scholarly journals Inflorescence Initiation in Lolium Temulentum L. XIII. the Role of Gibberellins

1969 ◽  
Vol 22 (4) ◽  
pp. 773 ◽  
Author(s):  
LT Evans
Keyword(s):  
Light Intensity ◽  
Stem Growth ◽  
Lolium Temulentum ◽  
Long Day ◽  
Short Days

Both stem growth and flowering in plants exposed to 1 long day showed an increasing response to gibberellins with increase in the concentration of the injected solution, up to 12 X 10-4M. With plants in short days both responses were asymptotic or showed an optimum at 4 X 1O-4M, depending on the light intensity.

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

2003 ◽  
Vol 285 (4) ◽  
pp. R873-R879 ◽  
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.

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

1977 ◽  
Vol 4 (4) ◽  
pp. 467 ◽  
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.

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

1960 ◽  
Vol 13 (4) ◽  
pp. 429 ◽  
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.

scholarly journals Gibberellins and flowering in long day plants, with special reference to Lolium temulentum

1999 ◽  
Vol 26 (1) ◽  
pp. 1 ◽  
Author(s):  
L. T. Evans
Keyword(s):  
Environmental Control ◽  
Control Points ◽  
Subsequent Work ◽  
Feedback Effects ◽  
Factors Affecting ◽  
Lolium Temulentum ◽  
Long Day ◽  
Precise Role ◽  
Flowering Process

The relation between gibberellins (GAs) and flowering in some long day (LD) plants is reviewed, with particular emphasis on Lolium temulentum. Lang’s early experiments with rosette plants established the effectiveness of several GAs in replacing the need for LD. Subsequent work with mutants, especially of Arabidopsis, has clarified genetic and environmental control points in GA synthesis, various feedback effects and some of the factors affecting responsiveness to, as well as synthesis of, GAs in the flowering process. Further complexities are revealed in the experiments with Lolium temulentum, which have clearly shown that the structural requirements for effectiveness of GAs in the flowering process are quite different from those for elongation growth. The precise role of GAs in the long day induction of flowering remains unclear.

A note on the effects of previous photoperiod exposure and gradual transitions of light intensity at dawn and dusk on growth in Holstein heifers

1988 ◽  
Vol 46 (2) ◽  
pp. 300-303 ◽  
Author(s):  
S. A. Zinn ◽  
L. T. Chapin ◽  
H. A. Tucker
Keyword(s):  
Luteinizing Hormone ◽  
Light Intensity ◽  
Growth Response ◽  
Live Weight ◽  
Long Day ◽  
Serum Luteinizing Hormone ◽  
Serum Lh ◽  
Proportional Increase ◽  
Short Days

Long-day photoperiods of 16 h light (L) and 8 h dark (D) stimulate a proportional increase in live-weight (LW) gain of peripubertal Holstein heifers of 0·08 to 0·17 compared with heifers exposed to short days of less than 12 h L per day (Peters, Chapin, Leining and Tucker, 1978; Peters, Chapin, Emery and Tucker, 1980; Petitclerc, Chapin, Emery and Tucker, 1983; Zinn, Chapin and Tucker, 1986). One factor that could account for some of this variation in the magnitude of the growth response to long days is that the previous photoperiod exposure may influence the response to a subsequent different photoperiod (Moore-Ede, Sulzman and Fuller, 1982). For example, exposure to 13L: 11D induced pulsatile activity of serum luteinizing hormone (LH) in ewes previously exposed to 16L: 8D, but reduced serum LH to undetectable levels in sheep previously exposed to 8L: 16D (Robinson and Karsch, 1987). Thus, sheep exposed to identical photoperiods exhibited different responses depending on previous photoperiod exposure.

Inflorescence Initiation in Lolium temulentum L. XIV. The Role of Phytochrome in Long Day Induction

1976 ◽  
Vol 3 (2) ◽  
pp. 207 ◽  
Author(s):  
LT Evans
Keyword(s):  
Initial Period ◽  
Red Light ◽  
Pharbitis Nil ◽  
Initial Exposure ◽  
Continuous Irradiation ◽  
Long Day ◽  
Optimum Proportion ◽  
Subsequent Exposure ◽  
Short Days

Plants of L. temulentum grown in short days were exposed at various times during one night to mixtures of red (R) and far red (FR) light or to prolonged irradiation on a spectrograph. Irradiation with red light through the latter half of the 16-h night was inductive of flowering, its effect being enhanced by exposure to FR during the first 6 h after the period in daylight. Brief exposure to FR during this initial period was as effective as continuous irradiation with FR, and its effect was reversible by brief subsequent exposure to R, implicating the pigment phytochrome. Brief exposures to mixtures of R + FR at various times during the first 6 h in darkness were used to chart apparent changes in the two forms of phytochrome. To judge from the R + FR mixtures giving null responses, phytochrome reverted from the Pfr to the Pr form progressively over the first 5 h of darkness. There was no evidence of inverse reversion after an initial exposure to FR. Optimum flowering response required most of the phytochrome to be present in the Pfr form in the initial hours after daylight, followed by a rise in the proportion of the Pfr form to that set by R. Reflecting this shift during the night in the optimum proportion of Pfr, the spectrograph experiments indicated peak effectiveness in the far red region of the spectrum for irradiation at the end of the period in daylight, and in the red region (~670 nm) for irradiation during the latter part of the night. Flower induction in this long day plant is optimal when phytochrome is mostly in the Pr form early in the night, and in the Pfr form later, a sequence opposite to that required by short day plants such as Pharbitis nil and Chenopodium rubrum.

scholarly journals Inflorescence Initiation in Lolium Temulentum L. IV. Translocation of the Floral Stthiulus in Relation to that of Assimilates

1964 ◽  
Vol 17 (1) ◽  
pp. 1 ◽  
Author(s):  
LT Evans ◽  
IFW ardlaw
Keyword(s):  
Shoot Apex ◽  
Small Proportion ◽  
Inhibitory Effect ◽  
Lolium Temulentum ◽  
Long Day ◽  
Short Days

Translocation of labelled assimilates to the shoot apex and other parts of the plant was followed from an upper leaf held in long-day conditions, when lower leaves in short days were either present or removed. Similarly a comparison was made of the distribution of assimilates from an upper long-day leaf and a lower leaf held in short days. The presence of lower leaves did not reduce the movement of assimilates from the upper leaf to the shoot apex, and the lower leaf supplied only a small proportion of the assimilates reaching the shoot apex, although it supplied much to the roots. It is concluded that the previously established inhibitory effect of lower leaves in short days on inflorescence initiation in L. temulentum is unlikely to be due to their interference with translocation of the long-day stimulus to the shoot apex, or to their diluting it with assimilates, but rather to their production of a transmissible inhibitor of initiation.

SCN lesions block responses to systemic melatonin infusions in Siberian hamsters

1991 ◽  
Vol 260 (1) ◽  
pp. R102-R112 ◽  
Author(s):  
T. J. Bartness ◽  
B. D. Goldman ◽  
E. L. Bittman
Keyword(s):  
Serum Prolactin ◽  
Suprachiasmatic Nuclei ◽  
Fat Pad ◽  
Short Day ◽  
Siberian Hamsters ◽  
Long Day ◽  
Testicular Regression ◽  
Body Weights ◽  
Short Days

The role of the suprachiasmatic nuclei (SCN) in the response to short-day melatonin (MEL) signals was examined in long-day-housed pinealectomized (PINX) Siberian hamsters. Five- or ten-hour MEL infusions that mimicked the peak nocturnal durations of serum MEL levels in long or short days, respectively, or control saline infusions were given for 5 wk. Half the hamsters in each infusion group also received bilateral electrolytic SCN lesions. The 10-h MEL infusions reduced testes weight, body and fat pad weights, and serum prolactin (PRL) and follicle-stimulating hormone (FSH) concentrations in unoperated controls. These short-day-type effects were blocked by SCN lesions, which often produced hyperprolactinemia. Circadian rhythms of locomotor activity were disrupted or sparse in hamsters with lesions in or near the SCN. In a second experiment, 5 wk of long-day-like, short-duration (5-h) MEL infusions were administered to hamsters that had been PINX after 8 wk of short-day exposure. Control hamsters given 5-h MEL infusions, but not 10-h MEL or saline infusions, exhibited testicular growth and increased serum PRL levels. Hamsters with SCN lesions showed similar responses, regardless of the duration or type of infusion. Although the blockade of 10-h MEL infusion-induced testicular regression by SCN lesions in experiment 1 may have been due to stimulation of the testes by PRL, it is unlikely that the hyperprolactinemia accounted for the ability of SCN lesions to block effects of 10-h MEL infusions on fat pad and body weights. Therefore, the SCN and/or neighboring structures may participate in the response to short-day MEL signals in Siberian hamsters.

The Polycomb group methyltransferase StE(z)2 and deposition of H3K27me3 and H3K4me3 regulate the expression of tuberization genes in potato

2020 ◽  
Author(s):  
Amit Kumar ◽  
Kirtikumar R Kondhare ◽  
Nilam N Malankar ◽  
Anjan K Banerjee
Keyword(s):  
Target Genes ◽  
Polycomb Group ◽  
Altered Expression ◽  
Trithorax Group ◽  
Chip Sequencing ◽  
H3k4 Trimethylation ◽  
Long Day ◽  
Trithorax Group Proteins ◽  
Short Days

Abstract Polycomb repressive complex (PRC) group proteins regulate various developmental processes in plants by repressing target genes via H3K27 trimethylation, and they function antagonistically with H3K4 trimethylation mediated by Trithorax group proteins. Tuberization in potato has been widely studied, but the role of histone modifications in this process is unknown. Recently, we showed that overexpression of StMSI1, a PRC2 member, alters the expression of tuberization genes in potato. As MSI1 lacks histone-modification activity, we hypothesized that this altered expression could be caused by another PRC2 member, StE(z)2, a potential H3K27 methyltransferase in potato. Here, we demonstrate that a short-day photoperiod influences StE(z)2 expression in the leaves and stolons. StE(z)2 overexpression alters plant architecture and reduces tuber yield, whereas its knockdown enhances yield. ChIP-sequencing using stolons induced by short-days indicated that several genes related to tuberization and phytohormones, such as StBEL5/11/29, StSWEET11B, StGA2OX1, and StPIN1 carry H3K4me3 or H3K27me3 marks and/or are StE(z)2 targets. Interestingly, we observed that another important tuberization gene, StSP6A, is targeted by StE(z)2 in leaves and that it has increased deposition of H3K27me3 under long-day (non-induced) conditions compared to short days. Overall, our results show that StE(z)2 and deposition of H3K27me3 and/or H3K4me3 marks might regulate the expression of key tuberization genes in potato.

scholarly journals Multiplication of seed potatoes by tuber formation in leaf axils of stems derived from single-bud stem cuttings.

1987 ◽  
Vol 35 (1) ◽  
pp. 29-36
Author(s):  
J. Marinus
Keyword(s):  
Soil Surface ◽  
Stem Growth ◽  
Tuber Formation ◽  
Stem Cuttings ◽  
Single Node ◽  
Seed Potatoes ◽  
Short Day ◽  
Long Day ◽  
Short Days

Single-node cuttings of 3 cultivars were planted in such a way that the buds were some centimetres above the soil surface. Some of the plants were grown under long-day conditions, the others under short days during stem growth, this being favourable to tuber formation in normal plants. Stems growing from the buds showed abundant tuber formation in the leaf axils of Jaerla (early) and Bintje (mid early), especially under short-day conditions, but fewer tubers were formed in Alpha (late). This cultivar formed many thickened branches instead of tubers under short-day conditions. Under long days Jaerla and Bintje formed many above-ground tubers, whereas half of the cuttings of Alpha did not form tubers. When planted, above-ground tubers produced good yields. (Abstract retrieved from CAB Abstracts by CABI’s permission)

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