scholarly journals Interacting Effects of Light and Temperature on Sporulation of Peronospora tabacina on Tobacco Leaves

1976 ◽  
Vol 29 (3) ◽  
pp. 281 ◽  
Author(s):  
YigaI Cohen
Keyword(s):  
Light Level ◽  
Inhibitory Effect ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Present System ◽  
Tobacco Leaves ◽  
Spore Yield ◽  
Role Of Light ◽  
Effect Of Light

The interacting effects of light and temperature on spore formation of P. tabacina on tobacco leaves were investigated. The following points indicated that an enzymic build-up of an antisporulant during a wet light period and its enzymic decay over a dry dark period may explain the inhibitory effect of light upon sporulation, and its reversal by darkness. (1) Fluorescent blue light of relatively low photon flux density (3 �7 /lE m - 2 S -1) inhibited sporulation by 99 % at 20oe. (2) Light level and temperature during the sporulation period determined spore yield of the pathogen: at high temperatures (in the range 8-24�C) sporulation was inhibited at low light level, whilst no inhibition occurred at much higher light levels at low temperatures. (3) Preceding dry dark treatments given at 200e considerably diminished the inhibitory effect of light, but not if given at 100e. (4) The diffusion of an inhibitory compound from irradiated to unirradiated areas of detached leaves was demonstrated. (5) The continuing photosynthetic activity of the host in the light at 20oe, and the lack of sucrose following dark periods at lOoe, were not associated with the inhibitory effect of light. The similarity between the role of light in the present system and the role of light in activation and decay of phenylalanine ammonia-lyase is discussed.

The role of resonance radiation in the propagation of a positive pre-breakdown ionization wave in long discharge tubes

2021 ◽  
Author(s):  
Aleksei V Siasko ◽  
Yuri B Golubovskii ◽  
Sergei Valin
Keyword(s):  
Discharge Tube ◽  
Tube Wall ◽  
Finite Size ◽  
Ionization Wave ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Radiation Trapping ◽  
Discharge Tubes ◽  
Electron Photoemission

Abstract The work is devoted to calculating the flux of resonance photons towards the boundary of a cylindrical discharge tube of a finite size during the propagation of a pre-breakdown ionization wave of positive polarity. A cylindrical discharge tube of finite dimensions with argon at the pressure of p=1 Torr is considered. The propagation mechanisms of metastable and resonance atoms are compared. For the considered discharge conditions, the space-time distributions of metastable and resonance atoms are calculated. The manuscript presents a technique for calculating the flux of resonance photons onto the discharge tube wall with the account of the radiation trapping. It is shown that for the studied conditions the photon flux density towards the longitudinal boundary of the tube ahead of the ionization wave can reach 1013 cm-2s-1. The obtained results allow describing the appearance of seed electrons ahead of the positive ionization wavefront during its propagation due to the electron photoemission from the discharge tube wall.

scholarly journals Effect of Light Spectrum on Gas Exchange, Growth and Biochemical Characteristics of Einkorn Seedlings

Agronomy ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1042 ◽  
Author(s):  
Maria Luce Bartucca ◽  
Daniele Del Buono ◽  
Eleonora Ballerini ◽  
Paolo Benincasa ◽  
Beatrice Falcinelli ◽  
...  
Keyword(s):  
Nutritional Status ◽  
Light Emitting Diode ◽  
Co2 Assimilation ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Vegetable Production ◽  
Light Spectrum ◽  
Beneficial Effects ◽  
Iron And Zinc ◽  
Effect Of Light

The use of Light Emitting Diode (LED) lights in microscale vegetable production is more and more widespread. In this context, the effect of light spectrum on photosynthesis, growth, shoot yield, pigment content, and nutritional status of einkorn seedlings (Triticum monococcum L. ssp. monococcum), germinated and grown in a nutrient solution, was investigated. Plants were subjected to six different LED light treatments, all having a photon flux density (PFD) of 200 μmol m−2 s−1. Two light treatments were monochromatic (red or blue), three dichromatic (blue and red in the proportion), and one of a wider spectrum (selected as a control). All the light treatments affected the morphological, biochemical, and nutritional status of einkorn seedlings. Overall, the dichromatic treatments were the most effective in stimulating biomass production, CO2 assimilation, and evapotranspiration, as well as contents in chlorophyll a and b and carotenoids, and additionally nitrogen, phosphorous, manganese, iron, and zinc. These results are of relevance for the beneficial effects of dichromatic LED treatments in maximizing einkorn shoot yield and nutritional values, and in limiting energy consumption in indoor cultivation.

scholarly journals LightCue: An Innovative Far-Red Light Emitter for Locally Modifying the Spectral Cue in Outdoor Conditions with Global Consequences on Plant Architecture

Plants ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2483
Author(s):  
Alain Fortineau ◽  
Didier Combes ◽  
Céline Richard-Molard ◽  
Ela Frak ◽  
Alexandra Jullien
Keyword(s):  
Plant Architecture ◽  
Light Emitting Diode ◽  
Red Light ◽  
Inhibitory Effect ◽  
Photosynthetic Photon Flux Density ◽  
High Irradiance ◽  
Light Signal ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Light Emitting

Plasticity of plant architecture is a promising lever to increase crop resilience to biotic and abiotic damage. Among the main drivers of its regulation are the spectral signals which occur via photomorphogenesis processes. In particular, branching, one of the yield components, is responsive to photosynthetic photon flux density (PPFD) and to red to far-red ratio (R:FR), both signals whose effects are tricky to decorrelate in the field. Here, we developed a device consisting of far-red light emitting diode (LED) rings. It can reduce the R:FR ratio to 0.14 in the vicinity of an organ without changing the PPFD in outdoor high irradiance fluctuating conditions, which is a breakthrough as LEDs have been mostly used in non-fluctuant controlled conditions at low irradiance over short periods of time. Applied at the base of rapeseed stems during the whole bolting-reproductive phase, LightCue induced an expected significant inhibitory effect on two basal targeted axillary buds and a strong unexpected stimulatory effect on the overall plant aerial architecture. It increased shoot/root ratio while not modifying the carbon balance. LightCue therefore represents a promising device for progress in the understanding of light signal regulation in the field.

The Role of Light and Photosynthesis During Pathogen Defence in Tobacco Leaves

2008 ◽  
pp. 1557-1560
Author(s):  
Hardy Schön ◽  
Judith Scharte ◽  
Jutta Essmann ◽  
Ina Schmitz-Thom ◽  
Engelbert Weis
Keyword(s):  
Tobacco Leaves ◽  
Pathogen Defence ◽  
Role Of Light

scholarly journals Effect of Light Quality with Different Red/Far-red Photon Flux Density Ratio on Elongation of Pak-choi Seedlings Grown under High Temperatures.

2001 ◽  
Vol 70 (6) ◽  
pp. 774-776 ◽  
Author(s):  
Tatsuya Hayashida ◽  
Yasushi Shibato ◽  
Yuji Hamachi ◽  
Youichi Yamato ◽  
Hiroko Yamazaki ◽  
...  
Keyword(s):  
Flux Density ◽  
High Temperatures ◽  
Light Quality ◽  
Density Ratio ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Pak Choi ◽  
Effect Of Light

scholarly journals STUDIES ON THE CULTIVATION OF THE STRAWBERRY UNDER THE LIGHT TRANSMISSION TYPE SOLAR CELL CONDITION

2017 ◽  
Vol 7 (1) ◽  
pp. 991-996
Author(s):  
Takayuki Tanaka ◽  
Hitoshi Kinouchi ◽  
Masako Akutsu
Keyword(s):  
Solar Cell ◽  
Flux Density ◽  
Light Transmission ◽  
Fruit Size ◽  
Control Area ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Roof Panel

We examined the cultivation of the strawberry under the light transmission type solar cell (panel) condition that absorbs the ultraviolet light for electricity, and passes ca. 20% of visible light from 400nm to 800nm for photosynthesis. Though the color of leaves under the solar cell was lighter than that under control area, the length and width of the leaves were not so different among the treatments. On the other hand, the number of honeybees visiting flowers and SSC were significantly correlated with the integrated photon flux density, and the number of fruits harvested and the yield showed strong correlation coefficient with it. However, the coefficient of correlation between the number of flowers bloomed or fruit size and the integrated photon flux density were relatively low, suggesting that the light interception by the solar cell does not affect much on the number of flowers bloomed or fruit size. As the yield and the quality of the strawberry fruits decreased with the light intensity by the light transmission type solar cell, the yield and the quality of the fruits can be improved by widening the space between the panels. Originally, the transmission type solar cell had been expected not only as ecological role of power generation, but also as the source of light in a room. Here, the authors propose an additional role of the transmission type solar cell as a roof panel of a greenhouse.

Gas Exchange of Four Cassava Cultivars in Relation to Light Intensity

1982 ◽  
Vol 18 (4) ◽  
pp. 375-382 ◽  
Author(s):  
Jairo A. Palta
Keyword(s):  
Gas Exchange ◽  
Light Intensity ◽  
Flux Density ◽  
Direct Effect ◽  
Photosynthetic Rate ◽  
Photosynthetic Apparatus ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Light Saturation ◽  
Effect Of Light

SUMMARYGas exchange measurements were carried out on four cassava cultivars, M. COL22, M. MEX59, M. COL638, and M. VEN218, under a range of light intensities, to investigate possible differences in photosynthesis and transpiration. Over the range of photon flux density 100–1500 μE m−2 s−1 leaves showed a light saturation response typical of C-3 plants with little increase in photosynthetic rate above 1000–1500 μE m−2 s−1 (200–300 Wm−2 PAR). At light saturation there were significant differences in photosynthetic rates between cultivars, with the highest 10% greater than the lowest. Part of the response could be attributed to increased stomatal aperture, and a greater part to a direct effect of light intensity on the photosynthetic apparatus. Transpiration increased with light intensity levels, but no significant differences were observed between cultivars.

The effect of light:dark cycles of medium frequency on photosynthesis by Chlorella vulgaris and the implications for waste stabilisation pond design and performance

2003 ◽  
Vol 48 (2) ◽  
pp. 69-74 ◽  
Author(s):  
I.A.J. Ratchford ◽  
H.J. Fallowfield
Keyword(s):  
Oxygen Evolution ◽  
Chlorella Vulgaris ◽  
Oxygen Electrode ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Dark Cycle ◽  
Cycle Times ◽  
Total Light ◽  
And Performance ◽  
Effect Of Light

The effect of light/dark (L:D) cycle times on the recovery from photoinhibition of green micro-alga Chlorella vulgaris (CCAP211/11c) and the cyanobacterium Synechococcus (CCAP1479/5) was investigated using an irradiated, temperature controlled oxygen electrode. The onset of photoinhibition in both organisms occurred at irradiances > 300 mmol m-2s-1 at temperatures >15°C. Light/dark cycle times were controlled independently using a relay timer and shutter placed between the quartz iodide light source and the oxygen electrode chamber. Oxygen evolution decreased rapidly when cells were continuously irradiated at 300, 500 and 750 mmol m-2s-1. However, Chlorella cells irradiated at 300, 500 and 750 mmol m-2s-1 on a L:D cycle of 60s:20s, 30s:60s and 60s:120s respectively, maintained a constant rate of oxygen evolution over a 24 h incubation period. Exposure time to a given incident irradiance rather than the total light dose received appeared to determine the effect of light/dark cycle times on photosynthesis. A relationship was established between L:D ratio required to maintain constant oxygen production and incident photon flux density. The results suggest that the adverse effects of high irradiances on algae near the surface of a stratified waste stabilisation pond might be ameliorated by controlled mixing of algal cells through the depth of the pond.

Effect of Light, Watering Frequency, and Chlorsulfuron on Canada Thistle (Cirsium arvense)

Weed Science ◽  
1991 ◽  
Vol 39 (4) ◽  
pp. 590-594 ◽  
Author(s):  
Robert L. Zimdahl ◽  
Jingzhu Lin ◽  
Armando A. Dall'Armellina
Keyword(s):  
Leaf Area ◽  
Field Experiments ◽  
Dry Weight ◽  
Photosynthetic Photon Flux Density ◽  
Water Levels ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Canada Thistle ◽  
Root Dry Weight ◽  
Effect Of Light

Greenhouse and field experiments were conducted to determine effects of light, water, and chlorsulfuron on growth of Canada thistle. In the greenhouse, shoot and root dry weight, leaf area, and number of inflorescences decreased as light and water levels decreased. In the field, shoot and root dry weight, leaf area, and number of Canada thistle inflorescences were positively correlated with light intensity from 1832 to 30 μmol m−2s−1photosynthetic photon flux density (PPFD). The greatest effect of light was on inflorescence production which was eliminated at 30 μmol m−2s−1(PPFD). The combined effect of water stress and chlorsulfuron decreased root and shoot growth but did not eliminate it.

scholarly journals (50) Evaluating Low Light Level Effects on Chlorophyll Content and Commercial Quality in Several Species of Bambuseae

HortScience ◽  
2006 ◽  
Vol 41 (4) ◽  
pp. 1037B-1037
Author(s):  
Harry G. Simmons ◽  
Alisara Menakanit ◽  
Surawit Wannakrairoj ◽  
Poonpipope Kasemsap
Keyword(s):  
Chlorophyll Content ◽  
Extreme Temperature ◽  
Light Level ◽  
Photosynthetic Photon Flux Density ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Light Levels ◽  
Foliage Plant ◽  
Reduced Light

Bamboo has increasingly become a popular exterior ornamental plant because of its durability, versatility, and evergreen qualities in conditions of extreme temperature and moisture variations. Use as an interior foliage plant has been limited due to the difficulty of finding species adaptable to lower light levels. Nineteen species from seven genera (Bambusa, Cephalostachyum, Dendrocalamus, Gigantochloa, Schizostachyum, Thyrsostachys, and Vietnamosasa) were evaluated. Fifteen plants from each species were potted in like conditions (50% leaf mold; 50% topsoil; 5 g of 14–14–14 controlled-release fertilizer) and grown under a maximum daily photosynthetic photon flux density (PPFD) range between 1200 to 2000 μmol·m-2·s-1 for 6 weeks. Chlorophyll content of leaves was measured. The commercial quality of leaves, culms, and general appearance was also recorded. Light was then limited to a maximum PPFD of 150 to 300 μmol m-2s-1 for 6 weeks and all measurements were again recorded. Five species had significant increases in chlorophyll content after the 6-week period of reduced light levels. Species with a larger maturity size had a greater mortality percentage as well as lower quality leaf and overall appearance when grown under reduced light levels. Culm quality remained constant in 18 of the 19 species after the 6-week period. Vietnamosasa ciliata showed the greatest increase in chlorophyll levels as well as highest commercial quality of leaf and overall appearance.

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