scholarly journals Growth and Physiology of Lettuce Plants Grown under Artificial Light of High Intensity in Short-Day Regime.

1995 ◽  
Vol 33 (2) ◽  
pp. 103-111 ◽  
Author(s):  
Masahisa ISHII ◽  
Tadashi ITO ◽  
Tooru MARUO ◽  
Keizoh SUZUKI ◽  
Kohzoh MATSUO
Keyword(s):  
High Intensity ◽  
Artificial Light ◽  
Short Day

A PORTABLE LIGHT FRAME FOR ARTIFICIAL ILLUMINATION OF PLANTS

1962 ◽  
Vol 42 (1) ◽  
pp. 173-175
Author(s):  
Peter W. Voisey ◽  
W. Kalbfleisch
Keyword(s):  
High Intensity ◽  
Artificial Light ◽  
Expensive Equipment ◽  
Artificial Illumination

A portable high-intensity artificial light fixture was developed to secure the maximum in flexibility and utility in this type of expensive equipment. The frame is made of aluminum, the electrical switch gear is movable and the entire assembly can be located or installed at any location where there is a source of power.

Effect of light on spring breeding of mutton merino ewes

1969 ◽  
Vol 73 (2) ◽  
pp. 177-180 ◽  
Author(s):  
H. Goot
Keyword(s):  
Birth Weight ◽  
Sexual Activity ◽  
Breeding Season ◽  
Control Group ◽  
Artificial Light ◽  
Breeding Activity ◽  
Short Day ◽  
Light Group ◽  
Effect Of Light ◽  
Length Of Gestation

SUMMARYMutton Merino ewes, all of which had lambed in the preceding in-season, were divided into two groups some 30 days after lambing.The ‘light’ group was subjected, over 84 days, to a simulated decrease in daylength, achieved by first adding artificial light to the daylight and then stepping down the light at weekly intervals, from approximately 17 h, on 22 January, to natural daylength (13 ¾ h), on 20 April 1967. The control group was exposed to the normally increasing daylength.Starting on 1 March, the ewes in both groups were ‘teased’ and hand-service commenced on 20 April.The breeding activity (oestrus, ewes lambing, lambs born and twin births) as well as the length of gestation and birth weight appeared to be unaffected by the light.It would appear that the ‘short-day’ photoperiodic theory is not applicable to all breeds of sheep, and it is suggested that in sheep with a long sexual season genetic heterozygosity may be responsible for regulating the breeding season by allowing other environmental stimuli, besides light, to trigger-off sexual activity.

Influence of length of the illumination period on root formation in cassava, Manihot utilissima Pohl.

1966 ◽  
Vol 14 (4) ◽  
pp. 251-254 ◽  
Author(s):  
G.G. Bolhuis
Keyword(s):  
Root Formation ◽  
Light Period ◽  
Artificial Light ◽  
Short Day ◽  
Weak Light

Sprouted cuttings of 6 cassava cultivars were subjected to light periods of: 10 h daylight, 10 h daylight plus 2 h weak light, 10 h daylight plus 4 h weak light and 10 h daylight plus 6 h weak artificial light, respectively, to study root formation under these conditions. The optimal light period was about 12 h; longer light periods inhibited root formation. Cassava was considered to be a short-day plant.-A.G.G.H. (Abstract retrieved from CAB Abstracts by CABI’s permission)

scholarly journals Photons from NIR LEDs can delay flowering in short-day soybean and Cannabis: Implications for phytochrome activity

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0255232
Author(s):  
Paul Kusuma ◽  
F. Mitchell Westmoreland ◽  
Shuyang Zhen ◽  
Bruce Bugbee
Keyword(s):  
Glycine Max ◽  
Plant Development ◽  
High Intensity ◽  
Near Infrared ◽  
Cannabis Sativa ◽  
Dark Period ◽  
Sensitive Species ◽  
Long Wavelength ◽  
Short Day

Photons during the dark period delay flowering in short-day plants (SDP). Red photons applied at night convert phytochromes to the active far-red absorbing form (Pfr), leading to inhibition of flowering. Far-red photons (greater than 700 nm) re-induce flowering when applied after a pulse of red photons during the dark period. However, far-red photons at sufficiently high intensity and duration delay flowering in sensitive species. Mechanistically, this response occurs because phytochrome-red (Pr) absorbance is not zero beyond 700 nm. We applied nighttime photons from near infrared (NIR) LEDs (peak 850 nm) over a 12 h dark period. Flowering was delayed in Glycine max and Cannabis sativa (two photosensitive species) by 3 and 12 days, respectively, as the flux of photons from NIR LEDs was increased up to 83 and 116 μmol m-2 s-1. This suggests that long wavelength photons from NIR LEDs can activate phytochromes (convert Pr to Pfr) and thus alter plant development.

Photoperiodicity in Suffolk sheep

1950 ◽  
Vol 40 (1-2) ◽  
pp. 143-149 ◽  
Author(s):  
D. S. Hart
Keyword(s):  
Pituitary Gland ◽  
Milk Yield ◽  
Contrast Effect ◽  
Artificial Light ◽  
Essential Factor ◽  
Short Day ◽  
Suffolk Sheep

1. A gradually decreasing plane of light and increasing plane of darkness is not an essential factor for stimulating the onset of oestrus in sheep.2. Sheep being short-day breeding animals, a standard and regularly maintained rhythm of short-light and long-dark will stimulate the onset of oestrus.3. The terms short and long are used in the relative sense only, since their significance is solely a means of supplying the necessary contrast impulse to the pituitary gland.4. A ratio of 1 part of light to 2 parts or more of dark is sufficient to supply the contrast effect.5. Oestrous cycles induced by artificial light rhythms appear to be normal in all respects, con forming to the normal intervals between heat periods and associated with the ovulation of normal ova.6. The anoestrous period varies in depth, and sheep which have just entered it may be brought back into oestrus very much faster than animals which are in deep anoestrum.7. The milk yield of lactating ewes does not appear to be unduly depressed by the onset of oestrous periods induced by an artificial light-dark rhythm.

Photoperiodism and rhythmic flower induction: complete substitution of inductive darkness by light

1969 ◽  
Vol 47 (8) ◽  
pp. 1241-1250 ◽  
Author(s):  
Bruce G. Cumming
Keyword(s):  
White Light ◽  
High Intensity ◽  
Dark Period ◽  
Flower Induction ◽  
Flower Initiation ◽  
Response Type ◽  
Short Day ◽  
Long Day ◽  
Sufficient Energy ◽  
Promotive Effect

In a short-day response type of Chenopodium rubrum (ecotype 60°47′ N), light of a relatively low red/far-red ratio—but of sufficient energy to allow photosynthesis—can bring about induction of flowering when it completely replaces a single dark period interrupting continuous white light. When high-intensity white incandescent light was interrupted for less than a 24-hour period, a longer period of inductive light than darkness was required even for minimal induction. An inductive light interruption of at least 60 hours was required for 100% flower induction. The result of such forcing of the system by inductive light, as compared with the circadian rhythmic induction that occurred in darkness, was a change towards a more linear inductive response and there were indications (requiring confirmation) of oscillations of higher frequency.When seedlings were maintained continuously in optimal inductive light or in darkness, after an initial high intensity white light period, there was some flower initiation within 5 days in inductive light, but not until about 10 days in darkness, and then only when sucrose was supplied throughout darkness.There were suboptimal and (inhibitory) supraoptimal effects on induction when the R/FR ratio and (or) the energy of inductive light were decreased or increased, respectively. These results, in conjunction with the effects that were obtained when glucose and 3(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) were applied in inductive light as compared with darkness, implicate both photosynthate and phytochrome-Pfr as having a positive (promotive) effect during normal inductive darkness.These findings emphasize that the important controls in photoperiodism and flowering may be quantitative rather than qualitative in character, because it can now be questioned whether there is any essential dark-requiring reaction in the induction not only of long-day but also of short-day plants.

Influence de l'intensité lumineuse, de la température nocturne de l'air et de la concentration en CO2 sur la croissance de semis d'épinette noire (Piceamariana) produits en récipients en serres

1993 ◽  
Vol 23 (1) ◽  
pp. 101-110 ◽  
Author(s):  
Daniel Lord ◽  
Sylvain Morissette ◽  
Jacques Allaire
Keyword(s):  
Light Intensity ◽  
Treatment Period ◽  
Air Temperature ◽  
High Intensity ◽  
Black Spruce ◽  
Artificial Light ◽  
Air Concentration ◽  
Shoot Height ◽  
Dry Biomass ◽  
High Intensity Light

Growth of containerized black spruce seedlings grown in greenhouses was studied in relation to factors known to influence plant growth. Artificial light intensity (3.80 and 72.04 μmol•m−2•s−1) and night air temperature (5, 10, 12.5, 15, and 20 °C) were considered in a first experiment and artificial light intensity (4.24 and 59.57 μmol•m−2•s−1) and CO2 air concentration (ambient and 1000 μL•L−1) in a second one. Higher light intensity and CO2 enrichment increased dry biomass of seedlings as well as growth in height and stem diameter. Both factors similarly enhanced the last two parameters since height/diameter ratios showed little variation among treatments. Reducing night air temperature down to 10 °C did not significantly influence height growth nor biomass increase when high intensity light was provided. Lower light intensity raised the threshold to 12.5 °C. Shoot height, diameter, and dry biomass as well as the number of branches and buds per millimeter were strongly reduced by a 5 °C night air temperature. High intensity light enhanced growth of containerized black spruce seedlings more than CO2 enrichment or a 5 °C night air temperature. When used simultaneously, these growth enhancing factors had a synergistic effect during most of the treatment period; thereafter, the effect became partially additive. The relative growth rate peaked at the onset of exponential shoot growth and decreased after this point. However, the enhancing factors were still efficient since absolute growth differences between seedlings grown under the most favorable conditions and controls kept increasing. The faster growing pace imposed by these growth enhancing conditions during the treatment period was maintained over the entire first growing season.

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