Effect of stratification temperature,stratification period and seed coat on seed germination of peach cultivar ‘Sharbati’

Freshly harvested seeds of peach cultivar ‘Sharbati’ were found to be dormant and did not germinate at all. A specific low-temperature stratification treatment was required to overcome seed dormancy. 10° C stratification was found to be the best for breaking seed dormancy. Increased seed germination was recorded when the seeds were after-ripened without seed coats as compared to the seeds after-ripened with seed coats. There was no further increase in germination when seeds without seed coats were stratified beyond 60 days at 10° C, while a significant increase was recorded up to 75 days of stratification in the case of seeds with seed coats. Unstratified seed coats, soaked in water for 72 h, leached out a water-soluble inhibitor, which could suppress the germination of stratified peach seeds without seed coats. When this leachate was bioassayed by a cress-seed germination test, it showed the presence of an inhibitor at Rf 0.7-0.9. Hence, delayed germination of seeds with seed coats may be due to the presence of an inhibitor in seed coats.     

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.     

Biocontrol of mildew with Bacillus subtilis in bitter gourd (Momordica charantia L.) seeds during germination

The bitter gourd seed has a thick, hard seed coat. Mildew often occurs during germination and causes uneven and low rates of seed germination. However, the problems caused by mildew can be overcome by treating seeds with hot water, by soaking in water, or by using microorganisms. Seeds of the ‘Ching Pi’ bitter gourd were treated in a water bath at 60 °C for 10 min and then soaked in tap water at 25 °C for 24 h. The resulting germination percentage was 86.7%, and the resulting percentage of mildewed seeds was 10%. The biocontrol potential of three commercially available Bacillus subtilis solutions was examined. For seeds primed with Huodijun B. subtilis solution, the germination percentage was 73.3% and the mildewed percentage 6%. In dual cultures, the antibiotic content in the Huodijun B. subtilis solution was significantly greater than in Yunghsing and Huolibao, the other B. subtilis solutions examined. B. subtilis effectively inhibited the growth of Rhizoctonia solani mycelium and caused abnormal mycelial growth.     

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.     

Some aspects of seed germination in vegetables. II. The effect of temperature fluctuation,depth of sowing,seed size and cultivar,on heat sum and minimum temperature for germination

The germination period of seeds can be predicted for any soil temperature with the use of a heat sum (S) and a minimum temperature for germination (T_min). Experiments with vegetable seeds were carried out to establish whether S and T_min are affected by diurnal soil temperature variation, depth of sowing, variation in seed size (of radish) and whether great differences are to be expected between cultivars (of lettuce). In general the above mentioned variables do not affect T_min and S to a great extent. For practical purposes, an optimum temperature range for germination has been established.     

Physical dormancy in myrtle seed

The nature of dormancy in seeds of myrtle (Myrtus communis L.) was investigated. Scarification with cold acid or sand paper and soaking in water increased seed germination, whilst stratification, inserting the seeds in boiling water or hot acid treatment decreased the number of germinating seeds. The highest germination was obtained by treating the seeds with 100 % cold acid for 60 min or 80 % cold acid for 120 min. Hard seed coat was found to be the principal cause of poor seed germination.Scarified and non-scarified seeds were germinated for 2 weeks at 6 temperatures between 5 and 30° C, and 20° C was optimum.     

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。     

Optimized scarification protocols improve germination of diverse Rubus germplasm

Seed collections of the wild relatives of cultivated blackberry and raspberry (Rubus species) are maintained at the National Clonal Germplasm Repository, Corvallis, OR. Information on wild species germination requirements is rarely available, and germination may be poor or slow, making it difficult for scientists to use them for breeding improved cultivars. Eight diverse Rubus species in 6 of the 12 Rubus subgenera from seed stored at −20 °C for 1–23 years were studied. Seed weight, seed-coat thickness and hardness varied widely. Scarification with sulfuric acid (98% H₂SO₄) or sodium hypochlorite (14% NaOCl) was followed by germination treatments of deionized water (DI), smoke gas or a combination of gibberellic acid (2.03 mg/L GA₃) and potassium nitrate (34 mg/L KNO₃) during stratification. The commonly used scarification protocols were not effective for many species; but effective scarification exposure was established based on the amount of embryo damage seen with 2,3,5 triphenyl tetrazolium chloride (TZ) viability testing. H₂SO₄ scarification followed by a treatment with KNO₃ and GA₃ during stratification was highly effective for the most species. Two species in subgenus Anoplobatus had a hilar-end hole that allowed rapid germination of unscarified seed. Some species with extremely hard seed coats had little or no germination, and longer scarification times are suggested based on seed size, seed-coat thickness and hardness and viability testing.     

Relationship between changes in endogenous polyamines and seed quality during development of sh2 sweet corn (Zea mays L.) seed

Polyamines putatively affect tolerance to abiotic stresses and are believed to be important in organogenesis. Present experiments investigate the relationship between polyamines (PAs) and seed quality. Therefore, during seed development, the changes in free putrescine (Put), spermidine (Spd) and spermine (Spm) and physiological and biochemical parameters in F₁ seeds of sh₂ sweet corn were compared. Concentrations of Put, Spd and Spm increased from 14 to 30 days after pollination (DAP). After 30 DAP Put concentration declined with an opposite trend to that of Spd and Spm. The regression analysis between PAs and seed quality described by physiological and biochemical parameters including germination percentage, germination energy, germination index, seed size, seed fresh and dry weight, total soluble sugar, total soluble protein, Malondialdehyde (MDA) concentration, electrolyte leakage, peroxidase (POD) and catalase (CAT) activity were conducted. Spd was observed to have a closer relation with the comprehensive physiological changes of seeds during their development than that of Put and Spm. Moreover, the Spm concentration might be more suitable to forecast seed germinability during seed maturation period than Spd and Put. It indicated that endogenous Spd and Spm in dissociated form had more effect than Put during seed development progress of sweet corn.     

Effects of temperature and seed coat treatments on germination of sweet pea

Tests on seeds of sweet pea (Lathyrus odoratus L.) were set up to examine responses to temperature during germination and to investigate the effects of mechanical and chemical treatments on the permeability of the seed coat to water.Optimum temperatures for germination occurred at about 21 °C, and higher temperatures resulted in the production of fewer seedlings. Although temperatures below c. 15 °C also reduced the numbers of seeds which germinated, even at 2 °C more than 50 % germinated within 60 days.Treatments with concentrated sulphuric acid or the mechanical removal of part of the seed coat by filing greatly increased permeability to water and under some conditions improved germination responses. Filing, followed by exposure to excess free water, reduced germination rates, possibly as a result of loss of solutes from the seed during imbibition.     

Influence of harvest time and after-ripening on the seed quality of eggplant

Eggplant cv. Emi and Tsakoniki were cultivated for seed in an unheated greenhouse and fruits were harvested at 25–65 days after anthesis (DAA) in order to determine the optimum harvest time. In addition, the effect of after-ripening on seed quality (i.e. seed size and germination) was examined by storing harvested fruit at 25 °C for 20 days prior to seed extraction. From the results, it was concluded that the optimum time of harvest for seed production is 55 DAA. Seeds extracted from fruits that were harvested at 25–35 DAA did not germinate, but when fruits harvested at the same age were stored for 20 days at 25 °C prior to seed extraction (i.e. seeds were after-ripened) germination was induced. Seeds extracted from fruits harvested at 45 DAA showed a high percent germination, which decreased after storage at 25 °C for 3 months. This decrease, however, was reduced by after-ripening prior to extraction. It is concluded that although eggplant is a non-climacteric species and fruit do not ripen after harvest, nevertheless seeds within the fruit continue to fill and mature after harvest; hence storage of prematurely harvested fruit prior to seed extraction permits the seeds of these fruits to after-ripen in situ and thereby increases seed size and germination. The implication of this result for eggplant seed production is discussed.     

Methods to break seed dormancy in Cyclocarya paliurus (Batal)Iljinskaja

Cyclocarya paliurus is native to China and is the sole species in its genus. However, the seeds remain deeply dormant for 2 years in their natural environment. We tested different pretreatments of chemical scarification and exogenous application of gibberellic acid (GA₃) for efficacy in breaking dormancy and speeding germination. In contrast to scarified seeds, non-scarified seed did not germinate, indicating that C. paliurus seeds have hard, impermeable seed coat dormancy. Exogenous application of GA₃ significantly enhanced germination of scarified seeds. Compared with seeds stratified in sand with water, the germination of seeds stratified in sand moistened with 400 ppm GA₃ for 60 days was significantly increased and germination rate was over 90% after 120 days. Analysis of variance indicated that both GA₃ concentration and stratification medium had significant effects on seed germination and final germination percentage. Germination was higher for longer stratification periods, but no significant difference in germination was observed after 90 days. These results suggested that C. paliurus seeds exhibit both exogenous and endogenous dormancy. A combination of chemical scarification and exogenous application of GA₃ alleviated seed dormancy in a relatively short period of time.     

Effects of seed maturity,seed storage and pre-germination treatments on seed germination of cleome (Cleome gynandra L.)

The influence of seed maturity, seed storage and germination pre-treatments on seed germination of cleome (Cleome gynandra L.) were investigated. Seed maturation studies showed that capsules harvested at 18 days after anthesis possessed the highest dry weight with 19.2% moisture and 1% germination. Development of fresh-ungerminated seed was observed with increasing maturity of fruit, suggesting that cleome exhibited forms of seed dormancy. Storing mature seed at 15 °C and at room temperature for 5 months showed that seed dormancy was broken after 3 months under both storage regimes. When mature seeds were subjected to different treatments including various levels of GA₃, KNO₃, leaching, pre-chilling, soaking and pre-heating at different temperatures, it was found that pre-heating at 40 °C for period of 1–5 days was the most effective method in breaking dormancy in cleome.     

Chitosan specificity for the in vitro seed germination of two Dendrobium orchids (Asparagales: Orchidaceae)

The effects of different types of chitosan on seed germination and protocorm development were determined for two orchid species, Dendrobium bigibbum var. compactum and Dendrobium formosum. Six chitosan types derived from polymer or oligomer chitosan each with 70, 80 or 90% levels of deacetylation (P70, P80, P90, O70, O80 and O90, respectively), were evaluated as direct medium supplements at 0, 10, 20, 40 or 80 mg/L in modified VW medium by following seed germination and protocorm growth for 12 weeks. Chitosan of all six tested types and four concentrations were found to significantly enhance the proportion of D. formosum seeds that germinated, when compared to these germinated without chitosan. In contrast, chitosan caused no enhanced germination rate was noted for D. bigibbum var. compactum with all tested chitosans and doses tested. However, almost all types of chitosan at 10 mg/L, except O90, were able to significantly improve the growth of D. bigibbum var. compactum protocorms, whilst 10 or 20 mg/L of P70 chitosan was the best formula to enhance the growth of D. formosum protocorms. It is concluded that chitosan responses in seed germination and protocorm development were somewhat species and developmental stage dependent. Therefore, the appropriate chitosan application for each plant species should be evaluated first before use.     

脱落酸与种皮对杜梨种子休眠与萌发的影响

以当年新采收杜梨种子和自然贮藏1 a种子为试验材料,研究了种皮和不同浓度的脱落酸(ABA)对诱导杜梨种子休眠与萌发的影响.结果表明:杜梨种皮和脱落酸均能够抑制杜梨种子的萌发,种皮的抑制萌发效应显著大于ABA的作用,杜梨种子去除种皮后,休眠性可被部分解除.脱落酸对杜梨种子抑制萌发的效应在去皮和不去皮种子中表现明显差异,5 mg/L ABA浓度对未去皮种子产生明显抑制效应,20 mg/L ABA浓度对去皮种子产生明显抑制效应,说明未去皮种子对ABA的敏感性大于去皮种子.种皮与ABA的双重抑制效应,使种子对ABA浓度水平差异的敏感性增强.不同激素组合试验说明了GA3、6-BA和ABA在杜梨种子休眠与萌发中的作用.     

Effects of cadmium and copper on pollen germination and fruit set in pea (Pisum sativum L.)

In this work, pea (Pisum sativum) plants exposed to increasing cadmium and copper concentrations were tested for heavy metals accumulation in flowers and for ‘in vivo’ pollen germination. Based on the Cd and Cu accumulation amounts in the flowers, an evaluation of the same metals effects on ‘in vitro’ pollen germination was achieved. Moreover, the effects of both metals on fruits number and weight and on seed set and yield at individual plant level were examined. While cadmium concentrations did not affect ‘in vivo’ pollen germination, only higher copper concentrations rendered a significant reduction. This is in contrast with the clear negative effect on pollen germination in vitro and might be explained by the different dynamic and bioavailability of both metals. A clear effect of Cd and Cu was observed on two important yield components ie, fruit weight and seed set. Although results obtained herein cannot give a clear cut relationship between the effect of Ca and Cu on reproductive development and its consequences on yields, they represent emerging results on the potential consequences of metals contamination on reproductive development in plants.     

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.     

Seed dormancy and germination of Michelia yunnanensis (Magnoliaceae)

Michelia yunnanensis Franch. is a Chinese endemic ornamental shrub with potential for greater utilization as a landscape and medicinal plant if propagation was less difficult. Seed development and breaking of seed dormancy were investigated to improve propagation of M. yunnanensis. No fresh seeds germinated when tested at the time of dispersal. Newly matured seeds of M. yunnanensis contained differentiated linear underdeveloped embryos that were physiologically dormant. The embryo/seed length ratio of M. yunnanensis was 0.15. Warm stratification did not break seed dormancy. Dormancy was broken by cold stratification at 4 °C but not by flowing water or nitrate. Embryos developed grew inside seeds during cold stratification at 4 °C. In newly harvested dormant seeds, embryos were 0.94 mm long and increased in length 139% before radicle emergence (germination). GA₃ substituted for cold stratification to break dormancy in seeds of M. yunnanensis incubated at 25 °C or 20/25 °C. Mature M. yunnanensis seeds exhibited intermediate complex morphophysiological dormancy. Optimal germination of non-dormant seed in terms of both germination percentage and rate occurred at 20/25 °C.     

Symbiotic seed germination of Grammatophyllum speciosum Blume and Dendrobium draconis Rchb. f., native orchids of Thailand

In vitro symbiotic seed germination is an important tool not only for the study of orchid-fungus specificity but also for the production of mycobiont-infected healthy seedlings that could be valuable for both horticultural and conservation purposes. The current study compared effectiveness of eight putative orchid mycorrhizal fungi obtained from mature orchids in the genera Paphiopedilum, Cymbidium and Dendrobium, in promoting in vitro seed germination and protocorm development of Grammatophyllum speciosum Blume and Dendrobium draconis Rchb. f., native Thai orchids. The developmental stages of seeds and protocorms cultured on Murashige and Skoog (MS) medium, oat meal agar (OMA), or OMA inoculated with one of the eight fungal isolates were evaluated weekly. Two isolates of Epulorhiza repens (Bernard) Moore (=anamorphic species of Tulasnella calospora (Boud.) Juel), Da-KP-0-1 and Pv-PC-1-1, were found to be the most effective fungi in promoting protocorm development of G. speciosum. At week 13, protocorms co-cultured with either one of these two fungal isolates, on the average, were significantly more advanced than those sown on OMA. Protocorms co-cultured with isolate Pv-PC-1-1 were also significantly more advanced than those cultured on MS medium. For D. draconis seed germination, three fungal isolates of different anamorphic species of Tulasnella, C1-DT-TC-1, Pv-PC-1-1, and C3-DT-TC-2, were found to be the most effective fungi in promoting protocorm development. However, none of these fungal isolates outperformed MS medium. Additionally, the compatibility between the fungal isolates tested and the two orchid species was discussed.     

双氧水对茄子种子萌发的影响

新采收的茄子种子因休眠作用影响种子的萌发,会出现幼苗参差不齐的现象．影响了农业生产。为了打破种子的休眠,以南京市蔬菜科学研究所培育的黑骠茄子和日本砧木品种托鲁巴姆为试验材料,研究了双氧水对茄子种子发芽势、发芽率和发芽指数的影响。结果表明,在25℃下,双氧水浸种可以显著提高茄子种子的发芽势、发芽率和发芽指数,而且在低浓度处理下效果较好,随着浓度的提高,处理效果逐渐降低,当双氧水浓度达到1．2％时已基本没有效果,以0．3％双氧水浸种3h,可以使发芽势、发芽率和发芽指数达到最高。