Is Chilling a Prerequisite for Flowering and Fruiting in ‘Arbequina’ Olives?

Abstract

It is generally thought that olives (Olea europaea) require several days (over 80 days) of chilling temperatures (7.2°C) for flower induction; minimum nighttime temperatures of 2-4°C and maximum daytime temperature of 15.5-19°C are considered optimum for flower and fruit production. Environmental chamber studies were conducted on potted olive trees for the purpose of defining flowering conditions for ‘Arbequina’. We repeatedly observed that good flower and fruit production in ‘Arbequina’ can be achieved even when the plants are not subjected to “chilling” temperatures or any chilling criteria that had previously been described necessary for flower and fruit production in olives. This phenomenon could be of great practical value because the results obtained can be exploited to cultivate olives in subtropical climates (e.g., southern and coastal Texas) where typical “chilling” temperatures are not commonly observed for prolonged periods of time.     

Chilling requirements of Paeonia cultivars

Dormant second year potted plants of Paeonia ‘Coral Sunset’, ‘Monsieur Jules Elie’, and ‘Sarah Bernhardt’ were placed into three chilling regimes (constant 1, 4, or 7°C) for different durations (3, 6, 9, or 12 weeks) to ascertain their chilling requirements for shoot and flower production. Chilling was followed by forcing for up to 5 weeks at 18°C, then plants were maintained in a controlled greenhouse until flowering had finished. Mean number of shoots and flowers per plant were recorded and the time taken for shoots to sprout was calculated.Control plants (forced immediately without chilling) produced no shoots or flowers. For all cultivars, the proportion of plants that sprouted, and the mean number of shoots and flowers increased as plants were subjected to colder chilling temperatures, or longer chilling durations. However, there were no significant within-cultivar differences between different treatments of 9 weeks or more. The time taken for sprouting to occur after the completion of each chilling treatment consistently decreased as the duration of the chilling treatment increased. In most cases, lower chilling temperatures lead to more rapid sprouting once plants were placed in the 18°C forcing conditions.When a simple model was fitted where the chilling temperature and duration of each treatment was described by a cumulative normal curve rising from zero to some maximum value (or potential) once adequate chilling had been received, we found that temperatures of 4 and 7°C provided only 83 and 59%, respectively, of the chilling accumulated per unit time at 1°C. ‘Coral Sunset’, an interspecific hybrid early flowering type, required the greatest amount of chilling to sprout consistently, while ‘Sarah Bernhardt’, a very late flowering type, required the least. Of the three cultivars, ‘Sarah Bernhardt’ also required the least amount of chilling to achieve its potential shoot and flower numbers, while ‘Monsieur Jules Elie’, a mid-season flowering type, required the most chilling to achieve the same end for these two variables. This suggests that the response to spring temperatures as well as chilling influences the time of flowering.     

Flowering and Fruiting in ‘Arbequina’ Olives in Subtropical Climates Where Olives Normally Remain Vegetative

Abstract

It is generally assumed that lack of flowering and fruiting in olives in subtropical climates of southern Texas (e.g. Weslaco Texas area; N 26.16° Latitude 97.96° Longitude) is due to fewer chilling days (<7.2°C) during winter than most olive growing areas of the world. However using controlled environmental chambers we have recently shown that flowering and fruiting in the ‘Arbequina’ cultivar of olives can be achieved without any chilling days. This raised the question of why olive trees don't flower in southern Texas where they do experience some chilling days. We hypothesize that the absence of flowering in olives growing in southern Texas and a similar climate elsewhere is due not to the lack of enough chilling days but most likely due to high temperatures during the day (≥°C) that inhibit flowering. To test our hypothesis we provided cooling to olive trees growing under Weslaco Texas climate by simple shading or by evaporative cooling. These treatments resulted in good flowering and fruiting in ‘Arbequina’ olives in Weslaco Texas after a typical winter period although normally olive trees in this subtropical climate remain vegetative even after winter months.     

The response of bud break and flowering to cool winter temperatures in kiwifruit (Actinidia deliciosa)

Summary

A range of temperatures (7°C, 10°C or 13°C mean) were imposed under controlled conditions on four year old, container-grown ‘Hayward’ kiwifruit vines. The treatments were applied for periods of from one to four months during the dormant period from May to September (Southern Hemisphere). Following these treatments the vines were held at a “forcing” temperature of 16°C mean until flowering. The objective was to define the response of bud break and flowering in spring to temperatures experienced during the preceding winter. Cool winter temperatures dramatically increased flower numbers, increased the proportion of bud break, advanced the day of bud break, and increased the duration from bud break to flowering. These responses were much larger between 13°C and 10°C than they were between 10°C and 7°C. For any treatment duration, the temperature imposed during dormancy had no effect on the time of flowering. Two months at cool temperatures produced the greatest number of flowers per winter bud, with reduced numbers at three and four months. The proportion of winter buds that produced shoots showed a similar response. The Richardson chill unit is frequently used to describe the effects of winter chilling on kiwifruit. It proved unreliable as an index to integrate the effects of temperature and time on any of the developmental variables monitored in this experiment.     

Temperature effects on dormancy,bud break and spear growth in asparagus (Asparagus officinalis L.)

Summary

The effects of the length of chilling, chilling temperature and growing temperature on dormancy of asparagus crown buds and subsequent rates of spear growth were examined. The results showed that prior chilling enhanced bud break at low growing temperatures and stimulated the growth of spears.Thus, chilling should facilitate commercial production by hastening bud break and spear growth rates at lower temperatures. If sufficient chilling was given, the minimum temperature for rapid bud break was approx. 12.5°C for ‘Rutgers Beacon’ and ‘Jersey Giant’, and around 10°C for ‘UC 157’ and ‘Apollo’. The optimum chilling temperature appeared to be closer to 5°C than to 10°C or 2°C for ‘Rutgers Beacon’ plants grown at 12.5°C. Increasing the growing temperature had a significant effect on the relative spear growth rate (RSGR) in all cultivars. Prior chilling had no effect on the RSGR for ‘Dariana’ and ‘Apollo’; but, for ‘UC 157’, chilling plants at 5°C for 5 or 10 weeks increased growth rates at 12.5°C and at 20°C. These results demonstrate that release of bud dormancy and spear growth rates depended not only on the growing temperature, but also, at least in some cultivars at some temperatures, on the duration and temperature of chilling during the previous Winter.     

Flower formation in Calceolaria × herbeohybrida Voss

At high light intensity Calceolaria × herbeohybrida ‘Zwerg Meisterstück’ is a long-day plant with a critical day-length of 14–15 h. At low light intensity (e.g. as in winter) flowering will take place if the long-day treatment is preceded by a chilling period (10°C) or by short days at 15–20°C. During the chilling period day-length is of little influence. With increasing duration of the chilling period the requirement for long days decreases and the critical day-length becomes shorter. After a sufficient chilling period, flowering occurs both in long and short days. If the chilling period lasts approx. 40 days, however, flowering in short days is delayed, phyllody occurs and only a small number of flowers develop in comparison to long days. After at least 70–75 days of chilling plants show almost the same reaction in short and long days. Plants not chilled under conditions of high light intensity and short days flower either in naturally long days or by day extension with incandescent light. After chilling, fluorescent light of the type L 39 is also effective for day extension. A night break with incandescent light in a 16-h dark period induces flowering only after a chilling period. Incandescent but not fluorescent light causes a slight yellowing and more upright position of the leaves and an elongation of the internodes.     

Effects of Environment on Flower Initiation in Carnation

The main object of the investigation was to attempt the separation of effects of photoperiod and total incident light energy in controlling flower initiation in the glasshouse carnation, variety White Sim.

Low light intensities delayed flower initiation. The delay was associated with reduced rates of growth in terms of dry weight, reduced rates of leaf initiation and increased number of leaves formed below the flower. Short days also delayed flower initiation and increased the number of leaves formed below the flower. Photoperiod, however, had no appreciable effect on growth in terms of dry weight or on rates of leaf initiation, but internode length was greater in long days than in short days. A period of illumination given in the middle of the night was more effective in promoting flower initiation than an equivalent period given to extend the day. Internode length was similar in these treatments. Effects of night temperature were less consistent than those of light intensity or daylength but, under most of the conditions tested, high night temperatures (minimum 65° F. (18° C.)) delayed flower initiation and increased the number of leaves formed below the flower. Low temperature treatment of plants at 40° F. (4.5° C.) for one month promoted subsequent flower initiation and reduced the number of leaves formed below the flower.     

Effects of air and soil temperatures on flower development and morphology of satsuma mandarin

Three experiments were conducted in growth chambers to observe effects of air and soil temperatures in early and mid-winter on flower development and morphology of satsuma mandarin (Citrus unshiu Marc. cv. Okitsu Wase) budded on trifoliate orange. Four year old trees were used in Experiments I and III, and one year old ones in Experiment II. In Experiments I and II, air and soil temperature treatments of 15/15, 15/30, 30/15 and 30/ 30°C were started on 16 December, 1988. The trees sprouted flowers within seven days at 30/30°C, 11 days at 30/15°C, 21 days at 15/30°C, and 33 days at 15/15°C, respectively. There were few flowers at 30/30°C, extremely few at 30/15°C and many at both 15/15°C and 15/30°C. The days required to flowering and the flowering period were longer at the low air temperature. The number of flowers per tree, the number of flowers per node and the sprouting rate were greater at the low air temperature. A combination temperature of 30/15°C greatly decreased sprouting rate, the number of flowers per node and the number of flowers per tree. It seems likely that the chilling requirement might not be satisfied by mid-December. The trees might continue to accumulate chilling temperature at 15°C in the growth chamber. The trees at the high air temperature developed smaller flowers and ovaries. At an air temperature of 15°C, higher soil temperature resulted in bigger flowers and ovaries. In Experiment III, temperature treatments of 25/15,25/25 and 25/30°C were imposed on 6 January, 1989. The trees at 25/15°C required longer days to sprout and to blossom than at 25/25 and 25/30°C. The last two treatments did not differ in their effects. Soil temperature treatments did not result in significant effects on flower morphology, when they were applied after the chilling requirement was satisfied.     

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.     

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.     

Anatomical and morphological study of apple (Malus × domesticaBorkh.) flower buds growing under inadequate winter chilling

Summary

Some apples cultivars produce low yields when grown in regions with inadequate winter chilling. Their unsatisfactory development is attributed to the lack of climatic adaptation which causes some abnormalities in bud differentiation. The development of reproductive spurs is erratic, leading to vegetative shoots, and the flower index is very low. The purpose of this work is to understand the flower differentiation problem. An assessment was made through morphological and histological studies, also an analysis of climatic data was performed in an attempt to identify the responsible factors. The number of chilling hours recorded was about 695. Defoliation was delayed and happened during the second week of January. Bud break was advanced by 10 d in comparison with the average period. The spurs density (12 and 23 spurs per m of twigs) was similar to the values observed in normal situation. The buds carried by these spurs evolved into vegetative shoots for all variety × rootstock combination used in this study. The average of this transformation was 47 and 50% for ‘Golden Delicious’ and ‘Starking Delicious’, respectively. A flowering index obtained was very low (1.3 kg per tree). Anatomical observations carried out on buds collected in October showed that differentiation was undertaken and the floral primordium was already formed with some abnormalities in flower development in later stage. At anthesis, internal structures of the buds showed primordia disorganized. Reproductive organs presented pistil abortion with low microsporogenesis. Xylem vessel elements were not observed at the base of the bud and vascular connection was not established. This problem in flower development occurred at this stage which was affected by external factors. The winter was characterized by periods of high temperatures which affect negatively the accumulation of chilling units. The mode of action of temperature, notably of chilling on the formation of flowering organs and vessels, remains to be determined.     

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.     

Warm Storage of Narcissus Bulbs in Relation to Growth,Flowering and Damage Caused by Hot-Water Treatment

Three experiments are described on the effects on flowering of warm storage of narcissus bulbs before (and in some cases after) hot-water treatment (h.w.t.) against eelworm infection. Almost complete loss of the flower crop occurs if the bulbs are not warm stored, compared with the production of about 90% marketable flowers following warm storage. Optimum temperatures and durations of warm storage are not clearly defined; there is very little difference between the two recommended treatments, 34° C. for 3 days and 30° C. for 7 days, with the latter giving slightly better results. In another experiment, best results were obtained following 32·5° C. for 8 days or 35° C. for 5 days, with some varietal differences. These combinations were superior to most at 30° C., and to all of only 2 days duration. Higher temperatures and longer durations generally result in earlier flowering, with no adverse effect on flower quality. Bulb yield in the field following h.w.t. is higher when the bulbs are warm-stored before h.w.t. and, when forced in the following season, they give more flowers. Post-h.w.t. warm storage reduces flower quality and bulb yield in the field; although some minor benefits were observed, this treatment cannot be recommended. The possible mechanism for the protection afforded by warm storage is discussed.     

The effect of different temperatures on the viability of ovules in cherries

The effect of different temperatures on the senescence of ovules was investigated in 2 sweet and 3 sour cherry cultivars using a fluorescent-microscopic method. Detached twigs were kept in growth chambers at constant temperatures of 5, 10, 15 or 20°C. Increasing temperature substantially shortened the viability of the ovules. At 5°C, most ovules were senescent 5 days after anthesis, and at 20°C this period was shortened to 1–2 days.     

Effect of temperature on growth,dry matter production and starch accumulation in ten mango (Mangifera indica L.) cultivars

Summary

Ten mango cultivars of tropical and subtropical origin (Carabao, Kensington, Nam Dok Mai, Alphonso, Dashehari, Florigon, Glenn, Irwin, Haden and Sensation) were grafted onto cv. Kensington seedling rootstock and held at four day/night temperatures for 20 weeks (15/10°C, 20/15°C, 25/20°C and 30/25°C). Vegetative growth increased with increasing temperatures. All grew vegetatively at 25/20°C and 30/25°C. Cultivars which did not grow at 20/15°C were Carabao, Kensington and Dashehari. Cultivars Kensington, Nam Dok Mai, Alphonso, Florigon, Glenn, Irwin, Haden and Sensation produced flower panicles at 15/10°C. The rise in temperature increased the average number of growth flushes (in responsive cultivars) from 0.48 at 15/10°C to 3.21 at 30/25°C, and the number of leaves per growth flush (1.22 at 15/10°C to 13.63 at 30/25°C). Distribution of dry matter from new growth was mostly to the roots at the lowest temperature (95% at 15/10°C) and to the leaves (58%) at 30/25°C. The mean daily temperature for zero vegetative growth was calculated to be 15°C. Temperature and related growth activity also affected the concentration of starch in the woody tissue of rootstock trunks at the end of 20 weeks (15.9% starch at 15/10°C v. 4.8% starch at 30/25°C). ‘Irwin’ had the highest starch concentration at the two higher temperatures (twice that of any other cultivar at 30/25°C) while ‘Kensington’ the lowest starch level at 25/20°C, ca. 50% of most other cultivars.     

Effect of chilling on runner formation and flower initiation in the everbearing strawberry

Fresh and cold-stored plants of the everbearers ‘Rabunda’ and ‘Ostara’ were placed for 90 days, from the end of August, in glasshouses of the IVT phytotron at 14, 20 and 26°C and a daylength of 16 hours.In the fresh plants hardly any runners were formed at 14 and 20°C, but flowers were initiated, while at 26°C both runners were formed and flowers initiated. In the cold-stored plants, runners were formed first and thereafter flowers were initiated at all temperatures.It was concluded that (1) chilling induces runner formation, but can be replaced by high temperature, and (2) chilling delays flower initiation.     

Ethylene Production During Senescence of Flowers

A method of determining ethylene production by detached flowers is described. A surge of ethylene has been shown to accompany the wilting of carnation flowers at the end of senescence. This surge is independent of fungal infection and it is concluded that in the infected flower the major source of ethylene production is the host tissues.

A similar surge of ethylene production has been observed when the inflorescence wilts on the plant between 20 and 40 days from flower opening.

At temperatures above 7·2° C. (45° F.) the ethylene surge was accompanied by collapse of the petals and rapid loss of water. Cut flowers kept continuously below 7·2° C. slowly declined in weight, the petals became flaccid and ethylene production was negligible. Infection of the flowers with fungus did not materially alter the effect of temperature on the ethylene production.     

Seed germination of seven pepper cultivars at constant or alternating high temperatures

Summary

Seeds of seven pepper (Capsicum annuum L.) cultivars (Anaheim TMR 23, California Wonder 300, Coronado, Jalapeno M, Ma Belle, Mercury, and Yolo Wonder B) were germinated at constant day and night temperatures of 25,30,35 and 40°C or at alternating temperatures of 40/25,40/30 and 40/35°C for 14 days. Germination percentages and rates were similar at 25 and 30°C. Largest differences in cultivar responses occurred at 35°C where germination percentages ranged from 24 to 96%, and rates, calculated as summation of the number of seeds germinated on a given day divided by day number, varied from 3 to 26 (theoretical maximum value of 100). At 40°C, germination percentages were less than 5% and rates were less than one for all cultivars. Cultivars with the most heat tolerance were ‘Mercury’ and ‘Yolo Wonder B’. At alternating temperatures, germination percentages and rates were higher than those at constant 40°C. The increases were greatest when the temperature was lowered by 15°C (40/25°C) and least when temperatures were lowered by 5°C (40/35°C). Tetrazolium tests showed that a large percentage of the ungerminated seed was still viable from the highest temperature. At lower temperatures, fewer ungerminated seeds were viable with no viable ungerminated seeds from the lowest temperature.     

The effect of storage temperature on quality and decay percentage of ‘Pairi’ and ‘Taimour’ mango fruits

The effects of storage temperatures, especially chilling-temperatures, and the duration of exposure to them, on quality and decay percentage, and on the shelf-life of ‘Pairi’ and ‘Taimour’ mango fruits were studied. ‘Taimour’ fruits had better keeping-quality, storage ability and a longer marketing period than ‘Pairi’ fruits under all storage temperatures. Both cultivars were affected by storing at 0 °C and the severity of chilling was proportional to the duration of cold storage. ‘Taimour’ fruits were less sensitive to chilling-injury than ‘Pairi’ fruits. Storage at 5 °C or slightly higher was the most suitable temperature for both cultivars, followed by 10 °C.