scholarly journals SENSITIVITY OF WATERMELON PLANT GROWTH TO PHOTOMORPHOGENIC SIGNALS DURING THE LIGHT OR DARK PHASE OF THE PHOTOPERIOD

HortScience ◽  
1992 ◽  
Vol 27 (11) ◽  
pp. 1177d-1177
Author(s):  
Heather. H. Friend ◽  
Arne Sæbø ◽  
Dennis R. Decoteau
Keyword(s):  
Plant Growth ◽  
Light Quality ◽  
Dark Period ◽  
Individual Treatment ◽  
Dark Phase ◽  
Internode Elongation ◽  
Growth Responses ◽  
Light Phase ◽  
Multiple Exposures ◽  
Affected Plant

Previous research has demonstrated that watermelon plants are sensitive to changes in light quality, as suggested by an individual treatment of plants with 15-min of end-of-day (EOD) red (R)and far-red (FR) light. FR-induced growth responses (i.e., petiole elongation, internode elongation, reduced petiole angles) were reversed by immediately following the FR light treatment with R light implicating phytochrome as the light quality perception mechanism. The objective of the present experiment was to determine the influence of individual and multiple FR light treatments (each treatment of 15-min duration) during the light and dark phase of the photoperiod on photomorphogenic growth responses of young watermelon plants. Light regulated growth responses of watermelon were influenced by the timing and the number of light quality exposures during the light or dark phase of the photoperiod. Individual FR treatments during the light phase except for the EOD exposure did not affect plant growth responses. In contrast, individual FR treatments at selected intervals during the dark period affected plant development. The most effective individual FR treatment to induce growth responses was at the beginning of the dark period, with decreasing responses as the FR treatment was delayed into the dark period. Multiple exposures of FR during the dark slightly increased growth responses as compared to a single EOD FR treatment.

scholarly journals PHOTOMORPHOGENIC DEVELOPMENT AND CARBOHYDRATE COMPOSITION OF YOUNG WATERMELON PLANTS AS AFFECTED BY INDIVIDUAL OR MULTIPLE FR SIGNALS DURING THE DARK PHASE OF THE PHOTOPERIOD

HortScience ◽  
1992 ◽  
Vol 27 (6) ◽  
pp. 641e-641
Author(s):  
Heather Hatt ◽  
Arne Sæbø ◽  
Dennis R. Decoteau
Keyword(s):  
Plant Growth ◽  
Citrullus Lanatus ◽  
Light Signal ◽  
Diurnal Fluctuation ◽  
Dark Phase ◽  
Tissue Analysis ◽  
Carbohydrate Composition ◽  
Growth Responses ◽  
Composition Distribution ◽  
Light Signals

Treatment of young watermelon (Citrullus lanatus cv. Sugar Baby) plants with individual and multiple FR light (15 min) treatments during the dark phase of the photoperiod influenced plant growth and development (i.e., petiole elongation, internode elongation, and reduced petiole angles) as compared to plants not treated with FR signals. The timing for the most effective light signal for inducing a growth response was when the signal was delivered immediately after the plant entered into the dark phase of the photoperiod. Decreasing growth responses to FR signals were observed as the signals were delayed after the plant entered into the dark phase. Multiple FR signals during the dark phase slightly increased growth responses as compared to plants that received the signal immediately after the light period. Young watermelon plant growth responses to FR light signals do not appear to be photoperiodic as plants similarly treated with a white light signal did not generate growth responses. Tissue analysis of petioles, leaves, stems, and cotyledons from plants treated with individual and multiple FR signals suggested that carbohydrate composition, distribution, and diurnal fluctuation were affected by the light quality treatments.

scholarly journals Analysis of the hupSL Operon of the Nonheterocystous Cyanobacterium Lyngbya majuscula CCAP 1446/4: Regulation of Transcription and Expression under a Light-Dark Regimen

2005 ◽  
Vol 71 (8) ◽  
pp. 4567-4576 ◽  
Author(s):  
Elsa Leitão ◽  
Fredrik Oxelfelt ◽  
Paulo Oliveira ◽  
Pedro Moradas-Ferreira ◽  
Paula Tamagnini
Keyword(s):  
De Novo ◽  
Dark Period ◽  
Repetitive Sequences ◽  
Hydrogenase Activity ◽  
Regulatory Sequences ◽  
Regulation Of Transcription ◽  
Dark Phase ◽  
Uptake Hydrogenase ◽  
Light Phase ◽  
Lyngbya Majuscula

ABSTRACT This work presents the characterization of an uptake hydrogenase from a marine filamentous nonheterocystous cyanobacterium, Lyngbya majuscula CCAP 1446/4. The structural genes encoding the uptake hydrogenase (hupSL) were isolated and characterized, and regulatory sequences were identified upstream of hupS. In silico analysis highlighted various sets of long repetitive sequences within the hupSL intergenic region and downstream of hupL. The transcriptional regulator that operates global nitrogen control in cyanobacteria (NtcA) was shown to bind to the promoter region, indicating its involvement in the transcriptional regulation of hupSL. Under N2-fixing conditions and a 12-h light/12-h dark regime, H2 uptake activity was shown to follow a daily pattern with a clear maximum towards the end of the dark period, preceded by an increase in the transcript levels initiated in the end of the light phase. Novel antibodies directed against HupL of Lyngbya majuscula CCAP 1446/4 were used to monitor the protein levels throughout the 24-h period. The results suggest that protein turnover occurs, with degradation taking place during the light phase and de novo synthesis occurring during the dark phase, coinciding with the pattern of H2 uptake. Taking into account our results and the established correlation between the uptake hydrogenase activity and N2 fixation in cyanobacteria, it seems probable that both processes are confined to the dark period in aerobically grown cells of Lyngbya majuscula CCAP 1446/4.

Melatonin and Jet Lag Syndrome: Experimental Model and Clinical Implications

CNS Spectrums ◽  
2003 ◽  
Vol 8 (2) ◽  
pp. 139-148 ◽  
Author(s):  
Gregory F. Oxenkrug ◽  
Pura J. Requintina
Keyword(s):  
High Performance ◽  
Dark Period ◽  
Monoamine Oxidase A ◽  
Dark Phase ◽  
Jet Lag ◽  
Light Phase ◽  
Light Onset ◽  
Spontaneously Hypertensive ◽  
Environmental Light ◽  
Pineal Serotonin

AbstractWhat is the effect of melatonin on jet lag syndrome? Jet lag desynchronizes the internal sleep-wakefulness cycle with the environmental light/dark cycle. Advance (but not delay) of light onset is known to abolish pineal N-acetyltransferase activity and urine excretion of 6-sulphatoxymelatonin. Measurements of pineal serotonin, the substrate of melatonin biosynthesis; N-acetylserotonin (NAS), the immediate melatonin precursor; and melatonin (high-performance liquid chromatography-fluorimetric method) in the animal (rat) model of jet lag revealed that prolonged delay of darkphase onset disrupted the rhytms in comparable ways as the advance of light-phase onset. Advance of dark phase onset resulted in less severe disturbances of rhythms as compared with the advance of light phase onset. Melatonin, but not NAS, injections at the beginning of a new dark period accelerated recovery of NAS and melatonin, but not serotonin, rhythms. Spontaneously hypertensive rats were more sensitive to advance of light onset and less responsive to melatonin injections than normotensive rats. NAS and methylene blue, an inhibitor of monoamine oxidase A, attenuated light-induced disruption of NAS but not melatonin rhythms. We draw the following conclusions from our data: the beginning of the dark period may be preferable to the beginning of light period as the arrival time on eastward flights; the efficacy of melatonin in alleviating jet lag may be enchanced by administering it before, during and after rapid transition through time zones; and hypertension may exaggerate jet lag syndrome.

scholarly journals Melatonin MT1 and MT2 Receptors Exhibit Distinct Effects in the Modulation of Body Temperature across the Light/Dark Cycle

2019 ◽  
Vol 20 (10) ◽  
pp. 2452 ◽  
Author(s):  
Martha López-Canul ◽  
Seung Hyun Min ◽  
Luca Posa ◽  
Danilo De Gregorio ◽  
Annalida Bedini ◽  
...  
Keyword(s):  
Body Temperature ◽  
Receptor Antagonist ◽  
Partial Agonist ◽  
Receptor Subtypes ◽  
Dark Phase ◽  
Light Phase ◽  
Dark Cycle ◽  
Simultaneous Activation ◽  
Type 3 ◽  
G Protein Coupled

Melatonin (MLT) is a neurohormone that regulates many physiological functions including sleep, pain, thermoregulation, and circadian rhythms. MLT acts mainly through two G-protein-coupled receptors named MT1 and MT2, but also through an MLT type-3 receptor (MT3). However, the role of MLT receptor subtypes in thermoregulation is still unknown. We have thus investigated the effects of selective and non-selective MLT receptor agonists/antagonists on body temperature (Tb) in rats across the 12/12-h light–dark cycle. Rectal temperature was measured every 15 min from 4:00 a.m. to 9:30 a.m. and from 4:00 p.m. to 9:30 p.m., following subcutaneous injection of each compound at either 5:00 a.m. or 5:00 p.m. MLT (40 mg/kg) had no effect when injected at 5 a.m., whereas it decreased Tb during the light phase only when injected at 5:00 p.m. This effect was blocked by the selective MT2 receptor antagonist 4P-PDOT and the non-selective MT1/MT2 receptor antagonist, luzindole, but not by the α1/MT3 receptors antagonist prazosin. However, unlike MLT, neither the selective MT1 receptor partial agonist UCM871 (14 mg/kg) nor the selective MT2 partial agonist UCM924 (40 mg/kg) altered Tb during the light phase. In contrast, UCM871 injected at 5:00 p.m. increased Tb at the beginning of the dark phase, whereas UCM924 injected at 5:00 a.m. decreased Tb at the end of the dark phase. These effects were blocked by luzindole and 4P-PDOT, respectively. The MT3 receptor agonist GR135531 (10 mg/kg) did not affect Tb. These data suggest that the simultaneous activation of both MT1 and MT2 receptors is necessary to regulate Tb during the light phase, whereas in a complex but yet unknown manner, they regulate Tb differently during the dark phase. Overall, MT1 and MT2 receptors display complementary but also distinct roles in modulating circadian fluctuations of Tb.

scholarly journals A Meta-Analytical Approach on Arbuscular Mycorrhizal Fungi Inoculation Efficiency on Plant Growth and Nutrient Uptake

Agriculture ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 370
Author(s):  
Murugesan Chandrasekaran
Keyword(s):  
Plant Growth ◽  
Arbuscular Mycorrhizal Fungi ◽  
Nutrient Uptake ◽  
Mycorrhizal Fungi ◽  
Host Plants ◽  
Plant Biomass ◽  
Meta Analysis ◽  
Arbuscular Mycorrhizal ◽  
Growth Responses ◽  
Mycorrhizal Plants

Arbuscular mycorrhizal fungi (AMF) are obligate symbionts of higher plants which increase the growth and nutrient uptake of host plants. The primary objective was initiated based on analyzing the enormity of optimal effects upon AMF inoculation in a comparative bias between mycorrhizal and non-mycorrhizal plants stipulated on plant biomass and nutrient uptake. Consequently, in accomplishing the above-mentioned objective a vast literature was collected, analyzed, and evaluated to establish a weighted meta-analysis irrespective of AMF species, plant species, family and functional group, and experimental conditions in the context of beneficial effects of AMF. I found a significant increase in the shoot, root, and total biomass by 36.3%, 28.5%, and, 29.7%, respectively. Moreover, mycorrhizal plants significantly increased phosphorus, nitrogen, and potassium uptake by 36.3%, 22.1%, and 18.5%, respectively. Affirmatively upon cross-verification studies, plant growth parameters intensification was accredited to AMF (Rhizophagus fasciculatus followed by Funniliforme mosseae), plants (Triticum aestivum followed by Solanum lycopersicum), and plant functional groups (dicot, herbs, and perennial) were the additional vital important significant predictor variables of plant growth responses. Therefore, the meta-analysis concluded that the emancipated prominent root characteristics, increased morphological traits that eventually help the host plants for efficient phosphorus uptake, thereby enhancing plant biomass. The present analysis can be rationalized for any plant stress and assessment of any microbial agent that contributes to plant growth promotion.

Growth responses of Leymus chinensis (Trin.) Tzvelev to sheep saliva after defoliation

2010 ◽  
Vol 32 (4) ◽  
pp. 419 ◽  
Author(s):  
Xing Teng ◽  
Lei Ba ◽  
Deli Wang ◽  
Ling Wang ◽  
Jushan Liu
Keyword(s):  
Plant Growth ◽  
Aboveground Biomass ◽  
Field Experiments ◽  
Perennial Grass ◽  
Leaf Length ◽  
Leymus Chinensis ◽  
Growth Responses ◽  
Time Duration ◽  
Positive Effects ◽  
Leaf Weight

Many studies indicated that saliva from herbivores might be involved in plant growth responses when plants have been grazed. However, there is currently no general agreement on whether saliva can affect plant growth. Our aims were to determine the growth response of plants to sheep saliva after defoliation under diverse environmental conditions (different sward structures), and whether the effect of saliva is influenced by time (duration) after its application. We conducted field experiments with clipping treatments and the application of sheep saliva to the damaged parts of tillers to simulate sheep grazing on the perennial grass Leymus chinensis (Trin.) Tzvelev during the early growing seasons. Results demonstrated that clipping with saliva application significantly increased tiller numbers 8 weeks after treatments in comparison with clipping alone. A key finding is that the effect of sheep saliva on plant growth was short-lived. Clipping with saliva application increased leaf weight in the second week, while clipping alone had no effect. Moreover, clipping with saliva application promoted the elongation of new leaves (not the old ones) in the first week whereas clipping alone was ineffective. Results also showed that there were no differences between clipping with saliva application and clipping alone for relative height growth rate and aboveground biomass. Therefore, we concluded that saliva application to clipping treatment would produce an additional effect compared to clipping alone for the plant and the positive effects are time dependent. The additional effects primarily embodied in the individual level of plant, such as the changes of leaf weight and leaf length. Beyond the level, the effects of saliva only produced many more tiller numbers rather than the accumulation of aboveground biomass.

Plant Growth Responses

1964 ◽  
pp. 183-195
Author(s):  
R. P. Mericle ◽  
L. W. Mericle ◽  
A. E. Smith ◽  
W. F. Campbell ◽  
D. J. Montgomery
Keyword(s):  
Plant Growth ◽  
Growth Responses

Changes in the responses to light quality during ontogeny in Chenopodium album

2003 ◽  
Vol 81 (2) ◽  
pp. 152-163 ◽  
Author(s):  
Humberto Fabio Causin ◽  
Renata D Wulff
Keyword(s):  
Plant Growth ◽  
Light Quality ◽  
Chenopodium Album ◽  
Intraspecific Variability ◽  
Reproductive Fitness ◽  
Stem Length ◽  
Shade Avoidance ◽  
Late Flowering ◽  
Total Leaf ◽  
Avoidance Responses

Morphological shade-avoidance responses have been hypothesized to be a form of adaptive plasticity to improve competition for light; however, little is known about their intraspecific variability and their effect on reproductive fitness. To compare plant responses either at a common age or at a common phenological stage, two experiments were conducted with early- and late-flowering Chenopodium album plants exposed to different red (660 nm) to far red (730 nm) ratios. In the first experiment, plant height and number of leaves were recorded at several times during the vegetative stage, and at the onset of flowering, each plant was harvested and other growth traits were measured. In the second experiment, three destructive harvests were performed across the whole plant cycle. Plant growth and development markedly differed between early- and late-flowering plants in all of the conditions tested. Light treatments significantly affected stem length, total leaf number, total leaf area, and relative allocation to leaf biomass. In all families, the response of stem elongation to light treatments decreased later in the development, while changes in the other plastic responses were mostly due to variations in plant growth. No significant treatment effect was found on relative biomass allocation to reproductive structures. However, individual seed mass significantly differed between certain groups, indicating that light quality can affect reproductive fitness through changes in traits other than fruit or seed set.Key words: Chenopodium album, fitness, intraspecific variability, phenotypic plasticity, red to far red ratio, shade-avoidance responses.

Locomotor activity responses in juvenile sockeye salmon, Oncorhynchus nerka, to melatonin and serotonin

1970 ◽  
Vol 48 (6) ◽  
pp. 1425-1427 ◽  
Author(s):  
John E. Byrne
Keyword(s):  
Locomotor Activity ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Dark Phase ◽  
Light Phase ◽  
Selective Activity

Intraperitoneal injections administered for 3 consecutive days to juvenile sockeye salmon resulted in selective activity responses to either the light or the dark phase of the photoperiodic cycle. Serotonin increased locomotor activity only during the dark phase, while melatonin decreased locomotor activity only during the light phase.

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