Environmental factors during seed development of narrow-leaved bird's-foot-trefoil (Lotus tenuis) influences subsequent dormancy and germination

Narrow‐leaved bird's‐foot‐trefoil (Lotus tenuis) is a perennial forage legume adapted to waterlogged and heavy and infertile soils and can replace alfalfa (Medicago sativa) in areas with these soils in Argentina. Its seeds are hard and water‐impermeable but the effects of environmental factors on seed dormancy and germination are not known. The objective was to evaluate the hypothesis that water availability during seed development and maturation affects the degree of hardseededness in L. tenuis by changing seed coat properties, conditioning water uptake through the seed coat; and subsequently affecting dormancy, germination and speed of germination. Seeds were harvested in December/January and in February in both 1993/1994 and 1994/1995 from a permanent pasture of L. tenuis growing in a Hapludol soil in San Miguel del Monte province of Buenos Aires. Environmental conditions of each anthesis‐harvest period were determined. Seeds of each harvest were subjected to chilling, washing and mechanical scarification. After 12 months seeds from each harvest were observed in a scanning electron microscope. The water deficit of the soil and relative humidity were greater in the second than the first anthesis‐harvest period in both seasons. In 1993/1994 the control treatment in December had a higher germination rate than the February control seeds (0·40 vs. 0·20) and a faster germination rate. Mechanical scarification and chilling significantly enhanced the germination rate (0·95) and its speed in seeds of both harvests. Low temperatures significantly enhanced germination rate, starting after 60 d for the seeds harvested in December, and 90 d for the seeds harvested in February. In 1994/1995 the results were similar but both the January and February control treatments had higher germination rates (0·60 vs. 0·40) than in the previous year. Seeds harvested in February were more dormant in both years. These differences could be explained by the conditions in February anthesis‐harvest period in both years that could have hastened the natural dehydration process of seed, changing integument structure and enhancing its impermeability.     

Variability in germination behaviour of Paspalum dilatatum Poir. seeds is genotype dependent

Dallisgrass (Paspalum dilatatum Poir.) is a warm‐season grass, native to South America. Its adoption as a pasture crop has been hindered by low seed germination and slow establishment. However, variability in germination behaviour for this species has never been systematically analysed. For Paspalum spp., dry‐storage and moist cold or warm pre‐conditioning treatments have been reported as effective for the relief or breaking of seed dormancy. In the present work, seed germination responses at 32°C were assayed for sixteen P. dilatatum genotypes, representing its known natural genetic variability, to two moist pre‐conditioning treatments (at 5 and 20°C) and without pre‐conditioning, and three seed storage periods (0, 3 and 6 months). Pre‐conditioning at 20°C showed high germination percentages (>80%), with ratios equal to or higher than pre‐conditioning at 5°C, suggesting that cold is not required to break dormancy. Longer storage times resulted in increases in germination responses for most of the genotypes, while other biotypes showed no effect. Biotypes Virasoro and Chirú showed a remarkably different behaviour with higher germination percentages of untreated freshly harvested seeds. Our results show that diversity for traits involved in seed germination exists among naturally occurring P. dilatatum genotypes and the characterization of these traits should be addressed during ecotype characterization and evaluation of potential domesticates of this species.     

Quality and germination capacity of seed material harvested from an Arrhenatherion meadow

Arrhenatherion meadows are an endangered type of semi‐natural grassland in Europe, and their conservation and restoration is an important policy objective. Recent research has led to development of techniques for harvesting seed material from regional donor sites and strategies for re‐establishment of species‐rich grassland, but their practical application requires that consumers are guaranteed sufficient seed quality of directly harvested material. Methods for the evaluation of purity, thousand seed weight (TSW) and germination capacity were developed and tested, a pre‐condition to define the optimal seeding rate for this vegetation type (2000–3000 seeds m^?2). The assessment was based on seed obtained by two harvesting techniques: on‐site threshing (OST) and seed stripping (SS). Materials from both methods obtained 63% pure seeds. The TSW differed significantly between harvesting methods: the OST provided greater seed weight (1·057 g) than the SS (0·84 g). Two trials were implemented to define criteria for the germination capacity test. Organic growing media obtained the best and most homogenous results in a first comparative germination test. In the second trial, different dormancy‐breaking treatments were compared, each with and without pre‐chilling, namely: addition of potassium nitrate (KNO₃), addition of gibberellic acid (GA3) and without addition of chemicals (WA). The germination capacity of the treated variants KNO₃, GA3 and pre‐chilling was lower than that for WA. The harvesting method significantly influenced quality and quantity of the seed material, whereas the substrate and dormancy‐breaking treatments had no effect.     

Breaking the dormancy of rice seeds with various dormancy levels using steam and high temperature treatments in a steam nursery cabinet

This study aimed to determine the appropriate steam treatment conditions, using a steam nursery cabinet, to break the dormancy of Japanese rice cultivar seeds exhibiting various dormancy levels. The influence of the temperature and duration of the steam treatments on the germination percentage and germination rate was investigated. In highly dormant ‘Takanari’ seeds, the steam treatment at 40 °C for 7 d increased the germination percentage and decreased the 50% germination time (T_50S; based on seed number); this treatment was as effective as the dry heat treatment at 50 °C for 7 d. For the medium dormant ‘Moeminori’ and ‘Hitomebore’ seeds, the steam treatment at 40 °C for 5 d decreased T_50S sufficiently and more effectively than did the dry heat treatment at 50 °C for 7 d. For the slightly dormant ‘Moeminori’ seeds, the steam treatment at temperatures ranging from 24 °C to 40 °C for 7 d decreased T_50S without a corresponding decrease in germination percentage to <90%. For the non-dormant ‘Moeminori’ and ‘Takanari’ seeds, the same steam treatments had no, or a little if any, useful effect on the germination percentage and T_50S. Therefore, we concluded that, for the highly dormant seeds, steam treatment at 40 °C for 7 d was appropriate. Moreover, for less dormant seeds, steam treatment at 40 °C for 5 d was appropriate, and the steam treatment was not necessary for the non-dormant seeds.     

大株红景天种子休眠特性及解除

为有效解决大株红景天种子发芽率低的问题,探讨了大株红景天种子的休眠原因,采用不同浓度的GA3溶液浸种法,观测其发芽情况,结果表明大株红景天种子的休眠是由吸水障碍和含有抑制发芽物质所致,用水或50mg.L-1的GA3溶液浸种48h可解除大株红景天种子休眠。     

Breaking primary dormancy in seeds of the perennial pasture legume tedera (Bituminaria bituminosa C.H. Stirt. vars albomarginata and crassiuscula)

Tedera (Bituminaria bituminosa vars. albomarginata and crassiuscula) is a perennial pasture species with agronomic characters ideally suited to Mediterranean climates. Tedera seed has a period of after-ripening or primary dormancy typically lasting three months, which delays assessment and breeding of elite hybrid varieties. Temperature, chemical and mechanical methods were investigated in conjunction with in vitro culture to circumvent this dormancy period across a range of parental and hybrid genotypes. Temperature treatment of T5 (Tedera accession 5) and T48 (Tedera accession 48) alone was not sufficient to break dormancy (24.0% and 14.7% germination); however, when combined with soaking in gibberellic acid (GA₃) and mechanical scarification resulted in 79.7% and 84.3% germination respectively. In an effort to further improve this result for valuable hybrid genotypes, we combined mechanical scarification with removal of seed coat after imbibition and in vitro culture on B5 medium until radicle emergence. This resulted in breaking dormancy from 96% to 100% of parent seeds and 100% of hybrid seeds. Hardening the germinated F₁ or F₂ seedlings 4 d after first transfer to in vitro culture resulted in 100% survival of plants to soil. This procedure is now used on a routine basis in the Australian tedera breeding programme.     

皇后帝王花种子休眠及解除方法研究

皇后帝王花（Protea magnifica）种子具有休眠性,不经任何处理难以发芽。本研究以皇后帝王花种子为试验材料,通过测定皇后帝王花种子生活力、种子萌发率、种子各部分粗提液对白菜种子发芽的影响,并以不同的方式（短时高温+变温层积、酸蚀处理+变温层积、赤霉素处理+变温层积）处理种子,研究皇后帝王花种子的休眠原因及解除方法。结果表明：试验所用皇后帝王花种子的生活力高达90.00%,但不去除种皮的完整种子30 d内不发芽。种皮粗提液不仅抑制白菜种子的发芽,还显著影响白菜种子的根与地上部分的生长。皇后帝王花种子的休眠可能是种皮的机械障碍和种皮的内源抑制物共同引起的综合休眠。时长为2 min的不同高温（40~120 ℃）处理+变温层积、不同时间（10~ 70 min）的98%浓硫酸酸蚀处理+变温层积、不同浓度（0.3、0.5、0.7 mg/L）的赤霉素溶液处理+变温层积都可以打破种子的休眠,提高皇后帝王花种子发芽率和发芽势。其中各处理分别以60 ℃的短时高温处理、30 min的酸蚀处理、0.7 mg/L的赤霉素溶液处理效果最好。综合比较,30 min的酸蚀处理为解除皇后帝王花种子休眠的最佳方法。此外,赤霉素处理对皇后帝王花种子的休眠解除有着一定的促进作用,但相比其他两种处理方式效果并不理想。     

Thermal time approach to predicting seedling emergence dates of red clover,white clover and lucerne in farm fields

A practical method for predicting seedling emergence dates of red and white clovers, and lucerne is proposed. The germination response at seven different constant temperatures ranging from 5 to 35°C was examined. Germination rate, which is a reciprocal of the duration for 50% germination of seeds, was linearly regressed against temperature to calculate the base temperature and thermal constant of seed germination. The calculated values were 3·9°C and 15·8 degree days for red clover, 4·2°C and 13·6 degree days for white clover, and 2·9°C and 17·7 degree days for lucerne. Using the base temperatures, thermal constants, and the daily mean air temperatures at the study site, the seedling emergence dates of the three forage legumes were predicted. At the same time, in an outdoor pot experiment, seeds of these legumes were sown approximately every 3 weeks and seedling emergence dates were determined. The predicted dates of seedling emergence generally fitted the observed dates. Another prediction was attempted using the base temperatures, thermal constants, and normal daily mean air temperatures recorded over more than 30 years in the study site. This prediction showed that the seedlings of the three forage legumes began to emerge at the beginning of April and could continue to emerge until the beginning of November when their non‐dormant seeds were present in the site, and that when the seeds were sown from mid‐November of one year to late March of the next year, the emergence of seedlings was delayed until the beginning of April.     

Seed characterization and direct sowing of native grass species as a management tool

There is insufficient information about germination, seed biology and seedling establishment of native grass species of the cerrado (Brazilian savannah) to recommend their use in restoration of disturbed areas. We evaluated the production, percentage of fertile seeds, germination, seedling growth and establishment in the field of eighteen native grass species and one exotic invasive species (Melinis minutiflora) and also the effects of different storage periods on germination. The percentage of fertile seeds varied from 6·0 to 94·2% among native species. Ten species produced a minimum of 800 fertile seeds per gram. Germination rate was in the range of 11·0 to 98·8%. Storage for 1 year reduced the germination rate in one species, did not affect germination of three species and increased germination (by 2–10 times) in 14 species. After 2 years of storage, six species showed reductions in germination. Three different patterns of resource allocation were observed and might provide mechanisms for increasing seedling establishment under different environmental conditions. In the field, only two species flowered in the first year after sowing and an additional eight in the second year of observation. Melinis minutiflora is an aggressive species with more than three times the fertile seed production of native species (2820 seeds per gram), high germination rate (55%) and a high number of germinable seeds (1551 per gram). Despite the wide variation in seed characteristics and the delay in flowering, it is concluded that most native grass species can be used in projects aiming at the restoration and management of degraded areas.     

三种浸种剂对Na2SO4胁迫下小麦种子萌发期耐盐性的影响

为了解黄腐酸、褪黑素、水杨酸三种浸种剂对硫酸盐胁迫下小麦种子萌发期耐盐性的调节效应,分别采用不同浓度的黄腐酸(0.5、1.0和1.5 g·L^-1)、褪黑素(0.01、0.05和0.10 mmol·L^-1)、水杨酸(0.1、0.5和1.0 mmol·L^-1)对小麦进行浸种处理,随后与未处理的小麦种子一并采用100 mmol·L^-1 Na₂SO₄溶液培养,测定各处理下小麦种子萌发期的生长生理指标,并通过主成分分析综合评价其耐盐性。结果表明,0.5～1.5 g·L^-1的黄腐酸、0.01～0.10 mmol·L^-1褪黑素、0.1～0.5 mmol·L^-1水杨酸浸种均提升了小麦根系活力、体内抗氧化酶活性,降低了小麦体内超氧阴离子自由基■产生速率及丙二醛(MDA)含量,缓解了盐分对小麦种子萌发的胁迫程度,增强了小麦种子萌发期的耐盐性,促进了小麦的萌发生长。其中,1.5 g·L^-1的...     

In situ sprouting and regulation of fresh-seed dormancy in Spanish type groundnut (Arachis hypogaea L.)

Two hundred groundnut (Arachis hypogaea L.) germplasm accessions and 21 cultivars belonging to the Spanish group (ssp. fastigiata var. vulgaris) were screened for pod loss due to sprouting of seed in the field. Some cultivars were also tested for germination of the fresh-seed with or without testa and treated or untreated with ethrel or abscisic acid (ABA). Large variation in pod loss due to in situ sprouting of seed, and fresh-seed dormancy (FSD) was found among the accessions and cultivars. Fresh-seed dormancy index (FSDI) varied from 2% in Chico to 88% in ICGS 44 (the check with high FSD). Cultivars with an FSDI value of less than 10% showed more pod loss in situ than the cultivars with high FSDI. Thus pod loss due to in situ sprouting increased with a decrease in FSDI. Cultivar SB XI did not show any in situ sprouting or pod loss. A direct relationship (r, 0.86^**) existed between fresh-seed germination of accession/cultivar in the laboratory and the percentage of its plants with sprouted seed in the field. Seed of two Spanish cultivars ICGS 11 (dormant) and GG 2 (non-dormant) when tested for germination after treatment with ethrel or ABA at various seed development stages showed different germination response to these chemicals. Seed of GG 2 showed up to 40% germination even at an early stage (S₁) of seed development, whereas the seed of ICGS 11 responded to the ethrel only at maturity (S₄). Regulation of FSD appeared to be more under the control of the testa than the cotyledons. The variation in the degree of in situ sprouting can be used for breeding Spanish cultivars with various desirable levels of FSD.     

不同花生品种种子休眠特性的研究

休眠性是作物重要的农艺性状之一。本研究对31个刚收获的花生品种(系)进行发芽试验,以评价不同品种的休眠特性。结果表明,发芽率和萌发率都可以作为评价种子休眠性的指标。不同品种种子发芽率的变异范围为0～71.11%,20个品种(系)的发芽率低于10.0%,其中,徐9641等6个品种(系)的发芽率为0,表现为较强的休眠性;启海花生的发芽率为71.11%,休眠性较弱。相关分析表明,种子休眠性强弱与荚果、籽仁形状和小叶长度有关,长粒型种子和小叶较长的品种休眠性较强,而与其他农艺性状相关不显著。     

H2O2浸种对低温胁迫下花生种子萌发的调控作用

为了研究H2O2浸种对低温胁迫下花生种子萌发的调控作用，本研究以白沙1016和花育9122两个花生品 种为材料，通过种子萌发试验，设置（22±1）℃常温对照和（12±1）℃低温处理，首先采用不同浓度的H2O2进行浸种预 处理，分析了H2O2浸种对花生种子低温萌发相关指标的影响，筛选最适H2O2浸种浓度，然后采用最适H2O2浸种处 理后，测定其对发芽花生种子胚中氧化损伤和活性氧含量、脯氨酸代谢相关指标的影响。结果表明，低温显著降低 两个品种花生的相对发芽率、芽长/种长比、发芽指数及种子的活力指数，延长了平均露白时间，H2O2浸种预处理可 显著缓解低温对花生种子萌发的抑制，以1% H2O2浸种效果最好。同时，H2O2浸种预处理还显著降低了H2O2的积累 以及膜脂过氧化程度，促进了脯氨酸的积累，提高了脯氨酸合成酶鸟氨酸转移酶（OAT）和△1-吡咯琳-5-羧酸合成 酶（P5CS）活性，抑制了脯氨酸降解限速酶脯氨酸脱氢酶（ProDH）活性。表明H2O2浸种预处理可通过调控脯氨酸代 谢途径，促进低温条件下萌发花生种子内脯氨酸的积累，缓解氧化损伤，从而增强花生种子的低温萌发能力。     

34份花生种质休眠性筛选与鉴定

利用日晒干燥的34份花生种质进行发芽试验,初步筛选出2份休眠性差别明显的材料即休眠性强的y-1和缺乏休眠性的x-166。次年将这两份材料种植于田间,收获后在遮荫处干燥,进行萌发试验,其休眠性得到进一步确认。     

丁草胺对无芒稗种子的诱杀作用研究

 无芒稗颖果（俗称种子）切皮处理的发芽率达62%～81%。其休眠原因之一为籽实皮坚硬透水性差，胚得不到充足水分而处于休眠状态（属强迫型休眠）。丁草胺1.08 kg a.i./hm²能诱导休眠的无芒稗种子萌发并将其杀灭，其诱杀率达63%。丁草胺溶液浸种7 d。无芒稗种子有效发芽率达72%。较高温度（昼／夜：35℃／25℃）促进丁草胺诱导休眠无芒稗种子萌发。丁草胺作用于无芒稗颖果籽实皮，使中果皮细胞“栅栏”间距明显增大，内皮层管细胞减少，从而使无芒稗颖果籽实皮透水性增强，促进萌发。     

Changes in seed growth,levels and distribution of flavonoids during tartary buckwheat seed development

We investigated the change in seed shape and weight as well as the accumulation and distribution of anthocyanins, melanin, and flavonoids during tartary buckwheat seed development. Pericarp dry weight increased slowly while the increase in flour dry weight was much greater. Increases in the dry weight of the embryo and endosperm were associated with change in seed shape. The highest anthocyanin content was observed in stage two while the highest melanin content occurred in stage five. There was a considerable decrease in total flavonoids, rutin, quercetin and kaempferol in mature seeds relative to seeds that were still developing. Additionally, there were significant correlations (correlation coefficient > .900, p < .05) among the changes in rutin, quercetin and kaempferol between flour and the pericarp. In mature seeds, 95% of the flavonoids were present in flour.     

Alleviation of salinity stress on germination of Leymus chinensis seeds by plant growth regulators and nitrogenous compounds under contrasting light/dark conditions

The effects of plant growth regulators (PGRs) and nitrogenous compounds on alleviating salinity stress on seed germination of Leymus chinensis in light (12 h light/12 h dark) and dark (24 h dark) conditions were determined in a laboratory experiment. Seed germination was compared at various combinations of salinity and germination‐promoting compounds. Seed germination percentages were 57 and 74% under non‐saline conditions in light and dark, respectively, suggesting that germination was light‐inhibited. Germination decreased significantly with increasing salinity level in both light and dark conditions, and the reduction was greater in light than in dark at each salinity level. Seed germination percentage decreased to 22 and 7% in light but only to 51 and 27% in dark, in 100 and 200 mm NaCl solutions respectively. The influence of PGRs and nitrogenous compounds in alleviating salinity stress varied with light and salinity condition; e.g., gibberellins (GA_4 + 7) significantly increased germination percentages from 22%, 7% and 0·3% to 47%, 23% and 15% in light at 100, 200 and 300 mm NaCl, respectively, while they showed no effect on germination in darkness. In contrast, sodium nitroprusside and cytokinin significantly increased germination percentage in darkness at all salinity levels, but showed no effect on germination in light at 200 and 300 mm NaCl. Fluridone was very effective in alleviating salinity stress on germination in both light and dark; however, it was lethal to seedlings. Thiourea had no effect in alleviating salinity stress in either light or dark. Thus, alleviation of salinity stress on seed germination of L. chinensis by germination‐promoting compounds is strongly dependent on chemicals and light conditions.     

The effect of row spacing on alfalfa seed and forage production under irrigated Mediterranean agricultural conditions

We evaluated the effect of row spacing on seed and forage yields in alfalfa (Medicago sativa L.) using combined seed and forage production plots, in an irrigated Mediterranean agricultural environment. We compared three row distances (20, 40 and 60 cm) in two cultivars at a seed rate of 25 kg ha^?1 over a period of 4 years. We measured the seed yield and yield components as well as forage production. The 4‐year average revealed an overall clean seed yield of 367 kg ha^?1 declining over time, without significant differences in row distances. The number of shoots per square metre differed significantly as a function of row spacing, with averages of 357, 226 and 172 shoots m^?2 for row widths of 20, 40 and 60 cm respectively. The row spacing did not affect the number of racemes per shoot (23·1), the number of pods per raceme (7·2), the number of seeds per pod (6·5) or the thousand seed weight (1·667 g). The average forage production was 20·1, 18·5 and 17·9 Mg DM ha^?1 for row distances of 20, 40 and 60 cm, respectively, with higher yields associated with smaller row distances. Our data demonstrate that row spacing >20 cm does not confer any advantage to the production of alfalfa seed under irrigated Mediterranean agricultural conditions and that close spacing can significantly increase forage yields in the same environment.     

芸薹属种子休眠特性的研究 Ⅱ.风干处理、果壳阻抑对种子休眠的影响

本文研究了风干处理、发芽温度条件及果壳阻抑对芸薹属三个种种子休眠与萌发的影响,结果表明:(1)风干处理可使花后不同天数的种子完成后熟作用,促进种子的萌发,其破眠效果,尤以休眠浅的甘蓝型油菜为显著;(2)果壳对种子发芽有明显的阻抑作用,产生“强迫休眠”现象,其对种子的诱眠率,以休眠浅的甘蓝型油菜高于休眠深的芥莱型油菜;(3)油菜种子采收后先经风干,再在变温条件下发芽,其破眠效果高于单一风干或变温发芽。同时能有效地解除开花后20天以上幼嫩种子的休眠。