Prevention of hot-water treatment damage in narcissus bulbs by pre-warming

Summary

Hot-water treatment (HWT) used to control stem nematode in narcissus bulbs can lead to yield loss through damage to flower, leaf and root initials. Warm storage of bulbs, usually at 30°C, reduces this damage. The effects of two pre-warming treatments (18°C for two weeks or 30°C for one week before HWT) were investigated in bulbs hot-water treated at a range of dates (from early-July to late-September). Experiment 1 was conducted on bulbs of cv. Carlton lifted on three dates. In the year after HWT, flower numbers were much reduced when HWT was applied after mid-August following storage at ambient temperatures, or after late-August following storage at 30°C, but numbers were only slightly reduced even with late-September HWT when given after 18°C storage. Pre-warming was somewhat more effective after early lifting. Late HWT reduced yields of bulbs harvested after two years' growth, but 18°C treatment largely prevented these losses. In Experiment 2, the beneficial effects of 18°C treatment were confirmed in cvs Carlton and Golden Harvest but not in cv. Barrett Browning. These findings are discussed in terms of growth retardation by warm temperatures.     

Accelerated rooting of carnation ‘Red Baron’ by temperature pre-treatment

Rooting of carnation cuttings was promoted by storage temperatures above 0°C with an inverse relationship between the level of temperature and the duration of the treatment. The effect of temperature on root dry weight was far more important than the effect of duration of storage. A long storage and a high temperature increased the incidence of Fusarium. Storage at temperatures lower than 13°C gave better results with auxin applied after storage, while temperatures higher than 13°C gave better results with a pre-treatment of auxin. During storage for 14 days at 9°C, the position of the cuttings had no clear effect on rooting. Horizontal storage, however, appeared to be unfavourable. Removal of 0.5 cm of the base of the stem after storage nullified the storage effect. Carbohydrates in the removed pieces decreased during storage, more so at 13°C than at 0°C. Anatomically, an acceleration of cell division at the base of the cutting was observed during storage at 9°C as compared to 0°C.At a commercial nursery, storage of cuttings for 12 days at 14°C improved rooting by 84% compared to storage at 0°C. The presented technique tends to shorten the expensive and vulnerable period from planting to rooting.     

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.     

Effect of night temperature and growing-practices on the winter yield of roses

The effect of night temperatures on the yield and quality of the rose, cultivars ‘Baccara’, ‘Sonia’ and ‘Belinda’, was studied during the winters of 1974/75 and 1975/76. Lower night temperature decreased the number of saleable flowers, reduced flower stem length, and increased ‘Baccara’ flower malformation. Sacrificing autumn yield (October–November) increased the number of mid-winter flowers and their stem length while significantly decreasing ‘Baccara’ flower malformation. The favorable response to sacrificing early yield is attributed to an enhanced rate of lateral bud breaking, as well as to a prolonged accumulation of summer metabolites and a more satisfactory balance of growth substances which reduce the incidence of flower malformation.     

Effects of basal temperature on the rooting of hardy hybrid Rhododendrons

The effects of 3 basal temperatures; 15°, 20° and 25°C, on rooting of the hardy hybrid Rhododendron cultivars ‘Pink Pearl’, ‘Mrs. R.S. Holford’ and ‘Fastuosum Flore Pleno’ have been studied.A temperature of 15°C gave least rotting in all 3 cultivars and therefore more cuttings survived to root. Rotting increased and rooting decreased with increasing temperature.In cuttings without evident rotting, 25°C gave better rooting than 15°C, indicating that with improved control of disease, propagation at the higher temperature may be beneficial.The ease of rooting in unrotted cuttings was similar in R. ‘Fastuosum Flore Pleno’ and R. ‘Pink Pearl’ but lower in R. ‘Mrs. R.S. Holford’. Rotting was greatest in R. ‘Mrs. R.S. Holford’ and least in R. ‘Fastuosum Flore Pleno’.     

Root shoot interactions in passionfruit (Passiflora sp.) under the influence of changing root volumes and soil temperatures

Summary

Passionfruit are grown in the tropics and subtropics where mean monthly soil temperatures at 15 cm range from about 10° to 30°C. The choice of rootstock can also influence production with most industries exploiting either the purple (Passiflora edulis f. edulis) or golden passionfruit (P. edulis tflavicarpa). We examined the relationship between shoot and root growth in purple x golden hybrid E-23 grafted onto golden passionfruit seedlings. Growth was manipulated by varying the volume of the soil available to the roots or temperature of the root zone. Shoot and root growth increased as root zone volume increased from 0.3, 1.4, 4, 12 to 24 1. Shoot weight (W_s) was correlated with root weight (W_R):W_S = 12.697 + 5.272 W_R + 0.195 W_R² (r² = 91%, P<0.001), with the plants allocating a smaller proportion of dry matter to the roots as root weight increased. Differences in shoot growth with pot volume were not due to changes in water or nutrient status. In the temperature experiment, the two critical root zone temperatures at 90% of maximum growth were about 20° and 35° C for vine extension, leaf area, node and leaf production, and 20° and 30°C for flower production. Leaf and stem dry weight were optimal between about 18° and 34°C, while maximum root growth occurred at 38°C. There was a weak relationship between shoot (W_s) and root dry weight (W_R): W_s = ?19.346 + 24.500 W_R ?1.046 W_R² (r² = 53%, .P<0.001). Apparently, variations in shoot growth at different soil temperatures cannot be explained solely by differences in root growth. Reduced growth at 10°C was associated with lower chlorophyll concentration, stomatal conductance and net CO₂ assimilation, but not lower leaf water potential. The concentration of most nutrients were lower at 10°C than at higher temperatures, but none was outside the range which would be expected to restrict growth. There appears to be a co-ordination of shoot and root growth as the soil volume available for root growth increases, whereas root temperature affects the roots and tops differently. The results of the pot volume experiment demonstrate the importance of rootstock vigour in passionfruit breeding. Productivity would be affected in cool subtropical areas with soil <20°C and in tropical areas with soil >30°C.     

Nutritional and cultural factors affecting rooting of papaya (Carica papaya L.) in vitro

Summary

Experiments were conducted to optimize nutritional and cultural requirements for initiation and growth of roots on papaya in vitro. Axillary shoots were obtained from plants which had been sub-cultured monthly for two years. Root initiation was enhanced when 1 to 2 mm of stem base was removed and shoots were growing actively before transfer to the rooting medium. Decreasing daylength during incubation from 24 h to 12 h promoted root initiation. Within the day temperature range of 22 to 29°C, optimum rooting occurred at 27°C and higher temperatures produced higher mean root weights per shoot. High concentrations of growth factors and the absence of sucrose in the medium both reduced root initiation, however, varying the concentration of sucrose and removing growth factors affected mean root weight per shoot. All media contained a modified de Fossard et al. (1974) basal medium plus 10 μM IBA.     

Effect of Season on the Carnation (Dianthus Caryophyllus L.). III Flower Quality

Carnation flowers, cv White Sim, of three market grades from commercial-type beds were examined monthly to relate their grading to various quality parameters and to determine the extent of any seasonal changes in these values. Some showed small seasonal changes, e.g. percentage dry weights of flowers and stems, whereas others showed very large seasonal changes, e.g. flower diameter, stem strength and the proportion of the dry weight in the flower head relative to that in the stem. Regression analyses showed that flower fresh weight was related to the mean daily radiation and temperature integrals in the period from the early bud-visible stage to anthesis:

Fresh weight (g)=5.022+10.537 log_e cal cm-² day-¹-2.215 temp. °C.

Stem strength was also related to radiation and temperature in this period:

Stem strength (coded value)=34.825–9.027 log_e cal cm-² day-¹+1.214 temp. °C.

Unlike fresh weight and stem strength, in which solar radiation played a greater role than temperature, flower diameter was largely dependent upon temperature, high temperatures producing small flowers. Temperature and light integrals in the period from the early bud-visible stage to the bud reaching 1 cm diam. gave the best relationship to flower diameter at anthesis:

Diameter (cm)=9.361–0.1567 temp. °C+0.1353 log_e cal cm-² day-¹.

The environmental conditions required to produce good quality carnation flowers were found to be high solar radiation integrals coupled with low ambient temperatures.     

Growth and development of Lilium longiflorum ‘Nellie White’ during bulb production under controlled environments : II. Effects of shifting day/night temperature regimes on scale bulblets

One-year old scale bulblets of Lilium longiflorum Thunb. ‘Nellie White’ (Easter lily) were grown for 107 days during growth period 1 (GP-1) in six growth chambers under constant day/night temperature regimes of 30/26, 26/22, 22/18, 18/14, 14/10 and 10/6 °C. Subsequently, half of the plants in each temperature regime were transferred to 18/14 °C and the other half continued at the six constant temperature regimes. Both groups of plants were grown for an additional 89 days in growth period 2 (GP-2). Continuous temperatures of 26/22, 26/22–22/18 and 26/22–18/14 °C produced the greatest increase in basal bulb fresh weight (the main planted bulb), basal bulb circumference and stem bulb fresh weight, respectively. However, shifting these optimal temperatures to 18/14 °C during GP-2 resulted in a lower increase in basal bulb fresh weight and circumference. The optimum range for stem bulb production was expanded to 30/26–14/10 °C by shifting to 18/14 °C. The greatest increase for basal root growth occurred at 14/10–10/6 °C and for stem root growth at 14/10 °C. The temperature shift did not affect either root type. Maximum increase for stem length was at 26/22 and 22/18 °C and for stem plus leaf weight at 14/10 °C under constant temperature regimes. Transferring the plants from 10/6 to 18/14 °C resulted in the greatest increase in stem length and from 10/6 and 14/10 to 18/14 °C in the greatest increase in stem plus leaf weight. The greatest increase in the number of leaves occurred at 26/22 and 10/6 °C, but this growth parameter was unaffected by shifting to 18/14 °C, indicating that leaf number was determined in GP-1. Bulbils developed only when bulbs at high GP-1 temperature regimes (30/26 and 26/22 °C) were transferred to 18/14 °C during GP-2. Lower temperatures tended to favor an increase in flower bud production under continuous temperature regimes, while shifting to 18/14 °C increased flower bud production after initially high and low temperatures. Meristem abortion was greatest at 30/26 °C followed by 26/22 °C, but was not affected by temperature shifts in GP- 2. Thus, it is concluded that the abortion was induced or initiated during GP-1.     

Growth responses of some greenhouse plants to environment. II. The effect of soil temperature on Chrysanthemum morifolium Ramat

The effect of a wide range of soil temperatures (6–26°C) on growth and flowering of Chrysanthemum morifolium Ram. ‘Horim’ were studied at the favourable air temperature of 18°C. Shoot growth was severely reduced at soil temperatures below 10°C which may be explained by poor root growth, while flowering was enhanced by approximately 2 days compared to higher soil temperatures. Increasing the soil temperature to 18°C was beneficial. Further increase had no positive effect on growth. Measurements of net photosynthetic rates revealed no effect of lowering soil temperatures from 18 to 6°C.Mother plants grown at 18°C air temperature revealed no effect of soil temperatures ranging from 13 to 21°C on number and fresh weight of the cuttings. Neither did mother plants grown at the less favourable air temperatures of 12 or 15°C. Cutting production was, however, affected by air temperature.     

The effect of soil temperature on lateral shoot formation and flower-bud formation in apple in the first year after budding

Under controlled environment conditions the influence of four soil temperatures (7°, 14°, 21°, and 28°C) on vegetative development and flower-bud formation of apple trees (cvs ‘Rode Boskoop’ and ‘Elstar’) were evaluated in the first year after budding. Relative air humidity was high, air temperature was 20°C. Broadly speaking, for both cultivars shoot growth clearly increased with increasing soil temperature. The effects on growth were mainly reflected in the number (not length) of the lateral shoots; the growth of the main shoot was little influenced by soil temperature. At 7°C the lateral shoots usually occurred higher along the main stem than at the higher temperatures. Flowering on the parent stem and on the lateral shoots was little affected by the soil temperatures tested. In general, flower-cluster quality was rather poor. If only clusters having more than four well-developed flowers are considered, flowering was favoured by higher soil temperatures; at 28°C, especially, cluster quality was much better than at the other soil temperatures. It is concluded that soil temperature is important in controlling the degree of lateral shoot-formation as well as the formation of well-developed flower clusters.     

Effects of different diurnal temperature combinations on fruit set of sweet pepper

Trials were carried out on sweet pepper, Capricum annuum L. cultivar ‘Ma'or’ under controlled temperature conditions and natural light. In the first trial, we examined night temperatures of 15, 18, 21 and 24°C (± 1) in combination with a day temperature of 24°C, and in the second trial day temperatures of 22, 25 and 28°C (12 hours) and divided day temperatures of 28-32-28°C (4+4+4 hours) in combination with a night temperature of 18°C. The highest fruit-set was obtained at the lowest night temperature; the highest night temperature caused considerable blossom drop. The highest tested day temperature did not cause increased blossom drop.     

Temperature effects on flower formation in saffron (Crocus sativus L.)

The temperature conditions for shoot growth and flower formation were characterised for saffron (Crocus sativus L.). Leaf withering occurred during late winter or spring depending on location, and coincided with a rise in temperature. No growth was detectable in the buds during the first 30 days after leaf withering, neither in underground corms nor in lifted corms incubated in the laboratory under controlled conditions. Flower initiation occurred during the first growth stages of the buds. The optimal temperature for flower formation was in the range from 23 to 27 °C, 23 °C temperature being marginally better. To ensure the formation of a maximum number of flowers, the incubation at these temperatures should exceed 50 days, although incubation longer than 150 days resulted in flower abortion. Flower emergence required the transfer of the corms from the conditions of flower formation to a markedly lower temperature (17 °C). Incubation of the corms after lifting at a higher temperature (30 °C), reduced flower initiation and caused the abortion of some of the initiated flowers. No flowers formed in corms incubated at 9 °C. A variable proportion (20–100%) of the corms forced directly at 17 °C without a previous incubation at 23–27 °C formed a single flower. The wide differences in the timing of the phenological stages in different locations we found in this study seemed related to the ambient temperature. Leaf withering was followed shortly by flower initiation, which occurred during late spring or early summer as the rising temperature reached 20 °C. A long hot summer delayed flower emergence which occurred in late autumn as the temperature fell to the range of 15–17 °C.     

Temperature and irradiance effects on Sandersonia aurantiaca flower shape and pedicel length

Sandersonia flowers can vary from being lantern- to tubular-shaped. Lantern-shaped flowers are considered to be most commercially desirable when the ratio of the widest to the narrowest diameters of a flower, termed the ratio of hips to waist, is 1.5 or greater. Pedicel length can also affect the overall appearance of a flower stem. Short pedicels are considered more desirable. The influences of temperature and irradiance on Sandersonia aurantiaca flower shape and pedicel length were examined in controlled environment (CE) growth rooms. The growing environments were at constant temperatures of 15, 18, 21, 24 or 27 °C; or day/night temperature differentials of −6, 0, +6, +12, or +18 °C, with a mean of 21 °C. Photosynthetic photon flux densities (PPFD) were 700, 460 or 210 μmol m⁻² s⁻¹. At harvest, measurements were made of the widest and narrowest diameters of the oldest flower on each stem and the ratio of these parts was calculated. The pedicel length of the oldest flower was also measured. Environments with constant temperatures below 23 °C and the least day/night temperature differentials (−6, 0 and +6 °C) produced flowers of the most desirable shape, defined as having a hips to waist ratio of 1.5 or greater. At these temperatures, irradiance had a variable effect on flower shape. Pedicel length was also highly dependent on temperature and PPFD. As mean temperatures increased or as the temperature differential changed towards a differential of 12 °C, and as PPFD decreased, pedicel length increased significantly. Hip diameter was more sensitive to environmental changes than waist diameter and thus had a greater effect on flower shape. This work indicates to growers that they can enhance Sandersonia flower quality by producing more desirably shaped flowers with short pedicels through maintaining relatively low (less than 23 °C) mean temperatures, minimising temperature differentials, and maintaining irradiance levels as high as possible.     

Effects of temperature on growth and development of hybrid Tea-rose seedlings

Hybrid Tea-rose seedlings were grown, from germination to first flowering, at 6 constant temperatures between 10 and 26°C in greenhouses of our phytotron. All seedlings flowered regardless of temperature. When temperature increased, the juvenile period, the number of days to first flowering, the length of the leaved part of the shoot, the length of the flower stalk, the fresh weight of the shoot and of the root decreased; leaf number was not affected.     

The effect of temperature on growth and development of cultivars of radish under winter conditions

Leaf and root growth and development of 7 early radish cultivars and strains were studied at a series of constant temperatures varying from 10°C to 26°C under winter conditions. Maximum leaf growth was observed at 23°C, maximum root growth initially at 14°C and later on at 10°C. Total dry matter production was highest at 23°C. Between the cultivars/strains distinct differences in rate of leaf and root growth were noted, but no clear interactions of temperature X cultivar/strain were found. The prospects of shortening the growing-period in winter of early radish by means of regulating environmental factors and plant breeding are discussed.     

Effects of air and soil temperatures on the growth of gerbera

The effect on gerbera cultivar ‘Fredaisy’ of air and soil temperatures in the range 11–21°C has been studied in home-made growth-cabinets providing a sufficient thermal insulation between air and soil. Certain characteristics of the plants in cabinets were compared to those in a greenhouse.Amongst the growth characteristics, the length of the maturation period of the flower and the elongation rate during the early stage of the stem growth were more influenced by air temperature; the interval of appearance of new buds, the final stem length, and the elongation rate at the end of the stem growth, were more influenced by soil temperature.The elongation rates allowed a reasonably accurate prediction of the thermal zero of vegetation.     

Maturity of apple cv. Elstar as affected by temperature during a six-week period following bloom

Summary

In two experiments under controlled conditions, the effect of temperature (16, 20 and 24°C, experiment 1; 16 and 22°C, experiment 2) during a six-week period immediately following bloom on the progress of ripening around the normal picking time was evaluated for fruits of cv. Elstar. After six weeks, the temperature in experiment 1 was kept at 20°C throughout. In experiment 2 the temperature was 22°C from week 6 to 14, and 16 or 22°C from week 14 to 22. Post-bloom temperature clearly affected the rate of fruit ripening as reflected in ethylene production, background colour, starch content, firmness and red blush, but these variates did not respond to the same degree. The effect of temperature late in the season on ripening (just during the maturation period) was almost absent when the post-bloom temperature was 16°C. However, when post-bloom temperature was 22°C, fruits were greener, firmer, contained more starch and showed more red blush at 16 than at 24°C given from week 14 to 22. The acid content at ripening was lower at the higher post-bloom temperatures. Irrespective of the post-bloom temperature, acid content was also reduced at the higher temperature given during the maturation period. The content of soluble solids showed no consistent pattern.     

An Instrument for Measuring the Firmness of Brussels Sprouts

The effects of CO₂ supplementation from November to early February on the winter bloom production of Sonia roses was investigated in a glasshouse divided into four compartments. A comparison was made between no enrichment and enrichment to a controlled level of 1000 vpm CO₂ with each treatment being replicated twice. For the period December-April, plants in the CO₂-enriched compartments produced 23 % more marketable blooms than those not enriched, the monthly increases ranging from 18% in December to a maximum of 31 % in February. Other beneficial effects .obtained from plants in the CO₂-enriched compartments were a higher proportion of first grade blooms, particularly in the shorter stem length categories, and a correspondingly smaller proportion of second grade blooms. The monthly increases in marketable blooms obtained in the CO₂-enriched compartments were the result both of a reduction in the numbers of blind shoots present and of the stimulation of greater numbers of axillary buds into growth.

At 1972–73 prices the monthly increases in cash returns obtained from the CO₂-enriched compartments ranged from 28p per sq m of bed area in December to 43p per sq m in February.     

Effects of soil temperature on head development of Cos lettuce

Cos lettuce plants (Lactuca sativa L. cultivar ‘Romana’) of 2 ages were grown for 30 days with soil temperatures of 12°, 20°, 28° or 36°C. The highest temperature caused poor growth and heading and quick head disintegration. Best heading occurred mainly at lower temperature, although the lowest one sometimes delayed growth. Higher temperatures did not enhance real bolting, as growth of the inner stem was accelerated.