) in the husk and bract. Experiments with ABA and gibberellin biosynthesis inhibitors fluridone and tetcyclacis suggested that ABA already presented in the pre-imbibed seeds, and not derived through post-dormancy de novo synthesis, contributed to the inhibition of seed germination. Examination of bleach and mechanical treatments indicated the physical barrier presented by the seed-encasing structures provided additional mechanism for the long-term delay of seed germination. Based on the results of this study and others, we discussed the implications of sawgrass seed dormancy and germination in relation to its natural habitat and proposed a hypothesis that the protracted seed dormancy in sawgrass offered an adaptive advantage in the pre-anthropogenic Everglades environment, but may become a liability in the current man-managed Everglades water system.

Most of the achenes produced by Rosa multibracteata Hemsl. & E. H Wilson are dormant on maturity and require pretreatment to stimulate germination. To investigate the mechanism of dormancy and to develop effective methods of improving germination, roles of the pericarp, testa, and embryo of R. multibracteata in regulating dormancy were studied by investigating the effect of different pretreatments on germination. The effects of temperature and water stress were also tested with achenes treated by warm plus cold stratification. In freshly harvested achenes, pericarps are permeable and the embryo fully developed, which eliminates the possibility of physical, morphological, or morphophysiological dormancy. Germination percentage remained low (<5%) despite softening the pericarp or even removing it fully. However, fully removing the testa improved germination significantly (39%), indicating the possible presence of germination inhibitors in the testa. Dry storage, scarification with sulphuric acid (H₂SO₄), and warm stratification proved ineffective by themselves but when combined with cold stratification, improved germination and shortened the cold stratification period needed to break dormancy. Dry storage for 68 weeks followed by cold stratification for 16 or 24 weeks resulted in maximum germination (72-79%) among all the treatments. In achenes scarified with H₂SO₄, germination increased with an increase in the duration of cold stratification. Neither gibberellic acid (GA₃) nor 'smoke water' (water through which smoke had been bubbled for 2h) had any positive effect on germination even on seeds that had been mechanically scarified or stratified. Both high temperature and water stress lowered germination in achenes treated with warm plus cold stratification. Our results suggest that R. multibracteata achenes have an intermediate physiological dormancy, and that dry storage for 68 weeks followed by cold stratification for 16 or 24 weeks is the best method for propagating R. multibracteata from seed.