scholarly journals Anatomical Changes in Rudbeckia hirta L. during Transition to Flowering

1993 ◽  
Vol 118 (6) ◽  
pp. 835-839 ◽  
Author(s):  
Richard L. Harkess ◽  
Robert E. Lyons
Keyword(s):  
Leaf Primordium ◽  
Floral Initiation ◽  
Anatomical Changes ◽  
Rudbeckia Hirta ◽  
Floral Stimulus ◽  
Long Day ◽  
Dividing Cells ◽  
Histochemical Examination ◽  
Short Days ◽  
Transition To Flowering

Histological and histochemical examination of floral initiation was conducted to determine the pattern of flowering in Rudbeckia hirta, a long-day (LD) plant. Plants were grown under 8-hour short days (SDs) until they had 14 to 16 expanded leaves. Half of the group of plants was moved to LD conditions consisting of natural daylength plus a 4-hour night interruption. Rudbeckia hirta had a pattern of differentiation in flowering similar to that reported in species requiring one inductive day for initiation. Rudbeckia hirta required 8 LDs for evocation and 18 LDs for completion of initiation. Involucral bracts initiated after 18 LDs, after which the receptacle enlarged and was capped by a meristematic mantle of cells signaling the start of development. Floret primordia did not initiate, even after 20 LDs. Increases in pyronin staining were observed in actively dividing cells of the procambium, leaf primordium, and corpus of the vegetative meristems. After 8 LDs, the pith rib meristem stained darkly, a result indicating the arrival of the floral stimulus. An increase in pyronin staining was also observed in the meristematic mantle covering the receptacle after 18 LDs, a result indicating increased RNA levels.

scholarly journals FLORAL INITIATION IN THE LONG-DAY PLANT Rudbeckia hirta

HortScience ◽  
1991 ◽  
Vol 26 (6) ◽  
pp. 719A-719
Author(s):  
Richard L. Harkess ◽  
Robert E. Lyons
Keyword(s):  
Methyl Green ◽  
Floral Initiation ◽  
Serial Sections ◽  
Sodium Cacodylate ◽  
Rudbeckia Hirta ◽  
Long Day ◽  
Cacodylate Buffer ◽  
Ethanol Series ◽  
Inductive Photoperiod ◽  
Short Days

A study was undertaken to determine the rate of floral initiation in Rudbeckia hirta. R. hirta plants were grown to maturity, 14-16 leaves, under short days (SD). Paired controls were established by placing half of the plants under long days (LD) with the remainder left under SD. Beginning at the start of LD (day 0), five plants were harvested daily from each photoperiod group for twenty days. Harvested meristems were fixed in 2% paraformaldehyde - 2.5% glutaraldehyde in 0.1 M sodium cacodylate buffer (pH 7.0) for 24 hrs, dehydrated in an ethanol series, embedded in paraffin and sectioned at 8 μm. Serial sections were stained with Methyl-green Pyronin, with adjacent sections treated with RNase for nucleic acid comparison. All events of floral initiation were identified, The results of limited inductive photoperiod indicate that 16-18 LD were required for flowering.

Flowering of Stylosanthes guianensis in controlled temperatures under natural photoperiod

1984 ◽  
Vol 35 (2) ◽  
pp. 219 ◽  
Author(s):  
RL Ison ◽  
LR Humphreys
Keyword(s):  
Floral Initiation ◽  
Minimum Duration ◽  
Stylosanthes Guianensis ◽  
Short Day ◽  
Long Day ◽  
Natural Photoperiod ◽  
Low Levels ◽  
Short Days

Seedlings of Stylosanthes guianensis var. guianensis cv. Cook and cv. Endeavour were grown in naturally lit glasshouses at Brisbane (lat. 27� 30' S.) at 35/30, 30/25 and 25/20�C (day/night), and were sown so as to emerge at 18-day intervals from 18 January to 11 June. Cook behaved as a long day-short day plant, with seedlings emerging after 5 February flowering incompletely or remaining vegetative until the experiment was terminated in mid-October. In the 25/20�C regimen flowering was incomplete in Cook; in Endeavour flowering was delayed but a conventional short-day response was observed. At 35/30�C Endeavour flowering was inhibited in the shortest days of mid-winter, suggesting a stenophotoperiodic response, but short days were confounded with low levels of irradiance. Minimum duration of the phase from emergence to floral initiation was c. 66-70 days in Cook and c. 40-45 days in Endeavour; the duration of the phase floral initiation to flower appearance was linearly and negatively related to temperature.

The early-flowering mutant efs is involved in the autonomous promotion pathway of Arabidopsis thaliana

Development ◽  
1999 ◽  
Vol 126 (21) ◽  
pp. 4763-4770 ◽  
Author(s):  
W.J. Soppe ◽  
L. Bentsink ◽  
M. Koornneef
Keyword(s):  
Arabidopsis Thaliana ◽  
Flowering Time ◽  
Double Mutant ◽  
Plant Size ◽  
Early Flowering ◽  
Wild Type ◽  
Late Flowering ◽  
Long Day ◽  
Short Days ◽  
Transition To Flowering

The transition to flowering is a crucial moment in a plant's life cycle of which the mechanism has only been partly revealed. In a screen for early flowering, after mutagenesis of the late-flowering fwa mutant of Arabidopsis thaliana, the early flowering in short days (efs) mutant was identified. Under long-day light conditions, the recessive monogenic efs mutant flowers at the same time as wild type but, under short-day conditions, the mutant flowers much earlier. In addition to its early-flowering phenotype, efs has several pleiotropic effects such as a reduction in plant size, fertility and apical dominance. Double mutant analysis with several late-flowering mutants from the autonomous promotion (fca and fve) and the photoperiod promotion (co, fwa and gi) pathways of flowering showed that efs reduces the flowering time of all these mutants. However, efs is completely epistatic to fca and fve but additive to co, fwa and gi, indicating that EFS is an inhibitor of flowering specifically involved in the autonomous promotion pathway. A vernalisation treatment does not further reduce the flowering time of the efs mutant, suggesting that vernalisation promotes flowering through EFS. By comparing the length of the juvenile and adult phases of vegetative growth for wild-type, efs and the double mutant plants, it is apparent that efs mainly reduces the length of the adult phase.

scholarly journals Juvenility and Photoperiodic Flowering Requirements of Chrysanthemum ×superbum `G. Marconi' and `Snow Lady' Grown under Short- and Long-day Conditions

1995 ◽  
Vol 120 (2) ◽  
pp. 241-245 ◽  
Author(s):  
M. Peggy Damann ◽  
Robert E. Lyons
Keyword(s):  
Microscopic Examination ◽  
Main Stem ◽  
Floral Initiation ◽  
Flower Buds ◽  
Terminal Flower ◽  
True Leaf ◽  
Photoperiodic Flowering ◽  
Long Day ◽  
Cotyledon Stage ◽  
Short Days

Juvenility and flowering requirements of Chrysanthemum ×superbum Bergmans ex J. Ingram `G. Marconi' and `Snow Lady' were examined by growing plants under short days (SDs) and transferring them to long days (LDs) upon reaching specific true leaf stages. `G. Marconi' plants did not flower in continuous SDs and only sparse flowering occurred in plants transferred to LDs. `Snow Lady' plants transferred from SDs to LDs at the cotyledon stage flowered fastest from seeding (75 days) and had the fewest number of main stem leaves and total leaves (9 and 15, respectively) at the time of first flower. Plants moved from SDs to LDs at the 24 true leaf stage flowered 123 days after seeding and averaged 28 leaves on the main stem and 37 total leaves at the time of first flower. To examine apical floral initiation, plants were distributed between SDs and LDs following transplanting and five plants per treatment were sampled each week thereafter. Microscopic examination revealed floral initiation in plants sampled after just 1 week in LDs and, after 5 weeks, macroscopic terminal flower buds were present. Under SDs, apical floral initiation began after 5 weeks, yet, 9 weeks were required for floral initiation in all five plants sampled.

Timing in Chenopodium rubrum of export of the floral stimulus from the cotyledons and its action at the shoot apex

1972 ◽  
Vol 50 (4) ◽  
pp. 697-702 ◽  
Author(s):  
R. W. King
Keyword(s):  
Cell Division ◽  
Mitotic Index ◽  
Shoot Apex ◽  
Essential Role ◽  
Floral Development ◽  
Dark Period ◽  
Chenopodium Rubrum ◽  
Floral Stimulus ◽  
Dividing Cells ◽  
Short Days

When the cotyledons of 6-day-old seedlings of Chenopodium rubrum were removed at various intervals after exposure to a single 13.5-h dark period, defoliation during the first 6 h after darkness prevented flowering. If the cotyledons remained on the plant for a further 5 or more hours flowering gradually increased. Within 20 h after the end of the dark period, the cotyledons had completed their essential role and subsequent defoliation had no influence on flowering. A cotyledon area of about 30 mm2 was required for maximal floral induction.It can be concluded that a transmissible factor—often termed floral stimulus—was produced in the cotyledons following a short-day exposure. It is also apparent that flowering in Chenopodium rubrum depends on the generation of a floral stimulus in short days, rather than on control by a transmissible inhibitor of flowering produced under long days.After arrival of the floral stimulus at the apex there was a doubling from 2% to 4% in the percentage of cells undergoing mitosis. This increased value of the mitotic index was maintained during floral development and probably reflected an increased rate of cell division. There were rapid and sometimes rhythmic fluctuations in the percentage of dividing cells.

Photoperiod and Temperature Influence on Flower Initiation and Development for Euphorbia pulcherrima Grown Under Florida Conditions

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 509a-509
Author(s):  
C.E. Wieland ◽  
J.E. Barrett ◽  
D.G. Clark ◽  
G. J. Wilfret
Keyword(s):  
Subsequent Development ◽  
Flower Initiation ◽  
Euphorbia Pulcherrima ◽  
Floral Initiation ◽  
Temperature Influence ◽  
Average Temperature ◽  
Long Day ◽  
Time To Initiation ◽  
Growth Room ◽  
Maximum Temperatures

Four poinsettia cultivars were grown in glass greenhouses in Gainesville, Fla., in the Fall 1997 to evaluate differences in floral initiation and subsequent development. Three means of regulating photoperiod were 1) natural days 2) long-day lighting to 6 Oct. and then natural days (lights out) 3) long-day lighting to 6 Oct., and then short-day conditions by black cloth for 15 h (black cloth). At 2-day intervals, sample meristems were collected and examined for initiation of reproductive development. Average minimum and maximum temperatures during the first two weeks of October were 22 and 29 °C, respectively, with an average temperature of 25.3 °C. The overall average temperature was 23.2 °C from planting to anthesis. Differences in anthesis dates among cultivars were primarily due to time to initiation vs. rate of development. Under natural days, `Lilo' initiated first on 8 Oct. and `Freedom', `Peterstar', and `Success', followed by 6, 8, and 18 days, respectively. Lights out resulted in `Lilo' initiating 17 Oct., followed by `Freedom', `Peterstar', and `Success' initiating 7, 12, and 15 days later, respectively. Differences between cultivars in time of initiation was reduced under black cloth, where `Lilo' initiated 14 Oct., followed by `Freedom' 2 days later, and `Peterstar' and `Success' 7 days afterward. Initiation was positively correlated to visible bud and anthesis. First color was positively correlated to initiation and visible bud, with the exception of `Lilo'. Growth room studies conducted using various high temperatures and photoperiods indicated similar trends.

Novel Loci Control Variation in Reproductive Timing inArabidopsis thalianain Natural Environments

Genetics ◽  
2002 ◽  
Vol 162 (4) ◽  
pp. 1875-1884 ◽  
Author(s):  
Cynthia Weinig ◽  
Mark C Ungerer ◽  
Lisa A Dorn ◽  
Nolan C Kane ◽  
Yuko Toyonaga ◽  
...  
Keyword(s):  
Genetic Basis ◽  
Allelic Variation ◽  
Developmental Pathways ◽  
Natural Environments ◽  
Reproductive Timing ◽  
Controlled Environments ◽  
Photoperiod Pathway ◽  
Differential Involvement ◽  
Short Days ◽  
Transition To Flowering

AbstractMolecular biologists are rapidly characterizing the genetic basis of flowering in model species such as Arabidopsis thaliana. However, it is not clear how the developmental pathways identified in controlled environments contribute to variation in reproductive timing in natural ecological settings. Here we report the first study of quantitative trait loci (QTL) for date of bolting (the transition from vegetative to reproductive growth) in A. thaliana in natural seasonal field environments and compare the results with those obtained under typical growth-chamber conditions. Two QTL specific to long days in the chamber were expressed only in spring-germinating cohorts in the field, and two loci specific to short days in the chamber were expressed only in fall-germinating cohorts, suggesting differential involvement of the photoperiod pathway in different seasonal environments. However, several other photoperiod-specific QTL with large effects in controlled conditions were undetectable in natural environments, indicating that expression of allelic variation at these loci was overridden by environmental factors specific to the field. Moreover, a substantial number of QTL with major effects on bolting date in one or more field environments were undetectable under controlled environment conditions. These novel loci suggest the involvement of additional genes in the transition to flowering under ecologically relevant conditions.

Ethylene formation in the leaves of short- and long-day tobacco during transition to flowering

1988 ◽  
Vol 30 (6) ◽  
pp. 422-426 ◽  
Author(s):  
Veronika N. Lozhnikova ◽  
V. I. Rakitin ◽  
J. Krekule ◽  
Ivana Macháčková ◽  
M. KChailakhyan
Keyword(s):  
Ethylene Formation ◽  
Long Day ◽  
Transition To Flowering

Responses of Some Turkish Wheat Cultivars to Vernalization and Photoperiod

1988 ◽  
Vol 24 (2) ◽  
pp. 237-245
Author(s):  
Serpil Terzioğlu
Keyword(s):  
Bread Wheat ◽  
Normal Development ◽  
Photoperiodic Response ◽  
Reliable Information ◽  
Floral Initiation ◽  
Wheat Cultivars ◽  
Primary Shoot ◽  
Time Of Year ◽  
Short Days

SUMMARYThe vernalization and photoperiodic response of six locally adapted bread wheat cultivars grown under natural daylength conditions during the summer or winter months was examined in glasshouse experiments. The wheat was vernalized by chilling imbibed grains at 2 ± 1°C for 0, 15 or 45 days. Vernalization for 45 days followed by long summer days led to floral initiation in all cultivars within 28 days but vernalization for 0 or 15 days only led to floral initiation in one cultivar. Vernalization followed by long days reduced the time from transplanting to anthesis, resulting in early ear emergence. Vernalization followed by short days accelerated the development of all the cultivars, but normal development could also occur without vernalization at this time of year. Apical differentiation of the primary shoot and its length and development gave the most reliable information on the period of vernalization required.

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