Characteristics of Dormancy of June-Bearing Strawberry(Fragaria Xananassa Duch. cv. Elsanta)

Abstract

The development of Fragaria xananassa Duch. cv. Elsanta was analyzed during summer and fall in order to define the sequence of growth alteration and dormancy with regard to inflorescence initiation. The leaf growth as well as the initiation of the inflorescence buds were followed in the fall by conditions imposed in a climate chamber, with plants then being transfered to conditions favorable for growth. Results pointed to clear changes in leaf growth characteristics over the late summer-early fall (September-October) period while the leaf emergence rate remained constant up to mid-October when it stopped. The first sign of inflorescence initiation started in early October, and the differentiation of the terminal flower reached the stamen initiation stage within 2 weeks. From early November, the terminal flower had initiated the carpel primordia and no further differentiation was detected later on. The plant growth potential, expressed by the size, at full growth, of the leaf or inflorescence axis emerging from the terminal bud, decreased progressively from early September and reached a minimum between October and November. By mid-December, the growth capacity of the plant was restored to a situation similar to that described for early September.     

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.     

Responses of native Lupinus varius (L.) to culture conditions: effects of photoperiod and sowing time on growth and flowering characteristics

The effects of photoperiod and sowing time on growth and flowering characteristics of Lupinus varius were investigated during two growing periods to determine its responses to culture conditions as a potential native cut-flower crop. The seeds were sown in an unheated plastic greenhouse on 28 September, 28 October and 28 November under natural, 14- and 16-h day-length treatments. 14- and 16-h day-lengths were established by lengthening the natural day-lengths to 14 and 16 h with the use of night break photoperiodic lighting at 1.8–1.9 μmol m⁻² s⁻¹ in 400–700 nm. Photoperiodic lighting, in particular the 16-h day-length treatments, slightly (maximally 15 days) shortened days to flowering and increased plant height in all sowing times relative to natural photoperiods. There were no significant differences in stem and branch inflorescence diameters, in lengths of branch, in main and branch inflorescences in plants grown under natural photoperiod, and 16-h day-length treatments. The highest main inflorescence diameter, the number of branches per plant, and flower numbers on main and branch inflorescences were recorded in plants grown under natural photoperiods, whereas 14-h day-length treatments did not provide sufficient specimens to allow for the measurement of most of the characteristics studied. These findings were interpreted to indicate that L. varius behaves as a facultative long day plant. Additionally, there was a particular shortening of days to flower and growth, and flowering quality decreased linearly with delayed sowing dates under all photoperiodic treatments. The earliest and latest flowering dates were recorded for plants sown in September under 16-h day-length, and plants sown in November under natural photoperiods, respectively. Therefore, sowing in September under natural photoperiods or 16-h artificial day-length resulted in earlier flowering dates and a longer time from sowing to flowering and was consequently the best sowing time with respect to all of the characteristics considered in this study.     

Flowering in pyrethrum (Tanacetum cinerariaefolium L.). I. Environmental requirements

SUMMARY

Floral evocation in pyrethrum {Tanacetum cinerariaefolium) is stimulated by a period of vernalization. Night temperatures of 6°C and 12°C for two weeks and three weeks, respectively, promote rapid inflorescence initiation and development. A night temperature of 18°C does not satisfy the vernalization requirement. Longer periods of vernalization stimulate more rapid inflorescence initiation and development and result in a larger number of inflorescences being initiated. The vernalization stimulus may be modified by the daily light integral. Both inflorescence initiation and inflorescence development are promoted by long days. The number of leaves formed before flower bud initiation is not affected by daylength. Night-break lighting does not promote flowering. It is suggested that the stimulatory effect of long days may be in supplying photosynthetic assimilates to the developing meristems. Floral development is retarded by low photon flux density conditions regardless of day temperature. High day temperatures (25°C) combined with low photon flux (350 umol m"2 s"' or less) prevented pyrethrum from flowering in otherwise inductive conditions.     

Effect of photoperiod and light integral on flowering and growth of Eustoma grandiflorum (Raf.) Shinn.

The aim of the study was to examine the effects of different photoperiod and light integral on floral initiation, development and subsequent growth of Eustoma grandiflorum (Raf.) Shinn. Six-weeks-old seedlings of ‘Echo Blue’ and ‘Fuji Deep Blue’ were placed under short day (SD, 10 h) and were transferred to long days (LD, 20 h) at 2-week intervals from 6 to 14 weeks after seeding. Plants initiated flower buds regardless of light regimes. Flower bud initiation was delayed by SD compared to LD; plants transferred after 6 weeks from seeding initiated flower buds at least 21 and 10 days earlier at LD at high (HL) and low (LL) daily light integral, respectively, compared to those at SD. Light regimes had little or no effect on time to flower bud development after initiation. Thus, it seems likely that LD and HL affected the initiation rather than development. Both the photoperiod and light integral strongly influenced the subsequent growth after initiation. SD delayed the time to visible bud (VB), increased the number of nodes to first open flower, number of branches, stem diameter and shoot dry weight compared to LD. HL promoted flowering and increased several shoot characteristics and flowering compared to LL.The results indicate that Eustoma is a quantitative long-day plant. LD, and more specifically HL, enhanced flower bud initiation, development and subsequent growth. An initial SD period is preferred to increase the number of branches, number of flowering buds and flowers, stem diameter and shoot dry weight.     

Juvenile Phase and Flower Initiation in Brilliant Stocks (Matthiola Inc Ana R.Br.)

The effect of temperature and day-length on growth and flowering of the Scandinavian Brilliant-type stock (Mattkiola incana R. Br.) has been studied. Flower differentiation and development were examined.

Flower initiation was favoured by low temperature and long days, but a temperature as high as 20° C. (68 °F.) did not prevent flowering even under short-day (9 hours) conditions. A close interaction between temperature and day-length was observed.

High temperature was favourable for further development of the flowers, but abnormal flowers were developed if the plants were removed to high temperature before the first flower primordium was visible under the microscope.

Flower initiation was associated with accelerated stem elongation. Therefore, optimal temperature conditions for stem elongation changed with the developmental stages of the plants.

The plants responded to a low-temperature treatment as early as 12 days after germination, at which stage they had only two small leaves in addition'to the cotyledons. The Brilliant stocks have evidently a much shorter juvenile phase than that previously described for the Column type. This might be the main reason why the Brilliant stocks flower very early.

In single-flowered plants the differentiation of floral organs took place in the following sequence: sepals, stamens, carpels, petals. In this respect the stock showed a similar behaviour to that previously described for certain other cruciferous genera.

The results of the experiments are discussed in the light of previous studies concerning low-temperature effects, vernalization and related phenomena, on flowering. It is concluded that no true vernalization process is involved. The facts that the initiation took place immediately after exposure to low temperature, and that removal to high temperature caused abnormal flower development unless differentiation had reached a certain stage, form the main basis for this conclusion.     

The effect of temperature and light on flower development in Pelargonium × domesticum

Factors influencing the number of flowers produced in Pelargonium × domesticum cultivar ‘Lavender Grand Slam’, and their rate of development after the plants had been given a period of low-temperature flower induction, were studied.Under short days progressive abortion reduced flower numbers as the temperature regime during the forcing-period was increased. Under long days this effect was less marked and the high-temperature regime advanced flowering by over a month. When long days and high temperatures were used for forcing, it was necessary to maintain a high light intensity, 335 J/cm²/day giving the best results in terms of earliness of flowering and the number of flowers produced. At lower irradiance there was some risk of flower abortion, particularly in the first inflorescence.     

Effect of temperature and irradiance on vegetative and generative development in Pelargonium × hortorum ‘Radio’

Vegetatively propagated plants of Pelargonium × hortorum ‘Radio’ were grown at 8 combinations of irradiance and temperature levels; 4 or 22 W m^?2 combined with 12, 15, 18 or 21°C. Increase in leaf number, leaf area, shoot and number of inflorescences per plant were all greater at 22 W m^?2 than at 4 W m^?2. At 22 W m^?2, increase in temperature affected leaf number, leaf area and shoot number, but not inflorescence number. However, at 4 W m^?2, number of inflorescences — but not leaf or shoot number — was affected by temperature. When effects of temperature differences were observed, the highest temperature resulted in the greatest number of leaves and shoots and the largest leaf area, but the lowest number of inflorescences per plant. The results indicate that photosynthesis or energy metabolism is of importance to floral initiation in Pelargonium × hortorum.     

冬春季节遮阴处理对香蕉假植苗生长的影响

冬季 (12～ 1月 )、春季 (3～ 4月 ) ,将从培养瓶中移出的香蕉组培苗置于大棚内 ,在 4种遮阴水平下进行假植炼苗 ,光照条件分别为 10 0 % (S10 0 ) ,33% (S33) ,10 % (S10 ) ,3 % (S3)。结果表明 ,不同光照强度下 ,香蕉苗的苗高、基径、叶长、叶宽、叶片数、叶面积、总根数和长根数都存在显著差异 ,但不同的性状对光照强度的反应不同。冬季有利于根系的生长 ,春季则更有利于地上部性状的生长。冬季和春季都以S33光照处理为最优 ,即适度遮阴有利于香蕉假植苗的生长发育。但春季各性状对遮阴水平适应的范围比冬季更宽 ,并且各性状在不同的季节对同一遮阴水平的反应也不相同 ,这表明光照强度与季节之间存在互作效应     

Effect of photoperiod and temperature on inflorescence appearance and subsequent development towards flowering in onion raised from sets

The plants of two onion cultivars Sturon and Stuttgarter were raised from sets and placed in a growth room at 12 °C, a light flux density of 120 μmol m⁻² s⁻¹ and a 16 h photoperiod. Cultivar Stuttgarter took 195 days to initiate, whereas time for initiation in cv. Sturon was 201 days. After initiation the plants were transferred to wide range of photo-thermal regimes consisting of six set point temperatures (6, 10, 14, 18, 22 and 26 °C) and four photoperiods (8, 11, 14 and 17 h day⁻¹). An overall mean temperature for all developmental stages under each photo thermal combination was 12.2, 12.4, 15.9, 17.8, 23 and 24.4 °C. Time to inflorescence appearance, spathe opening and floret opening decreased linearly as temperature and photoperiod increased. At low to mild temperatures (12.2–17.8 °C), longer photoperiod enhanced florets per umbel, whereas at higher temperatures (23–24.4 °C), the floret number declined with lengthening photoperiods. As the photoperiod extension in each temperature advanced inflorescence appearance, spathe opening and floret opening and this would be beneficial in a programme to accelerate seed production in onion.     

Gkowth and Flowering of the Tomato in Relation to Natural Light Conditions

Continuous-recording photometers were used to measure the amounts of light entering a glasshouse during certain growth periods of young tomato plants. Fresh and dry weights of the tops of the plants and the number of days between cotyledon expansion and anthesis of the first flower of the first inflorescence were related to the recorded light values as follows :

1. The relationship between log dry weight and the light-time integral was linear up to 220,000 foot candle hours, after which a marked reduction in growth occurred.

2. The departure from linearity occurred at about the same light integral even when additional nutrients were supplied to the standard volume of compost, but was delayed when a larger container was used.

3. The number of days to anthesis and the recorded light-time integrals show the following relationships : in winter, light integrals are constant (about 400,000 f.c.h.) while time is variable ; in summer, time is constant (about 40 days) while the light integrals are variable.

4. In summer, neither the reduction of the natural day-length to 9 hours nor the reduction of the light intensity to 75% normal materially influenced the number of days to anthesis.

It is concluded that in winter growth is limited by, and is therefore proportional to, the amount of available photosynthetic light, while in summer the young tomato is light-saturated and growth is limited by factors other than light.

The results indicate that the amount of photosynthetic light is the major factor determining the seasonal pattern of days to anthesis. There was no indication of any photoperiodic response.     

Environmental factors affecting flowering of rice flower (Ozothamnus diosmifolius,Vent.)

Rice flower (Ozothamnus diosmifolius, Vent.), native to east Australia, is a spring flowering perennial shrub. It is a new cut flower plant, recently introduced into cultivation in Australia and in Israel. Its response to environmental conditions, which affect growth and flowering, are not yet known. The purpose of the present study was to evaluate the effects of growth temperature, photoperiod and total solar energy on flowering. Experiments were conducted with plants of the cv. Cook’s Snow White. Plants were grown in three cycles under controlled conditions in the phytotron, at four day/night temperature regimes: 17/9, 20/12, 23/15 and 26/18°C. Two photoperiods — short day (SD) of 10 h natural day light and long day (LD) of 10 h natural light plus 10 h incandescent light — were employed. High temperatures enhanced vegetative growth but blocked flowering under both LD and SD. Under medium–moderate temperatures plants were absolute LD plants and did not flower under SD conditions. Under lower temperatures plants flowered under both LD and SD, but SD delayed flowering. High total solar radiation under LD did not affect flowering time but greatly promoted the number of flowering stems.     

Flower and corm development in gladiolus as affected by photoperiod

Gladiolus plants cultivar ‘Spick and Span’ were grown in winter under natural short day (SD) or under long day (LD), with 4 hours low intensity light at midnight. Growth of the various organs was followed by periodic sampling. SD promoted flower development and advanced anthesis but reduced the final size of the flower. LD increased weight and size of leaves and flowers.Initial growth of the corm was similar under both photoperiods, but while corm growth continued throughout the growing-period under SD, it was checked under LD when flowers were developed at an enhanced rate and until anthesis. At this stage, the allocation of assimilates was directed towards the flower sink and away from the corm sink.Final corm weight was also promoted by LD. This is interpreted as an indirect effect due to increased photosynthesis of the larger LD plants. In non-flowering plants raised from cormels, SD specifically promoted corm growth, although no competing flower sink was present.It is concluded that photoperiod affects growth and development of gladiolus in two ways: directly — by affecting the partitioning of assimilates between the flower or the corm; and indirectly — by affecting the total photosynthates available to the plants by influencing foliage size and the total growth period.     

The effects of growth substances and photoperiod on the development of shoot apices of Vitis cultured in vitro

‘Rougeon’ grapevines were recovered from shoot apices using in vitro culture. Shoot development from apices 0.5–1 mm in length, which contained 2–4 leaf primordia was obtained with 5 × 10^?6M benzylaminopurine and 5 × 10^?7M naphthaleneacetic acid (NAA) under a 10-hour photoperiod, but not under continuous light, in a 15-hour photoperiod, or in darkness. At least one vigorous shoot was produced by 100% of the cultures.Rooting of these shoots was induced under the same photoperiod with the same basal culture media containing only 10^?7 M NAA. Roots were produced by 91% of the cultures. Zero-, 16- or 24-h photoperiods were ineffective in promoting root development.Rooted plantlets were transferred into soil with 80% of them surviving. The grapevines were allowed to reach an average length of 2 m in a growth chamber before growth conditions were modified to induce dormancy. Vines were planted in a vineyard; after 2 growing-seasons we were unable to distinguish the micropropagated vines from ‘Rougeon’ vines propagated in the standard manner, on the basis of fruit or vegetative morphology.     

Inflorescence development of flowering and blasted gladiolus plants in relation to development of other plant parts

Flower differentiation in Gladiolus × grandiflorus takes place immediately after initation of all the leaves. The prefloral stage was observed in shoots 3–4 mm long and the shoot apex was floral when the first foliage leaf was half extended.Initiation of individual florets continued up to the 7-leaf stage. Flower development is acropetal and continued up to anthesis of each individual floret.Flower blasting generally starts at the tip of the inflorescence and advances towards the base of the flower stalk. Blasting starts as a stoppage in the growth of the inflorescence, the flower stalk and the leaves on the stalk. Later these organs shrivel. Daughter corms fill early as a consequence of blasting.     

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.     

Interactions of photoperiod,temperature, duration of short-day treatment and plant age on flowering of Fragaria x ananassa Duch. cv. Korona

The effects of photoperiod (10, 12, 16, 20 or 24 h), day-temperature (12, 15, 18, 24 or 30 °C), the number of short days (14, 21 or 28 days), plant age (4, 8 or 12 weeks) and their interactions on flower and inflorescence emergence were investigated in strawberry cv. Korona. No flowers emerged in plants exposed to photoperiods of 16, 20 or 24 h or to a short-day treatment for 14 days. All plants exposed to short days at daily photoperiods of 10 or 12 h for 21 days or longer, emerged flowers at temperatures between 12 and 18 °C. A further increase in temperature led to a drastic decrease in the total number of flowers per plant. A short-day treatment (10 or 12 h photoperiod) of 28 days resulted in highest numbers of inflorescences and flowers per plant, while a short-day treatment of 21 days resulted in the highest numbers of flowers per inflorescence. Complete flower induction was observed in only 4-week-old runner plants. The number of inflorescences and the number of flowers per inflorescence increased with plant age. However, the start of flowering was delayed with increasing plant age.     

Changes in apical morphology during floral initiation and development in pyrethrum (Tanacetum cinerariaefolium L.)

Summary

Changes in apical morphology during floral initiation and development in pyrethrum (Tanacetum cinerariaefolium L.) were investigated by scanning electron microscopy. The sequence of events may be divided into eleven stages of apical development which are distinctive in both morphology and size. The environmental stimulus promoting rapid flower initiation was demonstrated to be vernalization. Flower initiation occurred after four months under non-vernalizing conditions through an autonomous flower induction process. Devernalization was observed under short day (10 h daylength), low photon flux density (200 µmol m² s^?1) conditions. Apices were never observed to revert to vegetative growth after the initiation of the first involucral bract and therefore this was considered to be the developmental stage at which the apex was committed to generative development.     

The effect of sucrose on the expression of the VvTFL1 and VFL genes during flower development in the “Xiangfei” grapevine

VFL and VvTFL1 genes expression patterns and the effects of sucrose on the expression of VFL and VvTFL1 genes in different organs of the “Xiangfei” grapevine (Vitis vinifera L.) were investigated. VvTFL1 gene expression was detected in the meristem of the apical bud and lateral bud, but was not detected during inflorescence differentiation and flower organ development. After sucrose treatment, VvTFL1 gene expression increased in the apical bud, but decreased in the lateral bud. These results suggested that the VvTFL1 gene might be mainly involved in the apical growth process of shoots, and exogenous sucrose had an effect on the VvTFL1 gene by increasing shoot apical meristem initiation of apical buds. The VFL gene was expressed primarily during inflorescence differentiation and early flower organ development, but it gradually reduced in later flower development. After sucrose treatment, VFL gene expression increased in the inflorescence and small or middle flower, but a little change was seen in the large flower. These results suggested that the VFL gene plays important roles in the initiation of inflorescence meristems and the morphological formation of flower organs. Exogenous sucrose had an effect on VFL gene expression at the early stage of flower development.     

Flowering control in Watsonia: Effects of corm size,temperature, photoperiod and irradiance

The role of corm size, light and temperature in flowering of Watsonia species was evaluated to facilitate their commercial production. In addition to exhibiting desirable ornamental attributes, the species selected represented the major climatic regions in South Africa. A day/night temperature regime of 12/7 °C released vegetative dormancy in all species and thereafter elicited vernalization in Watsonia pillansii – highlighting an obligate cold requirement for this species. Flowering of Watsonia borbonica and Watsonia tabularis was not enhanced by additional chilling, but rather by long (16 h) or day-neutral (12 h) photoperiods. Microscopic examination of the shoot apical meristem revealed that extension of the 2nd leaf was a critical stage developmentally, and signified the anatomical transition to flowering. Late-development temperatures to a maximum of 25 °C ensured healthy vegetative growth and supported the maturation of the inflorescence and the opening of floret buds. Irradiance did not affect flower induction, but a minimum light intensity of 150 μmol m⁻² s⁻¹ proved essential in sustaining the energetic demands of the competitive growth and reproductive processes. Excessively high irradiance (950 μmol m⁻² s⁻¹) impacted negatively on attractiveness through increased bud blasting. Flowering success was not correlated to corm mass, but rather to the environment under which the corm was stored, or the conditions under which the plant was grown. Understanding the phenology of these species in situ and the link between flowering and season provide a useful tool for predicting the artificial requirements necessary to elicit optimal flowering under industry conditions.