The germination of watercress (Rorippa nasturtium- aquaticum) seeds. II. The relationship between seed colour and germination

Freshly-harvested seeds of green watercress were pale yellow, rapidly turning to pale brown under ambient laboratory conditions. Older seeds ranged from pale to very dark brown, the darker seeds losing more electrolyte than the pale ones when immersed in water. Dark seeds germinated more readily than pale ones when the seeds were freshly harvested, but with old seeds germination was generally greater with paler seeds than darker ones. The results suggested that darkening of the seed coat was associated initially with a loss in dormancy and ultimately a loss in viability. Darkening of the seeds was enhanced by moisture. It could be induced by high humidity storage at 40°C, a treatment which resulted in increased electrolyte leakage from the seeds, or by holding individual seeds dormant at 35°C, although only the former treatment reduced germination. The results suggest that the ability of the seeds to germinate and the colour of the seed coat are not directly linked but that both are influenced by RH and temperature during storage.     

Studies on sulphur nutrition and flavour production in watercress (Rorippa nasturtium-aquaticum (L) Hayek)

The effects of sulphate nutrition on watercress were investigated with respect to visual deficiency symptoms, growth response and flavour content as determined by sensory and gas-chromatographic methods. The plants were grown in a glasshouse, both in solution culture using plants propagated vegetatively and in sand culture using plants raised from seed, at six concentrations of sulphate in the nutrient medium. The two methods were complementary and led to substantially similar conclusions. There were steep increases in weight per plant, sulphur content and flavour strength with initial increases of sulphate concentration in the nutrient medium, followed by levelling off^- at the highest sulphate concentrations. Sulphur requirements for maximum growth were satisfied at lower sulphate concentrations (0.20-0.25 meq/1) than those for maximum flavour development (0.75 meq/1).

There is evidence that watercress flavour consists of at least two types of components: (a) components which impart a bland, generalized vegetable taste and odour and (b) a specific component or components which are perceived as a burning sensation in the mouth accompanied by a characteristic odour. Production of the former is independent of sulphur nutrition. Enzymatic production of ß-phenylethyl isothiocyanate from the corresponding glucosinolate is believed to be responsible for the latter. There were highly significant correlation coefficients between the isothiocyanate content of fresh tissues and their total and organic sulphur contents.

The possibility of controlling watercress flavour in commercial production, with a view to meeting consumer preferences, is briefly discussed.     

Characterisation of the germination responses to temperature of vegetable seeds. I. Tomatoes

Tests in incubators and on thermo-gradient bars were done with 13 cultivars of tomato (Lycopersicum esculentum Mill.) to establish the main features of their germination responses to temperature. Differences found between cultivars including F₁ hybrids, out-door strains, and plants with golden and red skinned fruits were small. Optimum temperatures occurred between 26 and 32°C; maxima for fifty percent rates of germination were between 35 and 38°C, and minima between 8 and 10°C. Seed of Lycopersicum pimpinellifolium and small fruited subspecies of L. esculentum germinated at lower temperatures, down to 6°C, and more rapidly at median temperatures. Results of experiments on thermo-gradient bars showed that statistically significant differences occurring between responses at particular temperatures in incubators may be of minor biological or economic significance when used to assess temperature tolerance of different cultivars, and demonstrated that tests over a range of temperatures are essential for such determinations. A method is proposed for using results obtained in the early part of an experiment to provide regressions which can be projected to indicate the course of germination over a long period.     

Influence of polymer coatings on water uptake and germination of onion (Allium cepa L. cv. Aki) seeds before and after storage

The purpose of this work was to test the effect of different polymer coating materials on water uptake (imbibition and water vapour uptake) and germination performance before and after storage of onion seeds. Coating the seeds with hydrophobic polymers especially LS (linseed oil), PE (polyethylene), PVDC-1 (Daran 8600C) and VA (Vinamul 3240) reduced imbibition, but only PVDC-2 (Daran SL112) significantly reduced water vapour uptake. LS, PE and VA coatings significantly reduced germination before and after storage in 85% RH for 10 weeks at 25 °C. These polymers formed a hard film which appeared to form a physical barrier to primary root protrusion. Moisture contents after storage of untreated and coated seed were similar (between 13.0 and 13.3%), indicating that no coatings reduced water vapour uptake in storage. Guidelines for an appropriate experimental approach in the search for effective coatings to reduce water vapour uptake and increase storage life are discussed.     

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.     

The effects of pre-sowing seed treatments on the germination and emergence of lettuce seeds at high salt concentrations

Radicle emergence in lettuce seeds cultivar ‘Hilde’ was reduced by NH₄NO₃ above 8×10^?2M, while radicle extension was inhibited by 8×10^?2M NH₄NO₃ and no seedlings emerged. Inhibition of radicle emergence by 8 and 16×10^?2M NH₄NO₃ was prevented by soaking seeds for 4 h before sowing in a mixture of $\text{GA}{}_{\mathrm{<mtext>4</mtext><mtext>7</mtext>}}$ and kinetin+phosphate buffer, and was partially prevented by soaking them for 4 h before sowing in phosphate buffer. These treatments did not prevent inhibition of radicle emergence by 32×10^?2M NH₄NO₃, but seeds soaked in growth regulators or phosphate buffer before sowing and taken from this NH₄NO₃ solution after 7 days and washed to remove excess salt gave 45–52% germination compared with 12 % for untreated seeds. Pre-treatment of the seeds did not prevent the inhibitory effect of NH₄NO₃ on radicle extension. In field experiments seeds treated with growth regulators + phosphate buffer or phosphate buffer alone gave a higher final percentage emergence from soils given 125 kg N/ha than did untreated seeds.     

Chilling-injury in cucumber fruits. I. Effects of storage temperature on symptoms and physiological changes

Cucumber fruits transferred to a warm temperature after chilling displayed various symptoms of chilling-injury. In cucumbers chilled to 0°C, vertical fine wrinkles and/or shallow pitting was observed, while after chilling to 5°C deep pitting and/or surface depressions were apparent. Moreover, in the 0°C fruit compared with 5°C fruit, a higher $\text{210}\text{264}$ mμ UV absorption ratio of leakage substances during chilling was observed. These results suggest that the causes of chilling-injury in the 0°C and 5°C fruit are distinct from one another. Weight loss after chilling, the amount of leakage substances, the exudate content from the cut surface of the fruit, redox potential, titratable acidity and respiratory activity were also checked after periods of chilling of 3 to 15 days.     

Low temperature storage and in vitro germination of cherimoya (Annona cherimola Mill.) pollen

Due to the protogynous dichogamy of cherimoya and to the absence of proper pollinating vectors, hand-pollination with fresh pollen is a common practice for cherimoya commercial production. In order to optimize the process of hand-pollination, in this work we have studied the conservation of cherimoya pollen at −20, −80 and −196 °C for up to 3 months. In vitro pollen germination of fresh pollen was 57.1% and it was progressively reduced with conservation time at the three temperatures studied reaching a minimum after 3 months of storage of 10.4%, 14.2% and 13.6% at −20, −80 and −196 °C, respectively. Differences in germination among temperatures were only significant during the first 2 weeks of storage. Field pollinations with pollen stored for up to 3 months at the three temperatures show no yield differences compared to pollinations performed with fresh pollen. The results indicate that pollen collected and stored at sub-zero temperatures at the beginning of the cherimoya blooming season can be used along the whole blooming season avoiding the need of collecting fresh pollen daily.     

钙、镁、钾浓度及光照、温度对西番莲花粉离体萌发的影响

【目的】探讨培养基中的钙、镁、钾浓度及光照、温度对西番莲花粉体外萌发及花粉管生长的影响。【方法】设置钙、镁、钾及光照、温度梯度,测量在该梯度下的花粉萌发率及花粉管延伸长度。【结果】钙、镁、钾非西番莲花粉离体萌发的必需培养基成分,钙对西番莲花粉离体萌发及花粉管生长具有显著影响,在质量浓度为0～300 mg·L^-1时,萌发率及花粉管长度均随浓度的增加而显著增加,在300～1200 mg·L^-1时最佳,大于1200 mg·L^-1时,萌发率及花粉管长度均显著降低。镁、钾对花粉萌发及花粉管生长均无显著影响。光照、温度对花粉萌发及花粉管生长均具有显著影响,黑暗条件下最佳,随着光照度的增加,萌发率及花粉管长度均显著降低;二次方程能较好地拟合温度对花粉萌发及花粉管生长的影响。【结论】培养基中钙浓度及光照、温度对西番莲花粉体外萌发及花粉管生长具有显著影响,镁、钾无显著影响,最适的C(aNO₃)₂·4H₂O质量浓度为300～1200 mg·L^-1,西番莲...     

Storability of onion seeds and effects of packaging and storage conditions on viability and vigour

Fresh onion seeds desiccated to 6.0% seed moisture content (SMC) were stored in various packaging materials under different storage conditions. Seeds packed in aluminum-laminated pouches beside those stored with silica gel at 25 °C maintained satisfactory germinability and vigour after 12 months. Desiccated seeds stored in moisture impervious containers produced more vigourous seedlings. Germination potential of onion seeds increased with reduced SMC besides storage in moisture impervious packets along with desiccants as physiological and biochemical attributes are regulated. Seed viability and vigour decreased with accelerated ageing due to increased lipid peroxidation, decreased activities of several free radical and peroxide scavenging enzymes. Electrical conductance of seed leachates also increased with ageing. Thus, adoption of appropriate storage temperature and moisture control techniques would significantly affect onion seed quality, which was due to minimum accumulation of free peroxide radicals and enhanced activity of free radical scavenging enzymes.     

The effects of temperature on in vitro pollen germination and pollen tube growth of Pistacia spp.

The pollen germination and pollen tube growth among nine Pistacia genotypes was quantified in order to identify differences in the tolerance of pollen to temperature variations. The effect of temperature on in vitro pollen germination and pollen tube growth was investigated in Pistacia vera (Uygur, Atli, Kaska, Sengel, Kavak), P. atlantica, P. khinjuk, P. terebinthus and P. palaestina. When pollen was incubated in a germination medium for 24 h in darkness, distinct differences were observed in pollen germination and pollen tube growth at different temperatures.     

The effects of storage temperature and fruit size on firmness,extractable juice,woolliness and browning in two nectarine cultivars

Fruit firmness, extractable juice, woolliness and browning of the mesocarp tissue in ‘Independence’ and ‘Flavortop’ nectarines stored at —0.5°, 3°, 5° and 7°C for four weeks were determined during ripening at 15°C. The firmness of both ‘Independence’ and ‘Flavortop’ during ripening decreased as storage temperatures increased. The percentage extractable juice after cold storage and during ripening varied considerably between cultivars and between the storage temperatures. The extractable juice of fruit stored at higher temperatures tended to increase during ripening, whereas fruit stored at lower temperatures tended to decrease first before increasing. At storage temperatures of —0.5° and 3°C both cultivars passed through a stage of woolliness during ripening, while less woolliness occurred after storage at 5° and 7°C. In both cultivars the percentage extractable juice during ripening was higher on average at storage temperatures of 5° and 7°C. Severe browning of mesocarp tissue in both cultivars occurred during ripening after storage at 3°C. The effect of fruit size on changes in firmness, development of woolliness and mesocarp browning in ‘Flavortop’ nectarines stored at — 0.5°C for four weeks and ripened at 15°C was also determined. Larger nectarines lost firmness more rapidly, woolliness occurred sooner and the mesocarp tissue was more prone to browning than smaller fruit during ripening.     

沼生蔊菜与荠菜的形态学特征比较研究

采用栽培、观察的方法比较了沼生蔊菜(风花菜)与荠莱形态及生物学特征,同时比较了根和叶的营养成分.结果表明,作为极为相似的两种山野菜,在形态及生物学特征和营养成分方面差别是显著的,在形态学方面表现在出土子叶、二真叶期、四真叶期、基生叶、茎生叶、种子、果实、花等方面的不同.在生物学特征方面,两种植物在物候及生活史方面显著不同.在营养成分方面,沼生蔊菜除叶片可以食用外,其肥大直根也可以食用,而且营养价值很高,两植物叶片的营养价值有差异.     

Effects of light,macronutrients, and sucrose on germination and development of the endangered fern Adiantum reniforme var. sinense (Adiantaceae)

Effects of light, macronutrients strength of Murashige and Skoog (MS) (1962), and sucrose in the culture medium on spore germination and gametophyte development of the endangered fern Adiantum reniforme var. sinense were investigated. The presence of light was found to be essential for both spore germination and gametophyte growth. Moreover, a medium consisting of 1/4 MS with 15 g/l sucrose was optimal for spore germination and early gametophyte development; whereas, MS medium with 30 g/l sucrose was optimal for further gametophyte development. Increasing amounts of sucrose (45–60 g/l) in the medium delayed gametophyte growth and development. Additionally, sporophyte formation and early growth of gametophytes in a medium consisting of clay and peat (v/v = 1:2) was higher than those in a medium consisting of pure river sand. These findings indicated that requirements for nutrients for spore germination and early gametophyte development of A. reniforme var. sinese were relatively low, but these increased with further gametophyte development, formation and growth of sporophytes.     

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.     

Controlled-atmosphere storage of kiwifruit. I. Effect on fruit firmness and storage life

The effect of atmospheres containing high CO₂ and low O₂ on the firmness of kiwifruit (Actinidia chinensis Planch.) during cool storage at 0°C has been studied. Atmospheres containing above 4% CO₂ with 15–20%O₂ caused a retardation in the softening of kiwifruit. This effect increased as the CO₂ content of the atmosphere increased from 4 to 10%, but additional CO₂ above 10% had no further effect on fruit firmness. Low O₂ (2–3%) with 3–5% CO₂ further delayed the rate of kiwifruit softening and increased storage life up to 3–4 months beyond normal air-storage life. Although controlled-atmosphere storage increases storage life of kiwifruit, the magnitude of the effect was found to vary from year to year. Contamination of the storage atmosphere by as little as 0.1 μl^?1 ethylene severely reduced the effectiveness of controlled-atmosphere storage in maintaining kiwifruit firmness, even at 0°C.     

Some aspects of seed germination in vegetables. 1. The determination and application of heat sums and minimum temperature for germination

Germination can be predicted at optimal soil moisture conditions by means of a heat sum in degree days (S) and a minimum temperature for germination in °C (T_min). These constants were analysed for 31 vegetables in a temperature range between 3 and 25°C. Some practical consequences of the combined effects of S and T_min on germination are given.     

The effect of conditions of storage on the respiration of apples. VI. The effects of temperature and controlled atmosphere storage on the relationship between rates of production of ethylene and carbon dioxide

Studies on freshly harvested fruit of three apple cultivars kept in air or under C.A. conditions at 12°, 7.2°, 3.3° and 0 °C have shown that the initiation of ethylene production is not necessarily associated with the onset of the respiration climacteric, and therefore cast doubt on the belief that ethylene is a ripening hormone. The dissociation of the two phenomena was effected by low temperatures and by storage under C.A. conditions.

The studies showed also that there is a linear relationship between rate of production of ethylene and its concentration in the intercellular spaces of the fruit.     

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.     

Environmental and cultural effects on vegetative growth and flowering of selected “bedding” ornamentals. I. Night temperature

Night temperatures warmer than those normally used in commercial production systems promoted vegetative growth in Tagetes patula and Matthiola incana seedlings. In the short (8 h) daylength regime employed, and with a day temperature of 16°C, cool nights (8°C) had a detrimental effect, especially when imposed for 6 weeks from pricking-out rather than later. Night temperatures between 8°C and 16°C did not substitute for the long-day requirement for flowering in Matthiola after 11 weeks' growth, and there was no advantage with respect to vegetative growth in maintaining night temperatures above 12°C. Warmer nights from pricking-out promoted flowering in Tagetes but if applied later (during weeks 7–11) the positive effects were largely on vegetative growth. The implications of these findings for commercial horticulture are discussed.