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1.
Development during storage of germinability of seeds of Amaranthus retroflexus L. harvested under different conditions The effect was studied of dry storage at 20 ± 1°C for 6 months or in soil 15 cm below the surface during one winter, on the germination behaviour of seeds of Amaranthus retroflexus L. harvested at the level of the main inflorescence on the parent plants grown under natural conditions or in different conditions of controlled photoperiod or temperature. At harvest, the seeds from plants which had developed late (July) in natural conditions were less dormant than those from plants appearing earlier (April); in controlled conditions, plants grown at 20°C in long days (16 h) produced seeds more dormant than those harvested from plants grown either at 20°C in short days (8 h) or at 25°C in long days (16 h). After dry storage or in the soil, this variation in germinability decreased but was never totally suppressed; the seeds retained the characteristics acquired during their formation and maturation. At harvest, for a defined growing condition, the dormancy of the seeds produced depends on the physiological state of the parent plants; after storage, the seeds which were the most dormant at harvest germinated more than the less dormant seeds. Finally, burying has a more favourable effect on breaking dormancy of the seeds than has dry storage.  相似文献   

2.
Freshly harvested seeds of Poa annua L. collected in south Louisiana were stored in moist soil at seven temperatures between 5°C and 35°C. At monthly intervals, seed lots were removed and germinated at each of the seven temperatures. Seed were dormant for at least 1 month at all test temperatures. Seeds stored for 2 months at 30 and 35°C showed conditional dormancy; there was 100% germination at 10 or 15°C, and poorer germination at 5 or 20°C. Seeds started to lose viability after 2 months at 35°C and were dead after 7 months. In seeds stored at 10–30°C, there were increased percentages and a wider range of germination temperatures as storage time or storage temperatures increased. Seeds stored at 10°C remained dormant for 9 months, but by 12 months of storage the seeds germinated only at 5 or 10°C. Nearly all seeds stored at the same temperatures in air dry soil remained dormant for 6 months, regardless of storage temperature. These results differ from other reports of low temperatures breaking seed dormancy in Poa annua L. and suggest an adaptation to subtropical climates.  相似文献   

3.
Emergence of Veronica hederifolia seedlings began in mid-October and continued into spring; few appeared from June to September. Ripe seeds shed in June were dormant but wben buried in soil outdoors developed a capacity for germination initially at low temperatures (constant4 C; daily alternations of 4-10° and 4-1 5 C) and later at somewhat higher temperatures, with peak germination in September-November. During winter, spring and early summer thc germination capacity declined, to increase again in late summer and early autumn. Cyclic physiological changes thus occur in seeds of V,hederifolia present in the soil, with which lhe consistent seasonal periodicity of seedling emergence is associated. In dry storage ihe capacity for germination progressively increased, but alter 12 months there was a sharp decline in germination at 4° C. Few seeds germinated at 20° C, but moistening with GA 4/7; brought about complete germination at this temperature.  相似文献   

4.
Seeds of Poa annua from original collections in Louisiana, Maryland and Wisconsin were grown together in Louisiana over a 3-year period. The freshly harvested seeds and samples stored in moist soil at 30°C were tested for germination at a range of temperatures to compare dormancy and germination characteristics. Seeds of the Louisiana population were dormant over the germination temperature range of 5–25°C, and imbibed storage for 2 weeks did not break dormancy. Freshly harvested seeds of the Maryland population germinated well (78%) at 10°C. With 1 week of imbibed storage at 30°C, germination was good over the range from 5 to 15°C and near 50% at 20°C. Storage for 2 weeks had little further effect. Freshly harvested seeds of two Wisconsin populations germinated above 50% throughout the range of temperatures, and imbibed storage for 2 weeks at 30°C had no effect on germination. The variations in the dormancy of freshly harvested seeds and the varying responses of dormancy breaking from storing imbibed seeds at 30°C suggests that these populations have adapted to avoid high summer temperatures in Louisiana and Maryland but to grow as a summer annual in Wisconsin.  相似文献   

5.
Incubation in gibberellin A3 (GA3) or a 1 h immersion pretreatment with 800 mm sodium hypochlorite (NaOCl) both promoted 20% germination of freshly harvested dormant wild oat (Avena fatua L.) seeds that had been imbibed on water for 10 days. GA3 immediately following 1 h NaOCl immersion pretreatment induced maximum germination. Moist storage (MS) after NaOCl immersion pretreatment resulted in less germination on transference of the seeds to GA3, indicating that GA3 responsiveness was lost during MS. These seeds required a repeal NaOCl immersion plus a GA3 treatment to induce maximum germination. However, GA3 still gave maximum germination if the seeds were stored dry after initial NaOCl immersion. Seeds with water-induced dormancy responded similarly to freshly harvested dormant seeds when treated with NaOCl, MS, or GA3. Seeds afterripened a longer time had a reduced requirement for exogenous GA3 in the breaking of dormancy indicating that the depth of the GA3-dependent dormancy decreased with duration of after-ripening. Dormant dehulled seeds with a brief NaOCl pretreatment germinated about 30% on water but gave maximum germination when incubated on GA3, an effect that persisted even after 21 days of MS. This effect, coupled with the previous findings, suggested that the NaOCl treatment weakened membrane barriers of the seed coat through a scarification-like effect, similar to the effects of piercing and acid immersion, and thereby produced increased sensitivity to the presence of GA3. The loss of responsiveness to GA3 in NaOCl-treated seeds during MS may involve the restoration of integrity of the seed coverings, a process occurring only in the imbibed state, and, presumably, most rapidly in freshly harvested, intact seeds.  相似文献   

6.
Emergence of Solanum sarrachoides began in late April, reached a peak in May or June and ceased in September. This pattern closely resembled that for S. nigrum L., whereas almost all seedlings of S. dulcamara L. emerged in April. Fresh seeds of S. sarrachoides were dormant but developed a capacity for germination at 25 and 30°C and at alternating (16 h low/8 h high) temperatures of 4/25, 10/25, 10/30 and 20/30°C when stored dry. kept moist at 4°C or buried in the field. Buried seeds also became capable of germinating at 10. 15 and 20°C and the temperature range for germination was widest during April-June. Induced dormancy developed during August and the range narrowed. The consistent seasonal emergence pattern appears to be associated with cyclic changes in the dormancy status of buried seeds.  相似文献   

7.
Germination of freshly harvested seeds of Commelina benghalensis L. varied from 0–3% for small aerial seeds, 20–35% for large aerial seeds and from 33% for small underground seeds to 90% for large underground seeds. Innate dormancy of all seed types was completely overcome by clipping the seed coat. Exposure to 90°C dry heat for 2 h was also effective in increasing germination of the three strongly dormant seed types. Optimum temperature for germination varied with the different seed types. Periods of likely major weed infestation from the four seed types were predicted using soil temperature data. Exposure to light increased germination but was not essential and underground seeds responded more to light than aerial seeds. Optimum depth of emergence for the four seed types was from 0 to 50 mm and there was a positive correlation between maximum depth of emergence and seed weight.  相似文献   

8.
Germination of Setaria chevalieri caryopses   总被引：3，自引：0，他引：3  
Germination studies were made on Setaria chevalieri caryopses (seeds). The seeds imbibed readily upon moist incubation. An after-ripening period which followed a cyclic patlern was necessary for maximum germination. Freshly harvested seed germinated in the presence of light, but only very sporadically in the dark. The germination of dark incubated seed was improved if the seeds were subsequently exposed to light. This photodormancy became less pronounced with dry storage. Treatment with red light increased germination. but was reversed by far-red light suggesting that a phytochrome system operates in the seeds. Sodium azide treatments did not stimulate germination in the dark but were effective in the presence of light.  相似文献   

9.
Fresh seeds of Lamium purpureum L. were dormant at maturity, and when buried and exposed to natural seasonal temperature changes they exhibited an annual dormancy/non-dormancy cycle. During burial in summer, fresh seeds and those that had been buried for 1 year afterripened and thus were non-dormant by September and October; light was required for germination. During autumn and winter seeds re-entered dormancy, and during the following summer they became non-dormant again. Dormant seeds afterripened when buried and stored over a range of temperatures, becoming conditionally dormant at low (5, 15/6°C) and non-dormant at high (20/10, 25/15, 30/15 and 35/20°C) temperatures. Conditionally dormant seeds germinated to high percentages at 5, 15/6 and 20/10°C, while non-dormant seeds germinated to high percentages additionally at 25/15, 30/15 and 35/20°C. Low temperatures caused non-dormant seeds to re-enter dormancy, while high temperatures caused a sharp decline in germination only at 30/15 and 5°C. The temperature responses of L. purpureum seeds are compared to those of L. amplexicaule L.  相似文献   

10.
Ryegrass (Lolium multiflorum Lam.) is one of the most difficult annual weeds to control in cultivation systems worldwide, especially in temperate regions. The widespread use of herbicides in the past two decades has selected resistant biotypes of ryegrass in crops in Southern Brazil. Ryegrass seeds are dormant when disseminated and germination can be staggered over time (crop‐growing season). Knowledge of the germination behavior of seeds from herbicide‐resistant plants has been little studied, but it would be very useful in integrated weed management. Thus, this study aimed to characterize the dynamics of the soil seed bank of two biotypes of L. multiflorum, one glyphosate‐resistant and the other glyphosate‐susceptible, under a no‐tillage system. The treatments were arranged in a bifactorial scheme, using seeds from biotypes (glyphosate‐resistant and glyphosate‐susceptible) with monthly periods of removal from field (one to 12 months). Seeds of each biotype were placed on the soil surface and covered with soil and straw to simulate no‐till conditions. The percentage of germinated, dormant, and dead seeds was evaluated every 30 days. The ryegrass seed bank of glyphosate‐susceptible and glyphosate‐resistant biotypes was reduced to 11 and 15% of dormant seeds, respectively, at the end of 12 months. However, there was no variation in germination, dormancy, and seed mortality between susceptible and glyphosate‐resistant ryegrass. Seeds of glyphosate‐resistant biotype and susceptible showed germination behavior with similar dynamics in the soil over a period of 12 months.  相似文献   

11.
The effects of concentrated sulphuric acid, dry heat, hot water and NaOCl treatments on the germinability of dormant large and small aerial Commelina benghalensis L. seeds were evaluated. Concentrated sulphuric acid and NaOCl treatments were more effective than the dry heat and hot water treatments in breaking the dormancy of C. benghalensis aerial seeds. Treatments increased germination of both seed types due to its effect on the seed coat integrity. A scanning electron microscope revealed that changes as a result of scarification occurred in the hilum region of the seed and in the seed coat surface. The large aerial seeds were affected by all treatments more than the small aerial seeds. Difference in germinability between the two seed types was related to the difference in their seed vigour.  相似文献   

12.
Spring-produced seeds of Lamium amplexicaule L. were dormant at maturity in May and after-ripened when buried and stored over a range of temperatures, becoming conditionally dormant at low (5, 15/6 and 20/10°C) and non-dormant at high (25/15, 30/15 and 35/20°C) temperatures. Conditionally dormant seeds germinated to high percentages at 5 and 15/6°C, and non-dormant seeds germinated to high percentages at 5, 15/6, 20/10, 25/15 and 30/15°C. Seeds that became conditionally dormant at 5°C afterripened completely (i.e. became non-dormant) after transfer to 30/15°C. Buried seeds that became non-dormant in a non-temperature-controlled glasshouse during summer were still non-dormant after 12 weeks of storage at 30/15°C, while those stored at 5°C for 12 weeks had entered conditional dormancy. Thus, low temperatures cause reversal of the afterripening that takes place at high temperatures, but not that which takes place both at low and at high temperatures. Low winter temperatures cause dormant autumn-produced seeds and non-dormant seeds in the soil seed pool to become conditionally dormant. The ecological consequences of these responses to temperature are discussed in relation to the timing of seed germination in nature.  相似文献   

13.
Carolina dayflower (Commelina caroliniana Walter), infesting soybean (Glycine max L.) fields on northern Kyushu Island, Japan, has seed heteromorphism; that is, it produces two types of seeds: pericarp and naked. However, there is no information about their germination behavior. The purpose of this study was to understand the germination characteristics of carolina dayflower seeds and to clarify the difference between the pericarp and naked seeds. On the shape of the seed, the pericarp seeds were significantly longer than the naked ones, with no significant difference in width or thickness. Both the pericarp and the naked seeds could germinate at >20°C, and at 30°C, their cumulative germination rate at 7 days after sowing was the highest, at >90%. Light had no effect on seed germination. The cumulative germination rate after 7 days, when the seeds had been stored dry, wet or under water at a low temperature, was significantly lower than after storage at room temperature, suggesting that a higher temperature and concentration of oxygen during the seed‐storage period affects the germination of carolina dayflower. However, there was no difference in the germination behavior between the pericarp and the naked seeds.  相似文献   

14.
Seeds of Poa trivialis L. were collected from one grassland and two arable habitats. Seeds from the grassland population were less dormant than the arable populations. Distal (upper) seeds were consistently more dormant than proximal (basal) seeds. Dry storage at 4°C and 15°C for 4 weeks after shedding resulted in a slightly greater loss of dormancy than storage at 23°C. Germination was enhanced by subjecting seeds stored at 15°C to repeated hydration and dehydration cycles. Germination of P. trivialis seeds was density-dependent. Germination of distal seeds was particularly impaired at high densities. The ecological implications of these results are discussed in relation to seed survival strategies.  相似文献   

15.
Spring-produced seeds of Lamium amplexicaule L. were buried in pots of soil in an unheated glasshouse in June 1978, and at 1–2-month intervals, for 27 months, they were exhumed and tested for germination in light and darkness at temperatures simulating those in the habitat from early spring to late autumn. Freshly-matured seeds were dormant, but by autumn 85% or more germinated in light at 15/6, 20/10, 25/15 and 30/15°C but only 7% or less in darkness. During late autumn and winter germination in light decreased at 25/15 and 30/15 °C but not at 15/6 and 20/10 °C, and germination in darkness increased at 15/6 and 20/10 °C. During late winter and early spring germination in light at 15/6 and 20/10 °C decreased, and seeds lost the ability to germinate in darkness. By the second autumn of burial, seeds germinated to near 100% in light at 15/6 to 30/15 °C and to 10–25% in darkness at 15/6 and 20/10 °C. The cycle of germination responses was repeated during the second winter and spring and the third summer of burial. Autumn-produced seeds were dormant when buried in November 1979, but by spring they germinated to 81 and 36% at 15/6 and 20/10 °C, respectively, in light. These seeds afterripened further during summer. The consequence of seasonal changes in germination responses is that (1) seeds can germinate in the habitat in late summer, autumn and spring but not in early- to mid-summer or in late autumn and winter and (2) during both germination seasons, seeds produced during the previous spring(s) and/or autumn(s) can germinate.  相似文献   

16.
MOHAMED  EJETA  BUTLER  HOUSLEY 《Weed Research》1998,38(4):257-265
Freshly harvested Striga asiatica L. seeds will germinate in response to a stimulant only after the passage of time, an after-ripening period, and exposure to moisture at a suitable temperature, a conditioning period. To investigate the role of seed moisture content in the regulation of the after-ripening period, seeds were placed in chambers having specific relative humidity of 6%, 14%, 33%, 75% and 91% for 30, 60, 90 and 150 days. The seeds were then conditioned and germination percentage, response to tetrazolium and seed moisture contents were measured. Seeds at moisture contents less than 10% at the start of conditioning had germination of greater than 93%. Seeds at moisture contents over 10% at the start of conditioning could germinate between 60% and 3%, with germination decreasing as seed moisture content at the start of conditioning increased. The highest moisture content (17%) and lowest germination percentage (3%) occurred in seeds stored at 91% relative humidity for 150 days. There was a linear relationship of a high degree of correlation (0.997) between a positive tetrazolium test and germination capacity. Germination capacity of seeds could be changed from 90% to 3% by prolonged storage in water (dilute benomyl solution), causing `wet dormancy', then returned to 90% germination by returning to dry storage. Seed moisture content at the beginning of conditioning appears to control the responsiveness of the seeds to germination stimulants. The implications of these findings to the control of the parasite are discussed.  相似文献   

17.
Physiological dormancy in weed species has significant implications for weed management, as viable seeds may persist in soil seedbanks for many years. The major stimulatory compound in smoke, karrikinolide (KAR1), promotes germination in a range of physiologically dormant weed species allowing targeted eradication methods to be employed. Control of Chrysanthemoides monilifera ssp. monilifera (boneseed), a Weed of National Significance in Australia, may benefit from adopting such an approach. In this study, we hypothesised that seeds of C. monilifera ssp. monilifera exhibit physiological dormancy, germinate more rapidly as dormancy is alleviated, show fluctuations in sensitivity to KAR1 and form a persistent soil seedbank. Seeds responded to 1 μM KAR1 (40–60% germination) even during months (i.e. March, April, July, August) when seeds were observed to be more deeply dormant (control germination: 7–20%). Seeds germinated readily over a range of cooler temperatures (i.e. 10, 15, 20, 20/10 and 25/15°C) and were responsive to KAR2 (~50% germination) as well. Eradication efforts for C. monilifera ssp. monilifera may benefit from use of karrikins to achieve synchronised germination from soil seedbanks, even at times of the year when C. monilifera ssp. monilifera seeds would be less likely to germinate, allowing more rapid depletion of the soil seedbank and targeted control of young plants.  相似文献   

18.
Fipronil seed treatments were evaluated to determine whether they directly influence germination and subsequent seedling growth in rice (Oryza sativa L). Continuous seed exposure to fipronil (four days) at 2 000 mg litre−1 significantly impaired germination (P < 0.001). When exposure was restricted to a 1-h period 48 h after the initiation of germination, early post-germination growth was also impaired (assessment two days after exposure, P < 0.05). The proportion of seeds satisfying our criteria for normal germination fell by 2.3 and 2.6% respectively across 17 cultivars. Cultivar effects were highly significant (P < 0.001). When exposure to fipronil (2 000 mg litre−1) was restricted to 2 h at initial seed wetting no significant growth impairment occurred. No significant differences (P > 0.05) were found between shoot lengths or root system dry weights of control plants and plants developing from seed exposed continuously (two days) to fipronil at rates of up to 2 000 mg litre−1 during germination and harvested nine days after sowing. Treating germinated seed with fipronil for 1 h immediately prior to sowing at rates of up to 4 000 mg litre−1 did not result in significant changes (P < 0.05) in plant growth parameters at either nine or 25 days after sowing. No evidence of fipronil having a direct phytostimulatory effect on rice was obtained. © 1999 Society of Chemical Industry  相似文献   

19.
A. C. GRUNDY 《Weed Research》1997,37(4):257-266
Experiments were made on seven dry-stored seed lots of Steliaria media (L.) Vill to assess the effect of water potential and temperature on germination. These seed lots were from different sources and their age ranged from freshly harvested to 5 years in dry storage. Germination was recorded at regular intervals at five constant temperatures (5-25°C) in all combinations with eight water potential regimes (from 0 to -1.4 MPa). The results showed that seed lot had a significant effect on the percentage, rate and spread of germination Differences in germination behaviour in the seed lots appeared to be related to the durations of dry storage. Freshly harvested seed exhibited signs of dormancy, with the lowest percentage and longest mean germination time. Seed lots that had been in dry storage for more than 1 year took increasingly longer to germinate, particularly under less favourable conditions. In contrast, germination percentages were highest in the 3-year-old seed. The constant temperature and water potential achieving maximum germination was independent of seed lot as was the water potential achieving the highest germination rates. However, the temperature achieving the highest germination rate was dependent on seed lot. The spread in germination time was largest for the freshly harvested and oldest seed samples. Rates of germination against temperature over the range of water potentials studied were complex.  相似文献   

20.
The seasonal changes in percentage of dormant seeds of Echinochloa crus-galli in the field were recorded for 4 years. The lots of seeds were wrapped in nylon fabric, buried 20 cm under the grass sward and exhumed at monthly intervals. The proportion of seeds germinating under light conditions at a constant temperature of 25 °C fluctuated between 0% and 96%, with maxima in May–July and minima in September–November. Small between-year differences in the course of summer dormancy induction and its winter termination were probably caused by variation of weather conditions.
Attributes of dormancy innate to seeds after maturation (primary dormancy) and dormancy induced in buried seeds during the summer (secondary dormancy) were compared by investigating the rate of dormancy termination during storage of (a) dry seeds at 25 °C, (b) imbibed seeds at 5°C and (c) in seeds buried under field conditions during October–June. Percentage of germination increased faster in secondary than primary dormant seeds at both constant 25 °C and 5 °C. The seeds with primary and secondary dormancy also differed in the response to `germination pre-treatment', a 10-day exposure of imbibed seeds at 25 °C that causes germination of the non-dormant fraction of seed materials. After this treatment the time to resuming germination in primary dormant seeds was substantially increased, whereas the secondary dormant seeds were much less affected. Annual variation in the proportion of germinable seeds explains the low efficiency of autumn soil cultivation for decreasing reserves of E. crus-galli seeds in the soil.  相似文献   

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