Showing papers in "Scientia Horticulturae in 1984"

In vitro propagation of some olive (Olea europaea sativa L.) cultivars with different root-ability, and medium development using analytical data from developing shoots and embryos

Abstract: Short- and long-term objectives for research on tissue culture of the olive are described. Sterile shoots were obtained from single-node woody explants or buds of 3 olive cultivars (‘Frantoio’, ‘Dolce Agogia’ and ‘Moraiolo’) with different root-ability, collected from shoots having different degrees of juvenility (suckers, vigorous nonfruit-bearing and fruit-bearing shoots, which are easy, medium and difficult to root, respectively). Because many of the media tested did not give a satisfactory growth rate and good quality shoots, a new medium was formulated by comparing data from analysis of the main mineral elements found in the apical shoots (4–5 mm long) and in mature embryos in olive and almond. Olive tissues were characterized by a high content of Ca, Mg, S, Cu and Zn compared to almond, which is easy to propagate on MS medium. In this newly derived medium, characterized by a high content of these elements, multiplication rate (number of nodes formed per explant) was about 9× in 40 days. The shoots grew more rapidly and were more tender than when grown in other media. Washing of the explants in water or GSH (reduced glutathione) solution, before sub-culturing, improved quality and growth rate of the shoots. Explants, with 2 or 3 nodes, rooted easily in half-strength MS, in Bourgin and Nitsch, or in half Knop macro and Heller microelements, agar media, with 1 mg 1 −1 NAA and 2% sucrose. Rooting was not affected by the different degrees of juvenility of the original explants used. Hardening-off was achieved by growing plants in a 1:1 mixture of perlite and peat-moss in a transparent plastic chamber with saturated circulating air for 1 month. GA 3 sprayed on the leaves was found to be beneficial in stimulating growth resumption of plantlets.

Post-harvest physiology and storage behaviour of pomegranate fruits

Abstract: Elyatem, S.M. and Kader, A.A., 1984. Post-harvest physiology and storage behaviour of pomegranate fruits. Scientia Hortic., 24: 287--298. Tested pomegranate fruits had a low respiration rate and a non-climacteric respiratory pattern. They produced trace amounts of C2H 4 and showed no response to exogenous C2H 4 treatments as measured by changes in skin colour, and juice colour and composition. Both CO2 and C2H 4 production rates increased with temperature. The Q10 values for respiration were 3.4 between 0 and 10°C, 3.0 between 10 and 20°C, and 2.3 between 20 and 30°C. Storage at 5°C or lower resulted in chilling injury to the fruits, and the severity of the symptoms increased with time and temperature-decrease below 5°C. Chilling-injury symptoms, which became more visible after transfer to 20°C for 3 days, included brown discoloration of the skin, surface pitting, and increased susceptibility to decay organisms. Internal symptoms were manifested as pale colour of the arils and brown discoloration of the white segments separating the arils (locular septa). Fruits held at 5°C for 8 weeks showed only a slight brown discoloration of the locular septa. Temperature during storage for up to 3 months had little effect on soluble solids content, pH, and titratable acidity of the juice.

Anthocyanin accumulation in apple skin during ripening: Regulation by ethylene and phenylalanine ammonia-lyase

Abstract: In ‘Jonathan’ apples in the field, the concentration of red anthocyanin pigments in the skin increased up to 3-fold before and during commercial harvest. The start of this increase coincided with the start of rapid ethylene production in the apples. Ripening, as measured by increased ethylene production, led to increases in the rate of anthocyanin accumulation and the level of the enzyme phenylalanine ammonia-lyase (PAL) in detached apples held under constant light and temperature conditions. When ethylene was applied to unripe apples, PAL activity and anthocyanin accumulation increased to levels similar to those in ripe apples. Ethylene applied to ripe apples did not increase PAL or the rate of anthocyanin accumulation. These observations suggest that ethylene initiates rapid anthocyanin accumulation during apple ripening by increasing the level of the rate-limiting enzyme, PAL, in the skin.

Effects of night time humidity and nutrient solution concentration on the calcium content of tomato fruit.

Abstract: Calcium intake into tomato fruits was greater when nights were humid rather than dry and nutrient solutions dilute rather than concentrated. The concentration of calcium in the wall tissue of the distal segment of fruits damaged by blossom-end rot was 0.03% of dry matter, but was 2- to 3-fold greater in the most favourable conditions of humidity and solution concentration, when fruits were undamaged. Adding extra calcium to the nutrient solution increased the calcium concentration in the proximal, but not in the middle or distal, segments of the fruit. The results support the hypothesis that a positive root pressure at night promotes transport of calcium into tissues and organs that have restricted transpiration.

Fruit growth of cucumber in relation to assimilate supply and sink activity

Abstract: Schapendonk, A.H.C.M. and Brouwer, P., 1984. Fruit growth of cucumber in relation to assimilate supply and sink activity. Scientia Hortic., 23: 21--33. Assimilate distribution in Cucumis sativa, cultivar 'Farbio', was studied during 36 days after emergence of the inflorescense in the 5th axil. The interaction between vegetative growth and reproductive development was examined. Daily net photosynthesis and the related assimilate supply were calculated by a simulation model. The actual dry matter accretion of vegetative and reproductive organs was derived from non-destructive measurements of organ dimensions and subsequent convertion to dry matter by statistical relations. Integrated over the total period of investigation, dry matter accretion derived either from the calculated assimilate supply or from ac~;ual measurements agreed well. However, a significant discrepancy appeared in the dynamic resolution where apparent periods of assimilate surplus were followed by periods of apparent shortage of assimilates. In this respect, the regulation of temporary storage and subsequent remobilization of assimilates is studied in relation to source--sink interactions. A hypothesis is formulated that relates the dynamics of fruit growth to assimilate supply and the sink activity of individual fruits.

The pattern and control of reproductive development in lychee: A review

Abstract: Often there is no relationship between yield and flower production in lychee (Litchi chinensis Sonn,). This is because of the high rate of premature flower and, especially, fruit abscission between floral initiation and fruit maturation. There is the possibility that low female-to-male sex ratio, lack of pollinating insects, poor pollen transfer, low pollen viability and failure of pollen tube growth may also reduce fruit set, while poor fruit development may reduce final fruit size. Detailed studies are required on the effects of genotype and environment (temperature, soil moisture, humidity and mineral nutrition) on the growth and abscission of the flowers and fruit. Potential techniques for improving the setting and retention of fruit include varietal selection, withholding of nitrogen fertilization during flowering and early fruit growth (to reduce vegetative flushing), and the maintenance of plant moisture status (irrigation, overhead misting and windbreaks).

In vitro propagation of ‘Troyer’ citrange from epicotyl segments

Abstract: Isolated epicotyl, root meristem and root segment tissues of ‘Troyer’ citrange [Poncirus trifoliata (L.) Rat. × Citrus sinensis (L.) Osbeck] were established in continuous culture to compare their regeneration potential. Callus was obtained from these explants on a Murashige—Skoog (MS) medium containing NAA (10 mg l−1) and BAP (0.1–10 mg l−1). Formation of shoots from root segments was direct without callus formation on MS medium containing BAP (10 mg l−1) and NAA (1 mg l−1). Shoot formation from epicotyl callus occurred on MS medium containing 0.25 mg l−1 BAP and 0.1 mg l−1 NAA. Formation of shoots from epicotyl segments occurred on MS medium containing BAP (0.5 mg l−1) and NAA (0.1–1.0 mg l−1), while rooting of regenerated shoots occurred in treatments containing 2.0 mg l−1 NAA alone. This system provides a rapid method for propagation of ‘Troyer’ citrange.

Effects of osmotic priming on seed germination and seedling growth in leek

Abstract: Priming four seed-lots of leek ( Allium porrum L.) cultivar ‘Winterreuzen’ in PEG solution significantly improved the rate and uniformity of seed germination, particularly in the slower-germinating lots. In both field and glasshouse conditions, priming improved the rate and generally improved the uniformity of seedling emergence. Earlier emergence after priming gave rise to higher mean plant weights 10 weeks after sowing. There was no effect of priming on seedling relative growth rate under controlled conditions. Drying-back the primed seeds slightly delayed germination and emergence (compared with seeds which had been primed but not dried-back) because of the time taken for the seeds to re-imbibe water. Most of the beneficial effect of priming was retained after drying-back.

In vitro somatic embryogenesis from Mangifera indica L. callus

Abstract: The nucellus and globular adventitious proembryos were removed from 2-month-old fruits of mango (Mangifera indica L.) cultivars ‘Ono’ and ‘Chino’, and were cultured on sterile, solid Murashige and Skoog (MS) medium that had been modified as follows: half-strength major salts and chelated iron; 20% (v/v) coconut water (CW); 6% sucrose; 100 mg l−1 ascorbic acid and 400 mg l−1 glutamine. Embryogenic explants were sub-cultured after 4–6 weeks in liquid modified MS medium containing 2 mg l−1 2,4-dichlorophenoxyacetic acid (2,4-D) instead of CW. Rapidly growing cultures were established and were sub-cultured monthly. Somatic embryogenesis was induced following sub-culture from MS medium with 2,4-D to MS without growth regulators and with or without activated charcoal (0.5%). Germination of somatic embryos appeared to be enhanced by 1 mg l−1 benzyladenine (BA); however, most of the germinating embryos became embryogenic.

Factors affecting shoot proliferation and root initiation in organ cultures of the apple ‘Northern Spy’

Abstract: Factors affecting the establishment, proliferation and adventitious root initiation of ‘Northern Spy’ are described. Shoot-tips established best in Linsmaier and Skoog medium with 5 μM BAP and 1 μM IBA supplemented with 1 mM phloroglucinol, but after the fourth sub-culture, proliferation was similar in media without phloroglucinol. Shoot proliferation was influenced by cytokinin type and concentration, light level and ex-plant type. Of the cytokinins tested, BAP was superior to zeatin, kinetin and 2iP. Proliferation was better with 10 μM BAP than with 5 or 1 μM BAP, but at 10 μM shoots were dwarfed. Single nodes and basal mass expiants produced significantly more shoots than did shoot-tips. Shoot proliferation was maximum at photon flux densities of 75 μmolm−2s−1. Roots can be readily induced with IBA, but salt concentration and the physical support on which shoot-tips are grown influence both root initiation and growth. Half-strength salts and 1 μM IBA gave best root initiation. With agar, coarse sand, perlite and rotated liquid medium, 90–100% root initiation occurs, but root growth was poor in agar.

Studies of the banana fruit surface in relation to the effects of TAL Pro-long coating on gaseous exchange

Abstract: The banana fruit surface was studied using light and electron microscopy. Browning which resulted from diffusion of chlorine into pieces of ripe fruit skin via the stomata was reduced by the prior application of TAL Pro-long. When the coating liquid was labelled with aurothioglucose, the presence of gold in stomatal apertures on areas of coated skin was demonstrated using energy dispersive X-ray analysis. Thus, the effects of coating on the permeability of the fruit skin to chlorine were caused by stomatal blockage, which physically impeded gaseous diffusion.

Importance of water loss in the chilling injury of grapefruit stored at low temperature

Abstract: Differences in chilling injury susceptibility of grapefruit from exterior and interior tree canopy positions were used to investigate the hypothesis that water loss is related to chilling injury symptom development during low-temperature storage. The sun-exposed surface of grapefruit from exterior canopy positions was more susceptible to chilling injury and had lower diffusive resistance than the shaded surface of the same fruit. Reducing the rate of fruit transpiration during the first week of storage by a pre-cooling treatment prior to low-temperature storage delayed, but did not eliminate, the development of chilling injury.

Leaching of applied phosphorus in container media

Abstract: Pre-plant P as superphosphate (8.7% P) at the rate of 1.5 kg m −3 was added to two root media in 16.5-cm azalea-type pots. Saturated media were periodically leached to 15% excess. Media type had a definite influence on P leached. Over one third of the total applied P was leached from a peat moss:vermiculite (PV) (1:1, v:v) mix after 9 weeks compared to less than 5% leached from a sand:soil:peat moss (SSP) (1:1:1, v:v:v) mix in a simulated plant watering scheme. Approximately the same amount of P was leached at any given watering in the PV (4.2%), whereas 2.6% of that applied was lost after an initial watering at 1 h and only 0.04% after an initial watering at 9 weeks in the SSP mix. This difference was related to differences in P fixation by the various root media components. P adsorption isotherms were conducted on 7 root media components or mixtures of components, including the 2 above-mentioned mixes, to determine the quantity of P adsorbed to give 0.2 ppm in the soil solution. The resulting plot of P adsorbed versus P in solution confirmed that the greater leaching loss of P in the soil-less mix was due to a lower P adsorption capacity. Maximum P adsorption capacity in the soilless media was reached with the addition of 262 g P m −3 . The adsorption capacities of soil, sand and SSP were not reached at the highest rate of P addition (524 g P m −3 . The higher P buffering capacity of these materials necessitates greater P addition to achieve 0.2 ppm soluble P, considered optimum for most plants, but ensures that the level of soluble P will be maintained for a longer period.

In vitro propagation of Pyrus pyrifolia

Abstract: A micropropagation method for an adult seedling tree of Pyrus pyrifolia Burm. f. is described. Shoot cultures were established and multiplied on media containing benzylamino purine and naphthaleneacetic acid, rooted on media containing naphthaleneacetic acid and phloroglucinol, and transplanted to potting mix. Addition of phloroglucinol to the rooting medium enhanced both the percentage of shoots forming roots and the survival of plantlets after transplantation. However, about 30% of the plants raised in vitro were lost owing to a shoot-collapse which was not prevented by the application of fungicides. Establishment and multiplication of shoot cultures was also achieved with 5 named cultivars of P. pyrifolia , but rooting of the shoots of these cultivars has not been satisfactory.

Changes in activity of polyamine biosynthetic enzymes and in polyamine contents in developing fruit tissues of ‘Murcott’ mandarin

Abstract: Arginine decarboxylase (ADC), ornithine decarboxylase (ODC), putrescine (Put) and spermidine (Spd) contents were analysed in growing ‘Murcott’ mandarin fruits from bloom to full development. Enzymes of polyamine synthesis and, to a lesser extent, polyamine contents roughly followed patterns of growth activity in fruit tissues, with a maximum at the early stages, a minimum at mid-summer and intermediate values at full fruit development. ADC/ODC and Put/Spd ratios were 2–8 and 2–30, respectively. Possible links between polyamine metabolism and citrus fruit set and development are suggested.

Use of humidity tents and antitranspirants in the acclimatization of tissue-cultured plants to the greenhouse

Abstract: Film-type antitranspirants and a humidity tent were tested on tissue-cultured chrysanthemum and carnation plants in order to determine the most effective way to increase the vigor and survival of the plants at the time of transfer to a greenhouse. Phytotoxicity necessitated applying most antitranspirants at concentrations lower than that recommended by the manufacturers. Plants grown in the humidity tent were significantly larger and more vigorous than plants in any other treatment. Although a silicone formulation had the greatest effect in reducing transpiration and water stress in transferred plants, it had the adverse effect of stunting plant growth. All other treatments with antitranspirants were ineffective in improving vigor and survival of plants compared to controls.

Screening of wild Cucumis species for resistance to cucumber powdery mildew (Erysiphe cichoracearum and Sphaerotheca fuliginea)

Abstract: A set of 57 accessions belonging to 20 wild species and varieties of the genus Cucumis , originating mainly from the African Gene Centre, was tested for resistance to Erysiphe cichoracearum and Sphaerotheca fuliginea , causal agents of cucumber powdery mildew. Seedlings were substantially more susceptible than adult plants. Inter- and intra-specific specificity was detected in the interactions of wild Cucumis species with both pathogens. Eighty percent of the accessions were susceptible to E. cichoracearum , and 40% to S. fuliginea , as adult plants. Adult plants of the species Cucumis ficifolius (IVT 1801, PI 280231), C. anguria (PI 147065), C. anguria var. anguria (CUC 9/1974), C. dinteri (PI 374209) and C. sagittatus (PI 282441) were resistant to both pathogens.

Inhibition of flowering in mango by gibberellic acid

Abstract: Flowering and early bearing of mango trees during the 1–4 years after planting suppress vegetative growth. The effects of different GA 3 concentrations and application times were examined as a means of flower inhibition. The extent of flower inhibition was the same with all GA 3 concentrations − 200, 50 and 25 mg l −1 — while the response of cultivars was very different. The optimal time of GA 3 application depends on climatic conditions and cultivation practices.

Initiation and development of pistillate flowers in Actinidia chinensis

Abstract: Initiation and development of pistillate flowers in Actinidia chinensis Planch, cultivar ‘Hayward’ (kiwifruit, Chinese gooseberry) was followed using light and scanning electron microscopy. Results indicate that dormant buds contain undifferentiated primordia in the leaf axils. These primordia remain undifferentiated until shortly before bud break, approximately two months before full bloom, when the primordia become trilobed as bracts and lateral flower primordia are initiated. The lateral flowers often abort in this cultivar. Acropetal development of the terminal flower proceeds rapidly. Five to seven sepals are initiated, followed by a whorl of five to seven petals. Stamen initiation is centripetal and the anthers develop to produce inviable pollen. The central portion of the floral apex is converted into a large compound pistil with numerous hollow styles, each terminated by an open stigma.

Diurnal fruit shrinkage in apple as affected by leaf water potential and vapour pressure deficit of the air

Abstract: In a series of experiments with potted apple trees cultivar ‘Cox's Orange Pippin’, daily shrinkage of fruits was measured over a wide range of vapour pressure deficits of the air. The trees were either well watered or the water supply was reduced to induce drought. Wrapping of fruits in aluminium-foil to prevent evaporation did not noticeably reduce shrinkage, but weight-loss data of detached fruits hanging in the tree under the same conditions showed that evaporation accounted for 20–35% of the fruit shrinkage. Shrinkage was much more closely related to leaf water potential than to the vapour pressure deficit of the air. Reverse flow of water to other parts of the tree was the main factor determining the degree of fruit shrinkage during the day.

Propagation of eight cultiv ars of Rhododendron in vitro using agar-solidified and liquid media and direct rooting of shoots in vivo

Abstract: Sterile cultures were obtained from expanding buds of Rhododendron cultivars ‘Pink Pearl’, ‘Nova Zembla’, ‘Gomer Waterer’, ‘Hugo Koster’, ‘Britannia’, ‘America’, ‘Wilgens Ruby’ and ‘Doncaster’. Shoot-producing cultures were obtained from all cultivars except ‘Doncaster’. Yield of shoots on agar-solidified medium varied with each cultivar. For ‘Pink Pearl’, shoot production with liquid medium was 10-fold higher than with agarsolidified medium. Shoots were readily rooted in vitro and in vivo. Rooting percentages of 50–70% were obtained after 5 weeks when unrooted shoots were transferred to a peat substrate. This was increased consistently to 80–90% by pre-treating shoots in a solution of minerals, vitamins and sucrose. Pre-treatments for at least 10 days in medium supplemented with indolebutyric acid (5–15 mg l−1) significantly (P ≤ 0.05) increased the number of roots produced per shoot. A pre-treatment period of at least 10 days was required for optimal rooting.

Interactions between root-zone temperature and light levels on growth, development and photosynthesis of Lycopersicon esculentum Mill. cultivar ‘Vendor’

Abstract: Six-week-old tomato plants were subjected to 5 root-zone temperatures, ranging from 12 to 36°C, and 4 light levels in a factorial design. Large increases in shoot dry weight, leaf area and fruit development resulted from soil warming to 24°C when plants were grown under high light conditions. Shoot growth and fruit weight were reduced at 24°C root temperature under low light conditions. Total plant photosynthesis, leaf area index, net assimilation rates and leaf chlorophyll content were related to plant growth and flower development for the various treatments. Our experiments have shown an interaction between root-zone temperature and light levels for greenhouse tomatoes. Soil warming caused large increases in shoot dry weight and fruit development when light was not limiting plant growth, but had deleterious effects on flowering and fruit set under shaded conditions.

Endogenous plant growth substances content in young fruits of seeded and seedless Clementine mandarin as related to fruit set and development

Abstract: The content of plant growth substances in the fruits of seedless (‘Fino’) and seeded (‘Monreal’) Clementine mandarin ( Citrus reticulata Blanco) during the early stages of development was investigated. Auxin-like substances were determined with the oat mesocotyl bioassay, gibberellin-like substances with the α-amylase bioassay, and abscisic acid (ABA) by gas chromatography—electron capture detector. Methanolic extracts of fruits of seedless Clementine had higher content of auxin-like compounds in the acidic and butanolic fractions than the seeded Clementine extracts. In particular, a compound with R f 0–0.25 in the chromatograms may be involved in the parthenocarpic fruit set development of ‘Fino’ Clementine ovaries. Diffusable gibberellin-like compounds ( R f 0.8–1.0), probably produced in the developing seeds, were obtained from seeded Clementine fruits after the time of anthesis. The content of ABA in the fruits was always low in ‘Monreal’ Clementine, whereas in fruits of ‘Fino’ Clementine and of ‘Monreal’ without seeds it increased dramatically after anthesis. It is suggested that the control of fruit set and development in Clementine mandarin is carried out through an equilibrium between auxin-like substances (‘Fino’) or gibberellin-like substances (‘Monreal’) and ABA.

Cold storage of rose flowers: effects of cold storage and water loss on opening and vase life of Mercedes roses

Abstract: The effects of storing ‘Mercedes’ rose flowers ( Rosa hybrida L.) without water at 2°C and 95% RH on flower opening and on vase life were studied. Flowers were held without water (“dry”) or with their stem bases in deionised water (“wet”). Dry storage for 10 days did not significantly reduce the water content of the petals, but did reduce the subsequent vase life at 22°C compared with freshly cut flowers. Dry storage also reduced the maximum flower diameter and the number of reflexed petals after transfer to 22°C. Flowers stored wet had higher petal water content but shorter vase life than dry-stored flowers. The effects of water loss induced at 22°C were studied and compared with the effects of cold storage. Flowers were held at 22°C and 65% RH without water for 24 or 36 h and then placed in water. Only when petal fresh weight loss reached 19% was the flower vase life reduced. Water loss also caused a reduction in maximum flower diameter, petal area and the amount of petal reflexing. The effects of water loss on petal life could be nullified by detaching petals from the flowers and placing them in water. This indicated that in intact flowers, water loss induced an obstruction to subsequent water uptake and rehydration of the petals. In contrast, detachment of petals did not alleviate the effect of cold storage on vase life. It was concluded that water loss during dry cold storage is not the cause of the reduced vase life of cold-stored rose flowers.

Calcium and magnesium interactions in browning of ‘Golden Delicious’ apples with bitter pit

Abstract: The role of Ca and Mg in the enzymatic browning of ‘Golden Delicious’ apples was explored. Enzymatic browning due to polyphenol oxidase (PPO) was stimulated with the addition of 0.8–10 mM MgCl2 to the reaction mixture, whereas 0.8–10 mM CaCl2 had little effect or decreased the rate of enzymatic browning. Within a week after vacuum infiltration with MgCl2, treated fruits exhibited browning symptoms that were similar to bitter pit. Six months after vacuum infiltration, when analyzed for enzyme activity, MgCl2-treated fruits exhibited higher rates of PPO activity, whereas CaCl2-treated fruits had lower activity than the MgCl2-treated fruits and the controls. A hypothesis is advanced that the initial visible symptoms of bitter pit, i.e. the localized browning, is caused by PPO, its activity being stimulated by the localized Mg/Ca imbalance present in the tissue. The results indicate that Ca is predominant in the prevention of this disorder, whereas a deficiency of Ca is involved in its induction.

Effect of day and night temperatures during short photoperiods on growth and flowering of Chrysanthemum morifolium Ramat

Abstract: The effect of day and night temperatures of 10, 14 and 18°C on growth and flowering under short days was studied with six cultivais of chrysanthemum. A high day temperature resulted in earlier flowering and taller stems, but did not influence flower number and final total fresh weight, and only slightly influenced the distribution of fresh matter over stem, leaves and flowers. A high night temperature resulted in earlier flowering, more flowers and reduced stem and leaf weight. It did not affect leaf number and it influenced height and total fresh weight only slightly. Except for height, the day temperature acted independently from the night temperature. The cultivars responded similarly, except for two cultivars which generally did not flower at 10/10,10/14 and 14/10°C D/N. One cul-tivar produced more flowers at 14 than at 18°C.

Seasonal effects of radiation and temperature on growth of greenhouse lettuce in a high insolation desert environment

Abstract: ‘Ostinata’, ‘Summer Bibb’ and ‘Grand Rapids’ lettuce were measured for seasonal growth in a greenhouse in a high-insolation desert environment. Growth of all 3 cultivars was positively correlated with radiation up to the highest level measured, 550 cal cm −2 day −1 . Crops grown in the autumn used light 2–3 times more efficiently than crops grown in spring. Daytime air temperatures were also positively correlated with growth, and there was a significant temperature × radiation interaction. The best predictor of growth was the product of day temperature and the log of radiation. This variable explained much of the difference between the growth of autumn and spring crops. Autumn crops were grown under higher temperatures and thus responded more steeply to radiation than spring crops. High temperatures during the summer rainy season were associated with bolting. A general curve to predict the length of the crop cycle from radiation data alone was constructed from data for Tucson, Arizona, U.S.A., crops and data from the literature for lettuce grown in Great Britain and the Great Lakes region of the United States.

Effects of high-humidity storage on quality, decay and storage life of cherry, lemon and peach fruits

Abstract: Sweet cherries ( Prunus avium (L.) ‘Lambert’ and ‘Blackboy’), lemons ( Citrus limon (L.) Burm. f. ‘Lisbon’) and peaches ( Prunus persica (L.) Batsch, ‘Summerset’) were stored at 77–83, 90–94 and 95–99% RH (high humidity) at near-optimal storage temperatures after harvest and treatment with fungicides. High-humidity storage did not increase the storage life of peaches held at 0°C, but the life expectancy of cherries (both cultivars) was extended by 7–10 days at 0°C, and of lemons by at least 4 weeks at 10°C when fruit were stored at 95–99% RH compared with levels below 95%. The beneficial effects of high humidity were attributed to retardation of peel desiccation and associated reductions in fruit deformation, peel de-greening, chilling-injury and decay in lemons and to the maintenance of a fresher stalk and a firmer, less shrivelled fruit in cherries. High humidity had no effect on decay in cherries or peaches, but it significantly reduced weight loss and delayed the appearance of shrivel in peaches stored at 0°C. However, after storage at high humidity for 4 weeks, peaches ripened with low rates of C 2 H 4 evolution and showed severe low-temperature injury, slight peeling-injury and a poor flavour ex-store.

Bulblet-productivity of explants from scales, leaves, stems and teplas of Lilium rubellum Baker

Abstract: The number of bulblets per cultured expiant was greatest in the expiants of leaves, i.e. 2.2 bulblets, followed in decreasing order by scale-, stem- and tepal-expiants. Bulblets formed in the expiants of stems were heaviest, 135 mg on average. The expiants of leaves were excellent for regenerating many bulblets per expiant, while those of stems produced the heaviest bulblets.

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

Abstract: 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.