Photon Flux Ratio Research Articles

Study of Plant Cultivation Using a Light-Emitting Diode Illumination System to Control the Spectral Irradiance Distribution

In plant cultivation, the number of photons is more important than the light energy from the chemical reactions that occur during photosynthesis. In addition, the blue and red photon flux (B/R) ratio is an important parameter for plant cultivation. Here we discuss the effect of the spectral irradiance distribution and the B/R ratio on plant cultivation. We cultivated lettuce seedlings, Lactuca sativa L. Cv. Okayama, using a light-emitting diode illumination system that can precisely control the spectral irradiance distribution and B/R ratio. The B/R ratio varied from 0.36 to 2.06 according to the intensity of the blue light when the photosynthetic photon flux density values were sufficient to ensure the 150 - 200 μmol⋅m−2⋅s−1. High photon flux densities of blue light result in reduced plant length, plant height, and leaf area, thereby suggesting its role in the suppression of leaf growth. Therefore, we conclude that a lower photon flux of blue light (B/R Ratio) is optimal for lettuce cultivation.

Tomato seedling physiological responses under different percentages of blue and red photon flux ratios using LEDs and cool white fluorescent lamps

Lamp spectral customization can be a strategy to achieve desirable plant characteristics when plants are grown under sole-source electric lighting. Vegetable transplants can be efficiently and economically grown under indoor-production systems with electrical lighting; however, species-specific light recipes have to be developed to improve plant growth, development and morphology, as well as to reduce electrical consumption. The objective of this study was to evaluate the growth and morphology of tomato transplants to a broad range of blue to red (B:R) photon flux (PF) ratios under LEDs and cool white fluorescent lamps (CWF). Tomato ‘Komeett’ and ‘Beaufort’ seedlings were grown in a climate control growth chamber. Using LEDs, seven light treatments with different blue (B), green (G) and red (R) PF ratios were used: 100R, 10B:90R, 20B:28G:52R, 30B:70R, 50B:50R, 75B:25R and 100B. In addition, a CWF treatment served as the control. Hypocotyl length of ‘Komeett’ decreased with the increase of percent B PF up to 75% B. Plant leaf area was 64–72% greater under treatments emitting both B and R PF than in the 100 B and 100 R treatments. Similarly, tomato ‘Komeett’ fresh mass, dry mass, leaf number and chlorophyll concentration was comparable among the treatments containing B and R PF and greater than in 100 B and 100 R treatments. However, plant compactness in the 30B:70R treatment was 42% greater than in the 10B:90R treatment. Anthocyanin concentration increased with the increase of percent B PF up to 75% B. Also, plants in 30B:70R and 50B:50R had 39% and 36% greater dry mass than in CWF, respectively. In addition, 30B:70R and 50B:50R LEDs had 172% greater growing efficacy (gkWh−1) than high output fluorescent lamps. The addition of G light did not have any effects on tomato physiological responses. ‘Beaufort’ plant morphology and growth were severely affected by intumescences development and intumescence severity decreased under higher percentages of B PF. In summary, 30B:70R, 50B:50R were the best spectrums to produce tomato seedlings under LEDs tested here; however, plant quality under CWF, 10B:90R, 20B:28G:52R, and 75B:25R was also acceptable.

Morphological, Photosynthetic, and Physiological Responses of Rapeseed Leaf to Different Combinations of Red and Blue Lights at the Rosette Stage.

Rapeseed (Brassica napus L.) is sensitive to light quality. The factory production of rapeseed seedlings for vegetable use and for transplanting in the field requires an investigation of the responses of rapeseed to light quality. This study evaluated the responses of the leaf of rapeseed (cv. “Zhongshuang 11”) to different ratios of red-photonflux (RPF) and blue-photonflux (BPF) from light emitting diodes (LEDs). The treatments were set as monochromatic lights, including 100R:0B% and 0R:100B%, and compound lights (CLs), including 75R:25B%, 50R:50B%, and 25R:75B%. The total photonflux in all of the treatments was set as 550 μmolm−2s−1. With an increase of BPF, the rapeseed leaves changed from wrinkled blades and down-rolled margins to flat blades and slightly up-rolled margins, and the compact degree of palisade tissue increased. One layer of the cells of palisade tissue was present under 100R:0B%, whereas two layers were present under the other treatments. Compared to 100R:0B%, 0R:100B% enhanced the indexes of leaf thickness, leaf mass per area (LMA), stomatal density, chlorophyll (Chl) content per weight and photosynthetic capacity (Pmax), and the CLs with high BPF ratios enhanced these indexes. However, the 100R:0B% and CLs with high RPF ratios enhanced the net photosynthetic rate (Pn). The leaves under the CLs showed growth vigor, whereas the leaves under 100R:0B% or 0R:100B% were stressed with a low Fv/Fm (photosynthetic maximum quantum yield) and a high content of and H2O2. The top second leaves under 100R:0B% or 0R:100B% showed stress resistance responses with a high activity of antioxidase, but the top third leaves showed irreversible damage and inactivity of antioxidase. Our results showed that the rapeseed leaves grown under 0R:100B% or CLs with a high BPF ratio showed higher ability to utilize high photonflux, while the leaves grown under 100R:0B% or CLs with a low BPF ratio showed higher efficiency in utilizing low photonflux. Under different R:B photonflux ratios, red and blue lights may play mutual roles in Pn. When the blue light dominated, the Pn showed a B-preference. When the red light dominated, the Pn showed an R-preference. Furthermore, CLs were suitable for the Pn of rapeseed seedlings.

Signal photon flux generated by high-frequency relic gravitational waves**Supported by National Natural Science Foundation of China (11305181,11322545,11335012) and Open Project Program of State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, China (Y5KF181CJ1)

The power spectrum of primordial tensor perturbations increases rapidly in the high frequency region if the spectral index nt > 0. It is shown that the amplitude of relic gravitational waves ht(5 × 109 Hz) varies from 10−36 to 10−25 while nt varies from −6.25 × 10−3 to 0.87. A high frequency gravitational wave detector proposed by F.-Y. Li detects gravitational waves through observing the perturbed photon flux that is generated by interaction between relic gravitational waves and electromagnetic field. It is shown that the perturbative photon flux (5 × 109 Hz) varies from 1.40 × 10−4 s−1 to 2.85 × 107 s−1 while nt varies from −6.25 × 10−3 to 0.87. Correspondingly, the ratio of the transverse perturbative photon flux to the background photon flux varies from 10−28 to 10−16.

Far-red and Blue Light Synergistically Mitigate Intumescence Injury of Tomato Plants Grown Under Ultraviolet-deficit Light Environment

Intumescence injury is an abiotic-stress-induced physiological disorder associated with abnormal cell enlargement and cell division. The symptom includes blister- or callus-like growths on leaves, which occur on sensitive cultivars of tomato when they are grown under ultraviolet (UV)-deficit light environment, such as light-emitting diodes (LEDs). Previous studies suggest that intumescence can be reduced by increasing far-red (FR) or blue light. In the present study, effects of end-of-day FR (EOD-FR) light and high blue photon flux (PF) ratio during the photoperiod on intumescence injury were examined using ‘Beaufort’ interspecific tomato rootstock seedlings (Solanum lycopersicum × Solanum habrochaites), a cultivar highly susceptible to intumescence injury. Our study showed that EOD-FR light treatment moderately suppressed intumescence injury. Using EOD-FR light treatment, the percent number of leaves exhibiting intumescences was reduced from 62.0–70.7% to 39.4–43.1%. By combining high blue PF ratio (75%) during the photoperiod and EOD-FR light treatment, the percent number of leaves exhibiting intumescences was further suppressed to 5.0%. Furthermore, the combination of high blue PF ratio and EOD-FR light treatment inhibited undesirable stem elongation caused by EOD-FR light treatment. We found that high blue PF ratio during the photoperiod combined with a small dose of EOD-FR lighting (≈1 mmol·m−2·d−1 provided by 5.2 µmol·m−2·s−1 FR PF for 3.3 minutes) could inhibit the problematic intumescence injury of tomato plants grown under LEDs without negatively influencing growth or morphology.

End-of-day far-red lighting combined with blue-rich light environment to mitigate intumescence injury of two interspecific tomato rootstocks

Effects of end-of-day far-red (EOD-FR, 700-800 nm) light and high blue photon flux ratio during the photoperiod on intumescence injury were examined for 'Beaufort' and 'Maxifort' tomato rootstock seedlings (Solanum lycopersicum × Solanum habrochaites) grown with 13 mol m-2 d-1 daily light integral (199 µmol m-2 s-1 photosynthetic photon flux, 18 h photoperiod). The EOD-FR light treatment (1.1 mmol m-2 d-1 provided by 6.0 µmol m-2 s-1 FR photon flux for 3 min at EOD) significantly reduced intumescence injury. For example, by the EOD-FR light treatment, the incidences of leaf abscission were reduced from 88 to 8% for 'Beaufort' and from 79 to 25% for 'Maxifort'. However, EOD-FR light caused undesirable stem extension (41% greater than that without EOD-FR light). By combining relatively high B (blue, 400-500 nm) to R (red, 600-700 nm) photon flux ratio (50%B-50%R) during the photoperiod with EOD-FR light, intumescence injury was further decreased without causing undesirable stem extension. For example, the incidences of leaf abscission were reduced from 88 to 0% for 'Beaufort' and from 79 to 0% for 'Maxifort', compared to those under 10%B-90%R without EOD-FR light. Also, the percentages of leaves that exhibited intumescences were reduced from 68 to 30% for 'Beaufort' and from 55 to 19% for 'Maxifort'. Our study demonstrated that blue-rich light quality combined with a small dose of EOD-FR lighting could be applied to mitigate the problematic intumescence injury of tomato seedlings grown under LEDs.

Growth and morphology of vegetable seedlings under different blue and red photon flux ratios using light-emitting diodes as sole-source lighting

Growth and morphology of vegetable seedlings under different blue and red photon flux ratios using light-emitting diodes as sole-source lighting

Physiological responses of cucumber seedlings under different blue and red photon flux ratios using LEDs

Light emitting diodes (LEDs) are frequently regarded as a new light source for the production of horticultural crops under closed-type conditions. However, before use of LEDs as the sole source of light can be advanced, plant responses to light quality have to be investigated for important horticultural plants. The objective of the present study was to evaluate cucumber (Cucumis sativus) seedlings physiological responses to different blue (B) and red (R) photon flux (PF) ratios using LEDs. Cucumber seedlings (cv. Cumlaude) were grown in a growth chamber until the second true leaf stage (17 days) with LED lighting and 18-h photoperiod. The treatments consisted of 100μmolm−2s−1 photosynthetic photon flux (PPF) with B:R PF ratios of 0B:100R%, 10B:90R%, 30B:70R%, 50B:50R%, 75B:25R%, 100B:0R%. Another treatment consisted of B, green (G) and R PF ratio of 20B:28G:52R%. Peak wavelengths of LEDs were 455nm (B) and 661nm (R) for the in the B:R treatments and 473nm (B), 532nm (G), 660nm (R) in the B:G:R treatment. Hypocotyl length decreased with the increase of B PF up to the 75B:25R% treatment. Hypocotyl length in the 0B:100R% treatment was 164% greater than in the 75B:25R treatment. Plants under the 100B:0R% treatment had unexpected greater plant height, hypocotyl, and epicotyl length than plants under all other treatments. For example, the hypocotyl length under the 100B:0R% was 69% greater than in the 0B:100R treatment and 346% greater than in the 75B:25R% treatment. Leaf area decreased with the increase of B PF when plants were irradiated with the combination of B and R PF. The response of leaf area under the 100B:0R% treatment was unexpected since plants in the 100B:0R% treatment had 48% greater leaf area than plants in the 75B:25R% treatment. Chlorophyll content per leaf area, net photosynthetic rate, and stomatal conductance increased with the increase of B PF. Shoot dry and fresh mass decreased with the increase of B PF when plants were irradiated with the combination of B and R PF. Plants under 0B:100R% had the lowest dry and fresh mass from all the treatments and plants under 100B:0R% showed the greatest fresh mass from all the treatments and equal dry mass as the plants under 10B:90R% treatment. The addition of G PF to the spectrum did not have any influence in cucumber plant responses. For cucumber seedlings, morphological responses influenced plant growth since B PF responses in growth parameters (i.e., dry mass) closely matched those in morphological parameter (i.e., leaf area). More research is needed to find the optimal spectrum for the growth and development of horticultural crops under sole source electrical lighting such as LEDs.

Growth and morphological response of cucumber seedlings to supplemental red and blue photon flux ratios under varied solar daily light integrals

High intensity light-emitting diodes (LEDs) have the potential to be used as supplemental lighting technology in greenhouses. However, LED light quality requirements of greenhouse crops grown when supplementing the solar spectrum are unknown. In this study, to find the requirements, cucumber (Cucumis sativus L. cv. Cumlaude) seedlings were grown in a greenhouse with and without supplemental LED lighting (PPF: 54±1.1μmolm−2s−1) at varied blue (400–500nm with the peak at 455nm) and red (600–700nm with the peak at 661nm) photon flux (PF) ratios (B:R ratios) under different solar daily light integrals (DLI). The treatments were 0B:100R% (54μmolm−2s−1 red PF), 4B:96R% (2.3 and 52μmolm−2s−1 blue and red PF, respectively), 16B:84R% (8.5 and 46.2μmolm−2s−1 blue and red PF, respectively), and a control without supplemental lighting. The solar DLIs during the experiment were 5.2±1.2 and 16.2±5.3molm−2d−1 created inside a greenhouse using shade screen. Regardless of B:R ratio, morphological and growth parameters of the seedlings were all improved under supplemental LED lighting compared to the no-supplemental-light control. Under high DLI conditions, no significant differences were found for any parameters between the different B:R ratios. Under low DLI, chlorophyll concentration increased with increasing B:R ratio (i.e., increasing blue PF without increasing photosynthetic photon flux, PPF) of the supplemental lighting. Dry mass, leaf number, and leaf area decreased with increasing B:R ratio under low DLI conditions. The reduction in dry mass and leaf number were attributed to the reduction in leaf area. Leaf net photosynthetic rate measured under ambient CO2, ambient temperature, and 1000μmolm−2s−1 PPF (light source: tungsten halogen lamp) also showed no difference among treatments of B:R ratios, indicating that B:R ratio treatments did not cause any changes in plant photosynthetic apparatus. When used for supplemental lighting in the greenhouse, use of 100% red LED is preferred for cucumber seedlings, and additional blue LED was not beneficial.

Studying the energy dependence of intrinsic conversion efficiency of single crystal scintillators under X-ray excitation

Single crystal scintilators are used in various radiation detectors applications. The efficiency of the crystal can be determined by the Detector Optical Gain (DOG) defined as the ratio of the emitted optical photon flux over the incident radiation photons flux. A parameter affecting DOG is the intrinsic conversion efficiency (nC) giving the percentage of the X-ray photon power converted to optical photon power. nC is considered a constant value for X-ray energies in the order of keV although a non-proportional behavior has been reported. In this work an analytical model, has been utilized to single crystals scintillators GSO:Ce, LSO:Ce and LYSO:Ce to examine whether the intrinsic conversion efficiency shows non proportional behavior under X-ray excitation. DOG was theoretically calculated as a function of the incident X-ray spectrum, the X-ray absorption efficiency, the energy of the produced optical photons and the light transmission efficiency. The theoretical DOG values were compared with experimental data obtained by irradiating the crystals with X-rays at tube voltages from 50 to 140 kV and by measuring the light energy flux emitted from the irradiated screen. An initial value for nC (calculated from literature data) was assumed for the X-ray tube voltage of 50 kV. For higher X-ray tube voltages the optical photon propagation phenomena was assumed constant and any deviations between experimental and theoretical data were associated with changes in the intrinsic conversion efficiency. The experimental errors were below 7% for each experimental setup. The behavior of nC values for LSO:Ce and LYSO:Ce were found very similar, i.e., ranging with values from 0.089 at 50 kV to 0.015 at 140 kV, while for GSO:Ce, nC demonstrated a peak at 80 kV.

The spectral ratio of red, green, and blue photon fluxes to the total flux of photosynthetic photons and the ratio of red to far-red photon fluxes of sunlight at Ayabe, Kyoto

The spectral ratio of red, green, and blue photon fluxes to the total flux of photosynthetic photons and the ratio of red to far-red photon fluxes of sunlight at Ayabe, Kyoto

New application of optical agent to image angiogenesis in hindlimb ischemia

Optical agents targeting α(v)β₃ are potential tools to image the angiogenic response to limb ischemia. The left (L) femoral artery was ligated in 17 mice and sham surgery performed on the contralateral right (R) hindlimb. Seven days later, IntegriSense (2 nmol) was injected into 11 mice and 6 were probe controls. Six hours later, mice underwent optical imaging. Ratios of photon flux in the L/R limbs were calculated. Tissue was stained for α(v) , CD31, and lectin. The signal was increased in the ischemic limbs compared to contralateral legs and ratio of photon flux in L/R limb averaged 2.37. Control probe showed no hindlimb signal. IntegriSense colocalized with CD31 by dual fluorescent staining. Ratios for L/R hindlimbs correlated with quantitative lectin staining (r = 0.88, p = 0.003). Optical imaging can identify and quantify angiogenic response to hindlimb ischemia.

Photo-induced Ag deposition on periodically poled lithium niobate: Concentration and intensity dependence

This research focuses on the formation of Ag nanopatterns on periodically poled lithium niobate (PPLN). The photo-induced process employs UV-light exposure while the PPLN is immersed in a AgNO3 solution. The Ag deposition was consistent with previous results, showing preferential deposition along the domain boundary as well as an increased density of particles on the positive domain surface in comparison to the negative domain. By tuning the chemical solution concentration and the UV-light intensity, the Ag+ ion flux and the electron flux are varied and the deposition pattern could be controlled to either enhance the nanowire-like structures along the domain boundary or create a more uniform deposition pattern over the positive and negative domains. To understand the deposition process, we investigated the relationship between the Ag+ ion flux because of diffusion and the electron flux initiated by the UV exposure of the ferroelectric surface. The subsequent results suggest that this relationship is responsible for the different deposition patterns. The observed variation of boundary-enhanced or boundary-depressed deposition is explained by consideration of the electric field distribution and the ratio of the Ag+ ion and photon flux. The results establish that the ratio can be controlled by varying the solution concentration and/or UV-light intensity to generate enhanced nanowire-like structures along the domain boundary or a more uniform deposition pattern over the positive and negative surface. Moreover, the specific value of the Ag+/photon flux ratio where the pattern changes is dependent on other factors including the nucleation limited growth mechanism and the Stern layer on the lithium niobate.

Responses of the invasive Ricinus communis seedlings to competition and light

Ricinus is an invasive species. We assessed its responses to intra- and interspecific competition, and different intensities and spectral qualities of light. To evaluate resource portioning, we obtained biomass measurements of juveniles in different densities of co-specifics and another species; we also compared the proportion of juveniles to determine if there is recruitment limitation. We obtained the same information for juveniles growing in different photosynthetic photon flux densities (PPFD) and ratios of red to far-red wavelengths (R/FR). Competition and light did not limit recruitment, resulting in differences in biomass allocation only. Biomass decreased more for plants subjected to interspecific competition than to intraspecific competition, suggesting that Ricinus is both a poor intra- and interspecific competitor. Juveniles growing under reduced PPFD and R/FR differed in biomass allocation and morphology as do shade-intolerant species subjected to shading. Our results show that Ricinus presents high plasticity, which may contribute to its invasion ability.

Photochemical and photophosphorylation activities of chloroplasts and leaf mesostructure in Chinese cabbage plants grown under illumination with light-emitting diodes

Leaf mesostructure, photochemical activity, and chloroplast photophosphorylation (PP) in the fourth true leaf of 28-day-old Chinese cabbage (Brassica chinensis L.) plants were investigated. Plants were grown under a light source based on red (650 nm) and blue (470 nm) light-emitting diodes (LED) with red/blue photon flux ratio of 7: 1 and under illumination with high-pressure sodium lamp (HPSL) at photon flux densities of 391 ± 24 μmol/(m2 s) (“normal irradiance”) and 107 ± 9 μmol/(m2 s) (“low irradiance”) in photosynthetically active range. At normal irradiance, the leaf area in plants grown under HPSL was twofold higher than in LED-illuminated plants; other parameters of leaf mesostructure were little affected by spectral quality of incident light. The lowering of growth irradiance reduced the majority of leaf mesostructure parameters in plants grown under illumination with HPSL, whereas in LED-illuminated plants the lowered irradiance reduced only specific leaf weight but increased the leaf thickness and dimensions of mesophyll cells and chloroplasts. The photochemical activity of isolated chloroplasts was almost independent of growth irradiance and light spectral quality. Light quality and intensity used for plant growing had a considerable impact on PP in chloroplasts. At normal light intensity, the highest activity of noncyclic PP in chloroplasts was observed for plants grown under HPSL; at low light intensity the highest rates of PP were noted for plants grown under LED. The P/2e− ratio, which characterizes the degree of PP coupling to electron transport in the chloroplast electron transport chain, showed a similar pattern. Thus, the narrow-band spectrum of the light source had little influence on leaf mesostructure and electron transport rates. However, this spectrum significantly affected the chloroplast PP activity. The PP patterns at low and normal light intensities were opposite for plants grown under LED and HPSL light sources. We suppose that growing plants under LED array at normal light intensity disturbed the chloroplast coupling system, thus preventing the effective use of light energy for ATP synthesis. At low light intensity, chloroplast PP activity was significantly higher under LED illumination, but plant growth was suppressed because of impaired adaptation to low light intensity.

RHESSIMicroflare Statistics. I. Flare‐Finding and Frequency Distributions

We present the first in-depth statistical survey of all X-ray microflares observed by RHESSI between 2002 March and 2007 March, a total of 25,705 events, an order of magnitude larger then previous studies. These microflares were found using a new flare-finding algorithm designed to search the 6-12 keV count rate when RHESSI's full sensitivity was available in order to find the smallest events. The peak and total count rate are automatically obtained along with count spectra at the peak and the microflare centroid position. Our microflare magnitudes are below GOES C class, on average GOES A class (background subtracted). They are found to occur only in active regions, not in the quiet Sun, and are similar to large flares. The monthly average microflaring rate is found to vary with the solar cycle and ranges from 90 to 5 flares a day during active and quiet times, respectively. Most flares are found to be impulsive (74%), with rise times shorter than decay times. The mean flare duration is ~6 minutes with a 1 minute minimum set by the flare-finding algorithm. The frequency distributions of the peak count rate in the energy bands, 3-6, 6-12, and 12-25 keV, can be represented by power-law distributions with a negative power-law index of -->1.50 ± 0.03, -->1.51 ± 0.03, and -->1.58 ± 0.02, respectively. We find that these power-law indices are constant as a function of time. The X-ray photon spectra for individual events can be approximated with a power-law spectrum [ -->dJ/d(hν) ~ (hν)−γ]. Using the ratio of photon fluxes between 10-15 and 15-20 keV, we find -->4 -1.7 ± 0.1. We estimate the total energy flux deposited in active regions by microflare-associated accelerated electrons (>10 keV) over the five years of observations to be, on average, below 1026 erg s−1.

Influence of pressure on the relative population of the two lowest vibrational levels of the C 3 Πu state of nitrogen for electron beam excitation

Continuous and pulsed 12 keV electron beams were used to excite nitrogen within a gas cell at pressures ranging from 10 to 1400 hPa. The pressure dependence of the ratio of photon fluxes for emission from vibrational levels v'=0 and 1 of the C 3Π u state has been studied. The results confirm the presence of a collisional excitation mechanism populating v'=0, 1 in addition to electron impact excitation. Rate constants of (1.27 ±0.04)×10-11 cm3s-1 [ v'=0] and (2.68 ±0.08)×10-11 cm3s-1 [ v'=1] were measured for C 3Π u quenching by ground state nitrogen. For electron beam conditions relative excitation efficiencies of 1:0.59:0.22 for vibrational levels 0, 1 and 2 were calculated. The recorded flux ratios are compared with the predictions given by a vibrational relaxation model.

Growth Promotion for Seedling of Vegetable Plants with Supplemental Lighting

A supplemental lighting system was installed at a large-scale seedling greenhouse (12.5 m×45 m), which supplies high quality and large quantity of seedlings to farmers through out the year. A test experiment of supplemental lighting for seedlings in this house was performed during the rainy season and winter-early spring to prepare for planting, when sunshine is sometimes insufficient. A mercury-free high pressure sodium lamp of 400W with a red to far-red photon flux (R/FR PF) ratio of 1.1 was developed and manufactured for this experiment. The average PPFD was 100μmol m-2 s-1. The experimental plants were lettuce, broccoli, and cabbage. In both rainy and winter-early spring experiments, we found that supplemental lighting was effective for seedling growth. Significant supplemental lighting effects in the rainy season were found for broccoli. Top fresh weights of both a 2h lit area before sunrise and after sunset were 30-60% greater than those of the non-lit area. A drop test of lettuce demonstrated that the remaining ratio of soil of both a 2h lit area before sunrise and after sunset were about 87%, and those of the non-lit areas were about 78%. Thus, good growth in roots was found. A significant supplemental lighting effect in winter-early spring was found in the lettuce experiment. Top fresh weights of both a 3h lit area before sunrise and after sunset were 165-200% greater than those of the non-lit area. In winter-early spring experiments, a clear difference between a 3h lit area before sunrise and after sunset was not found.

TeV neutrinos from supernova remnants embedded in giant molecular clouds

The recent detection of γ-rays with energy up to 10 TeV from dense regions surrounding some supernova remnants (SNR) provides strong, though still not conclusive, evidence that the nucleonic component of galactic cosmic rays is accelerated in the supernova outflows. Neutrino telescopes could further support the validity of such scenario by detecting neutrinos coming from the same regions. We re-evaluate the TeV range neutrino–photon flux ratio to be expected from pion decay, finding small differences respect to previous derivations. We apply our results and the recent HESS measurements of the very high energy γ-ray flux from the molecular cloud complex in the galactic centre, to estimate the neutrino flux from that region discussing the detectability perspectives for Mediterranean neutrino telescopes. We also discuss under which conditions neutron decay may give rise to a significant TeV antineutrino flux from a SNR embedded in molecular cloud complexes.

Development of Practical Plant Factory with Artificial Supplemental Lighting System for the Growth of Vegetable Seedlings

For stable mass production of vegetable seedlings with good quality, a commercial greenhouse nursery needs a supplemental lighting system that is not affected by light fluctuations under natural solar conditions. Therefore, a practical plant nursery covering a 12 × 24 m area, and using a supplemental lighting system, was developed for the growth of vegetable seedlings. The developed lighting system had 400-W mercury-free, high pressure sodium lamps with reflectors, which produced a red radiation to far-red radiation photon flux (R/FR PF) ratio of 1.1. This is similar to that of solar radiation. And over about 60 μmol m-2 s-1 of PPFD was realized for stable and healthy growth of vegetable seedlings. By using a simulation model of horizontal distribution of PPFD on two cultivation beds (each bed area: 4.6 × 22.6 m) under 100 lamps, it was found that the system had high uniformity of lighting on the two beds. Observed value of illuminance and PPFD and uniformity also satisfied the planned specifications. By repeating a seedling growth experiment using various plants in this greenhouse, it is expected that the practical and effective use of this supplemental lighting system will be possible in rainy seasons or in the late winter period.