Search Results (10)

Quercus longispica is a dominant shrub in the Himalayan subalpine region, demonstrating high levels of persistence despite high seed predation and extreme climatic conditions. However, its seed germination ecology and adaptations for seedling recruitment remain poorly understood. This study investigated the effects of temperature, water potential, and insect damage on seed germination and seedling establishment. Pre-germination seed traits and seed-to-seedling ontogeny were systematically analyzed. Our results demonstrated that seed germination percentages decreased with increasing insect damage across all temperature and water potential treatments. Cool temperatures (5–10 °C) yielded the highest germination percentages, potentially due to the suppression of parasitoid activity and mildew growth. While drought conditions also suppressed parasitoid activity, they significantly increased seed mortality. Despite a decline in seedling performance with increasing seed damage, overall seedling establishment remained robust. Several adaptive traits enable Q. longispica to persist in its harsh environment. Multi-seeded, non-apical embryos combined with rapid germination help embryos evade or escape damage from parasitism and predation. The rapid elongation of cotyledonary petioles pushes the embryo axis into the soil, with rapid nutrient and water transfer from the cotyledon to the taproot, thereby avoiding the threats of predation, drought, cold, and wildfire. Additionally, temperature-regulated epicotyl dormancy at the post-germination stage prevents the emergence of cold-intolerant seedlings in winter. This study provides the first comprehensive description of seed-to-seedling ontogeny in this Himalayan subalpine oak, offering crucial insights into the adaptive mechanisms that facilitate successful seedling recruitment in the challenging subalpine habitats. Full article

Paeonia peregrina Mill. is a protected, herbaceous species native to Southeastern Europe and Turkey. Due to its vulnerability, it has to be protected both in its natural habitats and through cultivation. Peonies are known to have a low potential for natural regeneration due to their seed dormancy, low germination rate, and long germination period. In this study, treatments with gibberellic acid (GA₃ 150, 200, 250, 300, and 350 mg L⁻¹ GA₃) and warm (at 20/16 °C day/night regime) and cold stratification (at 4 °C) were used to accelerate dormancy release and increase the germination rate. The seeds of P. peregrina from four natural habitats in Serbia and the Institute’s collection were collected and analyzed. They showed an underdeveloped embryo that needs to grow inside the seed before it can germinate. The application of GA₃ accelerated each stage of germination (seed coat rapturing, hypocotyl dormancy release, and epicotyl dormancy release) for approximately 10 days compared to the control. It was also found that two-day imbibition with 200 mg L⁻¹ GA₃ significantly accelerated and equalized germination. Higher GA₃ concentrations had a more pronounced impact on each stage but also resulted in greater seed infection after the seed coat rupture, elongated and weak seedlings, while lower concentrations did not result in obtaining uniform seedlings. There were no significant differences observed between localities. Restoring P. peregrina through seeds and nursery-produced plants is crucial for conserving the genetic diversity of the tested species. Full article

Helleborus thibetanus is an endemic species in China with important ornamental and medicinal value. However, the seeds have dormancy, and their germination percentage is low under natural conditions. This research was carried out to determine the seed germination requirements of H. thibetanus and to characterize the type of seed dormancy. The morphological post-ripening process of the seed embryo was studied according to the morphological anatomy, and the effects of temperature and gibberellic acid (GA₃) on seed germination were investigated in H. thibetanus. The H. thibetanus seeds had a heart-shaped embryo at maturity. The embryo fully grew within the seed through warm stratification, and the embryo/seed ratio increased from 8.58% to 42.6%. The shortest time for a radicle to emerge (58.33 d) and the highest radicle emergence percentage (84.44%) were obtained at a temperature of 15 °C. The results showed that the H. thibetanus seeds had a morphophysiological dormancy. In addition, 300 mg/L GA₃ treatments shortened the time of warm stratification and increased the radicle emergence percentage. Seeds with emerged radicles could not emerge epicotyl–plumule without cold stratification, which showed that the H. thibetanus seeds had epicotyl physiological dormancy. The length of the roots, cold stratification time, and GA₃ markedly affected the release of the epicotyl physiological dormancy in H. thibetanus. The seeds with 2.5 cm roots required the shortest time to break their dormancy (50 d), and the epicotyl–plumule emergence percentage was the highest. Additionally, GA₃ treatment also shortened the incubation time in cold stratification (5 °C) and successfully broke the epicotyl physiological dormancy. Our study showed that H. thibetanus seeds exhibited deep simple epicotyl morphophysiological dormancy. Temperature, GA₃, and duration of stratification played vital roles in the seed germination of H. thibetanus. This research will provide valuable data for seed germination and practical dormancy-breaking techniques and will promote the cultivation and conventional crossbreeding of H. thibetanus. Full article

Chinese cork oak (Quercus variabilis Blume) is a widespread tree species with high economic and ecological values. Chinese cork oak exhibits epicotyl dormancy, causing emergence heterogeneity and affecting the quality of seedling cultivation. Gibberellic acid-stimulated transcript (GAST) is a plant-specific protein family that plays a crucial regulatory role in plant growth, development, and seed germination. However, their evolution in Chinese cork oak and roles in epicotyl dormancy are still unclear. Here, a genome-wide identification of the GAST gene family was conducted in Chinese cork oak. Ten QvGAST genes were identified, and nine of them were expressed in seed. The physicochemical properties and promoter cis-acting elements of the selected Chinese cork oak GAST family genes indicated that the cis-acting elements in the GAST promoter are involved in plant development, hormone response, and stress response. Germinated seeds were subjected to gibberellins (GAs), abscisic acid (ABA), and fluridone treatments to show their response during epicotyl dormancy release. Significant changes in the expression of certain QvGAST genes were observed under different hormone treatments. QvGAST1, QvGAST2, QvGAST3, and QvGAST6 exhibited upregulation in response to gibberellin. QvGAST2 was markedly upregulated during the release of epicotyl dormancy in response to GA. These findings suggested that QvGAST2 might play an important role in epicotyl dormancy release. This study provides a basis for further analysis of the mechanisms underlying the alleviation of epicotyl dormancy in Chinese cork oak by QvGASTs genes. Full article

Seed germination is among the most crucial and vulnerable stages in plant life cycles. Quercus marlipoensis is a critically endangered sclerophyllous oak. Only one population has ever been found worldwide in the tropical montane cloud forests of southeastern Yunnan, China, and it has shown difficulties with regeneration. However, its seed biological traits and key restrictive germination factors remain unknown. We investigate the impacts of scarification, temperature, and water potential on the seed germination of Q. marlipoensis. Results show that the seeds show typical epicotyl dormancy. The seed germination increased when removing part or all of the pericarp and part of the cotyledon (one-third and two-thirds). The seeds can germinate at 5 to 30 °C, but the highest T₅₀ was achieved at 25 °C. When the water potential decreased from 0 to −1.0 MPa, the germination rate decreased but the germination time increased. Q. marlipoensis seeds are typically recalcitrant and highly sensitive to moisture loss, but the species can tolerate animal predation and low germination temperatures. The more frequent climatic extremes and droughts in the Indo-China region will severely degrade its natural habitats. Therefore, ex situ conservation to preserve its germplasm and introduce seedlings into a suitable habitat are essential for its conservation management. Full article

Ecological significance of dormancy in desiccation-sensitive seeds is poorly understood. Quercus exhibits mutually exclusive occurrence of physiological (PD) and epicotyl dormancy (ePD), with no reported co-occurrence or dormancy class in other genera. We aimed to understand the dormancy in three Castanopsis species and document desiccation sensitivity and germination patterns concerning the embryonic axis position. We hypothesized that Castanopsis acorns are recalcitrant and potentially dormant. Fresh and cold-stratified acorns of Castanopsis chinensis, Castanopsis purpurella, and Castanopsis sclerophylla were subjected to desiccation and germination. Seedling emergence and internal morphology was monitored following cold (CS) and warm (WS) stratification. Fresh acorns had radicles emerge only after CS but require WS for shoot emergence. Drying to 20% moisture content led to complete death. In C. purpurella and C. sclerophylla, the embryonic axis was near the scar, and germination occurred by cracking the pericarp near the scar, which contrasts with C. chinensis. Moderate drying relieved dormancy due to the mechanical resistance of the pericarp. All three acorns were desiccation-sensitive and dormant. This is the first explicit report on PD and ePD co-occurrence in desiccation-sensitive seeds, but literature surveys allow for inference of such coexistence. CS alleviated PD and WS relieved ePD. Winter temperatures break PD, and acorns germinate during spring, but shoot emergence is delayed until summer. Our results are instructive for research on the dormancy of desiccation-sensitive species and the reproduction of Fagaceae species in subtropical forests. Full article

Paeonia emodi is a type of wild herbaceous peony with high ornamental and breeding value. Cold stratification is the only method to break its seed epicotyl dormancy to date, however, the key physiological factors during this process are not clear. In this study, rooted seeds of P. emodi were treated with 4 °C stratification, and the changes of the embryo, four nutrients, and two endogenous hormones in the seeds were investigated. The results showed that the plumule elongated at S6 (i.e., ten weeks of cold stratification), and grew to nearly the same length as the cotyledon at S9. Cold stratification increased starch consumption, significantly decreased soluble sugar content in the later stages, and decreased soluble protein content at S9, but it did not influence crude fat content. The activities of α-amylase and β-amylase increased significantly at S4 and S4 to S6, respectively. At S8 and S9, acid protease activity increased, and the increase in lipase activity continued throughout the whole process. At the same time, the ABA content decreased significantly after S6; from this stage, the ABA/GA₃ ratio gradually decreased compared with that of the control, and the difference was significant at S9. Correlation analysis showed that the ABA/GA₃ ratio was significantly correlated with starch content and α-amylase activity. It can be concluded that both carbohydrates and proteins were the energy supply for the epicotyl dormancy breaking of P. emodi seeds, rather than crude fat. Cold stratification promoted substance transformation by increasing the corresponding enzyme activities. The balance of ABA and GA₃ suggested the key stage for the release of dormancy. Full article

Control of seed germination and dormancy is important in seed plant adaptation and evolution. When studying seed dormancy of Quercus species, we observed a substantially delayed shoot emergence following a fast root emergence in Quercus chungii F.P.Metcalf. Since epicotyl physiological dormancy (PD) has not been reported in Quercus section Cyclobalanopsis, we examined seed morphology and germination in Q. chungii and aimed to document epicotyl PD in the seeds. The embryo was fully developed in fresh ripe seeds. The elongating cotyledonary petiole pushed the embryo axis out of the seed during germination, which differed from observations in other Quercus species. Shoots emerged from seeds with developing roots after 3 months of warm stratification (35/25 °C), reaching the highest percentage of shoot emergence in seeds after 5 months. Seeds were recalcitrant and displayed a yet unreported epicotyl PD type, for which we propose the formula C_nd(root) ‒ Cp’’ 2b(shoot). Early emergence and development of the root system in Q. chungii seeds with epicotyl PD appears to be a mechanism to maintain a constant water supply to the shoot during plumule development and emergence. Our documentation of seed germination will provide guidance for the conservation and restoration of this species from seeds. Full article

The daffodil Narcissus pseudonarcissus L. contains alkaloids of pharmaceutical interest. Wild daffodil populations have diverse genetic backgrounds and various genetic traits of possible importance. Developing protocols for plant production from seeds may ensure the availability of a large reservoir of individuals as well as being important for species with bulbs that are difficult to acquire. The closely related Narcissus pseudonarcissus subsp. munozii-garmendiae and subsp. nevadensis were investigated in this study because the alkaloids isolated from both are of high pharmacological interest. At the dispersal time, the seeds of both were dormant with underdeveloped embryos, i.e., morphophysiological dormancy (MPD). Experiments were conducted outdoors and under controlled laboratory conditions. Embryo growth and the percentages of radicle and seedling emergence were calculated under different temperature–light stratifications. In N. munozii-garmendiae, embryo growth occurred during warm stratification (28/14 °C or 25/10 °C) and the radicle then emerged when the temperature decreased, but the shoot was dormant. In N. nevadensis, the seeds germinated when cold stratified (5 °C) and then incubated at cool temperatures. Thus, N. munozii-garmendiae and N. nevadensis exhibit different levels of MPD, i.e., deep simple epicotyl and intermediate complex, respectively. Plant production protocols from seeds were established for both taxa in this study. Full article

The effect of the exogenous hormone and light quality on breaking hypocotyl and epicotyl dormancy was studied. The results showed that the greatest percentage of hypocotyl dormancy breaking was observed with the Murashige and Skoog (MS) medium supplemented with or without 1.0 mg·L⁻¹ gibberellin 3 (GA₃), while ABA and endosperm greatly inhibited hypocotyl dormancy breaking. This suggests that hypocotyl dormancy of the Paeonia ostii ‘Fengdan’ embryo could be easily overcome by removing constraints of the surrounding endosperm, and ABA may be one of the constraint factors contained in the endosperm. The percentage of epicotyl dormancy breaking was also greatly affected by the concentration of 6-benzylaminopurine (BA) and GA₃. Compared to BA by itself, adding GA₃ to the medium containing BA highly enhanced epicotyl dormancy breaking, with the greatest percentage of epicotyl dormancy breaking in MS medium supplemented with both 0.5 mg·L⁻¹ BA and 0.5–1.0 mg·L⁻¹ GA₃. The percentage of hypocotyl and epicotyl dormancy breaking was also affected by light and its quality. Red light-emitting diodes (LEDs) had the same effect as a dark condition on the hypocotyl dormancy breaking, while blue LEDs and a combination of red and blue LEDs had a negative effect on the hypocotyl dormancy breaking. Unexpectedly, blue LEDs greatly enhanced, whereas red LEDs inhibited, epicotyl dormancy breaking. Conclusively, a two-stage culture method was recommended for breaking the hypocotyl and epicotyl dormancy: hypocotyl dormancy was broken first using the MS medium without any plant growth regulators in the dark (25 °C), and epicotyl dormancy was subsequently broken with the MS medium supplemented with both 1.0 mg·L⁻¹ GA₃ and 0.5 mg·L⁻¹ BA under blue light. Full article