Effects of pre-sowing seed treatments and temperatures on tomato seed germination and seedling emergence

Sowing pre-germinated seeds with radicles 2–3 mm long reduced the time from sowing to seedling emergence to 17 days compared with 41 days in untreated seeds at soil temperatures of 10°C, and to 5 days compared with 11 days at 18°C. Sowing pre-germinated seeds also improved percentage seedling emergence and reduced the variability of times of emergence of individual seedlings. Seeds imbibed for 56 h before sowing (radicles just emerging) emerged about 3 days earlier at both 10°C and 18°C than untreated seeds. Seeds soaked in a solution containing 1.5% each of KNO₃ and K₃PO₄ for 5 days at 24°C, or in “Carbowax 20 M” for 20 days at 15°C, and then dried before sowing, gave results similar to imbibed seeds. Soaking seeds in 70% of their weight of water followed by drying for different lengths of time and for different numbers of cycles of wetting and drying did not improve germination or seedling emergence.     

Temperature requirements for the germination of olive seeds (Olea europaea L.)

Summary

Olive seeds cv Chondrolia Chalkidikis were subjected to temperatures of 5°, 10°, 15°, 20°, 25° and 30°C for one, two or three months, and were then transferred to 20°C. Exposure to 10° and 15° for one month or more caused higher emergence percentages compared to that at a constant 20°C. The highest germination rate was observed when seeds subjected to 10°C for one month were then transferred to 20°C. Seeds at 5°, 25° and 30°C did not germinate while being held to these temperatures; even when transferred to 20°C the percentage and rate of emergence were lower than those of seeds held at constant 20°C. In another experiment, in which seeds were subjected to 10°C for 0, 2, 4, 6 and 8 weeks before being transferred to 20°C, it was found that four weeks exposure to 10°C was near optimal. Emergence percentages of seeds at constant 10°C or at diurnally alternating temperatures of 10° for 16 h/20° for 8 h were high and equal (92%), but emergence in the latter treatment was slower. Alternating 10° with 25°C resulted in a 95% reduction of the emergence percentage. Transferring seeds immediately after chilling at 10°C for three or four weeks to 25°C, partially reversed the effect of the low temperature. However, the chilling effect could not be reversed when the seeds were subjected to 10°C for five weeks.     

Flower formation of Chinese cabbage. I. Response to vernalization and photoperiods

The influence of temperature, vernalization duration and photoperiods on the leaf number and beginning of bolting of Chinese cabbage was tested in growth chambers. An increasing effect of vernalization was indicated by decreasing leaf number and premature bolting. Sensitiveness for vernalization started with germination and remained constant with increasing plant age. During their development on mother plants, seeds were not vernalized.Inductive temperature ranged between 0 and 20°C. The necessary vernalization duration was lowest at 5–8°C. For slight vernalization effects one week was sufficient; for complete vernalization about 3 weeks were needed. To achieve the same effect, the necessary vernalization duration increased considerably at temperatures below 5°C, but increased only slightly at temperatures above 8°C.Long days promoted bolting when the temperature rose after incomplete vernalization. In constant low or high temperature, no photoperiodic effect was perceptible.     

Comparisons of the use of pre-germinated,dry and pelleted seeds for block-raising of glasshouse lettuce

The use of pre-germinated seeds for establishing glasshouse lettuce in peat blocks was compared with dry and pelleted seeds. Sowing pre-germinated seeds gave between 1 and 6% higher seedling emergence than from pelleted seeds and between 1 and 3% higher emergence than from dry seeds. Seedling emergence was reduced from 100% to 56% when the seeds were covered with 5 mm of silver sand compared with no cover. Seedling emergence from seeds covered with Agrigel (sodium alginate) was reduced by 24% at a concentration of 0.25% and by 62% at 0.7% compared with no cover.Guar (a natural gum) and Laponite (a synthetic clay) gels also reduced emergence on certain occasions but not by as much as Agrigel. Satisfactory levels of emergence were obtained when seeds were sown into blocks having an inverted, cone-shaped depression for locating the seeds, but the seedlings showed poor root-hair development and had elongated hypocotyls. Normal seedling growth and high levels of emergence were obtained from the seeds sown into blocks having cylindrical holes 10 mm in depth and 5 or 10 mm in diameter. Pre-germinated seeds invariably emerged earlier than pelleted or dry seeds. At low propagating-temperatures (12.0°C maximum and 5.0°C minimum), emergence was 4 days earlier from pre-germinated than from dry or pelleted seeds and 2–3 days earlier at high temperatures (21.0°C maximum and 9.0°C minimum). Coefficients of variation of seedling weight at planting were lower from sowing pre-germinated than pelleted or dry seeds, but these differences were not evident at harvest.     

The effect of seed treatment on the germination and early growth of Euterpe edulis (family Palmae)

The germination rate of palm seeds can be improved by pre-treatment of the seed. Several methods proved effective for Euterpe edulis seed, but sulphuric acid immersion and hydrogen peroxide leaching treatments both decreased emergence of germinated seedlings and restricted plant growth up to 6 months after germination.The best overall results in germination and subsequent seedling development were from seed leached in water for 72 hours at 30°C. This treatment can be related to the natural conditions encountered by the seed in the highly leached soils of a tropical rain forest.     

The effects of temperature and daylength during the seedling stage on flower-stalk formation in field-grown celery

The occurrence of bolting in open-field winter- and spring-grown celery (Apium graveolens L.) reduces the quality and yield of the product. The temperature which prevails in the nursery and in the fields during the plant's vegetative growth is a consequential factor which controls the development of the flower stalk. Seedlings were exposed to various temperature (soil and air) and daylength conditions for different periods during their growth in the nursery. Exposing young plants to non-inductive temperatures (soil or air) brought about a delay in bolting in the field-grown spring celery, irrespective of the daylength which prevailed during the treatments.Moreover, exposure of nursery-grown celery seedlings to high temperatures (25, 30 or 35°C) for short periods just before transplanting them into the open field caused a significant delay in the rate of bolting. This short-period high-temperature treatment may be of economic importance and can provide partial control of bolting in spring-grown celery.     

Field Trials of,Dichloro-Diphenyl-Trichloroethane (D.D.T.) Against the Raspberry Beetle (Byturus Tomentosus Fabr.)

Summary

Crops of early leek cv. Prelina were grown in four experiments at Wellesbourne and in Cornwall from 1995 to 1997. Treatments applied included time of sowing, plant raising temperature, transplant type and covering regime. There was no effect of plant raising temperature on marketable yield or on the percentage of flowering plants. It is suggested that with cv. Prelina it is particularly the conditions during early field growth that affect the ability to flower. Larger plants at transplanting, resulting from earlier sowing or the use of peat blocks, increased the percentage of flowering plants but effects of fleece cover were variable, depending upon how close temperatures were to the optimum for vernalization, which was shown to be close to 78C. It is suggested that rather than planting early, with subsequent air temperatures near to the optimum for vernalization, which will result in high levels of bolters, it would be better to delay transplanting. Plants can then be maintained at a raising temperature that is higher than the optimum for vernalization and transplanted when there is a strong probability of air temperatures being higher. Simple models have been developed to predict first, the rate of increase of leek diameter and secondly, the rate of flower stalk extension, so that it will be possible to predict when the crop will be large enough to harvest and when flowering stalks will become unacceptably long.     

More rapid and uniform germination of Cyclamen persicum L.

Two pre-sowing treatments are described which permit the initial germination processes to proceed but prevent the emergence of any radicles prior to sowing. Such treatments can result in a distinct reduction in the time between sowing and germination and in the length of the germination period. One method employs an aerated osmotic solution, here polyethylene glycol (PEG) ‘6000’ at a water potential of ?8 to ?11 bars at 15°C for 3–5 weeks. The alternative method in which a thermodormancy-enforcing temperature (25–30 °C) is substituted for the osmotic solution is less effective. For best effects, treated seeds should only be surface dried and sown immediately, although some of the effect persists on air drying. It may be necessary to calibrate each batch of seeds for the conditions which advance the germination process as far as possible without permitting actual germination during the treatment.     

Methods of Raising Cocoa Seedlings in the Nursery and their Effect on Subsequent Growth in the Field

Trials were conducted near Ibadan, Western Nigeria, to find the best method of raising cocoa seedlings in the nursery, and the plants were subsequently transplanted to the field and observed for two further years. In one trial the experimental treatments were amount of shade, time of sowing, amount of watering and type of pot; in a second trial times of sowing and transplanting were varied and seed was also sown at its permanent site.

Seedlings grew well in the nursery in polythene pots under a shade of from eight to ten palm fronds per 10 ft. length and with light watering. Late sowing and early transplanting were satisfactory, so seedlings need only remain in the nursery for five or six months; in the Ibadan area this was achieved by sowing in December and transplanting in late Mayor early June. Younger plants also grow well in the field, but there are risks in sowing seed in January, when cold, dry harmattan winds may be expected. Provided a plant is big enough to transplant, its original size has no bearing on its subsequent growth in the field, as measured by trunk girth at threemonthly intervals. Sowing seed at permanent sites is risky, as beans may be eaten by rodents.     

The effect of day and night temperatures on the growth,development and yield of glasshouse cucumbers

The responses of January-sown cucumber cvs Farbio and Sandra to day and night temperature during the early post-planting stage (late February to mid-April) were examined in a glasshouse experiment. Three day temperatures (15°, 20° and 25°C) were combined factorially with three night temperatures (10°, 15° and 20°C). Comparisons were also made between two temperature regimes (21°C day: 19°C night and 24°C day: 17°C night) applied during the pre-planting stage (late January to late February) and between two mainstem cropping methods (restriction or retention of mainstem fruits). In the pre-planting stage the 24°C day: 17°C night temperature combination produced plants which were taller, heavier and leafier than those grown at 21°C day: 19°C night. During the first 12 weeks of harvesting the larger plants produced significantly more fruit and higher gross monetary returns than did their smaller counterparts. The difference then diminished and after 20 weeks of harvesting plants from the two pre-planting temperature treatments had produced similar weights of marketable fruit of equivalent value. In the early post-planting period increases in total leaf area and stem length were closely correlated with 24-h mean temperature. Earliness (first harvest) and total weight of fruit after four weeks of harvesting were also linearly related to mean post-planting temperature. Raising the 24-h mean air temperature (within the range 15.2° to 22.6°C) by 1°C during the early post-planting stage increased early (4 week) yield by 0.82 kg m^-2 and total (20 week) yield by 1.17 kg m^-2. There was no effect of day/night temperature amplitude. After 20 weeks of harvest, gross monetary returns and profitability were generally highest when mean temperature in the early post-planting period was high and fell progressively with reduced mean temperature. Restricting stem fruits to oné per leaf node produced no significant difference in either the yield or quality of fruit from plants of any of the temperature treatments. The results are discussed from physiological and practical viewpoints and a cost-benefit comparison of temperature treatments is presented.     

Manipulation of bolting and flowering in celery (Apium graveolens L. var. dulce). III. Effects of photoperiod and irradiance

SUMMARY

Photoperiods of 8 and 16 h during chilling at 5°C had no effect on bolting and macroscopic flower appearance in celery cv. New Dwarf White. Eight hour photoperiods during chilling however markedly increased the number of plants forming sessile flowers. Short photoperiods (8 h) after chilling decreased the proportion of young, but competent plants that bolted and flowered. Total darkness during chilling completely prevented any subsequent vernalization response either as bolting or as flowering. Reducing irradiance receipt by the plants during chilling from 85 to W m"2 (PAR) had no effect on their vernalization response. After chilling, a reduction in mean daily total irradiance in the glasshouse from 4.05 to 1.57 MJ m"2 d-1 had no effect on bolting and flowering. Confinement of competent plants to darkness for 4-8 d at 20°C just prior to chilling resulted in a highly significant delay (F>0.001) to bolting and reduced the number of plants flowering. Two days of darkness had no significant effect. The inhibitory effects of dark treatments prior to chilling was greater in plants chilled subsequently for six weeks than for nine weeks.     

A cold-treatment technique to improve the germination of vegetable seeds prior to fluid drilling

A simple method capable of treating large quantities of seeds prior to germination and fluid drilling is described. After an initial imbibition period at 20°C, seeds were placed at a temperature of 1°C; high enough for continued metabolism but too low for radical emergence. This treatment reduced the spread of time of germination, increased the percentage of seeds germinating and brought forward the mean germination time of seeds when transferred back to 20°C. Treated seeds emerged earlier and more uniformily than untreated seeds following pre-germination and fluid drilling in the field.     

Flower formation of Chinese cabbage. II. Anti-vernalization and short-day treatment

The influence of high temperature (anti-vernalization) and short-day treatment during the raising of transplants on the bolting of Chinese cabbage having early planting-dates has been tested. A temperature rise from 18 to 26°C resulted in a delay in bolting, but only caused a slight increase in leaf number. Hence, Chinese cabbage shows anti-vernalization effects. The raising of transplants below 20°C and with short-day treatment for energy saving cannot be recommended, since the effect of the short-day treatment is too small.     

The effect of intermittent irrigation with cold nutrient solution on the growth of tomato seedlings propagated in rockwool

Seedlings of tomato, cv. Counter, propagated in rockwool blocks were irrigated five times every 24 h with nutrient solution at 10°C or 18°C for up to three weeks. The mean block temperature was lowered by 3.5-4.0 degrees C by irrigation at 10°C. One week of irrigation at the lower temperature caused the seedlings to develop a characteristic dark purplish colour. This treatment reduced fresh weight and leaf area but not dry weight which suggests that water uptake was also reduced. Dry weight was reduced following two or more weeks of irrigation at 10°C. When seedlings which had been irrigated at 10°C were returned to irrigation at 18°C, the purple colour slowly disappeared and the percent dry matter decreased. When plants were grown on, the total yield of fruit was unaffected by these seedling treatments.     

Analysis of the Growth and Yield of Overwintered Onions

The growth of a number of onion cultivars sown on different dates during late summer in several years was assessed by regular sampling. The growth during the winter of five different winter-hardy cultivars was very similar, whereas that of Rijnsburger Bola, a cultivar normally sown in spring, was clearly slower. Sowing date was shown to affect final yield through its effect on overwintering size, which in turn influenced bulb size at harvest, the proportion of plants which bolted and the extent of winter losses. During the winter months the rate of leaf initiation appeared to be decreased to a lesser extent than the growth in dry weight, which itself was decreased less than growth in leaf area. The growth of the winter-hardy cultivars from all sowing dates and seasons was well summarized by a single linear relationship between the logarithm of plant dry weight and the accumulated day-degrees between 6° and 20°C from the day of seedling emergence. Using this relationship together with temperature records from past years it was possible to estimate the best average sowing date and the year-to-year variation in optimum sowing date. This approach may prove useful in predicting optimum sowing dates for other localities from past weather records.     

Field Establishment of Some Vegetable Crops: Response to a Range of Soil Conditions

Calabrese, carrot, onion and red beet seeds were sown at approximately weekly intervals throughout the spring and early summer of 1972–4. In a situation where soil tilth and seed placement in the soil were apparently non-limiting, regression analysis showed that in eight of the twelve crop × year combinations there were no significant relationships between seedling emergence and soil moisture or temperature at sowing. In 1972 emergence levels of beet and calabrese were depressed by either excess or lack of soil moisture at sowing, and calabrese emergence was positively related to temperature; in 1973 and 1974 onion emergence was negatively related to temperature at sowing. Rainfall occurring shortly after sowing was identified as a major factor causing emergence problems, apparently through the formation of a soil cap, but its effect varied with crop type, seed vigour and soil moisture content at the time of seedling emergence. The results suggest that low plant stands often found in agricultural practice may be due not to soil temperature or moisture, factors dependent largely upon the weather, but to soil tilth, fertilizer level, seed or soil infection, seed drill performance and seed vigour, over all of which except the last there is, theoretically, some control.     

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.     

Effect of bulb storage temperature on leaf emergence and plant development during scale propagation of Lilium longiflorum ‘White American’

Effects of temperature and duration of bulb storage on leaf emergence of scale bulblets and on the type of plant development were investigated in Lilium longiflorum ‘White American’. After the parent bulbs had been stored for 0, 5, 10 or 15 weeks at 30, 20, 10, or 0°C, scales collected from different parts of a bulb were scale-propagated at 25 or 14°C, or under the temperature regimes normally used in The Netherlands. Independently of the scale position, a higher storage temperature promoted leaf emergence from scale bulblets, whereas a lower temperature delayed it. Higher storage temperatures produced more epigeous type plants, especially from outer and middle scales. Sprouting of the parent bulb had no effect on leaf emergence from the scale bulblets nor on the type of plant development.     

Effect of photoperiods before,during and after vernalization on flower initiation and development and its varietal difference in Japanese bunching onion (Allium fistulosum L.)

Summary

To control the bolting of Japanese bunching onion (Allium fistulosum L.) photoperiodically, the effect of photoperiods before, during and after vernalization on flower initiation and development and the varietal differences were investigated using the two mid-season flowering cvs Kincho and Asagi-kujo, and a late-season flowering cv. Cho-etsu. A long-day photoperiod (LD, 16 h) given before vernalization inhibited flower initiation. Especially, the bolting rate of ‘Asagi-kujo’ decreased by about a half, compared with the short-day photoperiod (SD, 8 h). The interaction between the effect of night temperature (3°C, 7°C, 11°C or 15°C) and the effect of the photoperiod (SD and LD) during vernalization was also investigated. In ‘Kincho’, LD did not affect flower initiation at 3°C, but inhibited flower initiation at 7°C, 11°C and 15°C. In ‘Asagi-kujo’, flower initiation was significantly inhibited by LD under all temperature conditions. This inhibitory effect was stronger at 11°C and 15°C than at 3°C and 7°C. In ‘Cho- etsu’, LD significantly inhibited flower initiation at 3°C and 7°C, and flower initiation rarely occurred at 11°C and 15°C. In this study, generally, LD during vernalization inhibited flower initiation in all cultivars. Thus Japanese bunching onion required a short-day photoperiod in flower initiation, which was stronger in ‘Asagi-kujo’ and ‘Cho-etsu’ than in ‘Kincho’. From these results, we conclude that low temperature and a short-day photoperiod complementarily induce flower initiation in Japanese bunching onion. Varietal differences exist in the requirement of low temperature and a short-day photoperiod: the primary requirement in ‘Kincho’ is low temperature and that in ‘Asagi-kujo’ is a short-day. After flower initiation, the early stage of flower development is day-neutral, and after the floret formation stage, a long-day photoperiod promotes flower development and elongation of the seedstalk.     

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