Morphophysiological dormancy and germination ecology in diaspores of the subtropical palm Phoenix canariensis Chabaud

The timing of germination is a crucial event in a plant’s life cycle. Seed dormancy and germination mechanisms are important factors regulating seedling emergence. Since detailed experimental evidence for germination pattern of Phoenix canariensis colonizing sub-tropical climate is scarce, we investigated seed dormancy and germination ecology of P. canariensis. We found that the embryo is underdeveloped at the time of dispersal and doubles in size before the cotyledonary petiole (CP) protrudes through the operculum. The primary root and plumule emerge from the elongated CP outside the seed. In light/dark at 30/25°C, the CP emerged from 8% of the diaspores within 30 days and from 76% within 14 weeks. Thus, 8% of the diaspores have MD and the others MPD. Removal of the pericarp and operculum resulted in 100% germination within 5 days in light/dark at 30/25°C. Cold and warm stratification as well as treatment with GA3 significantly increased the germination speed, but the final germination percentage was not significantly increased. Seed germination was synchronized in early summer when seed dormancy was released by cold stratification in the soil over winter. A remote-tubular germination type and intricate root system provide an ecological advantage to the seedling establishment.

Non-deep physiological dormancy in seeds of Euphorbia jolkinii Boiss. native to Korea

Background Euphorbia jolkinii Boiss. is a perennial species native to Jeju Island and the southern coastal area of Korea. Particularly on Jeju Island, the yellow flowers of E. jolkinii Boiss. have a high ornamental value because of their contrast with basalt. This study was conducted to investigate the effects of different temperatures (5, 15, 20, and 25 °C) and gibberellic acid (GA3) concentrations (0, 10, 100, or 1000 mg/L) on seed dormancy and germination of E. jolkinii. In addition, we classified the seed dormancy type and compared types with those of other species in the same genus. Results The number of seeds with viable embryos and endosperms was approximately 66%. The final germination percentages at 5, 15, 20, and 25 °C were 51.7%, 83.5%, 2.6%, and 0.0%, respectively. In GA3 concentration experiments, the final germination percentages of 0, 10, 100, and 1000 mg/L were 83.5%, 91.7%, 79.1%, and 83.4%, respectively, at 15 °C conditions, and 0.0%, 6.9%, 13.2%, and 27.3%, respectively, at 25 °C. Conclusions Germination improved at temperatures of 15 °C or lower. Furthermore, GA3 treatment effectively reduced germination times. Thus, the seeds of E. jolkinni were classified as having non-deep physiological dormancy.

Understanding Seed Dormancy and Germination

Seeds are highly important part of living things, without which life would not exist. All of our daily necessities are totally dependent on seed and seed stock, like food and fruits, so also is many of the natural resources that we use as consumers such as, timber, cotton, paper, essential\edible oils, all which started their live as seeds. Basically, a seed consists of a tiny underdeveloped plant, the embryo, which is enclosed by a covering called the seed coat. Germination of seed occurs when the embryo grows into a functioning plant. It involves the rejuvenation of the metabolic pathways that lead to growth and the emergence of the radicle (root) and plumule (shoot). For germination to occur, three basic factors must exist, the seed must be viable, dormancy must be controlled and the proper environmental conditions for germination must be available. Dormancy simply means the inability of seeds to germinate even when the necessary environmental conditions (temperature, humidity, oxygen, and light) are favorable for germination. Dormancy is a principal factor restricting the production of crops. Several physical and chemical pretreatments can be applied to the organic material (seeds) to control dormancy. This review discusses the conditions necessary for germination and the fundamental factors necessary for breaking dormancy.

Clone x Tester Crosses on Compatibility Level of Sweetpotato (Ipomoea batatas L.)

Evaluation of compatibility on sweetpotato is very important to determine the crossing parents to increase the compatibility of controlled cross-pollination. This research was aimed to study the level of compatibility in controlled cross-pollination based on percentage of normal seedlings obtained from crosses. The research was conducted at Kendalpayak Experimental Station of ILETRI, Malang, Indonesia then followed by breaking seed dormancy and germination of seeds obtained. The genetic materials used were 17 accessions with high yielding potential and 3 accessions as tester for crossing. The results showed that there were differences in the compatibility levels of crossing combination and their compatibilities as male or female parents. Clone C-011 (Tester 2) was the most compatible as male parent, while clone C-141, C-007 and C-131 were the most compatible as female parents. Clone C-127 (Tester 3) was the most compatible as both male and female parents. Clone C-001 (Tester 1) could not be used as female parent due to high incompatibility.This compatible clone information is very useful in determining of both controlled crosses and open crosses in sweet potato in order to increase the breeding efficiency.

Seed Dormancy and Soil Seed Bank of the Two Alpine Primula Species in the Hengduan Mountains of Southwest China

The timing of germination has long been recognized as a key seedling survival strategy for plants in highly variable alpine environments. Seed dormancy and germination mechanisms are important factors that determining the timing of germination. To gain an understanding of how these mechanisms help to synchronize the germination event to the beginning of the growing season in two of the most popular Primula species (P. secundiflora and P. sikkimensis) in the Hengduan Mountains, Southwest China, we explored their seed dormancy and germination characteristics in the laboratory and their soil seed bank type in the field. Germination was first tested using fresh seeds at two alternating temperatures (15/5 and 25/15°C) and five constant temperatures (5, 10, 15, 20, and 25°C) in light and dark, and again after dry after-ripening at room temperature for 6 months. Germination tests were also conducted at a range of temperatures (5–30, 25/15, and 15/5°C) in light and dark for seeds dry cold stored at 4°C for 4 years, after which they were incubated under the above-mentioned incubation conditions after different periods (4 and 8 weeks) of cold stratification. Base temperatures (Tb) and thermal times for 50% germination (θ50) were calculated. Seeds were buried at the collection site to test persistence in the soil for 5 years. Dry storage improved germination significantly, as compared with fresh seeds, suggesting after-ripening released physiological dormancy (PD); however, it was not sufficient to break dormancy. Cold stratification released PD completely after dry storage, increasing final germination, and widening the temperature range from medium to both high and low; moreover, the Tb and θ50 for germination decreased. Fresh seeds had a light requirement for germination, facilitating formation of a persistent soil seed bank. Although the requirement reduced during treatments for dormancy release or at lower alternating temperatures (15/5°C), a high proportion of viable seeds did not germinate even after 5 years of burial, showing that the seeds of these two species could cycle back to dormancy if the conditions were unfavorable during spring. In this study, fresh seeds of the two Primula species exhibited type 3 non-deep physiological dormancy and required light for germination. After dormancy release, they had a low thermal requirement for germination control, as well as rapid seed germination in spring and at/near the soil surface from the soil seed bank. Such dormancy and germination mechanisms reflect a germination strategy of these two Primula species, adapted to the same alpine environments.