Endogenous circannual rhythms and photorefractoriness of testis activity, moult and prolactin concentrations in mink (Mustela vison).

Mink are seasonal photosensitive breeders; testis activity is triggered when days have less than 10 h light. Increasing and decreasing plasma concentrations of prolactin induce the spring and autumn moults. In a 5 year experiment, males were maintained under short days (8 h light:16 h dark) at 13 degrees C or long days (16 h light:8 h dark) at 21 degrees C, winter and summer conditions, respectively. Under winter and summer conditions, circannual cycles of prolactin secretion and moulting were observed at intervals of about 11 months. Recurrence of testis cycles was not evident. In a second experiment, males were maintained under an 8 h light:16 h dark cycle from the winter solstice or under 10 h light:14 h dark, 12 h light:12 h dark or 14 h light:10 h dark cycles from 10 February. Under 8 h light:16 h dark cycle, testis regression was slightly later than under natural conditions, indicating photorefractoriness. However, mink remained sensitive to light: the longer the photoperiod, the faster the testis regression. In a third experiment, males were transferred under 8 h light:16 h dark or 16 h light:8 h dark from 15 May (group 1), 12 June (group 2) or 4 July (group 3); males submitted to long days received melatonin capsules on the day of transfer. Increasing concentrations of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) and testis volume were shown by half the males in group 2 and nearly all the males in group 3; the constant release of melatonin from implants was more efficient than short days; but in the three groups, prolactin concentrations decreased in the few days after short-day or melatonin treatment. Overall, the results demonstrate endogenous circannual rhythms of prolactin secretion, body weight and moulting. Although a refractory period to short days was observed, the annual cycle of testis activity totally relies on the annual changes in daylength.     

Circadian rhythm of lactate dehydrogenase in rat testis

Activity of total lactate dehydrogenase (LDH) and of the isozyme X (LDH X or C4) have been determined at 2 hr intervals during 24 hr cycles in testis of adult rats maintained since birth in a photoperiod of 14 hr light: 10 hr dark. LDH X activity of epididymal sections (caput, corpus and cauda) from the same animals was also determined. Total LDH and LDH X activities in testis exhibited circadian rhythms with different timing. LDH X in the three portions of epididymis showed diurnal variations similar to those in testis. Rats subjected to constant light or constant dark presented marked modifications of LDH X profiles, indicating that the photoperiod plays a synchronizer role. While total soluble proteins did not show variations in testis of rats exposed to the photoperiod, a circadian rhythm was demonstrated in animals maintained in constant light or dark.     

Rhizome transition to storage organ is under phytochrome control in lotus <Emphasis Type="Italic">(Nelumbo nucifera)</Emphasis>

We examined photoperiodic response of lotus (Nelumbo nucifera) rhizome morphogenesis (its transition to a storage organ) by using seed-derived plants. Rhizome enlargement (increase in girth) was brought about under 8, 10 and 12 h photoperiods, whereas the rhizomes elongated under 13 and 14 h photoperiods. Rhizomes elongated under 14 h light regimes supplied as 8 h of natural light plus 6 h supplemental hours of white, yellow or red light, but similar treatments with supplemental blue, green or far red light, caused enlargement in girth of the rhizomes. A 2 h interruption of the night with white, yellow or red light, in plants entrained to 8 h photoperiod brought rhizome elongation, whereas 2 h-blue, green or far red light night breaks still resulted in rhizome increase in girth. The inhibitory effect of a red (R) light night break on rhizome increase in girth was reversed by a far-red (FR) light given immediately afterwards. Irradiation with R/FR/R inhibited the rhizome increase in girth. FR light irradiation following R/FR/R irradiation cancelled the effect of the last R light irradiation. It was demonstrated that the critical photoperiod for rhizome transition to storage organ is between 12 and 13 h photoperiod. It was also evident that the optimal light quality range for interruption of dark period (night break) is between yellow and red light and that a R/FR reversible reaction is observed. From these results, we propose that phytochrome plays an important role in photoperiodic response of rhizome increase in girth in lotus. This is the first report on phytochrome-dependent morphogenesis of storage organs in rhizomous plants.     

Effects of duration of daily illumination on reproductive organs and fertility of the meadow vole (Microtus pennsylvanicus).

The objective of this study was to determine the optimum simple, constant photoperiod for voles in a laboratory colony. Voles from an established colony maintained at 22 degrees C with a photoperiod of 14:10 hours of light:dark were transferred at 50 days of age to a photoperiod of 12:12, 14:10, 16:8 or 18:6 hours of light:dark. From Day 96 to Day 102, the 9--10 females per treatment group were paired with a male. Body and gonadal weights, spermatogenesis, ovarian activity and pregnancy were evaluated on Day 110. Reproductive function and body weight of both male and female voles maintained on a photoperiod of 16:8 exceeded (p less than 0.05) values for voles exposed to 12:12 hours of light:dark and tended to be more favorable than for voles in the 14:10 and 18:6 groups.     

光因子对石刁柏愈伤组织生长过程中蛋白质含量及酶活性变化的影响

在不同的光因子条件下,石刁柏愈伤组织的生长曲线均呈“Ｓ”型。愈伤组织的可溶性蛋白质含量以黄光最高,其次为蓝光、黑暗、白光、绿光、红光。在蓝光、黄光、红光条件上,愈伤组织的非特异性酯酶活性均出现３个峰、而绿光、白光、黑暗条件下则出现２个峰,以第２７天的峰植相比,其峰植的大小顺序为：黄光、蓝光、白光、红光、绿光、黑暗。除红光为２个过氧化物酶活性峰外,其他均为１个活性峰,其峰值的大小顺序是：黄光、蓝光、     

Influence of ambient light on the evolution of colour signals: comparative analysis of a Neotropical rainforest bird community

Rainforests offer two contrasted light environments: a bright canopy rich in blue and UV and a dark understorey, rich in green and orange. Therefore, natural selection for crypsis should favour dark brown signals in understorey and bright green signals in canopy, whereas sexual selection for conspicuousness should favour bright yellow‐red signals in understorey and dark blue and UV signals in canopy. Using spectrometry and comparative analyses, we examined the relationship between ambient light and colour signals in a bird community of French Guiana. It appears that brightness and hue are mostly naturally selected, while UV content of plumage is more likely sexually selected. At each height, both sexes present similar coloration but males display more conspicuous sexually selected patterns than females. These results show that ambient light drives the evolution of colour signals at community scale, and should be considered when studying signalling in other communities and light‐contrasted ecosystems.     

Precocious recrudescence of seminal vesicle and testis in catfish, Clarias batrachus (Linn.), subjected to a long photoperiod regime

The catfish C. batrachus were exposed to a long photoperiod of 14 hr light during resting--early preparatory (December-February) phases of the reproductive cycle. At 70-day sampling, both the seminal vesicle (SV) and testis registered marked stimulatory effects in comparisons to control fish maintained under approximately 10.55 L:13.45D as shown by the increased size and weight. In both the SV and testis, concentrations of total proteins, fructose, hexosamines, and sialic acid were significantly high compared to those of the control fish indicating increased activities of the organs. Serum levels of gonadotropin-II, testosterone, and estradiol-17 beta were significantly high in the long photoperiod group. The results show that exposure to long photoperiod can stimulate early development of both the SV and testis by activating the pituitary--gonadal axis.     

Effects of environmental colour on growth of Nile tilapia, Oreochromis niloticus (Linnaeus, 1758), maintained individually or in groups

Examined was the influence of different colours of light on the growth of adult Nile tilapia (Oreochromis niloticus) held either individually (initial size 12.8 ± 1.1 cm; 62.9 ± 15.6 g) or in groups (initial size 7.8 ± 0.8 cm; 17.2 ± 6.4 g). Various colours (blue 434.5 nm, violet 430.0 nm, red 609.7 nm, green 525.2 nm and yellow 545.2 nm) did not affect weight gain of fish held individually (initial to final weights: blue 62.5 ± 18.4 to 72.9 ± 16.0 g, violet 63.5 ± 17.8 to 78.0 ± 19.1 g, green 62.1 ± 13.0 to 72.9 ± 15.7 g, and yellow 60.4 ± 20.4 to 71.0 ± 21.1 g); red seemed to restrict growth (initial to final weights: 65.8 ± 13.3 to 71.8 ± 10.8 g). Final weight differences were observed among individuals in groups maintained under blue, violet, red and green light (smaller and larger fish: blue 13.2 ± 5.0 and 18.9 ± 7.0 g, violet 17.3 ± 5.2 and 23.8 ± 4.7 g, red 14.7 ± 3.3 and 23.9 ± 4.7 g, and green 19.4 ± 7.8 and 28.6 ± 8.1 g); however, under the yellow light there were no differences in final weights (smaller fish 19.1 ± 4.8 g; larger fish 26.2 ± 5.2 g). Under the red light, heterogeneity in growth was observed earlier than with the other colours. It is therefore suggested that the red colour might have some harmful effects on Nile tilapia growth, limiting weight gain when fish are individually maintained, and with weight differences increasing when fish are held in groups. On the other hand, the yellow light seems to be positive for Nile tilapia, as it appears not to affect individually‐held fish, but reduces variation in growth of group‐maintained fish, promoting growth homogeneity.     

Light-quality effects on Arabidopsis development. Red, blue and far-red regulation of flowering and morphology

Arabidopsis thaliana (L.) Heynh. race Columbia plants were grown in red. blue, red + far-red, blue + far-red and various light mixtures of red + blue + far-red light under 14 h light/10 h dark photoperiods. Each single light source and light mixture maintained a constant irradiance (50 μmol m⁻² s⁻¹) and the mixtures of red + blue + far-red maintained a constant ratio of red/far-red light, but varied in the ratio of blue to red + far-red light. Depending on the method used for calculation, values of the fraction of phytochrome in the far-red absorbing form (P_fr/P_tot) for these light mixtures were either constant or decreased slightly with increasing percentage of blue light in the mixtures. Arabidopsis flowered early (20 days) in blue, blue + far-red and red + far-red light and late (55 days) in red light. In mixtures of red + blue + far-red light, each of which established a nearly constant P_fr/P_tot flowering was in direct relation to time and irradiance level of blue light. Leaf area and petiole length were also correlated with blue light irradiance levels.     

Neuroimmunology: modulation of the hamster immune system by photoperiod

Groups of adult male Syrian hamsters were kept in a long photoperiod (LD 14:10) or a short photoperiod (LD 10:14). After 12 weeks, half of the animals in each light:dark cycle were immunized with an immunogenic amino acid polymer. Exposure to short photoperiod was associated with a significant reduction in testicular, accessory sex organ, splenic and brown fat weights. However, photoperiod length did not influence whole body, thymic, adrenal or kidney weights. Spleens of immunized animals in the long photoperiod were significantly heavier than those of unimmunized animals in the long photoperiod, and both were heavier than spleens from immunized or unimmuized animals in the short photoperiod. This reflected increased splenic lymphocyte and macrophage counts. However, there was no difference in antibody production between animals kept in different photoperiods. These results demonstrate that the daily photoperiod length affects both hamster reproductive competence as well as selected immune parameters (splenic weight and mononuclear cell hyperplasia) but does not alter antibody production.     

Characterization of the laser-induced blue, green and red fluorescence signatures of leaves of wheat and soybean grown under different irradiance

The blue, green and red fluorescence emission of green wheat ( Triticum aestivum L. var. Rector) and soybean leaves ( Glycine max L. var. Maple Arrow) as induced by UV light (nitrogen laser: 337 nm) was determined in a phytochamber and in plants grown in the field. The fluorescence emission spectra show a blue maximum near 450 nm, a green shoulder near 530 nm and the two red chlorophyll fluorescence maxima near 690 and 735 nm. The ratio of blue to red fluorescence, F450/F690, exhibited a clear correlation to the irradiance applied during the growth of the plants. In contrast, the chlorophyll fluorescence ratio, F690/F735, and the ratio of blue to green fluorescence, F450/F530, seem not to be or are only slightly influenced by the irradiance applied during plant growth. The blue fluorescence F450 only slightly decreased, whereas the red chlorophyll fluorescence decreased with increasing irradiance applied during growth of the plants. This, in turn, resulted in greatly increased values of the ratio, F450/F690, from 0.5 – 1.5 to 6.4 – 8.0. The decrease in the chlorophyll fluorescence with increasing irradiance seems to be caused by the accumulation of UV light absorbing substances in the epidermal layer which considerably reduces the UV laser light which passes through the epidermis and excites the chlorophyll fluorescence of the chloroplasts in the subepidermal mesophyll cells.     

Periodicity of reproductive behaviour by the blue tilapia,Oreochromis aureus

Synopsis Oreochromis aureus exhibits a diel periodicity of spawning when maintained on a controlled 14:10 light:dark photoperiod, with a peak in spawning activity during the 11th hour of light. That this periodicity of spawning is a response to light is supported by phase-shifting the light cycle by seven hours. This results in a corresponding shift in the times of spawning.     

Effects of short photoperiod on ATPase activities in the testis of the immature Siberian hamster.

The effects of changes in photoperiod length upon body weight; spleen, thymus, and testis weights; testis protein content; testis cation pump enzyme activities; and plasma testosterone were studied in the developing Siberian hamster, Phodopus sungorus. Male hamsters were exposed to a cycle of 16L:8D (long-day), until Day 18 when half were switched to a 10L:14D (short-day) cycle, until killed 0, 2, 4, 7, 10, 12, or 15 days later. Body weight and relative testis weight (expressed as percentage of body weight) increased steadily during the first week of exposure. After 10 days, the long-day hamsters consistently weighed more (p less than 0.05). Relative testis weights in the short-day group began to decrease (p less than 0.005) within 10 days and continued to decline. Testis homogenate K(+)-pNPPase- (as a measure of Na+,K(+)-ATPase) and Mg(2+)-pNPPase-specific activities closely paralleled testis weight, with the short-day animals (p less than 0.05) differing after 10 days. Plasma testosterone levels remained below adult levels through exposure Day 15, but were relatively lower (p less than 0.05) in the short-day group after 10 days. Spleen weights were similar for the long- and short-day groups. The short-day group had larger thymus weights after 12 days (p less than 0.05), but thymus enzyme activities did not differ between the two groups. We conclude that cation pump activities in the Siberian hamster testis are significantly affected by changes in photoperiod length.     

Photoperiod influences endogenous indoleamines in cultured green alga Dunaliella bardawil

Effect of light intensity and photoperiod on growth, indoleamines and carotenoid production was studied in unicellular green algae D. bardawil. Maximum biomass and carotenoid contents were found when cultures were grown in light (intensity of 2.0 Klux) at a photoperiod of 16/8h light and dark cycle. There was a profound influence of tested photoperiod conditions of light:dark viz. 8:16, 10:14, and 12:12 hr, continuous light on indoleamines (SER and MEL) production as estimated by HPLC and confirmed by mass spectral data obtained from LC-MS-ESI studies. Serotonin level increased from 908 to 1765 pg/g fresh wt with increase in light duration and melatonin level increased from 267 to 584 pg/g fresh wt during increase in dark phase. Carotenoids production was high in continuous light than other tested conditions.     

Green light stimulates somatic growth in the barfin flounder Verasper moseri

We examined the effects of different light wavelengths-blue, green, and red-on the somatic growth of the barfin flounder Verasper moseri, a flatfish. The light sources used were fluorescent lamps and a combination of daylight and fluorescent lamps that produced ambient light. These light sources were filtered using blue, green, or red filters. During the experiments, the fish were reared in indoor tanks with running seawater of natural temperature and fed with commercial pellets twice daily until satiety. The tanks were white in color. Fish were exposed to constant light emitted from the fluorescent lamps (9:15, light:dark; 08:00-17:00, light) for 14 weeks from October or September to January or to ambient light with a 14-week natural photoperiod from September to December. The wavelengths that were filtered from the fluorescent lamp light modified the growth of the fish, i.e., fish reared under green or blue light exhibited a greater total length (TL; P<0.01) and body weight (BW; P<0.01) than those reared under red light. In contrast, in the case of fish exposed to filtered ambient light, fish reared under green light exhibited a greater TL (P<0.01) and BW (P<0.01) than fish exposed to other wavelengths-blue-, red-, and nonfiltered ambient light. Our results indicate that flounder growth was modified by certain wavelengths, namely, green and red light, which had growth-stimulating and growth-inhibiting effects, respectively.     

Ecology of Indian desert

Summary In the present study, the effect of different photoperiods: 3, 6, 9, 12 and 18 hr followed by a dark period in a 24 hr cycle, as well as total darkness, continuous light and diffuse light in relation to growth behaviour was observed in Solanum surattense. The influence on the pattern of root and shoot development, stomata, chlorophyll content, green weight, dry weight, fresh weight, monosaccharides, total nitrogen have been analysed. It appeared that a photoperiod of 12 hr brought about optimum growth in this species.     

Photoperiodic regulation of receptacle induction in Sargassum horneri (Phaeophyceae) using clonal thalli

We developed a clonal culture of Sargassum horneri to investigate the effect of photoperiod on reproduction in this species. Regenerated vegetative thalli were obtained using lateral branches excised from a thallus grown from a single embryo under short‐day conditions (SD = 10:14 h light : dark cycle). Lateral branches excised from the SD‐regenerated thallus became vegetative thalli that remained in that phase as long as they were cultured under SD. When an excised lateral branch was cultured under long‐day conditions (LD = 14:10 h light : dark cycle), it began to enter the reproductive phase while still less than 50 mm long. Induction of the reproductive phase was accompanied by a distinctive morphological change – suppression of blade formation at the apical region of the branch; elongation of branches without blades was then followed by differentiation of receptacles bearing conceptacles on their surface. Apices of receptacles were able to interconvert between reproductive and vegetative phases, as blades resprouted upon transfer from LD to SD. The critical day length for induction of receptacle formation was between 13 and 14 h; receptacle formation was also induced under SD conditions with night breaks (NBs). These results strongly suggest that reproductive regulation of S. horneri is a photoperiodic long‐day response. NBs with blue and green light were effective for reproductive induction but not with red light. This suggests that blue‐ and/or green‐light photoreceptors are involved in the photoperiodic reproductive response of S. horneri.     

Light-quality and irradiance effects on pigments, light-harvesting proteins and Rubisco activity in a chlorophyll- and light- harvesting-deficient soybean mutant

Soybean ( Glycine max [L.] Merrill) plants, normal green (Clark L1) and mutant yellow (Clark y₉y₉), were grown in (1) full-spectrum solar irradiation; (2) either red plus far-red or blue plus far-red; (3) either red or blue light with no far-red light. Young leaves harvested from first (1TF) trifoliolate or fifth (5TF) trifoliolate stages of development showed that the mutant plants express pigment and protein deficiencies as a direct function of irradiance. Response of the mutant to light quality indicates that blue light slightly enhances expression of the mutation at higher irradiances. Direct response of light-harvesting proteins of photosystem 2 (LHCP2) and light-harvesting protein of photosystem 1 (LHCP1) to light quality increases the ratio of LHCP1/LHCP2 in blue light compared to that in red or red/far-red light. Rubisco proteins and Rubisco activity (leaf area basis) are directly related to irradiance level but are enhanced in blue light over equal irradiance red. This enhancement is not shown in the presence of far-red light.     

Effect of photoperiod on the diurnal rhythm of plasma testosterone, dihydrotestosterone and androstenedione in mature male chickens

1. The effects of different photoperiods on the concentrations of plasma androgens, testes weight and on the diurnal rhythm of plasma testosterone (T), dihydrotestosterone (DHT) and androstenedione (A) in mature, single comb White Leghorn male chickens were studied. 2. Birds were exposed to either 14 hr of light (lights on at 0600-2000 hr) or to 24 hr of light per day. 3. Blood samples were collected from birds in both groups at 3-hr intervals and plasma levels of T, DHT and A were measured using radioimmunoassays. Following blood collection, birds were weighed, killed and testis weights were recorded. 4. Under 14 hr of light, there was a diurnal rhythm of T and DHT with hormone concentrations peaking at the end of the dark period. There was no obvious rhythm for A. Exposure to 24 hr of light abolished the diurnal rhythm found under 14 hr of light. 5. There was an increase not only in testis weights but also in body weight and hormone concentrations under 24 hr of light. 6. It was concluded that photoperiod plays an important role in controlling the concentration and rhythm of androgens in mature male chickens.     

Protein,fatty acid,and pigment content of <Emphasis Type="Italic">Chlorella vulgaris</Emphasis> under different light regimes

The effects of irradiance and photoperiod on growth rates, chlorophyll a, β-carotene, total protein, and fatty acid content of Chlorella vulgaris were determined. The maximum growth rate (1.13 day⁻¹) was at 100 μmol photons m⁻² s⁻¹ and 16:8-h light/dark photoperiod. Chlorophyll a and β-carotene contents significantly differed under different light regimes with chlorophyll a content lower at high irradiance and longer light duration, while β-carotene showed the inverse trend. The total protein and fatty acid content also significantly differed in different light regimes; the maximum percentage of protein (46%) was at 100 μmol photons m⁻² s⁻¹ and 16:8 h photoperiod, and minimum (33%) was at 37.5 μmol photons m⁻² s⁻¹ and 8:16 h photoperiod; the total saturated fatty acids increased, while monounsaturated and polyunsaturated fatty acids decreased with increasing irradiance and light duration.