南亚热带森林几种乔木种子萌发和幼苗生长观察

本文对香椿（Ｔｏｏｎａｓｉｎｅｎｓｉｓ（Ａ．Ｊｕｓｓ．）Ｒｏｅｍ．）、木蝴蝶（Ｏｒｏｘｙｌｕｍｉｎｄｉｃｕｍ（Ｌ．）Ｖｅｎｔ．）、扁斗青冈（ＱｕｅｒｃｕｓｈｕｉＣｈｕｎ）、泡桐（Ｐａｕｌｏｗｎｉａｆｏｒｔｕｎｅｉ（Ｓｅｅｍ．）Ｈｅｍｓｌ）罗浮柿（ＤｉｏｓｐｙｒｏｓｍｏｒｒｉｓｉａｎａＨａｎｃｅ）、枳（ＢｅｒｃｈｅｍｉａｄｕｌｃｉｓＴｈｕｎｂ．）等南亚热带森林乔木种子萌发和幼苗生长进行观察．香椿、扁斗青冈、罗浮柿种子在轻阴（５５％光）条件下萌发率最高,分别为７０％、９０％、３０％,木蝴蝶种子在重阴（３８％光）条件下萌发率最高,为８０％,枳种子在光照条件下萌发率最高,为１５％．阳性树种香椿、木蝴蝶、泡桐、枳幼苗生长速度较快,属速生型树种,其幼苗在光照条件下生长速度最快,森林中树种扁斗青冈、罗浮柿幼苗生长速度较慢,属慢生型树种,其幼苗在轻阴条件下生长较好．随着施肥量的增加,幼苗生长速度明显提高．     

不同光强下几种南亚热带森林乔木的种子萌发和幼苗生长观察

对泡桐,春椿,木蝴蝶,枳Ｊｕ扁斗青冈和罗浮柿等亚热带森林乔木树种在不同强条件下的种子萌发及其幼苗生长进行观察,泡桐和枳Ｊｕ种子在光（１００％）条件下的萌发率最高,香椿和罗浮肺种子在轻阴（６２．２％）条件下的萌发率最高,木蝴蝶和扁斗青冈种子在中阴（３４．４％）条件下萌发率最高,阳性树种泡桐,香椿,木蝴蝶和枳Ｊｕ幼苗生长速度较快,属速生型树种,其幼苗在自然光条件下的总生物量最大;扁斗青冈和罗浮柿幼苗生     

Effects of seed colour heterogeneity on germination behaviour of the desert plant Lotononis platycarpa (Fabaceae)

We aimed to determine the ecological role of three seed morphs observed for the first time in a desert population of Lotononis platycarpa (Fabaceae), with respect to their germination requirements. Seeds sorted by seed coat colour (olive green, orange and brown) were germinated under laboratory conditions under two photoperiods (12/12‐h light and continuous dark) and three alternating temperature regimes (15/25, 20/30, 25/35°C). We found that the three distinct seed types differ in their seed mass, germination percentage and speed of germination. Overall, the light‐incubated seeds germinated with higher percentages than seeds in the total darkness. Furthermore, seeds with orange coat germinated with higher percentages at 15/25 and 25/35°C (up to 60%, for both) and significantly faster than the other two colour morphs. Our results suggest an adaptive significance of seed colour heterogeneity in the harsh desert habitat inhabited by the study species.     

Seed dispersal by carnivores in temperate and tropical dry forests

The seed dispersal mechanisms and regeneration of various forest ecosystems can benefit from the actions of carnivores via endozoochory. This study was aimed to evaluate the role of carnivores in endozoochory and diploendozoochory, as well as their effect on seed viability, scarification, and germination in two forest ecosystems: temperate and tropical dry forest. We collected carnivore scat in the Protected Natural Area of Sierra Fría in Aguascalientes, Mexico, for 2 years to determine the abundance and richness of seeds dispersed by each carnivore species, through scat analysis. We assessed seed viability through optical densitometry using X‐rays, analyzed seed scarification by measuring seed coat thickness using a scanning electron microscope, and evaluated seed germination in an experiment as the percentage of seeds germinated per carnivore disperser, plant species, and forest type. In the temperate forest, four plant species (but mainly Arctostaphylos pungens) were dispersed by four mammal species. The gray fox dispersed the highest average number of seeds per scat (66.8 seeds). Bobcat dispersed seeds through diploendozoochory, which was inferred from rabbit (Sylvilagus floridanus) hair detected in their scats. The tropical dry forest presented higher abundance of seeds and richness of dispersed plant species (four species) than in the temperate forest, and the coati dispersed the highest number of seeds (8,639 seeds). Endozoochory and diploendozoochory did not affect viability in thick‐testa seeds (1,480 µm) in temperate forest and thin‐testa seeds (281 µm) in tropical dry forest. Endozoochory improved the selective germination of seeds. Nine plant species were dispersed by endozoochory, but only one species (Juniperus sp.) by diploendozoochory. These results suggest that carnivores can perform an important ecological function by dispersing a great abundance of seeds, scarifying these seeds causing the formation of holes and cracks in the testas without affecting viability, and promoting the selective germination of seeds.     

Differential effects of camptothecin and interactions with plant hormones on seed germination and seedling growth

Effects of camptothecin, a naturally occurring alkaloid, on seed germination varied from promotive to inhibitory, depending on the species used. It markedly inhibited seedling root growth but its inhibition of hypocotyl growth varied among species. Camptothecin inhibited GA₃-induced dark germination of lettuce (Lactuca sativa L.) seeds and hypocotyl elongation of seedlings. In contrast to ABA, the camptothecin inhibition of GA₃-induced germination could not be overcome by cytokinin. When seeds were germinated at 29C with a 0.5 h light treatment, little or no germination occurred in the camptothecin treatment, but addition of cytokinin overcame this inhibition.     

异子蓬二型种子的萌发与休眠特性及其生态适应

异子蓬为中亚荒漠的特有种,其果实为胞果,花被片在结果时宿存包被果实形成浆果状的散布单位.对异子蓬的散布单位、果实形态进行比较观察,并在5/15℃、5/25℃、15/25 ℃(暗/光=12h/12h)3个温变周期下进行种子萌发实验,结果表明:(1)异子蓬的散布单位绿色、浆果状,有大小两种形态;大小两种散布单位内包被的果实在形状、大小、颜色上存在着明显差异.(2)大的散布单位内包被的果实圆形,扁平,褐色,无光泽,直径(2.64±0.03) mm,重量(3.68±0.04) mg;小的散布单位内包被的果实双凸镜形,黑色,有光泽,直径(2.40±0.04) mm,重量(2.86±0.06) mg.(3)褐色种子在3个温变周期下的萌发率都在81%以上,萌发速度快,而黑色种子萌发率低,萌发慢,具有休眠现象.(4)划破种皮及低温层积处理可显著提高黑色种子在3个温变周期下的萌发率,延长储存时间也可有效地促进黑色种子的萌发,表明黑色种子处于非深度生理休眠状态.异子蓬产生的两种不同类型的种子及其在时间和空间上的萌发差异对荒漠异质环境具有重要的适应意义.     

Two thrush species as dispersers of Miconia prasina (Sw.) DC. (Melastomataceae): an experimental approach.

We carried out a seed germination experiment using two thrush species in captivity. We compared the number of germinated seeds and germination time of control seeds (manually removed from fruits) and ingested seeds of Miconia prasina by two bird species, Turdus albicollis and T. amaurochalinus, and also compared retention times of seeds by both thrush species. Control seeds germinated more frequently than those ingested for one species, T. albicollis. The germination time of ingested seeds by T. amaurochalinus was similar to the control seeds but seeds ingested by T. albicollis took longer to germinate than the controls. Both thrush species had a similar seed defecation pattern. The cumulative number of defecated seeds increased by 2 hours after fruit ingestion. At the end of the first 30 minutes both species had already defecated approximately 50% of the seeds ingested Our results suggest that both species could act as disperser agents of M. prasina.     

Variation in seed germination of 86 subalpine forest species from the eastern Tibetan Plateau: phylogeny and life-history correlates

We have examined the seed germination strategy of 86 subalpine woody species from the eastern part of the Tibetan Plateau and assessed correlations between seed germination and phylogeny, life-history attributes, habitat, and altitude using stepwise analyses of variance (ANOVAs) and phylogenetically independent contrasts (PICs). A series of ANOVAs revealed that the total amount of variance in the arcsine-transformed value of germination percentage among species could be accounted for by phylogeny (19.2%) and dispersal mode (14.3%) in seeds incubated in the light and by phylogeny (29.3%) and dispersal mode (11.0%) in those incubated in the dark. In addition, the total amount of variance in T50 (days to half of the final germination) can be accounted for by phylogeny (22.7%) and dispersal mode (17%) in seeds incubated in the light and by phylogeny (32.1%) and dispersal mode (9.9%) in those incubated in the dark. PICs indicated a significant correlation between germination percentage and dispersal mode and a positive correlation between T50 and seed mass, showing that wind-dispersed seeds had higher germination percentages than both unassisted and vertebrate-dispersed seeds and that small seeds germinated faster than large ones. We suggest that phylogeny and dispersal mode may constrain variation in seed germination across species and that the speed of germination and seed mass may co-vary to adapt to a variable environment. Therefore, from an evolutionary perspective, seed germination might be the result of both selective pressures over long-term ecological time and phylogenetic constraints over the long-standing evolutionary history of the phylogenetic group.     

皂荚天然群体间种实表型特性及种子萌发的差异分析

对位于湖北京山、湖南城步、贵州兴义、重庆秀山、四川成都、广西桂林、山东费县和甘肃天水的8个皂荚（Gleditsia sinensis Lam．）天然群体间果实和种子表型特性及种子萌发率的差异进行了研究,在此基础上,对种子特性与萌发率的相关性进行了分析。结果表明：不同皂荚群体间荚果的长度、宽度、厚度和质量以及种子长度、宽度、厚度和百粒质量均存在极显著差异（P〈O．01）;在低纬度、高降雨量和干扰程度相对大的区域产生的荚果及种子均较大。在不同温度（昼／夜温度35℃／20℃、30℃／15℃、25℃／10oC和15℃／5℃）条件下,8个皂荚群体间种子萌发率无显著差异,平均萌发率为7．70％;种皮经人为损伤后种子萌发率总体上有所提高且在不同温度条件下差异显著,其中在昼／夜温度15℃／5℃的条件下种子萌发率低于其他处理温度。在不同温度条件下,种子的长度、宽度、厚度和百粒质量与萌发率均呈正相关,但总体上相关性不显著。研究结果说明：不同皂荚群体的荚果和种子特性变异较大,且在降雨量高的地区其果实和种子较大;低温对皂荚种子的萌发有一定抑制作用;种皮损伤处理可解除皂荚种子的物理性休眠,但皂荚种子还可能存在生理休眠现象;一定程度的种子复合休眠可能是皂荚群体适应不同生境的重要生存策略之一。     

Dormancy Release,Germination, and Electrolyte Leakage from Apple Embryos during Stratification in the Presence of Sucrose

The dynamics of dormancy release during the stratification of apple (Malus domestica Borkh.) seeds was quantitatively described by three characteristics of seeds germination: the percentage of seeds that germinated by the tenth day, mean germination time, and the sum of seeds germinated in each of ten days (Timson's parameter), which allowed the assessment of the viability, the rate of dormancy release, and seed heterogeneity. We showed that apple seeds were characterized by a combined (physical and physiological) type of dormancy, with the seed coat and the embryo envelope being involved in the maintenance of physical dormancy. The addition of sucrose to the stratification medium accelerated the release of seed dormancy and improved all characteristics that determine seed germinability. Electrolyte leakage from embryos hardly changed during stratification, which agrees with the fact that all seeds remained viable throughout the entire period of dormancy. We assume that the release of seed dormancy is not a single-stage process.     

The Induction of Seed Germination in Arabidopsis thaliana Is Regulated Principally by Phytochrome B and Secondarily by Phytochrome A

We examined whether spectrally active phytochrome A (PhyA) and phytochrome B (PhyB) play specific roles in the induction of seed germination in Arabidopsis thaliana (L.) Heynh., using PhyA- and PhyB-null mutants, fre1-1 (A. Nagatani, J.W. Reed, J. Chory [1993] Plant Physiol 102: 269-277) and hy3-Bo64 (J. Reed, P.Nagpal, D.S. Poole, M. Furuya, J. Chory [1993] Plant Cell 5: 147-157). When dormant seeds of each genotype imbibed in the dark on aqueous agar plates, the hy3 (phyB) mutant did not germinate, whereas the fre1 (phyA) mutant germinated at a rate of 50 to 60%, and the wild type (WT) germinated at a rate of 60 to 70%. By contrast, seeds of all genotypes germinated to nearly 100% when plated in continuous irradiation with white or red light. When plated in continuous far-red light, however, frequencies of seed germination of the WT and the fre1 and hy3 mutants averaged 14, nearly 0, and 47%, respectively, suggesting that PhyB in the red-absorbing form prevents PhyA-dependent germination under continuous far-red light. When irradiated briefly with red or far-red light after imbibition for 1 h, a typical photoreversible effect on seed germination was observed in the fre1 mutant and the WT but not in the hy3 mutant. In contrast, when allowed to imbibe in the dark for 24 to 48 h and exposed to red light, the seed germination frequencies of the hy3 mutant were more than 40%. Immunoblot analyses of the mutant seeds showed that PhyB apoprotein accumulated in dormant seeds of the WT and the fre1 mutant as much as in the seeds that had imbibed. In contrast, PhyA apoprotein, although detected in etiolated seedlings grown in the dark for 5 d, was not detectable in the dormant seeds of the WT and the hy3 mutant. The above physiological and immunochemical evidence indicates that PhyB in the far-red-absorbing form was stored in the Arabidopsis seeds and resulted in germination in the dark. Hence, PhyA does not play any role in dark germination but induces germination under continuous irradiation with far-red light. Finally, we examined seeds from a signal transduction mutant, det1, and a det1/hy3 double mutant. The det1 seeds exhibited photoreversible responses of germination on aqueous agar plates, and the det1/hy3 double mutant seeds did not. Hence, DET1 is likely to act in a distinct pathway from PhyB in the photoregulation of seed germination.     

光质及种子大小对普洱地区14种植物种子萌发的影响

以普洱地区14种常见植物种子为材料,在实验室条件下研究了其在白光、黑暗、红光和蓝光条件下的萌发特性,并分析了种子大小与萌发率、萌发速率、萌发开始时间的关系。结果表明:光质对四方蒿、沙针、尖子木、藿香蓟种子萌发率和萌发速率均有显著影响(P0.05)。光质对大叶斑鸠菊、云南山枇花、臭灵丹、车桑子、光萼猪屎豆、葫芦茶、云南地桃花、西南宿苞豆、岗柃、中国宿苞豆10个物种的种子萌发率和萌发速率均没有显著影响(P0.05),以上物种中除中国宿苞豆外,其他物种种子萌发率均在20%以下,处于休眠状态。四方蒿种子在白光(89.9%)和红光(84.7%)下萌发率最高,红光下种子萌发最快(4.93),蓝光下种子萌发开始时间最晚(11.3 d);沙针种子在白光下萌发率最高(80.4%)、萌发速率最快(2.71),在黑暗和蓝光下萌发率较低(43.9%和38%)、萌发速率最慢(0.73和0.85),白光、红光下萌发开始最早(11 d),黑暗条件下萌发开始最晚(21.7 d);尖子木种子萌发率在白光、黑暗、蓝光下均在86%以上,而红光下仅32%且萌发速率最慢(1.29),在蓝光下萌发开始时间最晚(13 d);藿香蓟种子萌发率和萌发速率在红光下最高(分别为71.3%和6.46),黑暗条件下最低(分别为42.5%和2.62);大叶斑鸠菊萌发开始时间在黑暗条件下最早(6 d),其次是白光下(7 d),蓝光和红光下较晚,分别为8 d和7.7 d。14个物种种子的萌发率与种子大小间均有显著负相关关系;种子萌发速率、萌发开始时间与种子大小间也有负相关关系,但不显著;种子大小与萌发率、萌发速率和萌发开始时间的关系不会随着光质的变化而发生变化。     

Temperature and water requirements for germination and effects of discontinuous hydration on germinated seed survival in Tillandsia recurvata L.

Tillandsia recurvata is an epiphytic bromeliad with a wide distribution in the Americas; however, little is known about the development of its post-seminal adaptations for survival in epiphytic environments. The purpose of this study was to define the temperature and water requirements for the germination of T. recurvata seeds. The absence of radicle emergence in T. recurvata seeds resulted in 2?stages of germination: swollen with broken seed coat (stage-1) and chlorophyllic embryos (stage-2). The effects of partial or discontinuous hydration on germinated seed survival were also assessed. The seeds were collected in a semi-arid shrubland of Mexico City. We explored: (1) whether water vapour can provide a sufficient water source for germination; (2) the temperature required for germination stage-1 and the optimal and critical osmotic potentials for germination in both germination stages; (3) the effect of seed incubation at different osmotic potentials that undergo subsequent dehydration on their survival in stage-2; and (4) the loss of dehydration tolerance during early post-seminal development. In addition, an image of T. recurvata seed anatomy was obtained to illustrate its structures. Germination stage-1 of T. recurvata seeds is rather similar across the tested temperature range. The seeds required to be in contact with liquid water to germinate. The interval of osmotic potential facilitating both germination stages was from 0 to ?0.6?MPa. Although germinated seeds displayed dehydration tolerance, this tolerance decreased in germination stage-2. The osmotic potential during germination affected the tolerance of the chlorophyllic embryos (stage-2) to subsequent dehydration.     

Seed rain and soil seed bank of Picea asperata Mast. in subalpine coniferous forest of western Sichuan,China

Abstract

Dragon spruce (Picea asperata Mast.) is widely planted on clear-cuts from natural subalpine coniferous forests in western Sichuan. To assess the natural regeneration potential of this species in spruce plantations of different ages, field studies on the seed rain, seed bank, and seedling recruitment were conducted in 20-year, 30-year, and 60-year plantations, and in a retained natural forest ca. 150 years old for comparison. Moreover, a series of temperature and light regimes were also designed in March 2003 to test germination/dormancy responses of the P. asperata seeds to different conditions. In the plantations considered, both the densities of seed rain and soil seed bank increased with increasing stand age, whereas they were both low beneath the natural forest partially due to low adult density of P. asperata adult trees. P. asperata has a transient seed bank, and ca. 60% of seeds were found in the litter layer. Seed decay and seed predation were the two most important factors affecting soil seed bank dynamics, which caused a number of seed losses from the soil. Only a small fraction germinated and produced seedlings, and the indices of the losses from the seed bank via germination in the 30-year plantation, 60-year plantation and natural forest were 4.75, 5.10, and 2.80%, respectively. High seedling mortality was observed after seedling emergence, and most of the germinated seedlings died out within one growing season. The P. asperata seeds showed a high percent germination and no significant differences under most light and temperature regimes except for full sunlight or temperature below 5°C. In conclusion, despite a substantial number of seed produced, the high depletion of soil seed, the low seedling output, and high seedling mortality may obscure the natural regeneration potential of this tree species.     

Effect of day length on germination of seeds collected in Alaska

Day length control can effectively limit seed germination to favorable seasons, but this phenomenon has been studied in relatively few wild plants. I tested species from interior Alaska for day length control of germination under controlled conditions, and I also monitored germination phenology in natural habitats. Unstratified and cold-stratified seeds were germinated on short (13 h) and long (22 h) day length and in the dark at constant and alternating temperatures. On long day length, unstratified Ledum decumbens and Saxifraga tricuspidata seeds germinated from 5 C to 20 C, but on short day length few or no seeds germinated at 5 C and 10 C and germination was reduced at higher temperatures. Unstratified seeds of Diapensia lapponica and Chamaedaphne calyculata germinated only at 15 C and 20 C on long day length, and short day length completely inhibited germination. Cold stratification widened the temperature range for germination on both long and short day lengths, but germination was still lower on short than long day length. Germination phenology in natural habitats was consistent with germination in controlled conditions. In these species, short day length and low temperatures interact to inhibit germination in the fall. After overwintering, seeds germinate in the spring at low temperatures and on long day lengths. The inhibitory effect of short day length is not important in the spring because day length is already long at snowmelt.     

Are fungi important for breaking seed dormancy in desert species? Experimental evidence in Opuntia streptacantha (Cactaceae)

Seeds of Opuntia spp. have physiological dormancy; they need a period of after-ripening to break dormancy, and the embryos have low growth potential. We evaluated the combined effects of seed age and presence of fungi on the testa on germination of Opuntia streptacantha, an abundant species in the Chihuahuan Desert (Mexico), assuming that older seeds have broken seed dormancy and fungi can reduce mechanical resistance to germination. In a preliminary experiment, we found no germination of 9-year-old (1998) and freshly collected (2007) seeds. However, we obtained 67% and 27% germination from 9-year-old and fresh non-sterilized seeds, respectively, and found fungi growing on the testa of all germinated seeds. Two fungal strains were isolated and identified using ribosomal internal transcribed spacer (ITS) sequence analysis: Penicillium chrysogenum and Phoma sp. In a second experiment, we inoculated seeds with strains of P. chrysogenum and Phoma sp., as well as Trichoderma koningii and binucleate Rhizoctonia (Gto17S2), to evaluate their ability to break seed dormancy. Seeds inoculated with P. chrysogenum, Phoma sp. and T. koningii had higher germination than controls for both seed ages, but germination was higher in older seeds. Scanning electron microscopy showed that these fungi eroded the funiculus, reducing its resistance. Binucleate Rhizoctonia did not lead to germination and controls had almost no germination. Our results strongly indicate that fungi are involved in breaking seed dormancy of O. streptacantha, and that the effect of fungi on seeds is species-specific.     

Germination ecology of the polycarpic grassland perennials Primula veris and Trollius europaeus

The seed germination behaviour of Primula veris and Trollius europaeus , both perennial, polycarpic grassland plants was compared The species have similar-sized seeds that are dormant at dispersal Seeds buried in soil and exhumed at regular intervals showed that for both species, primary seed dormancy was overcome by cold-stratification Hence, their germination in the field should occur in spring, following dispersal, or later Seeds of P veris became dormant again in the late spring/early summer, and dormancy was broken again in the second winter Seeds of T europaeus did not exhibit such changes in dormancy
Seeds of P veris did not germinate in darkness This suggests that P veris can accumulate a persistent seed bank because buried seeds are prevented from germinating Trollius europaeus , on the other hand, germinated equally well in darkness and in light which suggests that seeds might germinate even when they are too deep in the soil for seedlings to emerge Two lines of evidence confirm this difference in seed bank behaviour (1) Primula veris was detected in the persistent seed bank of a grassland site, whereas T europaeus was not (n) After 16 months burial, 85% of the P veris seeds but only 8% of the T europaeus seeds remained viable     

Parasitoid attack of the seed-feeding beetle Bruchus loti enhances the germination success of Lathyrus japonicus seeds

Hard seeds of some legume species can germinate after seed-feeding insects bore through the seed coat and consequently break seed dormancy. Larvae of bruchine beetles are the main seed feeders attacking many legume species. Boring of the hard seed coat by bruchine beetle larvae enhances the germination percentage of legume species, but consuming too much of a single seed may reduce the chances the seed will survive. We hypothesise that the early mortality of bruchine larvae due to parasitism contributes positively to seed germination because larvae are killed before consuming too large a quantity of the seed. Here, we tested this hypothesis using Lathyrus japonicus seeds and Bruchus loti, the main seed feeder attacking this plant. B. loti larvae were mainly parasitised by two species of idiobiont parasitoids—Pteromalus sp. and Dinarmus sp. The seeds from which Pteromalus wasps emerged germinated more successfully than did the seeds from which B. loti adults emerged. B. loti larvae parasitised by the two wasp species consumed the seeds less intensively than did unparasitised larvae. Thus, the results of experiments supported our hypothesis. However, the germination success varied significantly between the seeds from which Pteromalus and Dinarmus wasps emerged. The difference in the size of seeds the two wasp species chose for parasitism may have influenced the germination percentage.     

新疆短命植物小拟南芥(Arabidopsis pumila)种子萌发特性及其生态适应性

通过显微结构及不同处理条件下种子萌发率的观察,对早春短命植物小拟南芥(Arabidopsis pumila)种子萌发特性及影响因素进行了研究,并对其生态适应性进行了讨论。结果表明:(1)温度和光照变化对自然生境和温室收获种子的萌发率影响均不显著,说明此种群在前期萌发阶段对光、温不敏感;(2)自然生境中采收的小拟南芥种子萌发率显著低于温室收获种子,说明环境条件的变化对短命植物种子的发育具有重要作用,可显著改变种子的萌发行为;(3)赤霉素使自然生境收获种子胚活性增强从而对萌发有较大促进作用,可使萌发率增加50%以上;(4)对种皮进行各种机械损伤处理使得种皮松弛或透气,可以显著提高自然生境种子的萌发率(超过70%);(5)盐和干旱胁迫对种子萌发均具有明显的抑制作用,但复水后部分被抑制种子可重新萌发,显示盐和干旱胁迫可导致种子产生浅度休眠。结合小拟南芥自然生存环境及本研究的结果,显示其种子萌发特性与生境具有高度适应性。     

Seed germination requirements of Buck’s beard [Aruncus dioicus (Walter) Fernald (Rosaceae)]

Aruncus dioicus (Walter) Fernald (Rosaceae) is a perennial herbaceous plant whose young shoots are traditionally collected in the wild and consumed as a food in NE Italy. The aim of this study was to determine the germination requirements of its seeds in order to start its cultivation, and to assess the germination of six accessions of the species. Viability of seeds ranged from 86 to 97% in the various accessions. Germination rate was almost null in seeds of two accessions, and ranged from 10.5 to 37.3 in the other ones. The seed coat was permeable to water. Treatments with GA₃, KNO₃ and mechanical scarification did not enhance the germination, while the cold stratification treatment at 2 °C for different periods improved the germination rate and the mean germination time as compared with the untreated seeds. With 45 days of cold stratification, the germination rate and mean germination time (respectively, 90.1% and 7.7 dd) of seeds were different from those of the untreated seeds. Cold stratified seeds germinated under artificial light and did not germinate in the dark. Seeds of A. dioicus displayed an intermediate physiological dormancy, removable by a cold stratification treatment, requiring both light and cold conditions.