Photoperiod Perception Research Articles

Phytochrome-mediated photoperiod perception, shoot growth, glutamine, calcium, and protein phosphorylation influence the activity of the poplar bark storage protein gene promoter (bspA).

In poplars (Populus), bspA encodes a 32-kD bark storage protein that accumulates in the inner bark of plants exposed to either short-day (SD) photoperiods or elevated levels of nitrogen. In this study, poplars transformed with a chimeric gene consisting of the bspA promoter fused to beta-glucuronidase (uidA) were used to investigate the transcriptional regulation of the bspA promoter. Photoperiodic activation of the bspA promoter was shown to involve perception by phytochrome and likely involves both a low fluence response and a parallel very low fluence response pathway. Activity of the bspA promoter was also influenced by shoot growth. High levels of bspA expression usually occur in the bark of plants during SD but not long day or SD with a night break. When growth was inhibited under growth permissive photoperiods (SD with night break) levels of bark beta-glucuronidase (GUS) activity increased. Stimulating shoot growth in plants treated with SD inhibited SD-induced increases in bark GUS activity. Because changes in photoperiod and growth also alter carbon and nitrogen partitioning, the role of carbon and nitrogen metabolites in modulating the activity of the bspA promoter were investigated by treating excised stems with amino acids or NH4NO3 with or without sucrose. Treatment with either glutamine or NH4NO3 resulted in increased stem GUS activity. The addition of sucrose with either glutamine or NH4NO3 resulted in synergistic induction of GUS, whereas sucrose alone had no effect. Glutamine plus sucrose induction of GUS activity was inhibited by EGTA, okadaic acid, or K-252A. Inhibition by EGTA was partially relieved by the addition of Ca2+. The Ca2+ ionophore, ionomycin, also induced GUS activity in excised shoots. These results indicate that transcriptional activation of bspA is complex. It is likely that SD activation of bspA involves perception by phytochrome coupled to changes in growth. These growth changes may then alter carbon and nitrogen partitioning that somehow signals bspA induction by a yet undefined mechanism that involves carbon and nitrogen metabolites, Ca2+, and protein phosphorylation/dephosphorylation.

Regulation by photoperiod of seasonal changes in body mass and reproductive function in gray mouse lemurs (Microcebus murinus) : Differential responses by sex

Microcebus murinus exhibits highly seasonal biological rhythms to cope with extreme seasonality in availability of resources. To study the role of daylength on seasonal changes in body mass and reproductive function, we exposed male and female gray mouse lemurs to natural, constant, or alternating light cycles for 2 years under constant environmental conditions. When exposed to either constant short (SD: 10 h light/day), long (LD: 14 h light/day), or intermediate (ID: 12 h light/day) daylength, males and females maintained a constant body mass with no spontaneous cyclic variation. We only observed typical seasonal body mass changes in subjects exposed to alternating periods of SD and LD, the weight gain being triggered by SD, whereas weight loss occurred under LD. Reproductive activity in females proceeded from an endogenous rhythm that was expressed under constant daylengths. In contrast, changes in reproductive activity in males depended on daylength variation. In both sexes, SD and LD have direct inhibitory or stimulatory effects on reproductive activity. In females, daylength regulates breeding season by synchronizing an endogenous sexual rhythm with the season, whereas in males, the perception of a critical photoperiod is used to determine the subsequent onset or arrest of their breeding season. These sexual differences in the effect of daylength could be related to sex-specific differences in reproductive constraints.

Quantitative trait loci and candidate gene mapping of bud set and bud flush in populus.

The genetic control of bud phenology in hybrid poplar was studied by mapping quantitative trait loci (QTL) affecting the timing of autumn bud set and spring bud flush. The founders of the mapping pedigree were collected from widely separated latitudes to maximize segregating variation for dormancy-related traits in the F(2) generation-the female Populus trichocarpa parent is from Washington State (48 degrees N) and the male P. deltoides parent is from Texas (31 degrees N). Bud set and bud flush timing were measured on the F(2) generation in a replicated clonal field trial. Using a linkage map constructed of AFLP and microsatellite markers, three QTL controlling bud set and six QTL controlling bud flush were detected. Additionally, five candidate genes believed to be involved in perception of photoperiod (PHYB1, PHYB2) or transduction of abscisic acid response signals (ABI1B, ABI1D, and ABI3) were placed on the QTL map. PHYB2 and ABI1B were found to be coincident with QTL affecting bud set and bud flush.

Induction of reproductive diapause via perception of photoperiod through the compound eyes in the adult blow fly, Protophormia terraenovae

Covering and surgical removal of the compound eyes were performed to localize photoreceptors for photoperiodic responses in the blow fly Protophormia terraenovae (Diptera, Calliphoridae). Adult females showed a long-day photoperiodic response to control reproductive diapause. When the compound eyes were bilaterally covered with silver paint, diapause incidence increased under diapause-preventing conditions, i.e., a long-day photoperiod and constant light, as though flies were kept under constant darkness. Neither silver painting on a medial region of the head capsule nor control painting in which both compound eyes were painted in a clear solvent caused significant effects on diapause incidence. Unilateral painting of the compound eye caused an increment of diapause incidence under constant light but no effects under a long-day photoperiod. When the compound eyes were bilaterally removed, all the flies developed their ovaries both under a long-day and a short-day photoperiod. Unilateral removal of the compound eye also caused ovarian development under a short-day photoperiod, whereas removal of one antennal lobe or all ocelli caused no effects on diapause incidence. Since P. terraenovae completely lost responsiveness to photoperiod after blinding of the compound eyes, it is likely that this fly perceives photoperiod through its compound eyes.

Essential of the environmental control of insect seasonality as reference points for comparative studies in other invertebrates

A great body of knowledge of photoperiodic and other developmental reactions, governing seasonality in insects, may be helpful for similar investigations which are or will be conducted with other animal groups. The following principles, based on a recent hypothesis, seem the most significant to be tested in comparative studies. (1) On the level of the photoperiodic clock only quantitative perception of photoperiod takes place. (2) The following, presumably neuroendocrine, ‘managing’ level of the mechanism discriminates between long and short days, determines the type of the response, and integrates photoperiodic and temperature reactions. (3) A working hypothesis, to be tested with both insects and other invertebrates, is that the ‘managing’ mechanism described in the model of photoperiodic and temperature control of development may have several sensory inputs and, therefore, plays a central role in governing developmental reactions to different environmental cues.

Ultrastructural study of the optic nerve in blind mole-rats (Spalacidae, Spalax).

The optic nerve in two species of subterranean mole-rats (Spalacidae) has been examined at the ultrastructural level. The axial length of the eye and the diameter of the optic nerve are 1.9 mm and 52.5 microns in Spalax leucodon, and 0.7 mm and 80.8 microns in Spalax ehrenbergi, respectively. An anti-glial fibrillary acidic protein postembedding procedure was used to distinguish glial cell processes from axons. In both species, the optic nerve is composed exclusively of unmyelinated axons and a spatial distribution gradient according to the size or the density of fibers is lacking. The optic nerve of S. leucodon contains 1790 fibers ranging in diameter from 0.07-2.30 microns (mean = 0.57 microns), whereas in S. ehrenbergi, only 928 fibers, with diameters of 0.04-1.77 microns (mean = 0.53 microns) are observed. In S. ehrenbergi, a higher proportion of glial tissue is present and the fascicular organization of optic fibers is less obvious. Distribution gradients according to size frequency or density of fibers in the optic nerve are absent in both species. Comparison with other mammals suggests that although ocular regression in microphthalmic species is correlated with a significant decrease in the total number of optic fibers and the relative proportion of myelinated fibers, no difference in the absolute size range of unmyelinated axons is observed. The total absence of myelinated fibers in Spalax may be related to the subcutaneous location of the eyes.(ABSTRACT TRUNCATED AT 250 WORDS)

Photic induction of Fos immunoreactivity in the suprachiasmatic nuclei of the blind mole rat ( Spalax ehrenbergi)

Exposure to light during the dark phase entrains c- fos expression in cells of the suprachiasmatic nuclei in the blind mole rat ( Spalax ehrenbergi). Labeled cells are mainly located in the ventral region of the nucleus where retinal afferents terminate. Despite severe atrophy of the eye and regression of thalamic and tectal structures, the retinal pathways and central mechanisms involved in photoperiodic perception and circadian regulation appear to be similar to those in other rodents.

Diapause in phytoseiid mites: a review

This review briefly describes characteristics and occurrence of diapause in phytoseiid mites. This is followed by a discussion of factors involved in induction, maintenance and termination of diapause (e.g. photoperiod, temperature and food availability), of the physiological mechanism of diapause induction (photoperiodic perception and comparison of photoperiodic and thermoperiodic induction mechanisms), and of applied aspects of diapause in phytoseiid mites.

Role of Short Days in Timing the Onset and Duration of Reproductive Activity in Ewes under Artificial Photoperiods1

The objective of this work was to evaluate the role of short photoperiod in timing the onset and duration of reproductive activity in ewes. The perception of photoperiod was disrupted by pinealectomy following transfer from long (17L:7D) to short (8.5L:15.5D) photoperiod and the subsequent reproductive response was monitored. Ovariectomized ewes given Silastic implants containing estradiol-17 beta were exposed to long days until Day 0 (May 24) and then were allocated to the following groups (n = 5-6/group): Group 1) short-day control--moved to short days; Groups 2 to 5) pinealectomy after 0, 30, 60, or 90 short days, respectively; Group 6) long-day hold--kept on long days; Group 7) long days after 60 short days--moved to short days on Day 0 and returned to long days on Day 60. Six ewes kept outdoors served as additional controls. Reproductive neuroendocrine activity was assessed from plasma LH concentrations, high values being indicative of the breeding season and low values indicative of anestrus. Time of reproductive neuroendocrine activity onset (LH rise) did not differ among animals in the 7 groups kept indoors, but was advanced (p less than 0.05) relative to that of ewes outdoors. In contrast, duration of the LH elevation differed among ewes in groups kept indoors.(ABSTRACT TRUNCATED AT 250 WORDS)

Evolution of Nonvisual Communication and Photoperiodic Perception in Speciation and Adaptation of Blind Subterranean Mole Rats

AbstractThe evolution of vocal and vibrational communications and photoperiod perception in the blind subterranean mole rat of the Spalax ehrenbergi superspecies, are reviewed in the context of adaptation and active speciation in the subterranean ecotype. Progressive evolution of the acoustic system and regressive evolution of the atrophied eye coupled with progressive evolution in photoperiodic perception and biorhythmicity systems, are discussed. Prospects are suggested for future research at the molecular, anatomical and organismal levels, in the twin evolutionary processes of adaptation and speciation. Spalax appears to be a uniquely productive evolutionary model for the study of evolutionary structural reductions and hypertrophies as well as functional shifts in evolution. It provides particularly a rich observational and experimental material to critically evaluate the challenges recently levelled against the synthetic theory of evolution concerning gradualism in speciation, the "adaptationist programme", and the role of natural selection as a creative force in evolution.

Photic influences on the developing mammal.

In adult mammals, the daily light-dark cycle acts via the retinohypothalamic pathway to entrain the circadian clock in the suprachiasmatic nuclei (SCN) and to communicate information about daylength to photoperiodic species. Studies in rats show that during late fetal and early neonatal life, before the retinohypothalamic pathway has innervated the SCN, the maternal circadian system entrains the timing of the developing clock to prevailing lighting conditions. Although the nature of the maternal output signal(s) used to entrain the developing clock has not been elucidated, the maternal SCN are a necessary component of maternal entrainment during both prenatal and postnatal life. Maternal entrainment of the fetal and neonatal clock thus ensures that the developing circadian system is synchronized to the outside world until maturation of the retinohypothalamic pathway permits direct photic entrainment. The maternal circadian system is not only necessary for entrainment of the developing circadian system, but recent studies suggest it may also provide the immature mammal with important photoperiodic information. In the montane vole (Microtus montanus) and the Djungarian hamster (Phodopus sungorus), the prenatal photoperiod affects postnatal photoperiodic responses, and cross-fostering experiments show that this information about daylength is perceived by the fetus. This prenatal information, in conjunction with postnatal perception of photoperiod, allows the developing animal to determine which way the season is changing and to modify the rate of reproductive maturation accordingly.

Photoperiod perception in the blind mole rat (Spalax ehrenbergi, Nehring): involvement of the Harderian gland, atrophied eyes, and melatonin.

The involvement of the Harderian gland, atrophied eyes, and melatonin in the perception of photoperiodic changes has been studied in the mole rat, a fossorial blind mammal the thermoregulatory capacity of which is photoperiod-dependent. When transferred from a long photoperiod to a short one, mole rats increase their resistance to cold, a perfectly reversible phenomenon. After 2 weeks under short photoperiod the thermoregulatory capacities of animals without Harderian glands are less than those of the controls. The Harderian gland appears thus to be implicated in the detection of photoperiodic changes. After 5 weeks, however, the Harderianectomized animals had perfectly integrated the photoperiodic change, so demonstrating that other photoreceptor organs exist. The atrophied eyes, which, under these conditions, do not seem to play an important role, are involved when the animals are transferred from short photoperiod to long photoperiod. Melatonin, but not 5-methoxytryptamine, appears to be a crucial compound in such a phenomenon. These results, which demonstrate that in mammals (at least in the mole rat, as in nonmammalian vertebrates), nonocular photoreceptors exist, suggest that the mechanism by which mammals integrate photoperiodic changes is not the same when the animals are transferred from long to short photoperiod as when transferred from short photoperiod to long photoperiod.

Photoperiodic time signals during twilight

Abstract. Although daylength has a major effect on flowering and several other aspects of plant development, the actual environmental time signals for the beginning and the end of day are obscure. An intensive spectroradiometric study was carried out in three contrasting environments: namely, unshaded sites, a mature oak woodland and a sugar beet crop. Spectral photon distributions were obtained describing numerous twilight phases and intervening photoperiods throughout the year. From each, absolute photon fluence rates, photon fluence rate ratios and phytochrome photoequilibria were calculated. Although substantial changes in spectral composition occurred during twilight, they were less capable of providing reliable and accurate time signals than the absolute fluence rate; this was especially apparent beneath the canopies. Thus, spectral changes are unlikely to be valuable in photoperiodic perception. The results are discussed in relation to the possible involvement of the known plant photoreceptors in photoperiodism.

Importance of retinal photoreceptors to the photoperiodic control of seasonal breeding in the ewe.

Two experiments were performed to determine whether the eyes are necessary for photoperiodic control of reproduction in ewes. In the first, intact and estradiol-treated ovariectomized (OVX + E) ewes were housed in each of 2 photoperiod-controlled rooms with a vasectomized ram and subjected to 90-day alternations between long and short days. Prior to blinding, long days initiated anestrus in intact ewes and a suppression of serum luteinizing hormone (LH) levels in OVX + E ewes; short days caused onset of estrous cycles and an increase in LH levels in the intact and OVX + E ewes, respectively. After 1.5 years of such photoperiodic control, all ewes were blinded by bilateral orbital enucleation. Photoperiodic control was lost following blinding, but circannual alternations between cyclicity and anestrus or high and low LH levels, were maintained in most ewes for the remaining 2.5 years of the study. In one group of OVX + E ewes, serum LH levels remained synchronized to the 90-day shifts in photoperiod for about 1 year after blinding. Once the sighted ram was removed from the room, however, the 90-day rhythm in LH disappeared and a circannual pattern of LH became evident, suggesting that blind ewes may receive photoperiodic information from a sighted ram. This possibility was supported by the results of the second experiment in which 12 additional OVX + E ewes were blinded and exposed to 90 long days and 90 short days in the absence of a sighted ram. In these ewes, serum LH levels were not controlled by the changes in photoperiod. These results are consistent with the following conclusions: 1) the eyes are necessary for perception of photoperiod in the ewe and 2) ewes have an endogenous circannual rhythm of reproduction and/or they can be controlled by other environmental signals in the absence of photoperiodic input. Further, the results lead to the hypothesis that blind ewes can receive photoperiodic information indirectly from a sighted ram.

Vitamin A is essential for photoperiodic induction of diapause in an eyeless mite

The perception of photoperiod by insects and mites requires a photoreceptor which is probably located in the brain1–5. Recently, the functional involvement of carotenoids in the photoperiodic reaction of two mite species has been demonstrated using techniques based on mutant studies and nutritional studies respectively6–8. In dietary studies with insects, evidence for the participation of carotenoids in the photoperiodic induction of diapause has been found in one moth species9, whereas carotenoid deprivation has no effect in another moth10 and a butterfly11. Here we show that vitamin A as well as carotenoids with provitamin A function, but not vitamin A acid, restores the photoperiodic reaction in an eyeless predacious mite which has lost all sensitivity to the photoperiod after having been reared for more than one generation on pollen of broad bean, which constitutes a completely carotenoid-free diet. This study suggests that a rhodopsin-like pigment functions as the photoreceptor for the photoperiodic induction of diapause in these mites.

Localization of the photoperiodic perception in potatoes

It was found that probably all the leaves of young potato plants played a part in perceiving the photoperiodic stimulus which induces tuberization. The importance of the mature leaves in the photoperiodic perception is emphasized by the large tuber yield which could be obtained by subjecting these leaves to inductive photoperiods while the growing tip and young leaves were subjected to non-inductive photoperiods. Tubers were produced under non-inductive photoperiods when the young leaves and meristematic stem apices were removed. Tuberization in these plants could be inhibited by application of gibberellic acid. The developing leaves, therefore, seem to produce a substance, probably gibberellin, which prevents tuberization under long-day conditions. If a specific tuberforming substance is involved it is present in active concentrations even under non-inductive photoperiods. The results are in agreement with the theory that a balance between endogenous gibberellins and another substance(s) controls tuberization.

Effects of blinding and/or total darkness on ovarian recrudescence or regression during the appropriate periods of the reproductive cycle of the catfish,Heteropneustes fossilis(Bloch)∗∗

Abstract Three experiments were performed wherein intact and blind catfish were subjected to various photoperiodic regimes during the preparatory, the prespawning and the spawning period to ascertain the role of eyes in the perception of photoperiodic stimulus. In the first experiment, conducted during the prespawning period, intact and blind catfish were subjected to laboratory photoperiod (12 hr/day) or total darkness. The results indicate that ovarian recrudescence occurs in spite of the absence of eyes and light. But the tempo of ovarian recrudescence is slower in the blind animals than in the sighted animals. The results of second experiment where intact and blind catfish were subjected to total darkness for 163 days during the preparatory period show that ovarian recrudescence takes place in all the groups regardless of the presence or absence of eyes and/or of light. The magnitude of ovarian enlargement was greater in the intact control and intact catfish exposed to total darkness than in the corresponding blind groups. In the third experiment conducted during the spawning period, decreasing photoperiod induced a more precipitous ovarian regression in the presence than in the absence of eyes. Eyes, though important receptors for photoperiodic perception, are not indispensable. The presence of a self‐operating internal mechanism regulating reproduction in the catfish is envisaged. The significance of these findings is discussed.

Studies on the Role of the Leaf Epiderm in Photoperiodic Perception inKalanchoe Blossfeldiana

Experimental blocking of the stomatal apertures of single induced leaves by vaselining, or entire removal of either lower or upper epiderm by stripping, indicate that the leaf epiderm must play a significant role in photoperiodic perception. The results do not, however, allow a clear decision to be made as to whether the function of the epiderm is exerted through stomatal control of the internal atmosphere of the leaf, or through some direct perception by the epidermal cells themselves.

Photoperiodic Control of Germination in Seed of Birch (Betula pubescens Ehrh.)

IT is well known that the flowering response of both short-day and long-day herbaceous species is governed by the day-length conditions to which the mature leaves are exposed, and that the meristematic tissue of the shoot apex is insensitive. It has been shown for certain woody species, however, that direct photoperiodic perception may occur in the meristematic tissue of both dormant resting-buds and actively growing apices, in relation to dormancy phenomena. Thus, the unchilled resting-buds of dormant leafless seedlings of Fagus sylvatica and Betula pubescens 1,2 may be induced to expand by exposure to long-day conditions. Similarly, actively growing, leafy seedlings of Betula pubescens may be induced to form resting-buds by direct exposure of the apical region of the shoot to short-day conditions, regardless of the conditions of day-length under which the mature leaves are maintained. It is of interest, therefore, to investigate whether the embryos of such woody species also show photoperiodic effects in relation to dormancy, and experiments have been carried out with seeds of birch for this purpose.

Locus and Physiology of Photoperiodic Perception in Plants

Photoperiodic responses of intact plants whose bases and tops have been exposed to contrasted length of daylight, indicate that the stimulus is not normally transmitted from the exposed area.1 Flowering is usually restricted to the zone receiving the reproductive photoperiod. More recently, however, by the use of reciprocal grafts of photoperiodically sensitized plants, it has become possible to demonstrate stimulus transfer from one part to another across the graft union.2 Opaque boxes and cloth bags have also been employed in studies on the interrelationships of contrasted photoperiods on adjacent parts.1, 2, 3The graft technique is not wholly satisfactory in studies of this sort, however, because it is difficult, entails delay and post-operative care, causes considerable mortality and involves the extraneous stimulus of severe traumatism. The results of whip, cleft and bud grafts vary greatly.4, 5 The use of small bags or boxes impairs gas exchange and creates temperature differences between the expose...