Dormancy and germination in Stachys germanica L. subsp. bithynica (Boiss.) Bhattacharjee seeds: Effects of short-time moist chilling and plant growth regulators

We investigated the germination requirements of the species Stachys germanica L. subsp. bithynica (Boiss.) Bhattacharjee (Lamiaceae). We studied the effects of scarification, short-time moist chilling (+4 °C) for 15 and 30 days, and various doses of gibberellic acid (GA₃; 0, 100, 150 and 250 ppm), Kinetin (KIN; 50 ppm) and a combination of 250 ppm GA₃ and 50 ppm KIN. The hormone and moist chilling treatments were carried out under both continuous darkness (20 °C) and photoperiodic (20/10 °C; 12/12 h, respectively) conditions. Seeds failed to germinate in response to short-time moist chilling treatments with distilled water under both continuous darkness and photoperiodic conditions. Seeds were found to have dormancy. Treatments with GA₃ or a combination of GA₃ and KIN were successful at breaking seed dormancy. A maximum of 37% of the seeds germinated after GA₃ application in all series. When only KIN was applied at a 50 ppm concentration, germination (12%) was found only with moist chilling for 30 days under continuous darkness. The highest germination rates were found in seeds treated with combination of 250 ppm GA₃ and 50 ppm KIN. In the combination treatments, while the moist chilling treatments for 15 days resulted in 68 and 73% germination, respectively, these rates were up to 95% in the moist chilling treatments for 30 days under continuous darkness and photoperiodic conditions. Mean germination time (MGT) in GA₃ and KIN combinations was lower than in other treatments. Scarification with 80% sulphuric acid did not promote germination. The characteristics of physiological dormancy of S. germanica ssp. bithynica seeds are consistent with conditions of existence in the in alpine habitat of this species.     

Suitable water temperature for seed storage of Zostera japonica for subtropical seagrass bed restoration

Restoration of Zostera japonica is needed. Laboratory culture experiments to know the germination characteristics might be helpful for implementation of actual restoration. As a part of germination experiments, we explored suitable water temperature for long-term storage of Z. japonica seeds. This work was based on earlier reports of Zostera marina, which presumably has similar physiological properties to Z. japonica. This study consisted of two experiments: (1) preservation experiments to investigate the fate of stored Z. japonica seeds and (2) germination experiments to investigate the germination potential of the stored seeds. The results of the preservation experiments suggested that seed condition, that is, germinated, degraded, unstable, stable, etc., showed variations between the seeds stored at 4 and 23 °C. The majority of the seeds stored at 4 °C were germinated, while those at 23 °C seemed to be degraded, presumably by bacteria and mold. The germination experiments suggested high germination potential of seeds stored at 4 °C even after 302 days had elapsed. In conclusion, including previously reported results on Z. marina, low temperature was suitable for the preservation of seeds to maintain germination potential.     

Morphological characteristics of annual Zostera marina shoots at various germination temperatures

The timing of the transition from seed, seedlings and development into flowering is paramount importance in annual-type Zostera marina, because flowering is the first step of sexual reproduction. A majority of plants use environmental cues to regulate the transition to their developmental stages because plants must flower synchronously for successful outcrossing and must complete their sexual reproduction under favorable external conditions. The morphological characteristics (seeds and lateral shoot production, branch number, and inflorescence length) of reproductive shoots of Z. marina L. were examined in outdoor mesocosms to better understand the reproductive strategies of annual populations. Seeds in the germination experiment were divided into two groups: those exposed to cold (7 °C; vernalized group) and those left untreated (25-21 °C; non-vernalized group). All 600 seeds (300 from each group) were cultured for 2 months at 7, 10, 15, 20, and 25 °C in an indoor incubator. In the vernalized group, the germination rates were almost significantly higher than in the non-vernalized group. However, germination rates were not significantly affected by germination temperature. In outdoor mesocosms, production of vegetative shoots was observed in plants germinated at 15 and 20 °C in the vernalized group and at 10, 15 and 20 °C in the non-vernalized group. The highest number of vegetative shoots produced (35) was observed in plants germinated at 20 °C in the vernalized group, whereas seeds of either group failed to produce vegetative shoots when germinated at a low temperature (7 °C).In the flowering phase, the number of branches per shoot in the vernalized group was significantly higher than in the non-vernalized group. The total number of spadices on the 1st branches of plants in the vernalized group (germination at 20 °C) was significantly lower than that in the non-vernalized group at the same germination temperature. The total number of spadices per reproductive shoot in the vernalized group (germination at 10 °C) was also higher than in the non-vernalized group. Thus, both low temperature (vernalization) and seed germination temperature have implications for the sexual and asexual propagation of annual Z. marina populations.     

Seed germination at different temperatures and water stress levels,and seedling emergence from different depths of Ziziphus lotus

Ziziphus lotus (L.) Lam. is a deciduous shrub with intricately branched stems in the Rhamnaceae family. It's a dominant and economically important species widely distributed in active sand dunes in the southern desert of Tunisia. To provide basic information for its conservation and reintroduction, we studied the influence of environmental factors on seed germination patterns. The germination responses of seeds were determined over a wide range of constant temperatures (10–50 °C), polyethylene glycol (PEG)-6000 solutions of different osmotic potentials (0 to − 1 MPa) and burial depths (1–10 cm). Temperatures between 15 and 45 °C seem to be favorable for the germination of this species. Germination was inhibited by either an increase or decrease in temperature from the most suitable temperature found (35 °C). The highest germination percentages (100%) were obtained under control conditions without PEG, and increasing moisture stress progressively inhibited seed germination, which was less than 5% at − 1 MPa. When tested for germination in distilled water, after PEG treatments, seeds germinated to the same extent as when fresh. When seeds buried deeply, there was a significant decrease in seedling emergence percentage and rate. Seedlings of Z. lotus emerged well at depths of 1–2 cm and could not emerge when sand burial depth was > 4 cm.     

Seed germination of Lasia spinosa as a function of temperature,light, desiccation,and storage

Lasia spinosa seeds were not dormant at maturity in early spring. The most favorable temperatures for germination were between 25 and 30 °C, and final percentage and rate of germination decreased with an increase or decrease in temperature. When L. spinosa seeds were transferred to 25 °C, after 60 days at 10 °C (where none of the seeds germinated), final germination increased from 0% to 78%. Seeds germinated to high percentage both in light and in dark, although dark germination took more than twice as long as in the light. During desiccation of seeds at 15 °C and 45% relatively humidity, moisture loss decreased exponentially from 2.02 to 0.13 g H₂O g⁻¹ dry wt within 16 days, and only a few seeds (12%) survived 0.13 g H₂O g⁻¹ dry wt moisture content. Seeds stored at 0.58 g H₂O g⁻¹ dry wt moisture content at four constant temperatures (4, 10, 15, and −18 °C) for up to 6 months exhibited a well-defined trend of decreasing viability with decreasing temperature. Thus, we concluded that freshly harvested L. spinosa seeds are non-dormant and recalcitrant. Also, the seeds with 0.58 g H₂O g⁻¹ dry wt moisture content could be effectively stored for a few months between 10 and 15 °C although the most appropriate temperature for wet storage appears to be 10 °C, as it is close to the minimum temperature for germination and so there will be less pre-sprouting compared to 15 °C.     

Induction of secondary dormancy in Amaranthus caudatus seeds

Nondormant A. caudatus seeds germinated in the darkat temperatures between 20 and 35° but not at 45 °C.Incubation at this temperature for at least 10 h inhibited seedgermination over the temperature range 20 to 35 °C,temperatures previously suitable for germination. Thus incubation at 45°C induced secondary dormancy. Mechanical or chemicalscarification or exposure to pure oxygen caused complete or almost completegermination of dormant seeds although more slowly in comparison to nondormantseeds. Secondary dormant scarified seeds required a lower concentration of ABAthan nondormant seeds to inhibit germination. The high temperature, whichinduced dormancy, 45 °C, caused the seed coat to be partiallyresponsible for secondary dormancy. Involvement of ABA (synthesis orsensitivity) in the induction and/or maintenance of this dormancy should beconsidered.     

Tolerance and recovery responses of playa halophytes to light,salinity and temperature stresses during seed germination

Halogeton glomeratus (M. Bieb.) C.A. Mey., Lepidium latifolium Linn. and Peganum harmala Linn. are distributed in temperate salt playa habitats of Upper Hunza, Pakistan. Seeds were germinated under various salinity (0–500 mM NaCl), light (12 h-light:12 h-dark and 24 h-dark) and temperature (5/15, 10/20, 15/25, 20/30, and 25/35 °C, dark/light) regimes for 20 days to determine the optimal conditions for germination and recovery of seeds from these factors when exposed to less than optimal conditions. Seeds that failed to germinate in dark were transferred successively to 12 h-photoperiod, salinity to distilled water and from various temperature regimes to 20/30 °C, to determine the effect of these stresses and the ability of these seeds to recover respectively. Highest seed germination (H. glomeratus and L. latifolium: 100%; P. harmala: 80%) was obtained in non-saline control at 20/30 °C in 12 h-photoperiod, however, increase in salinity progressively inhibited seed germination. Seed germination of H. glomeratus and P. harmala was substantially inhibited and that of L. latifolium was prevented in dark. Salinity and dark treatments have a synergistic effect in inhibiting seed germination of all species. No seed of any species germinated at 5/15 °C; germination was substantially inhibited at 25/35 °C both for H. glomeratus and P. harmala while L. latifolium failed to germinate at 25/35 °C. Rate of germination also decreased with an increase in salinity at all temperature regimes but this effect was minimal at optimal temperature regime of 20/30 °C. After successive elimination of light, salinity and temperature stresses, final seed germination was identical to respective controls. The results indicate that seeds of these temperate halophytes could endure environmental stresses without losing viability and germinate readily when these stresses are removed. Under the extremely variable conditions of the playa habitat these species are highly opportunistic exploiting the windows of opportunity available during spring or early summer.     

Effects of seed burial on germination,protein mobilisation and seedling survival in Dodonaea viscosa

Ecological restoration of disturbed areas requires substantial knowledge of the germination of native plants and the creation of novel methods to increase seedling establishment in the field. We studied the effects of soil matrix priming on the germination of Dodonaea viscosa seeds, which exhibit physical dormancy. To this end, we buried both pre‐scarified (in H₂SO₄, 3 min) and non‐pre‐scarified seeds in the Parque Ecológico de la Ciudad de México. After seeds were unearthed, they were post‐scarified for 0, 2, 6 and 10 min and their germination percentages compared to the germination of a control batch of laboratory‐stored seeds. For both control and unearthed seeds, the protein pattern was determined in the enriched storage protein fraction in SDS‐PAGE gels stained with Coomassie blue. Percentage germination increased as the scarification time increased. Pre‐scarification significantly increased percentage germination of post‐scarified seeds in relation to the control and non‐pre‐scarified seeds. In seeds unearthed from the forest site, the buried pre‐scarified seeds had relatively high percentage germination, even in the absence of post‐scarification treatment. A 48‐kDa protein was not found in unearthed, pre‐scarified seeds nor in the control germinated seeds, indicating that mobilisation of this protein occurred during soil priming. Burying seeds for a short period, including the beginning of the rainy season, promoted natural priming, which increased protein mobilisation. Functionally, priming effects were reflected in high percentage seedling survival in both the shade house and the field. Seed burial also reduced the requirement for acidic post‐scarification.     

Breaking Setaria parviflora seed dormancy by nitrates and light is part of a mechanism that detects a drawdown period after flooding

We explored the hypothesis that, in flood-prone habitats, nitrates can signal to seeds that a drawdown period has begun. To investigate this issue, Setaria parviflora (Poir.) Kerguélen seeds were buried in a never-flooded upland and a nearby, flood-prone lowland grassland. Seeds were exhumed during the flooding period. Additionally, grassland mesocosms with buried S. parviflora seeds were flooded during 20 d (controls drained). After both field and mesocosm pretreatments germination was assayed in laboratory at 25 °C in a medium with or without nitrates, under red light pulses or in darkness. Seeds exhumed from the never-flooded upland showed no specific requirements to germinate. In contrast, seeds exhumed from the flooded lowland germinated ca. 65% when nitrates were combined with red light pulses, significantly higher than in the rest of the treatments. Seeds exhumed from drained mesocosms germinated equally in all treatments. However, in the seeds exhumed from the flooded mesocosms, nitrates increased germination by more than 20% compared with seeds imbibed in water. Seeds germinated ca. 85% when nitrates were combined with red light pulses, significantly higher than in the other treatments. We can conclude that after flooding, S. parviflora seeds require nitrate and light to germinate. Therefore, a large fraction of seeds do not germinate unless nitrates are combined with light, indicating a drawdown period after floods and vegetation gaps.     

Effects of pre-treatments and temperature on seed viability and germination of Juniperus macrocarpa Sm.

The effects of collecting season, collection site, laboratory pre-treatments and temperatures on seed viability and germination of Juniperus macrocarpa were investigated. Ripe cones were collected in four Sardinian dune systems, in two seasons, from plant and soil. Warm (W) and cold (C) stratifications, two combinations of them (W + C, C + W), and no pre-treatment (0) were applied. Seeds were incubated in a range of constant (10–25 °C) and an alternating (25/10 °C) temperature regime. Seed viability was low (ca. 40%) and varied significantly according to the collecting season. Seed germination was also low (ca. 10%), the 0 and W were the most effective pre-treatments on stimulating germination. The best germination temperature, without any pre-treatment, was 15 °C (ca. 20%). J. macrocarpa seeds are dormant and the achieved results suggested that the presence of secondary dormancy is induced by cold stratification. Spring appeared to be the best season for seed collecting, whereas autumn was the best for sowing. These results give new findings for restoration activities on this species.     

Seed germination in Marathrum schiedeanum and M. rubrum (Podostemaceae)

Marathrum schiedeanum and Marathrum rubrum are annual Podostemaceae, thus their seeds are important to their dispersal and persistence in their habitat. We assessed the effect on germination of (1) light (white, red and far red) and darkness, (2) temperature (15, 20, 25, 30 °C and alternating 20/30 °C), (3) osmotic potential (0 to −0.8 MPa), (4) proximity to moisture sources and (5) seed storage. Seeds of M. schiedeanum and M. rubrum were non-dormant and had a high germination capacity (96%). Seeds were positive photoblastic; at 15 °C germination drop to zero, and germination rate was slower at 20 °C and at 20/30 °C than at 25 °C. A small proportion of seeds of both species germinated even at osmotic potentials as low as −0.6 MPa (11%) for M. rubrum and −0.8 MPa (70%) for M. schiedeanum. Seeds germinated only when near to the source of moisture (91.3–87.1% and 53.3–35.6% for M. schiedeanum and M. rubrum, respectively) and 2 years in dry storage did not modify their capacity to germinate. At the beginning of the rainy season, light and temperature in the rivers may be high enough for germination. The ability to germinate at low osmotic potential may be related to early germination during the rainy season. This may be because the seed mucilage assists in diffusion of water from the substrate to the seed. Both species germinated faster at −0.06 MPa, than in distilled water, which may indicate appropriate conditions for germination of these short-lived species.     

Seed Dormancy,Seedling Establishment and Dynamics of the Soil Seed Bank of Stipa bungeana (Poaceae) on the Loess Plateau of Northwestern China

Studying seed dormancy and its consequent effect can provide important information for vegetation restoration and management. The present study investigated seed dormancy, seedling emergence and seed survival in the soil seed bank of Stipa bungeana, a grass species used in restoration of degraded land on the Loess Plateau in northwest China. Dormancy of fresh seeds was determined by incubation of seeds over a range of temperatures in both light and dark. Seed germination was evaluated after mechanical removal of palea and lemma (hulls), chemical scarification and dry storage. Fresh and one-year-stored seeds were sown in the field, and seedling emergence was monitored weekly for 8 weeks. Furthermore, seeds were buried at different soil depths, and then retrieved every 1 or 2 months to determine seed dormancy and seed viability in the laboratory. Fresh seeds (caryopses enclosed by palea and lemma) had non-deep physiological dormancy. Removal of palea and lemma, chemical scarification, dry storage (afterripening), gibberellin (GA₃) and potassium nitrate (KNO₃) significantly improved germination. Dormancy was completely released by removal of the hulls, but seeds on which hulls were put back to their original position germinated to only 46%. Pretreatment of seeds with a 30% NaOH solution for 60 min increased germination from 25% to 82%. Speed of seedling emergence from fresh seeds was significantly lower than that of seeds stored for 1 year. However, final percentage of seedling emergence did not differ significantly for seeds sown at depths of 0 and 1 cm. Most fresh seeds of S. bungeana buried in the field in early July either had germinated or lost viability by September. All seeds buried at a depth of 5 cm had lost viability after 5 months, whereas 12% and 4% seeds of those sown on the soil surface were viable after 5 and 12 months, respectively.     

Cold stratification,light and high seed density enhance the germination of Ottelia alismoides

The effects of cold stratification, light and seed clustering in petri dish on Ottelia alismoides seed germination were investigated. The seeds required light and an extended cold period in order to germinate, but neither treatment alone was effective. Seed germination significantly increased with length of the 4 °C cold stratification period. Freshly collected seeds failed to germinate while a 5-month period at 4 °C yielded 29 ± 9% germination in the light, but none in the dark. Treatment with sodium nitroprusside, a nitric oxide source, failed to promote germination in the light or dark. Seeds of O. alismoides showed an unusual and significant positive response to aggregation. Germination in the light, after 5-month 4 °C cold stratification, was stimulated to almost five-fold in the dishes that were more densely sown with seed (20 seeds versus 200 seeds). Likewise, clustering seeds in dense aggregations stimulated germination significantly. Germination more than quadrupled with an increase from 1 to 50 seeds per cluster (200 seeds per dish), reaching a value of 72 ± 4%. Linear regression analysis shows the correlation between seed cluster density (no. per cluster) and germination rate (%) was highly significant (R² = 0.85, P = 0.000). The extended cold stratification requirement is probably an over-wintering device. The mechanism of the density-dependent stimulation is unclear.     

Germination of stored and scarified seeds of Passiflora caerulea L. (Passifloraceae)

Abstract

This work evaluates the influence of storage and scarification in the germination of Passiflora caerulea L., in order to acquire the necessary knowledge to cultivate this economically important species. Seeds stored one month under different conditions (no storage, fermentation, desiccation) were submitted to various pre‐treatments (aril removal, mechanical and chemical scarification or combinations of these). Emergence was recorded periodically for 11 months in a greenhouse. Germination time, germination percentage and germination speed were calculated. Histochemical tests were applied to seeds maintained under the three storage conditions, for observing possible changes in the integument and storage tissue. Viability was maintained at least for the storage period tested, as germination occurred after that time. Because the seeds stored under desiccation germinated, the species is orthodox. Chemical scarification prevented germination in most cases. Although germination levels were low, they were higher in stored seeds (fermented and desiccated) than in fresh ones. Fermented seeds (which exhibited no storage tissue and less lignin in the integument) devoid of the aril germinated earlier, faster and in greater quantity. The type of dormancy of this species is discussed.     

Fire and flood: Soil‐stored seed bank and germination ecology in the endangered Carrington Falls Grevillea (Grevillea rivularis,Proteaceae)

Abstract Seed germination is dependent on the interaction between the dormancy state of a seed and the presence of favourable environmental conditions. Thus, the spectacular pulse of seedling recruitment in many Australian vegetation communities following disturbances such as fire can be attributed to changes in microsite conditions and/or the dormancy‐breaking effect of the disturbance on accumulated seed banks. Grevillea rivularis is a threatened species endemic to the area immediately above Carrington Falls in the NSW Southern Highlands. Most of the population is confined to the riparian vegetation zone in woodland and heath, and is therefore subject to periodic disturbance from fire and flood. For this species, a pulse of seedling recruitment has been recorded after fire, flood and mechanical soil disturbance. The aims of this study were to examine the density and vertical distribution of the soil‐stored seed bank and to investigate the role of heat and scarification as cues for germination of fresh and soil‐stored seed. There was a large seed bank under the canopies of established individuals (194 ± 73 seeds m^?2) and most seeds were found in the 0–2 cm and leaf‐litter layers of the soil profile. The germination response of soil‐stored and fresh seed was examined using a hierarchical series of laboratory experiments. Seeds of G. rivularis showed marked dormancy polymorphism. Thirty‐six percent of soil‐stored seed germinated without treatment, whereas no untreated fresh seeds germinated. Scarification or heating caused significant germination of dormant soil‐stored seed, but only scarification resulted in germination of dormant fresh seeds. These results highlight important differences in the dormancy state of soil‐stored and fresh seed. Thus, being a riparian species in a fire‐prone environment, the dormancy mechanisms in seeds of G. rivularis suit this species to disturbance by both fire and flood.     

Thermal thresholds as predictors of seed dormancy release and germination timing: altitude-related risks from climate warming for the wild grapevine Vitis vinifera subsp. sylvestris

Background and Aims

The importance of thermal thresholds for predicting seed dormancy release and germination timing under the present climate conditions and simulated climate change scenarios was investigated. In particular, Vitis vinifera subsp. sylvestris was investigated in four Sardinian populations over the full altitudinal range of the species (from approx. 100 to 800 m a.s.l).

Methods

Dried and fresh seeds from each population were incubated in the light at a range of temperatures (10–25 and 25/10 °C), without any pre-treatment and after a warm (3 months at 25 °C) or a cold (3 months at 5 °C) stratification. A thermal time approach was then applied to the germination results for dried seeds and the seed responses were modelled according to the present climate conditions and two simulated scenarios of the Intergovernmental Panel on Climate Change (IPCC): B1 (+1·8 °C) and A2 (+3·4 °C).

Key Results

Cold stratification released physiological dormancy, while very few seeds germinated without treatments or after warm stratification. Fresh, cold-stratified seeds germinated significantly better (>80 %) at temperatures ≥20 °C than at lower temperatures. A base temperature for germination (T_b) of 9·0–11·3 °C and a thermal time requirement for 50 % of germination (θ₅₀) ranging from 33·6 °Cd to 68·6 °Cd were identified for non-dormant cold-stratified seeds, depending on the populations. This complex combination of thermal requirements for dormancy release and germination allowed prediction of field emergence from March to May under the present climatic conditions for the investigated populations.

Conclusions

The thermal thresholds for seed germination identified in this study (T_b and θ₅₀) explained the differences in seed germination detected among populations. Under the two simulated IPCC scenarios, an altitude-related risk from climate warming is identified, with lowland populations being more threatened due to a compromised seed dormancy release and a narrowed seed germination window.     

Control of macaw palm seed germination by the gibberellin/abscisic acid balance

The hormonal mechanisms involved in palm seed germination are not fully understood. To better understand how germination is regulated in Arecaceae, we used macaw palm (Acrocomia aculeata (Jacq.) Lodd. Ex Mart.) seed as a model. Endogenous hormone concentrations, tocopherol and tocotrienol and lipid peroxidation during germination were studied separately in the embryo and endosperm. Evaluations were performed in dry (D), imbibed (I), germinated (G) and non‐germinated (NG) seeds treated (+GA₃) or not treated (control) with gibberellins (GA). With GA₃ treatment, seeds germinated faster and to a higher percentage than control seeds. The +GA₃ treatment increased total bioactive GA in the embryo during germination relative to the control. Abscisic acid (ABA) concentrations decreased gradually from D to G in both tissues. Embryos of G seeds had a lower ABA content than NG seeds in both treatments. The GA/ABA ratio in the embryo was significantly higher in G than NG seeds. The +GA₃ treatment did not significantly affect the GA/ABA ratio in either treatment. Cytokinin content increased from dry to germinated seeds. Jasmonic acid (JA) increased and 1‐aminocyclopropane‐1‐carboylic acid (ACC) decreased after imbibition. In addition, α‐tocopherol and α‐tocotrienol decreased, while lipid peroxidation increased in the embryo during germination. We conclude that germination in macaw palm seed involves reductions in ABA content and, consequently, increased GA/ABA in the embryo. Furthermore, the imbibition process generates oxidative stress (as observed by changes in vitamin E and MDA).     

Dormancy,viability and germination of Magnolia lanuginosa (Wall.) Figlar & Noot. seeds: A threatened tree species of Northeast India

The population of Magnolia lanuginosa a rare tree species of northeastern India has declined drastically owing to habitat destruction, low natural regeneration and over harvesting for its multipurpose uses. The present study was carried out to understand the type of dormancy and analyse the effect of storage on viability and germination behaviour of M. lanuginosa under various physical and chemical treatments. Seeds subjected to physical treatments such as water (cold, hot, and boiling), acid (H₂SO₄) and manual scarification failed in breaking dormancy. Seeds treated with growth regulators (GA₃) had a significant effect on germination. It reduced the germination time and the shortest T₅₀ was observed in seeds treated with 2000 mg/l of GA₃ (non-scarified seeds) and 1000 mg/l of GA₃ (scarified seeds). The use of KNO₃ did not have any significant effect in breaking dormancy. However, the use of KNO₃ along with GA₃, increased the germination percentage. Seeds cold stratified (CS) for 60 days at 5 °C was effective in breaking dormancy and resulted in 84.26% germination. This indicates the prevalence of Type-1 Non deep physiological dormancy in M. lanuginosa seeds that requires a crucial CS period for proper embryo growth and development. The seeds stored in moist sand at 5 °C remained viable even after 120 days with 48.88% viability. The study would be helpful in devising seed germination protocols for mass production and reintroduction of the species into the wild.     

The effect of temperature, water level and burial depth on seed germination of Myriophyllum spicatum and Potamogeton malaianus

The effects of temperature, water level and burial depth on seed germination of two submerged species, Myriophyllum spicatum and Potamogeton malaianus, were investigated under controlled laboratory conditions. There was no significant difference in final germination of M. spicatum among water level treatments, but P. malaianus germinations at 1 cm and 12 cm water levels were better than at 0 cm water level at temperatures of 20 °C and 30 °C. Little to no germination was observed for either species at the temperature of 10 °C. At 15 °C, however, germination increased significantly to 66.3-70.6% for M. spicatum and to 29.4-48.1% for P. malaianus under all three water level treatments. Increased temperature from 15 °C to 30 °C had no significant effect on the final germination of M. spicatum except at the 1 cm water level, but enhanced significantly the germination of P. malaianus. Analysis of the mean time to germination revealed that M. spicatum was a faster germinator relative to P. malaianus. The two species’ germination differed markedly in response to burial depth. Germination percentage of M. spicatum was 71.3% at 0 cm burial depth, but decreased to 5.0% and to 2.5% at depths of 1 cm and 2 cm, respectively; whereas germination percentages of P. malaianus were 40.0%, 23.8%, 12.5%, 7.5% and 1.3% at depths of 0 cm, 1 cm, 2 cm, 3 cm and 5 cm, respectively. We concluded that the two species respond differently to germination strategies. The findings provided further insight into how germination strategy contributes to the seed bank formation and species invasion.     

Proteomic analysis of response to long-term continuous stress in roots of germinating soybean seeds

Germination is a complex process, highly dependent on various environmental factors, including temperature and water availability. Germinating soybean seeds are especially vulnerable to unfavorable environmental conditions and exposure to long-term abiotic stresses may result in diminishing much of the yield and most importantly – restrained germination. In the present study, a proteomic approach was employed to analyze influence of cold and osmotic stress on roots of germinated soybean (Glycine max, L.) seeds. Seeds were germinating under continuous conditions of cold stress (+10 °C/H₂O), osmotic stress (+25 °C/−0.2 MPa) as well as cold and osmotic stress combined (+10 °C/−0.2 MPa). Proteome maps established for control samples and stress-treated samples displayed 1272 CBB-stained spots. A total of 59 proteins, present in both control and stress-treated samples and showing significant differences in volume, were identified with LC/nanoESI-MS. Identified proteins divided into functional categories, revealed 9 proteins involved in plant defense, 8 proteins responsible for plant destination and storage and 10 proteins involved in various tracks of carbohydrate metabolism. Furthermore, a number of proteins were assigned to electron transport, range of metabolic pathways, secondary metabolism, protein synthesis, embryogenesis and development, signal transduction, cellular transport, translocation and storage. By analyzing differences in expression patterns, it was possible to trace the soybean response to long-term abiotic stress as well as to distinguish similarities and differences between response to cold and osmotic stress.