Continuous Green Light Research Articles

Green light mediates atypical photomorphogenesis by dual modulation of Arabidopsis phytochromes B and A.

Although green light (GL) is located in the middle of the visible light spectrum and regulates a series of plant developmental processes, the mechanism by which it regulates seedling development is largely unknown. In this study, we demonstrated that GL promotes atypical photomorphogenesis in Arabidopsis thaliana via the dual regulations of phytochrome B (phyB) and phyA. Although the Pr-to-Pfr conversion rates of phyB and phyA under GL were lower than those under red light (RL) in a fluence rate-dependent and time-dependent manner, long-term treatment with GL induced high Pfr/Pr ratios of phyB and phyA. Moreover, GL induced the formation of numerous small phyB photobodies in the nucleus, resulting in atypical photomorphogenesis, with smaller cotyledon opening angles and longer hypocotyls in seedlings compared to RL. The abundance of phyA significantly decreased after short- and long-term GL treatments. We determined that four major PHYTOCHROME-INTERACTING FACTORs (PIFs: PIF1, PIF3, PIF4, and PIF5) act downstream of phyB in GL-mediated cotyledon opening. In addition, GL plays opposite roles in regulating different PIFs. For example, under continuous GL, the protein levels of all PIFs decreased, whereas the transcript levels of PIF4 and PIF5 strongly increased compared with dark treatment. Taken together, our work provides a detailed molecular framework for understanding the role of the antagonistic regulations of phyB and phyA in GL-mediated atypical photomorphogenesis.

Melanopsin and Rod–Cone Photoreceptors Play Different Roles in Mediating Pupillary Light Responses during Exposure to Continuous Light in Humans

In mammals, the pupillary light reflex is mediated by intrinsically photosensitive melanopsin-containing retinal ganglion cells that also receive input from rod-cone photoreceptors. To assess the relative contribution of melanopsin and rod-cone photoreceptors to the pupillary light reflex in humans, we compared pupillary light responses in normally sighted individuals (n = 24) with a blind individual lacking rod-cone function. Here, we show that visual photoreceptors are required for normal pupillary responses to continuous light exposure at low irradiance levels, and for sustained pupillary constriction during exposure to light in the long-wavelength portion of the visual spectrum. In the absence of rod-cone function, pupillomotor responses are slow and sustained, and cannot track intermittent light stimuli, suggesting that rods/cones are required for encoding fast modulations in light intensity. In sighted individuals, pupillary constriction decreased monotonically for at least 30 min during exposure to continuous low-irradiance light, indicating that steady-state pupillary responses are an order of magnitude slower than previously reported. Exposure to low-irradiance intermittent green light (543 nm; 0.1-4 Hz) for 30 min, which was given to activate cone photoreceptors repeatedly, elicited sustained pupillary constriction responses that were more than twice as great compared with exposure to continuous green light. Our findings demonstrate nonredundant roles for rod-cone photoreceptors and melanopsin in mediating pupillary responses to continuous light. Moreover, our results suggest that it might be possible to enhance nonvisual light responses to low-irradiance exposures by using intermittent light to activate cone photoreceptors repeatedly in humans.

Hydrogen production with a solar steam–methanol reformer and colloid nanocatalyst

In the present study a small steam–methanol reformer with a colloid nanocatalyst is utilized to produce hydrogen. Radiation from a focused continuous green light laser (514 nm wavelength) is used to provide the energy for steam–methanol reforming. Nanocatalyst particles, fabricated by using pulsed laser ablation technology, result in a highly active catalyst with high surface to volume ratio. A small novel reformer fabricated with a borosilicate capillary is employed to increase the local temperature of the reformer and thereby increase hydrogen production. The hydrogen production output efficiency is determined and a value of 5% is achieved. Experiments using concentrated solar simulator light as the radiation source are also carried out. The results show that hydrogen production by solar steam–methanol colloid nanocatalyst reforming is both feasible and promising.

Compact and Highly Efficient Intracavity SHG Green Light Source with Wide Operation Temperature Range Using Periodically Poled Mg:LiNbO3

A compact, high power SHG green light source with wide operation temperature range over 30 degrees Celsius has been developed by using a wavelength-locked laser diode and a 0.5mm-long periodically poled Mg:LiNbO3(PPMgLN). A continuous green light of 1.7W was generated by intracavity frequency doubling of a Nd:YVO4 laser with the PPMgLN. The wall-plug efficiency was as high as 18.9%. The volume of the green light source was 2cc.

Embryonic Growth, Hatching Time and Hatchability Performance of Meat Breeder Eggs Incubated under Continuous Green Light

The effects of dark-control (D) and continuous green light (GL) exposure of incubated meat-type breeder eggs (Hybro) on embryonic growth from 5 to 15 days of age, hatching time, hatchability per cent and chick hatching weight were investigated in three consecutive experiments at 33, 38, and 41 weeks of age. A total of 798 eggs were used in this study. Eggs were set in an incubator on trays either in the D or under two tubes of 20-watt green fluorescent light during the first 18 days of incubation. Eggs from both treatments were transferred to the dark hatching compartment at 19 days of incubation. The light intensity was in the range of 1,340 to 1,730 lux at the surface of the eggs. GL incubation of eggs significantly (p<0.01) increased weight (expressed as an absolute value) and daily weight gain of embryos at 11 and continued to 15 days of age, hatchability per cent by 4.8%, reduced dead embryos per cent and chick weight at hatch by 37 and 2%, respectively and accelerated hatching time by about 24 h when compared with the D-control incubation. Chicks hatched at 504 h of incubation had significantly (p<0.01) higher body weight, expressed as an absolute value or as a percentage of egg weight, than those hatched earlier at 456 h of incubation. It was concluded that the GL incubation of meat breeder eggs reduced incubation period and chick weight at hatch and increased embryonic growth and hatchability per cent. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 12 : 1702-1707)

High-powered green light generation by intracavity frequency doubling using grating feedback optics

Grating feedback optics is shown to contribute to narrowing the spectral bandwidth of a multilongitudinal-mode laser diode to less than 0.2 nm and tuning the lasing wavelength to the peak absorption wavelength of Nd:YVO(4). A continuous green light of 31 mW was efficiently generated by intracavity frequency doubling of the Nd:YVO(4) laser with a KTiOPO(4) crystal. A relative intensity noise of less than -140 dB/Hz was obtained in the frequency region greater than 2 MHz. The noise characteristics of generated green light are discussed as compared with the case of using a single-longitudinal-mode laser diode as the pumping source.

Phototaxis of Chlamydomonas eugametos Pairs is Controlled by the mt+ Partner

Summary The swimming behaviour of dark-adapted Chlamydomonas eugametos cells in response to flashes or continuousgreen light was investigated. Both phototactic and non-phototactic gametes were analysed together with different combinations of fused gametes as vis-a-vis pairs. The movement of individual cells and whole populations was examined using a computer supported motion analysis system and a taxigraph. Cells exhibited stop responses, disoriented tumbling during light adaptation and positive phototactic swimming. The general photobehaviour of pairs was dictated by the swimming mt + cell independent of its mt - partner. Pairs adapted more slowly to light stimuli than their parents with each response phase being extended.

Effects of duration, intensity, and spectrum of light exposure on sexual maturation time of female rats.

The present study was undertaken to evaluate the effects of daily duration, intensity, and spectral composition of light exposure on the sexual maturation of female rats. Pregnant rats (Holtzman) delivered their young in a controlled environment with various illuminations of defined duration, intensity, and spectral composition. Pups were weaned at 22 days of age and separated by sex. Only females were used in the present study. They were checked for vaginal opening twice daily starting at 29 days of age. A group of 5–6 rats was sacrificed from each experimental condition 2–3 days prior to and after the expected date of vaginal opening. Results indicate that exposure to either 22 or 24 h of light/day significantly advanced vaginal opening when compared to 14-h/day exposure. No difference was obtained between animals in 6- and 14-h/day exposure. Light intensity was a significant variable at 14-h/day exposure, but not at 24 h/day. Animals exposed to 14 h of light at 100 lm/m2 matured faster than those at 30 or 600 lm/m2, but not significantly earlier than those at 2400 lm/m2. Animals in blue light exhibited vaginal opening significantly earlier than in red light if exposure was provided for 14 h/day. In continuous exposure, red light was more stimulating. No significant differences between yellow and green light were detected either with 14- or 24-h/day exposure, except for a small population of rats in continuous green light in which vaginal opening was significantly delayed. A significant seasonal variation was also detected in animals raised in white fluorescent light of 14-h/day exposure. Rats raised in the summer months showed vaginal opening significantly earlier than those in the winter. Examination of ovarian and uterine weights prior to vaginal opening revealed no significant differences with increased daily duration but equal intensity of illumination. Increasing intensity between 30 and 600 lm/m2, on the other hand, produced significantly heavier weights prior to vaginal opening. Uterine weights were heaviest at 100 lm/m2. Animals exposed to blue light had significantly heavier ovarian weights before vaginal opening than those in red light, regardless of the duration of exposure. No other differences were detected with various spectral compositions. After vaginal opening, ovarian weights were greater in 22-h/day light exposure than in either 6 or 14 h/day. However, one of two experiments revealed significantly smaller ovaries in rats kept in continuous light than in rats kept in 14 h of daily light exposure. No differences in uterine weights were noted. No differences in ovarian weights were observed following vaginal opening in animals raised in various light intensities. A significant difference in uterine weights was detected between animals raised in 30 and 100 lm/m2 of light intensity at continuous exposure. Differences in spectral composition did not result in significant differences in either ovarian or uterine weights following vaginal opening. Results are interpreted to indicate, first, that variations in the daily duration, intensity, and spectral composition of light exposure can significantly influence the age at which vaginal opening occurs and, therefore, suggest that light can play a significant role in the timing of sexual maturation and should be carefully controlled in studying the role of photoperiods in reproductive function. Secondly, the present data suggest that while in long exposures, intensity may not play a significant role, in 14-h/day-exposure intensity can be a highly significant factor. Finally, our data give no evidence for a chronic stimulation of gonadotropin release as a result of increased photoperiods, but, in the case of increased light intensity, early maturation may have resulted from increased FSH and/or LH release, as evidenced by increased ovarian and uterine weights.

Effects of Light Quality on the Circadian Rhythm of Leaf Movement of a Short-Day-Plant

Studies were made of the effects of blue, green, red and far-red (FR) light on the circadian rhythm of leaf movement of Coleus blumei x C. frederici, a short day plant. Under continuous illumination with blue light, there was a significant lengthening of the period of the rhythm to about 24.0 hr, as compared to 22.5 hr in continuous darkness. Under continuous red light, the period length was significantly shortened to 20.5 hr. Under continuous green or FR, the period length was not significantly different from the dark control. It was observed that under continuous FR illumination, the leaves tended to oscillate in a more downward position. Eight-hr red light signals were effective in advancing the phase of the rhythm as compared to a control under continuous green light. Blue light signals were effective in delaying the phase of the rhythm. FR light signals were ineffective in producing either delay or advance phase shifts. Far-red light did not reverse the effects of either red or blue light signals. On the basis of these results it is suggested, that pigments which absorb blue or red light, rather than phytochrome, mediate the effect of light on the circadian rhythm of leaf movement.