Final Germination Rate Research Articles

Mating patterns in an indoor miniature Cryptomeria japonica seed orchard as revealed by microsatellite markers

To evaluate the practical application of an indoor seed orchard, we compared the seed production, final germination rates and mating patterns of potted Cryptomeria japonica D. Don clones in two miniature seed orchards: one in a glasshouse and the other outdoors. There was no statistically significant difference in total seed production between the orchards (P = 0.275, ANOVA). However, the final germination rate of seeds produced in the indoor orchard was significantly lower than that of seeds produced in the outdoor orchard (P < 0.01, Wilcoxon test). The average self-fertilization rate was higher in the indoor orchard (27.2%) than in the outdoor orchard (5.6%), and this parameter was strongly associated with the reduced final germination rates of the seeds harvested in the glasshouse. Pollen contamination was considerably lower in the indoor seed orchard (48.9% in the outdoor seed orchard and 4.4% in the indoor seed orchard). χ2 tests indicated that the paternal contributions of each constituent clone differed significantly in both orchards (P < 0.001 in both cases). The strong variations in paternal contributions among indoor orchard clones was significantly correlated with their respective pollen production capacities (Spearman ρ = 0.693, P < 0.001). To reduce the high self-fertilization rates, we recommend the use of orchard clones with similar pollen production capacity in indoor seed orchards.

Seed dormancy and germination of three herbaceous perennial desert ephemerals from the Junggar Basin, China

AbstractThe purpose of our study was to better understand seed germination ecology of the spring ephemeral herbaceous perennials,Ixiolirion tataricum,Tulipa iliensisandScorzonera pusilla, in the temperate desert in the Junggar Basin of northwestern China. Seeds ofI. tataricum,T. iliensisandS. pusillawere dormant at maturity but when subjected to cold, dry (2 months at 4°C) followed by cold, wet ( ≤ 40 days at 4°C) conditions, they germinated to 100%, 96% and 93%, respectively. After 2 months' dry storage at 4°C, seeds germinated to only 11%, 3% and 42%, respectively at 15°C, and no seeds germinated at 30°C. Seeds of the three species were not sensitive to light. Low ( &lt; 12.7%) and high (21.4%) soil moisture contents suppressed germination. In addition, both final germination percentages and rates of the three species decreased dramatically with a decrease in water potential from 0 to − 3.17 MPa. Thus, the low-temperature requirement for dormancy break and germination cues seed germination to occur in early spring when soil moisture is favourable for germination and subsequent seedling establishment.

Germination Responses of Purpletop and Big Bluestem Caryopses Subjected to Distilled Water or Potassium Nitrate Prechilling, Sodium Hypochlorite, and Storage

Purpletop [Tridens flavus (L.) Hitchc.] and big bluestem (Andropogon gerardii Vitman) are incorporated into native grass seed mixes for use in ecological restoration. Alleviation of low seed vigor and poor stand establishment would benefit the restoration process by increasing the animal habitat in restored zones. This study determined the effectiveness of prechilling with distilled water (dH2O) versus potassium nitrate (KNO3), sodium hypochlorite (NaOCl) treatments, and short-term storage conditions on seed germination, seedling growth, and stand establishment of purpletop and big bluestem. Prechilling of ‘Niagara, NY Ecotype’ big bluestem for 7 days at 5 °C in dH2O increased final germination percentage (FGP) and germination rate provided caryopses were not dried before sowing. Optimal FGP, germination rate, and germination synchrony were obtained for ‘VA Ecotype’ purpletop after prechilling for 14 days at 5 °C in dH2O without subsequent caryopsis drying or at 0.2% KNO3 with or without subsequent caryopsis drying. Prechilling increased germination synchrony for purpletop but not for big bluestem. NaOCl treatments did not enhance germination or seedling vigor of purpletop or big bluestem. Using nonstored, prechilled caryopses resulted in greater root lengths than stored caryopses or nontreated controls, although optimal purpletop growth required that they be sowed moist, whereas optimal big bluestem growth required that they be dried-back before sowing. In greenhouse experiments, higher seeding rates were correlated with increased number of seedlings for nontreated or prechilled big bluestem and for prechilled purpletop, but not for nontreated purpletop, which had poor stand establishment at all seeding rates. The results indicate that prechilling of caryopses before incorporation into a warm-season grass seed mix increased seedling establishment of purpletop but not big bluestem.

Effect of Light and Moisture Conditions and Seed Age on Germination of Three Closely Related Myosotis Species

Germination of three closely related species from the Myosotis palustris group (M. nemorosa, M. palustris subsp. laxiflora, M. caespitosa) differing in their habitats and capacity for clonal growth, was compared in two greenhouse experiments. To evaluate both inter- and intraspecific variation, each species was represented by seeds from several populations. Final germination percentage and germination rates T50 were compared both between species and populations within species. In the first experiment, we studied the influence of two external factors, moisture and light. Four moisture levels (dry, wet, periodically flooded and permanently flooded soil) and three types of shading (without shading, shaded with green foil, shaded with solid paper sheet) were combined in a complete factorial design. In all three species, total germination percentage was the same in the three wettest treatments, and decreased in the dry treatment. Germination in the treatments shaded with green foil (simulating vegetation cover, which changed light quality) was significantly slower than in treatments without shading and treatments shaded with a solid paper sheet. There were significant differences among species, but we also found very pronounced differences among populations within a species. M. caespitosa had the uniformly highest germination percentage (reaching in some cases 100%) and also fastest germination. Germination of M. palustris subsp. laxiflora populations was slower and reached lower final proportions, and medium variability among populations. Inter-population variability in the final germination percentage was highest, and the final germination the lowest in M. nemorosa. In addition, M. nemorosa, a species typical for permanent meadow communities was delayed by permanent flooding. In the second experiment, we studied the effects of seed age and storage conditions. Three combinations of seed age and storage were used: younger seeds (half year old) with no-chilling, younger seeds with chilling and old seeds (three years old) with chilling. M. caespitosa had again the highest final germination percentage and fastest germination rates T50. In addition, final germination percentage of this species slightly increased with seed age, whereas it decreased in the other two species. The germination behaviour corresponded well to expectation based on species life histories and habitat preferences. Remarkably stable and high germination percentages and fastest germination rates T50 were ascertained in M. caespitosa, a species of disturbed habitats, with lowest capacity for clonal spread. M. palustris subsp. laxiflora (species with highest clonal capacity) and M. nemorosa (species with medium clonal potential) achieved lower, but still very high final germination percentage. In addition, M. nemorosa showed the highest inter-populations variability in our experiments.

Quantitative trait loci associated with lettuce seed germination under different temperature and light environments.

Temperature and light are primary environmental cues affecting seed germination. To elucidate the genetic architecture underlying lettuce (Lactuca sativa L.) seed germination under different environmental conditions, an F8 recombinant inbred line population consisting of 131 families was phenotyped for final germination and germination rate. Seeds were imbibed in water at 20 degrees C under continuous red light (20-Rc), 20 degrees C continuous dark (20-Dc), 31.5 degrees C continuous red light (31.5-Rc), 31.5 degrees C continuous dark (31.5-Dc), or 20 degrees C far-red light for 24 h followed by continuous dark (20-FRc-Dc). Thirty-eight quantitative trait loci (QTL) were identified from two seed maturation environments: 10 for final germination and 28 for germination rate. The amount of variation attributed to an individual QTL ranged from 9.3% to 17.2% and from 5.6% to 26.2% for final germination and germination rate, respectively. Path analysis indicated that factors affecting germination under 31.5-Rc or 31.5-Dc are largely the same, and these appear to differ from those employed under 20-FRc-Dc. QTL and path analysis support the notion of common and unique factors for germination under diverse temperature and light regimes. A highly significant effect of the seed maturation environment on subsequent germination capacity under environmental stress was observed.

Salinity, temperature and light affect seed germination of Haloxylon salicornicum, a common perennial shrub of the Arabian deserts

Summary Haloxylon salicornicum (Moq.) Bunge ex Boiss. has been considered as one of the most promising species for re-seeding deteriorating desert range vegetation, and for sand dune fixation in the Arabian deserts. However, plant communities dominated by this species have become seriously degraded due to overgrazing. Reseeding degraded communities with this species requires information about light and temperature requirements and salinity tolerance at different temperatures of its seed germination. Seeds were germinated in saline concentrations (up to 800 mM NaCl) in incubators adjusted to 15, 20, 25 and 30°C, in both continuous light and dark. In non-saline treated seeds, germination in light conditions was similar for temperatures up to 25°C, but declined significantly at 30°C. Germination in darkness at either 15 or 20°C was significantly greater than at 25 and 30°C. Both final germination percentage and germination rate decreased as salinity increased. In higher salinity levels (500 – 700 mM), germination at moderate temperatures was greater than at both lower and higher temperatures. Recovery germination decreased as temperature increased. The lower salinity tolerance during germination in

Promotion by 5-aminolevulenic acid of pepper seed germination and seedling emergence under low-temperature stress

The effects of incorporating 5-aminolevulenic acid (ALA) into the priming solution on low-temperature germination and emergence percentage performance of red pepper ( Capsicum annuum cv. Sena) seeds before and after seed storage were investigated. Seeds were primed in 3% KNO 3 solution for 6 days at 25 °C in darkness containing 0 ppm, 1 ppm, 10 ppm, 25 ppm, 50 ppm or 100 ppm ALA. Following priming, seeds were either immediately subjected to germination and emergence tests at 15 °C or stored at 4 °C or 25 °C for 1 month after which they were subjected to germination and emergence tests at 15 °C. Priming pepper seeds in the presence of ALA improved final germination percentage (FGP) and germination rate (MGT) at 15 °C compared to non-primed seeds. The highest FGP was obtained from seeds primed in the presence of 25 ppm and higher ALA concentrations while the highest MGT was obtained from seeds primed in KNO 3 supplemented with 10 ppm ALA. Emergence percentages were the highest for the seeds primed in the presence of 25 ppm ALA and 50 ppm ALA while non-primed seeds had the lowest emergence percentage. Highest emergence rates (MET) and heaviest seedlings were also obtained from seeds primed in KNO 3 supplemented with 50 ppm ALA. Although all priming treatments improved germination and emergence performance of pepper seeds at 15 °C following 1 month of storage under two different temperatures, inclusion of 25 ppm and 50 ppm ALA into the priming solution resulted in higher germination and emergence percentages and faster germination and emergence compared to seeds primed in KNO 3 only and non-primed seeds. These results indicate that priming seeds in 25 ppm and 50 ppm ALA incorporated into the KNO 3 solution can be used as an effective method to improve low-temperature performance of red pepper seeds and that these seeds can be stored for 1 month at 4 °C or 25 °C and still exhibit improved germination and emergence performance at 15 °C.

Note on organic dormancy of estuarine Ruppia maritima L. seeds

Information on seed dormancy is one of the primary requirements for successful seedling propagation of submerged aquatics and seagrass. Studies on Ruppiamaritima seed germination have been done, but the presence, requirements, and the types of dormancy have not been well understood. A laboratory study was conducted to understand presence and types of organic dormancy of the seeds of estuarine R. maritima collected from Lake Pontchartrain, Louisiana, USA. Our study results indicate that the brackish estuarine R. maritima population produces seeds that do not have any noticeable initial morphological, physical, and physiological dormancy. Although dry stratification reduced seed viability and final germination rates, drying seems to induce an earlier germination in R. maritima. Desiccation also appears to induce an environmental dormancy that can be disrupted by exposure to water. Further study on environmental dormancy is needed to provide information to develop methods for long-term seed storage that can be employed in greenhouse seedling propagation.

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 H 2O g −1 dry wt within 16 days, and only a few seeds (12%) survived 0.13 g H 2O g −1 dry wt moisture content. Seeds stored at 0.58 g H 2O 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 H 2O 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.

Ecological efficiency and legitimacy in seed dispersal of an endemic shrub ( Lithrea caustica) by the European rabbit ( Oryctolagus cuniculus) in central Chile

The European rabbit ( Oryctolagus cuniculus) is an alien herbivore in central Chile. Although its diet is poorly studied, this rabbit is known to consume native fruits and seeds, and thus it could act as a seed-dispersal agent. We evaluated the effect of endozoochory by rabbits on the survival and germination of seeds of a native shrub ( Lithrea caustica, Anacardiaceae), as well as its consequences for seed dispersal. We extracted seeds by hand from parental shrubs, and compared the germination dynamics of seeds passing once and twice throughout the rabbit's gut (simulating its coprophagy) versus control treatments (seeds not consumed). Additionally, in permanent 2×2 m sampling plots placed in the wild, we evaluated the abundance of L. caustica seedlings and of its seeds in rabbit droppings. Results indicate that rabbits reduced seed survival to 82% on average with the first gut passage, and to an additional 52% with a second passage. Nevertheless, germination variables such as initiation time and germination, as well as final germination rate, increased significantly in comparison to non-ingested seeds. Sampling plots showed that L. caustica seedlings were concentrated principally underneath woody patches, which are then regarded as safe sites. Outside shrub cover, seedling abundance small, this indicates that open places are unsafe sites. We recorded that feces (and seeds contained) were deposited in higher proportion beneath woody cover. Thus, the native shrub L. caustica may be dispersed by alien rabbits through endozoochory, which provides legitimacy and efficiency in this dispersal service. Alien rabbits may fill a similar role played by native mammals, which have been reduced in abundance by human agency in central Chile. We suggest that the generalist syndrome, common among plants and dispersers, may be an arena of positive effects in ecological interactions between alien and native species.

Response of Transgenic Rice at Germination and Early Seedling Growth Under Salt Stress

The response of germination and early seedling growth of different transgenic rice lines (T-99, T-112, T-115 and T-121) were examined in different levels of salinity (0, 50, 100 and 150 mM NaCl). Final germination, germination rate (1/t50, where t50 is the time to 50% of germination) and early seedling growth were assessed. Final germination percentage was inhibited with increasing salt concentrations. The required time for germination also increased with increasing salinity levels. The seedling growth was also reduced by salt concentrations, particularly at 150 mM. Root and shoot lengths, root/shoot ratio, fresh weights of root and shoot were also decreased with increasing salt stress. T-99 and T-112 had shown greater performance at germination and early seedling growth as compared to other transgenic lines.

RETRACTED: Incorporation of Plant Growth Regulators into the Priming Solution Improves Sugar Beet Germination, Emergence and Seedling Growth at Low-Temperature

In a series of experiments, impact of inclusion of plant growth regulators into the KNO3 priming solution on low temperature seed germination, emergence percentage and seedling growth of sugar beet was investigated. Seeds were primed in 3% KNO3 solution for 6 days at 25 degrees C in darkness containing one of the following: 0, 0.05, 0.1, 0.5, or 1 mM acetyl salicylic acid (ASA) or 1, 3, 5 or 10 microM methyl jasmonated (MeJA). A non-primed treatment was also included in the experiment. Priming seeds in the presence or absence of plant growth regulators in general improved final germination percentage (FGP), germination rate (G50) and germination synchrony (G10-90) at 15 degrees C compared with non-primed seeds which had an FGP of 42%, G50 of 11.3 days and G10-90 of 11.7 days. Priming seeds in KNO3 solution containing 0.05 mM of ASA resulted in the highest germination percentage (89%), fastest germination rate (G50 = 5.3 days) and the most synchronous germination (G10-90 = 10.7 days). Emergence percentages were the highest for the seeds primed in the presence of 0.05 mM ASA (83%) and 3 microM MeJA (81%) while non-primed seeds had an emergence percentage of 40%. Fastest emergence rate (E50) were also obtained from seeds primed in KNO3 supplemented with 3 microM MeJA (E50 = 14.4 days) and 0.05 mM ASA (E50 = 14.4 days). Shoot fresh and dry weight of seedlings were significantly affected by treatments and priming in the presence of 0.05 mM ASA resulted in highest seedling shoot fresh and dry weight. These results indicate that priming seeds in 0.05 mM of ASA or 3 microM MeJA incorporated into the KNO3 solution can be more effective than KNO3 alone to improve low temperature germination performance of seeds and subsequent seedling growth.

Salinity, temperature and light affect germination of Salsola imbricata

Salsola imbricata (Chenopodiaceae) is a common succulent dwarf shrub growing in the coastal ecosystems of the Arabian Gulf region. The impacts of light, temperature and salinity were evaluated for fresh seeds collected from a big population on coastal sand dunes in the United Arab Emirates (UAE). Seeds were germinated in seven salinities (0, 100, 200, 300, 400, 500 and 600 mM NaCl) at 15, 20, 25 or 35°C. The highest germination was at 20°C (77.5%) and the lowest was at 35°C (23.3%). Germination in dark was significantly greater than in light at 15°C, but no significant difference was observed at the other temperatures. Both final germination and germination rate decreased with the increase in salinity. Salinity tolerance during germination depended on temperature. The highest tolerance achieved at 20°C. Most of the non-germinated seeds at the different salinities recovered their germination when transferred to distilled water. Germination recovery was significantly greater at 15°C and significantly lower at 35°C than other temperatures. The ability of S. imbricata seeds to maintain their viability during exposure to seawater salinity level (600 mM NaCl) and to recover their germination after transfer to distilled water indicates that the effect of NaCl is more likely to be a reversible osmotic inhibition of germination, rather than ion specific toxicity.

Seed germination in Miconia theaezans (Bonpl.) Cogniaux (Melastomataceae)

The effects of light and temperature were studied on the seeds of Miconia theazeans by isothermic and alternating temperature incubations. The optimum temperature for seed germination was determined by final percentage and germination rates as located in the range of 27.5 to 30 °C and by germination kinetics at the range of 19.5 to 30 °C. The germination was dependent on diffusion processes. The minimum and maximum temperatures were 12.5-15°C and 32.5-35°C, respectively. The seeds showed strong light dependence for germination with the necessity of daily 4-6 h white light irradiation for the maximum induction of germination. However, under 30-20 °C alternating temperatures, daily 2 hours white light was enough to induce germination and attained maximum under 4 h photoperiod. The results indicated that M. theazeans presented characteristics of early successional species.

Salt Stress Inhibits Germination and Early Seedling Growth in Cabbage (Brassica oleracea capitata L.)

Salinity induced inhibition in germination and early stages of cabbage (Brassica oleracea capitata L.) [two varieties (autumn cabbage and spring cabbage)] were measured in response to increasing NaCl concentration. The salinity (NaCl) concentrations in solution were 0 (control), 4.7, 9.4 and 14.1 dS m(-1). Different concentrations of salt stress had considerable effect on germination, germination rate (1/t50, where t50 is the time to 50% of germination), root and shoot lengths, root, shoot and plant fresh weight of cabbage. Final germination in cabbage (autumn cabbage and spring cabbage) showed significant inhibition with increasing salt stress up to 14.1 dS m(-1) NaCl. The required time for germination increased with increasing concentration of salt. The seedling growth was strongly inhibited by all salt levels, particularly at 14.1 dS m(-1). Furthermore Root growth was more affected then shoots growth by salt stress. Fresh weights of root, shoot and plant were also severely affected by different salinity treatments. Linear regression revealed a significant negative relationship between salinity and final germination, germination rate, root and shoot lengths and fresh weights of roots, shoots and plants.

Germination variability and the effect of various pre-treatment on germination in the perennial spurge Euphorbia nicaeensis All.

Patterns of seed germination of the perennial spurge Euphorbia nicaeensis were studied in three populations in south-western Spain. We investigated the variation in seed viability and germination among individuals, and among populations over 2 consecutive years. We also studied if diverse factors such as temperature, acid scarification, darkness or caruncle loss affect the germination of the seeds. Interindividual and interpopulation variability in seed viability was found. E. nicaeensis seeds are nondormant, so differences in interpopulation viability translate into differences in final germination rates. The germination percentage of the seeds from each population was similar in the 2 years studied. The effects of diverse factors were homogeneous in the two populations studied. Darkness has no effect on seed germination, and ecarunculate seeds germinated in the same proportions as carunculate seeds; this could allow the seeds to germinate in the chambers of deserted anthills. Acid scarification significantly reduced the germination percentage in only one of the populations, but over 50% of the seeds germinated, which could allow herbivores to act as occasional dispersing agents. The seeds that were preheated at 100 °C for 1 and 5 min germinated in the same proportions as the control group. The seeds that were preheated at 120 °C for 5 min displayed a significant decrease in germination, but the percentage was over 40% for both populations, indicating that the seeds could still germinate after the passage of a fire.

DISTINGUISHING THE EFFECTS OF GENOTYPE AND SEED PHYSIOLOGICAL AGE ON LOW TEMPERATURE TOLERANCE OF RICE (ORYZA SATIVA L.)

When differences are observed between genotypes in their response to low temperatures at germination, it has been generally assumed these are purely genetic. Laboratory experiments were carried out to evaluate the effects of physiological age on the temperature responses of 13 rice genotypes from Bangladesh in order to clarify whether (a) differences in seed germination at low temperature represented genetic differences or differences in the physiological state of the particular seed lot used and (b) whether genotype performance at higher temperatures was indicative of performance at lower temperatures. A higher initial seed moisture content (mc) was associated with lower initial viability (Ki). The base temperature for germination differed by less than 1 °C between genotypes. Seeds remaining ungerminated at low temperatures usually germinated when transferred to 21 °C. The thermal time requirement to reach t50 (θ) differed widely between genotypes. Lower optimum temperatures for germination were associated with lower thermal time requirements. Ageing seeds for 24 hours at 24 % mc and 45 °C significantly reduced final germination on a thermal gradient table at all temperatures below 20.8 °C in genotype BR29 but only below 16.5 °C in BR11. The rates of germination (seeds d−1) of aged seeds were also lower at all temperatures. Germination of high quality seeds of four genotypes were compared at 21 °C and 11 °C both before and after ageing (at 24 % mc and 45 °C). Ageing consistently reduced the rates of germination at both 21 °C and 11 °C. Increased ageing time progressively reduced the rate of germination of all seed lots at both temperatures. The rates of germination at 11 °C and 21 °C were positively and significantly (p &lt; 0.01) related to final germination at the lower temperature of 11 °C. These results demonstrate that seed physiological quality as well as genotype might influence the final germination and rate of germination of rice genotypes at low temperatures. This information will be useful for breeders involved in selection of lines suitable for growing in cooler seasons.

Enhancing the germination of three fodder shrubs (Atriplex amnicola, A. nummularia, A. undulata; Chenopodiaceae): implications for the optimisation of field establishment

Saltbush (Atriplex) species are widely grown in Australia as saltland pastures. Direct seeding practices for saltbush currently result in asynchronous and unreliable seedling establishment (5% successful establishment is not uncommon from field-sown seed). In part this may stem from a limited understanding of Atriplex seed germination requirements. This paper presents findings with 3 Atriplex species, A. amnicola (Paul G. Wilson.), A. nummularia (Lindl.), and A. undulata (D. Dietr), each of which differs in germination characteristics. For A. amnicola, the presence of light (and artificial substitution of light by 1000 ppm gibberellic acid) improved germination under controlled conditions and resulted in a 4-fold increase (70% total emergence) in field emergence of seedlings. For A. undulata, removing bracteoles increased germination under controlled conditions (~15%), with a 1.5-fold improvement in field seedling emergence (55% final emergence); however, seed priming or gibberellic acid application had no significant effect. In contrast, for A. nummularia, bracteole removal and light had minor positive effects on germination under controlled conditions, but this did not translate into improved emergence in soil or in the field. Under –0.5 MPa NaCl stress, application of gibberellic acid, salicylic acid, or kinetin to the germination medium significantly increased the final germination percentage of A. amnicola seeds (58, 16, and 14%, respectively) and improved the rate at which seeds germinated. All plant signalling compounds significantly increased final germination percentage and germination rate of A. undulata, albeit with a &lt;10% increase at –0.5 MPa NaCl. Priming seeds with plant signalling compounds had similar effects on seed germination under low water potentials compared to direct treatment of the germination media. The effects of seed priming on Atriplex seedling emergence from saline soils varied among species. Priming with water significantly increased emergence percentage of A. amnicola but had no effect on A. nummularia and A. undulata. Gibberellic acid improved A. amnicola germination parameters only, whereas salicylic acid and kinetin improved the rate of emergence in all 3 species at various levels of salinity. This study suggests that a basic understanding of seed dormancy and germination requirements has the potential to substantially improve field emergence of saltbush species.

Effects of temperature, light and other treatments on seed germination of Leymus chinensis

Leymus chinensis (Trin.) Tzvel., a perennial cool-season grass distributed widely in eastern Asia, is an ideal species for the rangeland industry and soil conservation, but the seed has a long dormant period and low germination rates. This study examined the effects of temperature, light and various treatments including stratification, H2SO4, NaOCl, gibberellic acid (GA3) and 6-benzyl adenine (BA), on the germination of Leymus chinensis seed. Seed stored over 1 yr and germinated at a temperature regime of 25/15°C with a 12/12-h photoperiod germinated best, and had a germination rate of 30.3%, with a minimum germination time of 12 d. In these germination conditions, germinated seeds were counted after 15 d to determine the effects of other treatments upon freshly harvested seed germination. The final germination rate for freshly harvested seeds stratified at 4°C for 0 to 10 wk ranged from 8.5 to 37.3%. Germination rates were 14.0 and 14.8% when seeds were treated with 70% H2SO4 for 3 and 6 min, respectively. Seed treated with 5.0% NaOCl germinated 17.5 and 16.0% when treated for 10 and 20 min, respectively. When seeds were soaked in 1000 mg L-1 GA3 solution for 24 h, 42.3% germinated, while treatment with 50 mg L-1 of BA resulted in 50.3% germination. The results indicate that various dormancy mechanisms may exist in the species. These findings will be helpful to farmers and breeders in selecting suitable treatments to improve seed germination and establishment. Key words: Seed dormancy, grassland and sand-dune reclamation, photoperiod, Northern China, Poaceae, seed priming

Seed germination of five Helianthemum species: Effect of temperature and presowing treatments

The germination behaviour of five Helianthemum species ( H. almeriense, H. appeninum, H. cinereum, H. hirtum, H. squamatum) has been studied under controlled conditions. Constant 15, 20 or 25 °C and alternating 25/15 °C temperature regimes and 16/8 h light/dark photoperiod conditions were used. Presowing treatments applied were manual scarification, boiling water, hot water, dry heat and sulphuric acid. Germination values recorded were final germination percentage and germination rate expressed as days to reach 50% of the final germination percentage ( T 50). Incubation temperature had no significant effect on final germination percentage for untreated seeds of the five Helianthemum species. However, variation due to temperature was significant for scarified seeds, with the lowest germination percentage attained at 25 °C. In all Helianthemum species studied, the highest germination percentages were obtained by manual scarification of seeds. Germination rate of scarified seeds decreased as germination temperature increased. The different presowing treatments investigated allowed some germination in some species, but none were any better than manual scarification. The high germination among most species studied, following mechanical rupture of the seed coat, shows that the mechanism of dormancy lies in the seed coat. The physical dormancy caused by impermeable seed-coat appears to be the main reason of poor germination of untreated seeds of Helianthemum species studied.