光照、温度和盐分对梭梭种子萌发的影响

梭梭是我国西北荒漠中分布的多年生植物,属中亚荒漠植被成分。其种子萌发的最适温度为10℃,亚适宜温度为15～20℃。从20℃起,温度越高,萌发比率越低。种子无论在光下和暗中都能萌发,萌发率无显著性差异。浓度低于0.2mol/L的NaCl溶液对萌发的影响不大;但从0.8mol/L起,萌发率随着浓度增高而降低,直至为零。将在盐溶液中处理9d的种子转移至蒸馏水后,原来较高浓度下的种子具有较高的萌发恢复率。不同浓度下的种子的萌发率和萌发恢复率要比蒸馏水中的低,表明NaCl处理后的部分种子永久地失去萌发力。     

Effect of environmental factors on seed germination and emergence of Lepidium vesicarium

Lepidium vesicarium is a weed species with a wide distribution in the rangelands and dry‐land farming in East Azarbaijan, Iran. The experiments were undertaken to assay the effects of light, temperature, pH, osmotic potential, NaCl concentration and burial depth on seed germination and emergence of L. vesicarium. Germination was maintained at high levels (> 80%) over a wide day/night temperature range (10/5 to 30/20°C), but a severe reduction in the germination rate of L. vesicarium was found below 20/10°C. Germination of L. vesicarium was influenced by different light/dark regimes, as the germination rate was highest at 16 h light for the all treatments (0, 8, 12, 16 and 24 h light). Germination was 92–95% over a wide range of pH (2‐10). Germination was >50% at a water potential of ?0.7 MPa and salinity of 21 dS/m, indicating that drought and salt conditions have a minimal impact on seed germination. With increasing burial depth from 0 to 2 cm, the number of days required for 50% emergence increased and no germination was observed at burial depths deeper than 3 cm. This suggests that L. vesicarium would become troublesome in the rangelands and for growers in reduced‐tillage cropping systems. The ability to emerge from shallow depths, coupled with tolerance of a wide pH range, drought and salinity at germination, should be taken into account when managing this weed species.     

Density-dependent germination and the role of seed leachate

Abstract While density dependence is a central issue in much of plant ecology, it is often overlooked during the crucial seed germination period of the plant life-cycle. Here, patterns of germination in relation to initial seed density for 12 phylogenetically-diverse perennial plant species are described from laboratory experiments. When each of the 12 species was analysed individually, seeds of Alysicarpus rugosus, Callistemon citrinus, Eragrostis curvula and Panicum miliaceum showed a significant decrease in the proportion of seeds germinating at high densities of conspecifics. A meta-analysis carried out by grouping 11 of the 12 species together revealed an overall significant effect for a decrease in the proportion of seeds germinating at high conspecific densities compared with low con-specific densities. Significant decreases in the proportion of seeds germinating are interpreted as risk reappraisal by seeds through dormancy in response to potentially hazardous conditions imposed by high density clusters of seeds all germinating at once. The four species that responded significantly to high densities individually were each treated at low densities with a leachate solution obtained from high density conspecifics. For Alysicarpus rugosus and Panicum miliaceum, this resulted in a significant decrease in the proportion of seeds germinating at simulated high densities implicating the leachate as a causative agent. Heterospecific effects were investigated similarly for A. rugosus and E. curvula by the addition of leachate from high density clusters of seeds of one species upon the other. Only A. rugosus decreased germination significantly through the addition of leachate. These results demonstrate the ability of seeds to predict environmental conditions of the habitat into which they will emerge in terms of potential competitive interactions from neighbouring seedlings.     

Mathematical description of the seed germination dependency on time and temperature

Abstract. A mathematical model which describes the germination percentage dependency on time and temperature of a seed population was derived from the experimental results with a seed population of Amaranthus patulus Bertol. under sub-optimal temperature conditions (Washitani & Takenaka, 1984). The equation of the model which is a modified thermal time model is where G is germination percentage at a certain time after the start of imbibition ( t ) at a certain temperature ( T ), μ _{T 1} and σ _{T 1} are the mean and standard deviation of lower limit temperature among the seeds belonging to the seed population, and Tb, m , and A are the parameters characterizing the linear relationship between the rate and temperature, namely, Tb is the base temperature, m , the median of the required thermal time and A , a parameter determining the pattern of the variation of the required thermal time within seed population, respectively. The equation yields time courses for germination which are very similar to those observed by experiment.     

古尔班通古特沙漠种子秋萌的环境依赖性

种子的萌发时间分散在不同季节,有利于资源的利用,种群的延续与扩增。通过野外对秋萌物种种类与分布特征进行调查,结合种子生物学特征和萌发对温度、水分的响应,探究古尔班通古特沙漠秋萌物种种子的共性特征及萌发的环境依赖性。结果表明:67个样地中有33个样地有秋萌物种分布,物种以1年生短命植物为主。秋萌物种的果实易开裂,种子寿命较短,且不休眠。萌发的高温阈值宽泛,萌发类型不是早春低温类型,与9—11月秋季温度对应;萌发对土壤水分响应敏感,冗余分析发现水分是种子选择萌发时间的限制因子,影响秋萌物种的分布。在气候变化背景下,秋冬降水增多,冬季冻期缩短,推断古尔班通古特沙漠秋萌物种的种类和数量都会呈增加趋势。     

Different ecological strategies during the seed germination phase of nine grasses inhabiting the hyper‐arid Arabian desert

The effect of photoperiod, thermoperiod and their interaction on seed germination and its rate was studied for nine grasses growing in the Arabian desert. Germination tests were conducted under two photoperiods and three thermoperiods. Germination of light‐incubated seeds of Hyparrhenia hirta, Pennisetum divisum, Stipacapensis, Centropodia forsskaolii, Stipagrostis plumosa, Cymbopogon parkeri and Panicum turgidum was significantly higher than that detected in the darkness. Photoperiod did not influence the seed germination of Aristida adscensionis and Imperata cylindrica. Seeds of all species, except P. divisum, C. parkeri and I. cylindrica, germinated indepen dently of the tested temperature. Our results indicate that species belonging to the same family and growing in the same hyper‐arid desert habitat may influence and act in different ways during the seed germination phase, causing species‐specific effects, and therefore might affect the ecology of each taxon in this harsh environment.     

Effects of thermoperiod on recovery of seed germination of halophytes from saline conditions

Recovery of seed germination from NaCl salinity of desert shrubs (Haloxylon recurvum and Suaeda fruticosa, and the herbs Zygophyllum simplex and Triglochin maritima was studied under various thermoperiods. The percentage of ungerminated seeds that recovered when they were transferred to distilled water varied significantly with variation in species and thermoperiods. Zygophyllum simplex had little recovery from all NaCl concentrations in all thermoperiods. Haloxylon recurvum, S. fruticosa, and T. maritima showed substantial recovery. Percentage recovery was highest in S. fruticosa, followed by T. maritima, and H. recurvum. Thermoperiodic effects varied with the species investigated. There was little thermoperodic effect on the percentage recovery of S. fruticosa, except in the higher salinity treatment at higher thermoperiods. Variation in thermoperiod appears to play an important role in recovery of germination of halophytes from salt stress when seeds are transferred to distilled water.     

Penetration of light into soil and its role in the control of seed germination

Abstract Light transmitted through soil, and the leaf litter of two tree species, was measured using a spectroradiometer. In general, a greater penetration by longer wavelengths, especially far-red, was noted. This was most marked in a dry sand sample. The effect was less in the case of clay-loam aggregates. Moisture in the samples had an opposite effect in these two cases, causing an increase in transmission through sand but a decrease through clay loam aggregates. Reduction in particle size was found to reduce both the total light transmitted and the red/far-red ratio (R : FR). Red wavelengths were also more attenuated by a layer of freshly fallen oak (Quercus rotrur) leaves than were far-red wavelengths. A layer of Corsican pine (Pinus nigramaritima) needles however, was found to act as a neutral density filter over the 400 800 nm range. Prolonged exposure to soil-filtered light was found to affect the germination of seven species tested. Plantago major demonstrated an approximately linear decrease in germination with increasing depth. Rumex obtusifotius showed an apparent threshold response at 4 6 mm depth, as did Cecropia obtusifolia but at a slightly greater depth. Digitalis purpurea germinated very poorly in darkness, yet was extremely photosensitive with very high germination even at 10 mm depth. Galiutn aparine and Chenopodium album showed a two-phase response with germination reaching a peak at 2 mm depth. The implications for the function of the photoreceptor phytochrome in the control of germination are discussed in relation to soil-transmitted light and with regard to the results of the germination tests.     

The effect of light and seed mass on seed germination of common herbaceous species from the eastern Qinghai‐Tibet Plateau

Smaller seeds might encounter more severe selective pressure than larger ones because they have fewer food reserves and are more easily buried; thus, seed mass can be considered to be directly related to the effect of light on germination. To investigate the effect of light on seed germination and associated seed mass variation within a whole plant community, we compiled germination data for common herbaceous species from an alpine meadow on the eastern Qinghai‐Tibet plateau. The results showed the following. (i) Light had a general positive effect on seed germination. Under light, the proportion of species with lower germinability was decreased, mean germination percentage was increased by 20% and the speed of germination was doubled. (ii) Irrespective of light environment, species with medium‐sized seeds (seed mass ranging from 0.11 to 0.5 mg) had higher germination percentage and speed when compared with species within the largest seed mass group. (iii) The germination of smaller‐seeded species was more dependent on light stimulation than larger‐seeded ones. In darkness, the species within the smallest seed mass group had the lowest percentage and speed of germination; however, under light, the species within the largest seed mass group had the lowest percentage and speed of germination. Our results suggested that the germination characteristics and especially seeds’ response to light among species in the alpine meadow might be an adaptation to natural selective pressure.     

A new role for phytochromes in temperature-dependent germination

Germination timing is a fundamental life-history trait, as seedling establishment predicates realized fitness in the wild. Light and temperature are two important cues by which seeds sense the proper season of germination. Using Arabidopsis thaliana, we provide evidence that phytochrome-mediated germination pathways simultaneously respond to light and temperature cues in ways that affect germination. Phytochrome mutant seeds were sown on agar plates and allowed to germinate in lit, growth chambers across a range of temperatures (7 degrees C to 28 degrees C). phyA had an important role in promoting germination at warmer temperatures, phyE was important to germination at colder temperatures and phyB was important to germination across a range of temperatures. Different phytochromes were required for germination at different temperatures, indicating a restriction or even a potential specialization of individual phytochrome activity as a function of temperature. This temperature-dependent activity of particular phytochromes reveals a potentially novel role for phytochrome pathways in regulating the seasonal timing of germination.     

Effects of saline‐waterlogging and dryness/moist alternations on seed germination of halophyte and xerophyte

In arid zones, precipitation distribution is extremely uneven, with saline‐waterlogging and dry–moist cycles appearing frequently, which negatively impact on seed germination and seedling establishment. The responses of two halophytes, Suaeda physophora and Haloxylon ammodendron, and a xerophyte, Haloxylon persicum, to saline‐waterlogging and dry–moist cycles were studied. The results showed that aeration increased seed germination for all species when seeds were submerged in NaCl, especially for xerophyte. Compared with S. physophora and H. ammodendron, seed germination, recovery germination, and total germination of H. persicum were much lower when seeds were submerged in 700 mm NaCl, especially for the recovery germination and total germination of nongerminated seeds when the seeds were desiccated and then transferred to distilled water. However, when the seeds were submerged in 700 mm NaCl with aeration, the seed germination, recovery germination, and total germination of nongerminated seeds transferred to distilled water increased dramatically for H. persicum. No adverse effect of desiccation was found on those values of nongerminated seeds pretreated in NaCl with or without aeration for the two halophytes. In conclusion, seeds of the two halophytes were more tolerant to waterlogging and dry–moist cycles than seeds of the xerophyte during emergence under saline conditions; these traits may be important for halophytes to survive extreme saline environments during the seed germination stage.     

Effects of salinity and temperature on ex situ germination of the threatened Gulf of St. Lawrence Aster,Symphyotrichum laurentianum Fernald (Nesom)

The threatened Gulf of St. Lawrence Aster, Symphyotrichum laurentianum Fernald (Nesom), is an annual coastal halophyte of the southern Gulf of St. Lawrence, Canada. We examined the effects of salinity (0–20 g/L) and temperature (16–30°C) on germination of S. laurentianum seeds over 32 days. The time‐course of germination was significantly affected by both salinity and temperature. At lower temperatures (16°C and 23°C), germination was inhibited by salt water at days 16 and 32. However, at 30°C germination rates after 16 days were highest at an intermediate salinity, whereas after 32 days germination was uniformly high in all salinity treatments. Overall, the effect of temperature on germination was much stronger than the effect of salinity. Delays in germination resulting from exposure to salinity or from low soil temperatures could set up strong size asymmetries between seedlings of S. laurentianum and the surrounding vegetation, leading to suppression of growing seedlings via shading. Because germination has the potential to be a significant population bottleneck for this seed‐dependent annual, conservation efforts should consider microsite suitability for germination in the management of natural populations and in the selection of sites for explants.     

光照和温度对百合属6种植物种子萌发的影响

对不同光照和温度条件对条叶百合（Lilium callosum Sieb.et Zucc.)、大花卷丹[L. leichtlinii Hook.f var.maximowicaii(Regel)Baker]、有斑百合[L.concolor Salisb.var.pulchellum(Fisch.)Regel]、川百合[L.davidii Duchartre)、毛百合（L. dauricum Ker-Gawl.)和东北百合（L.distichum Nakai)种子萌发的影响进行了研究。结果表明：光照对有斑百合、川百合和毛百合种子萌发有明显促进作用,可缩短种子萌发时间,提高种子萌发率。24h光照下种子萌发完全所需天数比12h光照少,种子萌发率以24h光照最佳。避光条件下温度对大花卷丹、有斑百合、毛百合、川百合及东北百合种子萌发率和萌发速度有影响,对条叶百合种子影响最大,其种子萌发最适温度为20℃,5～6d开始萌动,2～3周萌发完全,随着温度的升高或降低其种子萌发率下降。光照条件下,变温对种子萌发影响不明显。子叶留土类型的毛百合种子有二次休眼现象,9000lx光照能代替低温解除二次休眼。经不同前处理的百合种子萌发率和萌发速度不同。     

Differential effects of four abiotic factors on the germination of salt marsh annuals

Interspecific differences in responsiveness to temperature, photoperiod, soil salinity, and soil moisture confirm the hypothesis that abiotic factors differentially affect the germination of salt marsh plants. In growth chamber experiments, four of eight annual species responded to small differences in temperature or photoperiod. Increasing soil salinity decreased the final proportion of seeds germinating and slowed germination for each of the seven species tested. Higher soil moisture increased the proportion germinating of five species and germination speed of all seven species. Salinity and moisture interacted to affect the proportion germinating of five species and germination speed of all seven species. Although the abiotic factor with the largest effect on germination varied among species, more species responded to, and the magnitudes of the responses were larger for, soil salinity than for the other abiotic factors. These germination tests partially explained interspecific differences in the timing of germination in the field. Patterns of Hutchinsia procumbens, Lythrum hyssopifolium, Parapholis incurva, and possibly Lasthenia glabrata ssp. coulteri germination in response to a nonseasonal rainfall could be explained by their response to salinity, temperature, or photoperiod. Fine-scale differences in the timing of establishment within the typical germination window and spatial distributions along salinity and moisture gradients were not explained.     

Increasing in vitro germination of Musa balbisiana seed

Seeds of Musa balbisiana were soaked in water for five days prior to excision of embryos. Embryos with their longitudinal axis laid flat and half-way embedded on agar-solidified medium produced the highest germination and the most desirable plantlet characteristics. Germination in vitro was 94% within 7 days compared to 50% after 54 days for greenhouse-sown seeds.     

冻融过程对荒漠短命植物种子萌发的影响

荒漠区冻融交替显著改变土壤温度和水分条件,并进一步影响荒漠植物种子萌发.为解析荒漠土壤冻融过程对植物种子萌发的影响,本研究以古尔班通古特沙漠4种典型短命植物[东方旱麦草(Eremopyrum orientale)、卵果鹤虱(Lappula patula)、尖喙拢牛儿苗(Erodiumoxyrrhychum)和条叶庭荠(...