Exposure of ewes to long-day photoperiods before the winter solstice can disrupt refractoriness to 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.

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Flowering of Stylosanthes guianensis in controlled temperatures under natural photoperiod

Australian Journal of Agricultural Research ◽

10.1071/ar9840219 ◽

1984 ◽

Vol 35 (2) ◽

pp. 219 ◽

Cited By ~ 1

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.

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Photoperiod modulates the effects of norepinephrine on lymphocyte proliferation in Siberian hamsters

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00209.2003 ◽

2003 ◽

Vol 285 (4) ◽

pp. R873-R879 ◽

Cited By ~ 10

Author(s):

Gregory E. Demas ◽

Timothy J. Bartness ◽

Randy J. Nelson ◽

Deborah L. Drazen

Keyword(s):

Lymphocyte Proliferation ◽

Splenic Tissue ◽

Splenocyte Proliferation ◽

Short Day ◽

Siberian Hamsters ◽

Long Day ◽

Β Adrenergic Receptors ◽

Short Days

Siberian hamsters ( Phodopus sungorus) rely on photoperiod to coordinate seasonally appropriate changes in physiology, including immune function. Immunity is regulated, in part, by the sympathetic nervous system (SNS), although the precise role of the SNS in regulating photoperiodic changes in immunity remains unspecified. The goal of the present study was to examine the contributions of norepinephrine (NE), the predominant neurotransmitter of the SNS, to photoperiodic changes in lymphocyte proliferation. In experiment 1, animals were maintained in long [16:8-h light-dark cycle (16:8 LD)] or short days (8:16 LD) for 10 wk, and splenic NE content was determined. In experiment 2, in vitro splenocyte proliferation in response to mitogenic stimulation (concanavalin A) was assessed in spleen cell suspensions taken from long- or short-day hamsters in which varying concentrations of NE were added to the cultures. In experiment 3, splenocyte proliferation was examined in the presence of NE and selective α- and β-noradrenergic receptor antagonists (phenoxybenzamine and propranolol, respectively) in vitro. Short-day animals had increased splenic NE content compared with long-day animals. Long-day animals had higher proliferation compared with short-day animals independent of NE. NE (1 μM) further suppressed splenocyte proliferation in short but not long days. Last, NE-induced suppression of proliferation in short-day hamsters was blocked by propranolol but not phenoxybenzamine. The present results suggest that NE plays a role in photoperiodic changes in lymphocyte proliferation. Additionally, the data suggest that the effects of NE on proliferation are specific to activation of β-adrenergic receptors located on splenic tissue. Collectively, these results provide further support that photoperiodic changes in immunity are influenced by changes in SNS activity.

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Tagesperiodische antagonistische Schwankungen der Blauviolett- und Gelbrot-Empfindlichkeit als Grundlage der photoperiodischen Diapause-Induktion bei Pieris brassicae

Zeitschrift für Naturforschung B ◽

10.1515/znb-1960-0401 ◽

1960 ◽

Vol 15 (4) ◽

pp. 205-213 ◽

Cited By ~ 66

Author(s):

Erwin Bünning ◽

Gabriele Joerrens

Keyword(s):

Dark Period ◽

Red Light ◽

Pieris Brassicae ◽

Light Period ◽

Measuring Process ◽

The Third ◽

Long Day ◽

Critical Daylength ◽

Qualitative Responses ◽

Short Days

In Pieris brassicae, diapause is inhibited if long-day conditions are imposed during and immediately after the third molting. The critical daylength is approximately 14 hours. Under short-day conditions with a main light period of 6 or 12 hours’ duration, supplementary light given in the period from 14 to 16 hours after the beginning of the main light period will inhibit diapause. In contrast to this effect of late exposures to light, light given from 1 to 12 hours after the beginning of the main light period promotes diapause. Experiments with extremely long light periods (10—35 hours), but always with a dark period of 10 hours, show that these diurnal fluctuations in quantitative and qualitative responses to light can continue endogenously for several days. Thus, this time-measuring process operates through the mechanism of endogenous diurnal oscillations in just the same way as do photoperiodic reactions in plants.The inhibition of diapause by light in the second half of the diurnal oscillation (under long days or by light interruptions in the dark period) and the promotion by light in the first half (under short days) occur only with light of short wavelengths: ultraviolet, violet, and blue up to about 550 mμ. Yellow and red light act in the opposite fashion, giving diapause inhibition in the first half of the cycle and promotion in the second half. In white light the violet reaction predominates, so that diapause is promoted by short days and inhibited by long days.

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Temperature and Photoperiod Influence Flowering and Morphology of Four Petunia spp.

HortScience ◽

10.21273/hortsci.45.3.365 ◽

2010 ◽

Vol 45 (3) ◽

pp. 365-368 ◽

Cited By ~ 10

Author(s):

Ryan M. Warner

Keyword(s):

Base Temperature ◽

Optimal Temperature ◽

Flower Bud ◽

Breeding Programs ◽

Node Number ◽

Daily Light Integral ◽

Long Day ◽

Light Integral ◽

Short Days ◽

Petunia Axillaris

Flowering and morphology of four Petunia Juss. spp. [P. axillaris (Lam.) Britton et al., P. exserta Stehmann, P. integrifolia (Hook.) Schinz & Thell., and P. ×hybrida Vilm.] were evaluated in response to photoperiod and temperature. Photoperiod responses were evaluated under 9-h short days (SD), 9-h photoperiod plus 4-h night-interruption lighting (NI), or a 16-h photoperiod supplemented with high-pressure sodium lamps (16-h HPS). All species flowered earlier under NI than SD and were classified as facultative (quantitative) long-day plants. Increasing the daily light integral within long-day treatments increased flower bud number for P. axillaris only. In a second experiment, crop timing and quality were evaluated in the temperature range of 14 to 26 °C under 16-h HPS. The rate of progress toward flowering for each species increased as temperature increased from 14 to 26 °C, suggesting the optimal temperature for development is at least 26 °C. The calculated base temperature for progress to flowering varied from 0.1 °C for P. exserta to 5.3 °C for P. integrifolia. Flowering of P. axillaris and P. integrifolia was delayed developmentally (i.e., increased node number below the first flower) at 14 °C and 17 °C or less, respectively, compared with higher temperatures. Petunia axillaris and P. integrifolia flower bud numbers decreased as temperature increased, whereas P. ×hybrida flower bud number was similar at all temperatures. The differences in crop timing and quality traits observed for these species suggest that they may be useful sources of variability for petunia breeding programs.

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Short-day-like body weight changes do not prevent fat pad compensation after lipectomy in Siberian hamsters

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1997.272.1.r68 ◽

1997 ◽

Vol 272 (1) ◽

pp. R68-R77 ◽

Cited By ~ 5

Author(s):

M. M. Mauer ◽

T. J. Bartness

Keyword(s):

Body Weight ◽

Food Restriction ◽

Adipocyte Size ◽

Weight Changes ◽

Fat Pad ◽

Body Weight Changes ◽

Siberian Hamsters ◽

Long Day ◽

Long Duration ◽

Short Days

Long-day (LD)-housed Siberian hamsters show compensatory increases in white adipose tissue (WAT) weight after lipectomy, whereas hamsters exposed to short days (SDs) for a long duration (22 wk) do not. We tested whether SD-induced body weight changes prevent fat pad compensation after lipectomy. In experiment 1, hamsters with lesions of the paraventricular nucleus of the hypothalamus (PVNx) rapidly increased body weight similarly to 22-wk SD-exposed hamsters. In experiment 2, LD-housed hamsters were food restricted for 22 wk and then pair fed with SD-housed hamsters for 12 wk to produce body weight changes mimicking those of ad libitum-fed SD-exposed animals. Epididymal WAT (EWAT) lipectomy (EWATx) of PVNx or food-restricted hamsters elicited compensatory increases in retroperitoneal and inguinal WAT (RWAT and IWAT) weights. Unlike other fat pads, EWAT was less affected by food restriction or PVNx than by SD exposure. In general, food restriction decreased adipocyte number, whereas SD exposure decreased adipocyte size. PVNx increased RWAT adipocyte size and IWAT adipocyte number. These results suggest that the lack of body fat compensation by EWATx hamsters exposed to SDs for a long duration is due to SD-associated responses other than body weight changes per se.

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Photoperiodic Response of Peanut Species1

Peanut Science ◽

10.3146/i0095-3679-10-2-4 ◽

1983 ◽

Vol 10 (2) ◽

pp. 59-62 ◽

Cited By ~ 16

Author(s):

H. T. Stalker ◽

J. C. Wynne

Keyword(s):

North Carolina ◽

Day Treatment ◽

Photoperiodic Response ◽

Reproductive Capacity ◽

Arachis Species ◽

Short Day ◽

The North ◽

Long Day ◽

Wild Peanut ◽

Short Days

Abstract Many Arachis species collections do not produce pegs in North Carolina even though they flower profusely. To investigate reasons for the failure of fruiting, nine wild peanut species of section Arachis and three A. hypogaea cultivars representing spanish, valencia and virginia types were evaluated for response to short and long-day treatments in the North Carolina State Phytotron Unit of the Southeastern Environmental Laboratories. The objective of this investigation was to determine the flowering and fruiting responses of Arachis species to short and long-day photoperiods. Plant collections grown under a 9-hour short-day treatment were generally less vigorous, but produced more pegs than corresponding plants grown in long-day treatments which were produced by 9 hours of light plus a 3-hour interruption of the dark period. Annual species produced significantly more flowers and pegs than perennial species during both long and short days. The total number of flowers produced ranged from 0 during short days for A. correntina to more than 300 for A. cardenasii in long-day treatments. Only one plant of each species A. chacoense and A. villosa, and no plants of A. correntina, flowered in short days. Total numbers of pegs produced in short-day treatments were generally greater than in long-day treatments and the ratio of total number of pegs/total number of flowers was consistently greater during short-day treatments. A general trend was observed for more flowers produced in long-day treatments, but more pegs produced in short days. This study indicated that photoperiod can be manipulated to increase the seed set of some species and the success rate of obtaining certain interspecific hybrids. Furthermore, introgression from wild to cultivated species may possibly alter the reproductive capacity of A. hypogaea to photoperiod.

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Short Day Induction of Inflorescence Initiation in Some Winter Wheat Varieties

Functional Plant Biology ◽

10.1071/pp9870277 ◽

1987 ◽

Vol 14 (3) ◽

pp. 277 ◽

Cited By ~ 29

Author(s):

LT Evans

Keyword(s):

Winter Wheat ◽

High Irradiance ◽

Inflorescence Development ◽

Wheat Varieties ◽

Short Day ◽

Long Day ◽

European Winter Wheat ◽

Lower Irradiance ◽

Short Days ◽

Winter Wheat Varieties

Experiments in the Canberra phytotron with several European winter wheat varieties, especially cv. Templar, have shown that their need for vernalisation at low temperature can be replaced entirely by growth in short days at 21/16°C for the same period. In fact, although wheat is usually classified as a long day plant, inflorescence initiation at 21/16°C in unvernalised plants was twice as rapid in 8 h photoperiods as in 16 h ones. Short day induction was fastest in photoperiods of less than 12 h and was relatively insensitive to irradiance. Inflorescence development following initiation was faster the longer the photoperiod. At high irradiance, anthesis eventually occurred in 8 h days, but not at lower irradiance. These wheats are therefore short-long day plants, and may appear to be indifferent to daylength if only their time to anthesis is observed. Although short days can replace low temperatures, there are several important differences in their modes of action, and short day induction is better not referred to as short day vernalisation. Vernalisation of developing grains in the ear was more effective in long days.

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The Role of Photosynthesis in Flowering of the Long-Day Plant Sinapis alba

Functional Plant Biology ◽

10.1071/pp9770467 ◽

1977 ◽

Vol 4 (4) ◽

pp. 467 ◽

Cited By ~ 25

Author(s):

M Bodson ◽

RW King ◽

LT Evans ◽

G Bernier

Keyword(s):

Sinapis Alba ◽

High Irradiance ◽

Atmospheric Co2 ◽

Co2 Uptake ◽

Long Day ◽

Absolute Requirement ◽

Full Flowering ◽

Lower Irradiance ◽

Short Days

Flowering can be induced in the long-day plant Sinapis alba in 8-h photoperiods provided that the irradiance is close to that at which leaf photosynthesis is light-saturated (e.g. 96 J m-2 s-1). Three such 8-h cycles result in 10% flowering and six are required for full flowering, whereas only one long-day cycle of 16-20 h duration at a much lower irradiance (25 J m-2 s-1) is required for full flowering. High irradiance during the single long day promotes flowering when given for the first 8 h of a 16-h photoperiod, but is inhibitory over the last 8 h. Photosynthetic CO2 uptake is crucial for this response to high irradiance, as both its inhibitory and promotive effects on flowering are reversed by the removal of atmospheric CO2 during the period of high irradiance. Compared with plants kept in short days (8-h photoperiod), export of 14C-labelled assimilates from the leaf during a 24-h period was only 50-60% greater in plants exposed to a long day (20-h photoperiod), because plants in short days compensated to a degree for their shorter photosynthetic period by mobilizing leaf reserves during darkness. However, flowering can occur with no evident enhancement of supply of assimilate to the shoot apex, for example following dis- placement of the short day or on removal of atmospheric CO2 during the last 12 h of exposure to a 20-h long day. Also, the flowering response to radiant flux density during the second half of a long day shows an optimum between 15 and 70 J m-2 s-1, with reduced flowering both above and below this irradiance. Thus, although there is no absolute requirement for long days to induce flowering in S. alba, light reactions cther than photosynthesis probably contribute to photoperiodic induction in this species.

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Inflorescence Initiation in Lolium Temulentum l. II. Evidence for Inhibitory and Promotive Photoperiodic Processes Involving Transmissible Products

Australian Journal of Biological Sciences ◽

10.1071/bi9600429 ◽

1960 ◽

Vol 13 (4) ◽

pp. 429 ◽

Cited By ~ 30

Author(s):

LT Evans

Keyword(s):

Leaf Blade ◽

Light Period ◽

Continuous Illumination ◽

Rate Of Development ◽

Lolium Temulentum ◽

Short Day ◽

Long Day ◽

Inductive Treatment ◽

Short Days

Plants of Lolium temulentum, raised in short days, were given an inductive treatment by exposure of one leaf blade to a 32-hr period of continuous illumination. Then either the leaf exposed to this one long light period or varying areas of lower leaves which were simultaneously in short-day conditions were removed at intervals after the long-day exposure. The longer the long-day leaves remained on the plants, the greater was the proportion of plants which initiated inflorescences and the greater the rate of development of their inflorescences. This was so even when short-day leaves were present above the long-day ones. The longer the short-day leaves remained, and the greater their area, the lower was the proportion of plants which initiated inflorescences.

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