The effect of seed source, light during germination, and cold-moist stratification on seed germination in three species of Echinacea for organic production

Organic production of one of the most popular botanical supplements, Echinacea, continues to expand in the U.S. Echinacea seeds typically show a high degree of dormancy that can be broken by ethephon or gibberelic acid (GA), but these methods are currently disallowed in organic production. In order to determine the efficacy of non-chemical seed treatments, we evaluated the effect of varying seed source and supplying light, with and without cold-moist stratification, on seed germination of the three most important medicinal species of Echinacea, E. angustifolia DC, E. purpurea (L) Moench, and E. pallida (Nutt.) Nutt. Treatments included cold-moist stratification under 24 h light, 24 h dark, and 16/8 h light/dark to break seed dormancy. We found that germination was greater in the E. purpurea and E. pallida seeds from a commercial organic seed source compared to a public germplasm source. When seeds were not cold-moist stratified, 16-24 h light increased germination in E. angustifolia only. Echinacea angustifolia, E. purpurea, and E. pallida seeds that were cold-moist stratified under 16-24 h of light for 4 wk had a significantly greater percentage and rate of germination compared to seeds germinated in the dark. Therefore, cold-moist stratification under light conditions is recommended as a method to break seed dormancy and increase germination rates in organic production of Echinacea.     

Commercial Seed Lots Exhibit Reduced Seed Dormancy in Comparison to Wild Seed Lots of Echinacea purpurea

Seed germination patterns were studied in E. purpurea (L.) Moench grouped by seed source, one group of seven lots from commercially cultivated populations and a second group of nine lots regenerated from ex situ conserved wild populations. Germination tests were conducted in a growth chamber in light (40 μmol·m(-2)·s(-1)) or darkness at 25 °C for 20 days after soaking the seeds in water for 10 minutes. Except for two seed lots from wild populations, better germination was observed for commercially cultivated populations in light (90% mean among seed lots, ranging from 82% to 95%) and in darkness (88% mean among seed lots, ranging from 82% to 97%) than for wild populations in light (56% mean among seed lots, ranging from 9% to 92%) or in darkness (37% mean among seed lots, ranging from 4% to 78%). No germination difference was measured between treatments in light and darkness in the commercially cultivated populations, but significant differences were noted for treatments among wild populations. These results suggest that repeated cycles of sowing seeds during cultivation without treatments for dormancy release resulted in reduced seed dormancy in E. purpurea.     

Methods to overcome seed dormancy in Echinacea angustifolia DC

Some factors (light, prechilling, gibberellic acid, ethylene) affecting germination of seeds of Echinacea angustifolia DC. were investigated. Without any pretreatment, the seeds germinated better in darkness than in light, however, percentages germination were low in both cases. GA₃ did not increase germination in light. Prechilling for 7–15 days in light or in darkness hardly affected percentage germination but significantly increased the rate of germination. Ethephon during prechilling resulted in a large increase of percentage and rate of germination in light, but had hardly any effect on germination in darkness. The results showed that a prechilling treatment for about 11 days at 5°C in a 1 mM ethephon solution in continuous light, followed by a 2-week germination period in light (24 h per day) at 20/30°C, can induce >90% seed germination in E. angustifolia. The prechilling treatment in ethephon also increased the rate of germination.     

Effect of seed age,stratification, and soaking on germination of wild asparagus (Asparagus acutifolius L.)

Wild asparagus (Asparagus acutifolius L.) is a widespread species found in all the Mediterranean areas. The spears are highly valued by consumers and owing to its frugality, this species is a feasible new crop with high income potential, especially for Mediterranean marginal areas. Currently, the cultivation of this species is limited because of its low and erratic seed germination that makes difficult the production of seedlings for plant propagation. In this research, non-after-ripened (1 month-old) and after-ripened seeds (dry stored at room temperature for 13 months) were exposed for 30 days in the dark to three moist stratification treatments: cold (5 °C), warm (23 °C) or no stratification; subsequently they were soaked for 12 h in warm water (35 °C) or not soaked. The effect of these pre-germination treatments on three germination parameters (germination percentage, time to 50% of final germination – T₅₀ – and germination pattern) was studied, as well as some possible seed dormancy forms involved therein. The 1-year dry storage period proved to be effective in after-ripened seeds by enhancing seed sensitivity to the subsequent pre-germination treatments. After-ripened seeds exhibited higher and more rapid germination compared to non-after-ripened seeds. Soaking, cold or warm moist stratification had similar single effect on non-after-ripened seeds (27% germination). With after-ripened seeds, only soaking or warm stratification were effective (47% germination) when singularly applied, while cold stratification did not improve germination. By combining stratification and soaking treatments, a higher germination for both non-after-ripened and after-ripened seed-lots was achieved. The highest germination was obtained when after-ripened seeds were stratified and soaked (76%), without any significant difference between cold or warm stratification. Single or combined application of moist stratification (regardless of the temperature used) and soaking resulted always in a faster germination compared to that of no-treated seeds and especially with after-ripened seeds (T₅₀ = 6 days). A non-deep type 1 physiological dormancy can be hypothesized for the seeds of this species. Low stratification temperature induce secondary dormancy in after-ripened seeds that can be removed by soaking them at 35 °C for 12 h.     

Effects of after-ripening,stratification and GA3 on dormancy release and on germination of wild asparagus (Asparagus acutifolius L.) seeds

Seeds of wild asparagus (Asparagus acutifolius L.) were treated and compared in this research to investigate seed dormancy class and level involved in this species. Four seed lots were compared: (i) freshly harvested seeds in 2007 (07Fr); (ii) freshly harvested seeds in 2008 (08Fr); (iii) after-ripened (AR) 2007 seeds dry stored in glass jars (ARg); (iv) AR 2007 seeds dry stored in paper bags (ARp). The 07Fr seeds were exposed to (1) chemical scarification combined with gibberellic acid (GA₃) levels (0, 200, 400, and 600 mg L⁻¹) and to (2) 28-day moist stratification at 5 and 23 °C, and two sequences of 5/23 °C combined with 0 and 400 GA₃ mg L⁻¹ levels, and (3) together to the 08Fr and AR seeds were exposed to 56-day moist stratification at 5, 23, or 5/23 °C. With the 08Fr and AR seed lots this last stratification treatment was combined with 0 or 800 GA₃ mg L⁻¹ levels. The dormancy depth of 08Fr (32% germination) was less than 07Fr seeds (2%). The latter after-ripened during dry storage and when stored in glass germinated more (47.5%) than in paper (12%). Stratification for 4 weeks was ineffective in improving germination of 07Fr seeds; when chemically scarified they did not germinate at all. The highest (nearly 70%) and the most rapid and uniform germination were observed for all the lots when they were warm stratified for 56 days. Warm stratification improved germination more than alternate temperature stratification, while cold stratification inhibited germination especially for the 08Fr and ARg lots, thus seeds seem not to have a morphological component to their dormancy. GA₃ only improved germination of 07Fr seeds, at a low rate. A. acutifolius seeds fit the characteristics of a non-deep physiological dormancy.     

Soil seed banks are short-lived and triggered by the first effective rainfalls in the vacant lots of Santiago,Chile

We studied the temporal variation of the soil seed banks in the urban lots of Santiago, Chile. As most of the plants that emerge from the seed banks in lots are also found in open habitats and are easily germinable, we hypothesize that the seed banks in lots are highly dynamic and short-lived, with the bank depleted every year during the germination season to be reloaded with new seeds during the next seed dispersal period. In each 20 lots for two year (2017 and 2018), 9 soil samples were collected. These samples were obtained from three sampling points randomly distributed across the plots. The seed bank was estimated by seed germination in soil samples placed in plastic trays. The samples of all the lots were stratified at 2 °C by 3 months before sowing. In order to record the seed persistence, soil of three lots watered in 2017 for six months were dried and maintained under dark and non-watered conditions until re-sowing in autumn 2018. To determine if the seeds present cold-associated germination triggers, soils of five lots were maintained under dark conditions for 3 months (soils without cold stratification) for comparison with soils with cold stratification of the same lots. The above-ground plants were recorded in all lots for both years. Forty plant species were recorded in soil bank. The total emerged seedling densities ranged between 7,944 (2017) to 3,700 seedlings m^-2 (2018). Species per lot varied between 17 and 7 during 2017, and between 14 and 3 during 2018. In five lots, seedling densities were not statistically different between cold stratified soil at 2 ° C and non-stratified. In three lots with re-sown soil, seedling density of the first sowing (4,096 seedlings m^-2) was significantly higher than second sowing (201 seedlings m^-2). Thirty-seven plant species were recorded in the above-ground vegetation during 2017 and 42 species in 2018. Species frequency of the seed bank was positively correlated with species frequency of above-ground vegetation. Concluding, the bank is highly dynamic, short-lived, and is depleted every year during the germination season, which begins with effective rainfalls, would be reloaded with seeds during the seed dispersal period.     

In vitro germination of Paphiopedilum seed on a completely defined medium

Seed germination and seedling survival of Paphiopedilum cultured aseptically for 8 months in darkness or in the light varied with seed source, culture medium and incubation environment. In the light, germination was best and nearly equal on Burgeff EG-1, Thomale GD, and Norstog media, but more seedlings survived on Burgeff EG-1. Comparing incubation environments, the best germination and seedling survival occurred in the dark on either Norstog or Thomale GD, suggesting that increased production of Paphiopedilum from seed may require germination and early seedling growth in darkness. Since the Norstog medium is completely defined, it can be used to determine which organic constituents are vital for asymbiotic germination and growth of Paphiopedilum.     

几种药剂促进苦瓜种子发芽的研究

研究了不同浓度的乙烯利、赤霉素、双氧水处理对苦瓜种子发芽的影响.结果表明:乙烯利能够更有效地促进苦瓜种子的发芽.经过150 mg/L乙烯利液浸种16 h的苦瓜种子,不论发芽势、发芽率、发芽指数还是活力指数都极显著高于其他药剂处理.     

兴安杜鹃种子萌发特性研究

以兴安杜鹃为试材,采用常规观察方法与石蜡切片方法观察种子形态,通过对光照、温度、赤霉素浓度、NaCl胁迫等条件设置不同处理,研究了其种子形态与萌发特性,旨在为兴安杜鹃繁殖培育和苗木生产提供参考依据。结果表明:兴安杜鹃种子成熟时发育至成熟胚阶段,种子细小,千粒质量仅为0.100 4 g。兴安杜鹃种子需光萌发;最适其种子萌发的温度为25℃,过高或过低温度均不利于其种子萌发;一定浓度的赤霉素对其种子萌发有促进作用;NaCl胁迫下兴安杜鹃种子的发芽率、发芽势、发芽指数随盐离子浓度增加呈明显下降趋势,当NaCl浓度超过0.6%时,其种子完全不能萌发。因此,兴安杜鹃种子需光照萌发,最适其萌发温度为25℃,对盐胁迫较为敏感,经600 mg·L^-1赤霉素处理的种子萌发效果最佳,发芽率可达92.67%。     

白菜种子萌发的热抑制现象及其与细胞壁降解酶的关系

为了探讨白菜种子萌发热抑制的机制,以新收获的白菜种子为材料,研究了种子萌发对不同温度的响应,后熟、冷层积和植物激素处理对种子萌发的作用,以及种子萌发和不同处理与细胞壁降解酶之间的关系。结果表明,当萌发温度 ≥ 20 ℃时,种子的萌发率显著降低,热抑制的种子不表现次生休眠。后熟、层积和GA₃处理能有效地降低种子萌发的热抑制;相反,ABA处理则增强种子萌发的热抑制。种子萌发过程中内切–β–甘露聚糖酶、β–甘露糖苷酶和α–半乳糖苷酶的活性增加。与新收获的种子相比,后熟、层积和GA₃处理增加上述3种酶的活性;ABA处理增加内切–β–甘露聚糖酶的活性,但不影响β–甘露糖苷酶和α–半乳糖苷酶的活性。在不同温度下吸胀48 h的种子的内切–β–甘露聚糖酶和α–半乳糖苷酶的活性变化与随后种子的萌发没有直接关系。说明新收获的白菜种子具有明显的萌发热抑制,这种特性能被后熟、层积和GA₃处理以增强细胞壁降解酶活性的方式有效地解除。     

茗葱种子萌发的生态学特性研究

以茗葱种子为试材,对其种子萌发生态特征进行研究。结果表明:茗葱种子含水量达7.97%;四唑(TTC 0.1%)染色测种子的生活力为(80.8±2.3324)%;不同温度下茗葱种子发芽进程缓慢,20℃为发芽最适温度,发芽率达(84.00±6.00)%,与其它温度差异显著;光照与否对种子的发芽率及发芽势不具有显著差异。     

Effect of moisture stress on the ethephon response in tomatoes

Potted plants (cultivar ‘Napoli’) were maintained at 3 levels of moisture (continuously moist, moderate moisture stress and severe moisture stress) and sprayed to run-off with 3 levels of ethephon (0, 250 and 500 p.p.m.) in factorial combination, in order to examine the effect of moisture status on the ethephon-accelerated ripening-response in tomatoes. The largest increases in ripening-rate occurred where plants were moderately stressed and sprayed with 250 p.p.m. ethephon, or where plants were kept continuously moist and sprayed with 500 p.p.m. ethephon. No substantial increase in ripening-rate occurred at higher levels of either ethephon or moisture stress. Leaf senescence was rapid in all treatments other than the moderately stressed and continuously moist controls. In some of the water-stressed treatments a partial recovery of plant water potential occurred as a result of reduced transpiration due to rapid and extensive leaf loss.     

Effect of stage of ripening and ethephon treatment on color content of paprika pepper

In order to determine the proper time to harvest paprika pepper (Capsicum annuum L.) fruits to obtain maximum extractable color, two maturity indexes were evaluated. Most consistent results were obtained when fully shriveled fruits were harvested.Foliar applications of ethephon (50, 100, 200 and 500 ppm) were made on two cultivars, ‘Paprika-505’ and ‘Paprika-D.Z.’. Total extractable color and capsanthin content were determined using fully shriveled pericarp tissue. Some flower and leaf abscission was caused by treating plants with 500 ppm ethephon and leaves of plants treated with 200 or 500 ppm ethephon turned yellow. Ethephon stimulated ripening and increased the total extractable color and capsanthin levels of paprika fruits. ‘Paprika-505’ contained more total extractable color and capsanthin than ‘Paprika-D.Z.’ as a result of ethephon treatment.     

The mode of action of ethephon in increasing health of gladiolus corms

Gladiolus corms and cormels were treated with various combinations of ethephon and the fungicides methylethyl mercury benzoate, benomyl, thiobendazole and methylmercury dicyandiamide either before or after storage at 10 °C and 30 °C for 6 weeks. The treated corms were examined for germination, splitting and rot symptoms caused by Fusarium oxysporum f. sp. gladioli.

Ethephon increased corm splitting in all treatments; it also increased germination in corms stored at 30 °C, and it increased the proportion of corms showing typical Fusarium rot symptoms by stimulating the growth of latent internal Fusarium. The effectiveness of the fungicides tested against F. oxysporum f. sp. gladioli was enhanced by the addition of ethephon. Permeability of corms to methylethyl mercury benzoate was increased by ethephon, and it is concluded that ethephon improves the efficiency of this fungicide, and probably of other fungicides as well, by increasing their penetration into gladiolus corms.     

Effects of temperature on fruit thinning with ethephon in ‘Golden Delicious’ apples

The effect of temperature on the ability of 2-chloroethylphosphonic acid (ethephon), when applied at 20 mm stage of fruit development, to induce ethylene evolution of fruit and leaves and abscission of fruit and leaves was determined using 9-year-old root-bagged ‘Golden Delicious’/M.27 apple (Malus domestica Borkh.) trees in environment-controlled growth rooms. Ethephon at 400 μL L⁻¹ effectively thinned apples, and its thinning effect was not affected by increasing day/night temperature from 21.1/10 to 32.2/21.1 °C. Fruit ethylene evolution was enhanced by application of ethephon. Peak fruit ethylene evolution occurred 1 day after application of ethephon when day/night temperature was 32.2/21.1 °C whereas it occurred 2 days after application of ethephon at a day/night temperature of 21.1/10 or 26.7/15.6 °C. Ethephon increased leaf ethylene evolution drastically but it did not induce leaf abscission regardless of temperature.     

Alleviative effects of calcium acetate on defoliation and fruit drop induced by 2-chloroethylphosphonic acid in citrus

Experiments were conducted to evaluate the effects of calcium acetate on defoliation and fruit drop of ponkan (Citrus reticulata Blanco) and Meiwa kumquat (Fortunella crassifolia Swingle) trees treated with 2-chloroethylphosphonic acid (ethephon). Ethephon at 200 or 300 p.p.m. caused about 20% defoliation of ponkan trees, while this defoliation was materially alleviated by an addition of 0.05 M calcium acetate to the ethephon solution. Acceleration effects on fruit color did not differ with ethephon or ethephon + calcium acetate treatments. Ethephon at 400 p.p.m. caused about 30% fruit drop in kumquat trees, and an addition of 0.05 M calcium acetate to the solution almost completely prevented the fruit drop. Fruit color of kumquat was most advanced by the use of ethephon alone, and the addition of calcium acetate decreased the effect slightly.     

乙烯利对苦瓜种子的萌发及其生长发育的影响

以苦瓜品种早苦瓜为试材,利用不同浓度(50、100、150、200、250mg·L-1)的乙烯利处理苦瓜种子,研究乙烯利对苦瓜种子的萌发及其生长发育的影响,结果表明:乙烯利对苦瓜种子萌发有促进作用,对植株的生长具有一定的后效作用。发芽势、发芽率、发芽指数、活力指数、雌花数、产量、定植后期的叶面积及茎粗均随着乙烯利浓度的增加表现出先上升后下降的趋势,第1雌花节位和雄花数随着乙烯利浓度的增加表现出先下降后上升的趋势。其中150mg·L-1乙烯利处理效果最佳,各项指标与对照的差异均达到显著水平。     

Variation in the effects of ethephon on flowering and extension growth in chrysanthemum as a function of temperature,season, and genetics

Summary

Ethephon (2-chloroethylphosphonic acid), an ethylene-releasing agent, is used in the production of Summer-to-Autumn-flowering chrysanthemums (Chrysanthemum morifolium Ramat.) to avoid early budding under long-day conditions. This study was carried out to show the variation in response to ethephon due to temperature, season, and cultivar. The seasonality of growth and flowering capacities, growing temperatures, and the genetic background of chrysanthemum make the effects of ethephon unstable and variable. The most important factor modifying the effect was the response to temperature, which showed seasonal variation. Ethephon briefly suppressed extension growth and flowering after chilling and at high growing temperatures. On the other hand, it induced dormancy and rosette formation, and suppressed flowering after Summer, and at lower temperatures. This suggests that ethylene is involved in the induction of dormancy.     

Low temperature and gibberellic acid stimulation of germination in Sambucus caerulea Raf

Sambucus caerulea (elder) seeds did not germinate after 4°C cool treatments for up to 30 days, when monitored for a further 30 days at 21°C. When seeds were soaked for 24 h in gibberellic acid (GA₃) prior to and during cold treatment, germination percentage depended on GA₃ concentration and duration of cold treatment. The highest germination percentage was 55 (1000 mg l⁻¹ GA₃ for 30 days at 4°C). When seeds were treated with ethephon at 0, 100 or 1000 mg l⁻¹, no germination was recorded after a subsequent 30-day 4°C treatment. Ethephon added to GA₃ gave a strong interaction, leading to further promotion in germination. Optimal germination was obtained after 1000 mg l⁻¹ GA₃ and 100 mg l⁻¹ ethephon for 30 days at 4°C (69%).The addition of ethanol, acetone, dimethyl sulfoxide or polyethylene glycol to the GA₃ soak as infusion agents either reduced or did not change the germination percentage.     

外源水杨酸和甜菜碱对NaCl胁迫下茶花凤仙种子萌发的影响

以茶花凤仙(Impatiens balsamena)种子为试材,采用双层滤纸法,研究了100 mmol·L^-1NaCl胁迫条件下,外源SA(0.5、1.0、1.5、2.0 mmol·L^-1)和GB(0.4、0.8、1.2、1.6 mmol·L^-1)浸种预处理对茶花凤仙种子萌发及幼苗生长的影响,以期明确茶花凤仙种子萌发期2种外源物质对NaCl胁迫的缓解效应,降低NaCl胁迫对茶花凤仙的伤害。结果表明:NaCl胁迫显著抑制了茶花凤仙种子的萌发,发芽率、发芽势、发芽指数、活力指数、胚芽长、胚根长和苗鲜质量均显著下降,平均发芽时间显著延长;1.5 mmol·L^-1SA和0.8、1.2 mmol·L^-1GB对NaCl胁迫下茶花凤仙种子萌发和幼苗生长具有明显促进作用,而SA和GB浓度过高或过低则对NaCl胁迫的缓解效应下降,甚至加重盐害。利用隶属函数综合评价得出,100 mmol·L^-1NaCl胁迫下,1.5 mmol·L^-1SA和0.8 mmol·L^-1GB对茶花凤仙种子萌发及幼苗生长的综合调控效果较好,且0.8 mmol·L^-1GB对NaCl胁迫的缓解效果优于1.5 mmol·L^-1SA。