Reduction In Photoperiod Research Articles

Effect of constant and of changing photoperiods on age at first egg and related traits in pullets.

1. The effects of constant photoperiods and of single (5 h) changes in photoperiod applied at 12 or 17 weeks of age upon age at first egg (AFE) were studied using ISA Brown and Shaver 288 pullets. 2. Birds reared from 2 d of age until after maturity on constant 10 h photoperiods matured 8 d earlier than birds reared on constant 8 h and 5 d earlier than the average for 13 or 18 h photoperiods. 3. A single increment in photoperiod from 8 to 13 h advanced AFE by 23 d (compared to 8 h constant day controls) when applied at 84 d, but by only 6 d when given at 119 d. An increase in photoperiod from 13 to 18 h advanced AFE by only 4 d, averaged across breeds and age at increase. A reduction in photoperiod from 13 to 8 h delayed AFE by 22 d when given at 84 d and by 16 d at 119 d. A similar 5 h reduction in photoperiod, but from 18 to 13 h, retarded maturity by 11 d in ISA Brown pullets, but only when given at 84 d, and delayed AFE in Shaver 288 by 12 d, but only when given at 119 d. This interaction may be partly explained by the different physiological stages reached by the two breeds when the photoperiod was changed. 4. Under constant daylengths cumulative food intake before first egg was positively correlated with photoperiod, but the early AFE for birds on 10 h photoperiods resulted in this group having the lowest cumulative food intake to first egg. 5. A 5 h increase in photoperiod at 84 d significantly reduced the food consumed to first egg, but had no effect when given at 119 d. A 5 h decrease in photoperiod generally increased the food consumed to first egg, but the effect was only significant when the daylength was reduced from 13 to 8 h at 119 d. Food intake to first egg in birds subjected to a change in photoperiod was highly correlated with AFE. 6. The data confirm that sexual development in growing pullets responds more to changes in photoperiod than to the absolute daylength, that changes made at different daylengths are not equivalent and that sensitivity changes with age.

Survival and growth of seedlings from five Pinus pinaster Ait. provenances grown under different water regimes

Survival and growth parameters were measured in five Pinus pinaster Ait. provenances (Oria, Arenas de San Pedro, Oña, San Leonardo and Landas). Plantas were grown in nursery under cover in two different growing media, during one growing season and they were submitted to three water supply regimes, R1, R2, R3, set to field capacity every 1, 2 and 3 weeks respectively. General results show significative differences for water supply regimes, as well as for provenances and growing medium. With low water supply (R3) the growing medium with higher water storage capacity allows higher survival (80 p. 100) than the other (20 p. 100). The lowest survival is correlated to water potential less than -2.6 MPa. Landes and Arenas provenances show the highest height growth, Oria the lowest one. A common pattern to stop growth at the end of summer may be atributed to photoperiod reduction since temperature still allows growth. Significant differences throughout the growing season are found for seedling dry weight, mainly shoot weight, for provenances and for water supply regimes, as well as for their interaction; but water disponibility changes the ranking of provenances. Relative growth rate (RGR) is higher for R1. The water stress (R2, R3) has on RGR different effect among provenances and the ranking for them is not the same as for total dry weight at the end of growing period. Net assimilation rate (NAR) and RGR are positively correlated except for the end of summer. Low values for specific leaf area (SLA) and for leaf area ratio (LAR) point out a strategy to avoid lost of water. Their decrease in autumn is higher for R1 than for R2 and R3; it is expressed in higher dry weight and subsequent higher dry weight and subsequent higher reserves storage, since the growth height does not progress any more. It is concluded that under favourable water disponibility growth parameters in the first growing season, may be used as estimative criteria to predict future performance of provenances in the field.

A comparison of low temperature growth vs low temperature shifts to induce resistance to photoinhibition in spinach (Spinacia oleracea)

Plants of Spinacia oleracea L. cv. Savoy grown under cold‐hardening (5°C) and nonhardening (16°C) conditions were exposed to a photoinhibitory irradiance of 1300 μmol rrr: m‐2 S‐1 5°C for 12 h. Plants grown at 5°C exhibited a greater resistance to photoinhibition at low temperature in comparison to plants grown at 16°C as measured by the photochemical efficiency of photosyslem II. In contrast, tuily expanded leaves of plants grown at 16°C and then shifted to 5°C for 10 days did not exhibit increased resistance to photoinhibition. This was observed irrespective of the phoioperiod experienced during the shift to a lower temperature. Furthermore, spinach grown at 16°C and subsequently exposed to a stepped, daily decrease in temperature from 16 to 1°C over 10 days w ith a concomitant reduction in photoperiod. also did not exhibit any change in susceptibility to photoinhibition. Thus, a decrease in photoperiod accompanied by either an abrupt or stepped low temperature shift cannot induce increased resistance to photoinhibition. This confirms the hypothesis that growth and development at cold‐hardening temperature are absolute requirements for the acquisition of resistance to photoinhibition at low temperature.

Circadian and photoperiodic time measurement in male Syrian hamsters following lesions of the melatonin-binding sites of the paraventricular thalamus.

Autoradiographic studies using [125I]iodomelatonin in several species, including the Syrian hamster, have revealed that the rostral region of the anterior paraventricular nucleus of the thalamus (aPVT) contains a very high density of binding sites for melatonin. In two studies, small or large bilateral electrolytic lesions of the aPVT were made in adult male hamsters maintained on long days (LD 16:8). The hamsters were then transferred to short days (LD 8:16) to test whether testicular regression could occur in response to a decrease in photoperiod. Serum prolactin concentrations were measured as a second photoperiodic response. All unoperated control hamsters showed the typical short-day photoperiodic response: A decrease in serum luteinizing hormone (LH) and prolactin concentrations and testicular regression all occurred within 6 weeks in short days, followed by the development of scotorefractoriness. Lesions of the aPVT did not significantly affect the rate or the degree of the short-day-induced decline in serum levels of LH or prolactin, nor the pattern of testicular regression and the subsequent expression of refractoriness. To enable us to determine whether the aPVT might be involved in the entrainment or the expression of circadian rhythms, locomotor activity was monitored continuously in lesioned and control groups in Experiment 2, prior to and following the switch to short days. The reduction in photoperiod (involving an 8-hr advance in the time of lights-off and an 8-hr extension of the dark phase) caused a decompression of the nocturnal activity bout of control animals, so that after 2 weeks in short days, activity onset had also advanced to regain its phase relationship to the timing of lights-off. A similar pattern of reentrainment was observed in lesioned animals, and no differences were observed between treatment groups in the rate of entrainment and decompression. In addition, both intact controls and animals bearing large bilateral lesions of the aPVT exhibited robust free-running circadian rhythms of locomotor activity when held under constant dim red light. In summary, the integrity of the aPVT is not necessary for the seasonal response of the reproductive axis and prolactin secretion to photoperiod, nor for photic entrainment of activity rhythms, in the Syrian hamster.

What Photoperiodic Signal is Provided by a Continuous-Release Melatonin Implant?1

The purpose of this study was to evaluate whether the insertion of a continuous-release melatonin implant into ewes provides a short-day photoperiodic signal or acts as a functional pinealectomy (provides no specific photoperiodic signal but renders ewes incapable of responding to changes in photoperiod). Ewes primed with 60 long days (18L:6D) during the spring were moved to intermediate day length (13L:11D) for 66 days and then given one of five treatments: 1) short-day control, second drop in photoperiod to 8L:16D; 2) intermediate-photoperiod control, kept on 13L:11D; 3) pinealectomy and kept on 13L:11D; 4) melatonin implant and kept on 13L:11D; 5) melatonin implant and moved to 8L:16D. Mean number of estrous cycles per group and total duration of reproductive activity were determined. Ewes in all groups began to exhibit estrous cycles after the initial reduction in photoperiod. The number of estrous cycles and duration of reproductive activity differed among groups. The number of estrous cycles and duration of reproductive activity was extended in ewes receiving the second drop in photoperiod compared to that of the intermediate-photoperiod controls. Pinealectomized ewes had a number of estrous cycles and duration of reproductive activity similar to those of ewes maintained on the intermediate photoperiod. Melatonin implants increased the number of estrous cycles and prolonged reproductive activity in ewes maintained on the intermediate photoperiod; melatonin implants did not prevent the extension of reproductive activity in ewes receiving the second photoperiodic drop to the short daylength.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemical and environmental growth regulation of sweetpotato (Ipomoea batatas (L.) Lam.) in vitro

The need for conservation of biotic diversity is well recognized. However, improved techniques for the efficient, cost effective-preservation of plant germplasm are needed. The conservation and distribution of plant germplasm in vitro is gaining acceptance. However, increased usage is dependent upon the ability of curators to minimize culture maintenance requirements. This report examines the effect of various levels of sucrose, photoperiod, temperature, sorbitol and mannitol on minimal growth storage of Ipomoea batatas (L.) Lam. Growth was reduced 50% with a temperature reduction of from 21.1 to 15.6°C. Sucrose concentrations of 15 and 20 g l-1 resulted in reduced plant stature with few adverse effects on plantlet viability or morphology. Reduction of photoperiod from 16 to 4 h produced smaller, slightly chlorotic, but otherwise normal plants. The addition of sorbitol or mannitol to culture media generally produced undesirable effects on gross plant morphology and loss of apical dominance. Genotype x growth retarding treatment interactions were observed for all variables examined.

Genotypic and media effects on plant regeneration from cotyledon explant cultures of someBrassica species

Conditions were established for efficient plant regeneration from cotyledon explant calli in different cultivars ofBrassica juncea, B. campestris andB. carinata on Murashige & Skoog's (MS) medium supplemented with various combinations of cytokinins and auxins. Regeneration frequency, however, varied with genotype and the different growth hormone combinations in media. Almost in all species, MS medium with zeatin (1.0 mg 1-1) and IAA (0.1 mg l-1) was found to be best for shoot organogenesis followed by the ones containing high kinetin (2.0 mg l-1) and low IAA (0.02 or 0.2 mg l-1) concentrations. On these media, the cotyledonary explants invariably underwent callusing followed by multiple shoot formation, which could be separated and subcultured for further propagation. Number of shoots per cotyledon explant cultured varied from 0 to as many as 50. InB. juncea andB. campestris, the regeneration frequency declined sharply in the absence of auxin in medium. BAP in combination with NAA yielded no or a reduced number of shoots. Shoot organogenesis also declined with the reduction in photoperiod from continuous light to 16 hours. Shoots were easily rooted during prolonged incubation on the same medium and whole plants were transferred to pots in the greenhouse and grown to maturity.

Constant photoperiod regimes and the entrainment of the annual cycle of reproduction in the female rainbow trout ( Salmo gairdneri)

The effect of constant photoperiod regimes on the timing of maturation and the associated changes in serum oestradiol-17β (E 2), testosterone (T), and total calcium (Ca 2+, as an index of vitellogenin) were investigated in virgin female rainbow trout ( Salmo gairdneri). From mid-Janualy four groups of fish were maintained on constant long days (18L:6D) and one group on constant short days (6L:18D; group A). On May 8 the photoperiod of three of the groups on long days was abruptly reduced from 18L:6D to 6L:18D (group B), to 10L:14D (group C), or to 14L:10D (group D): Group E remained on 18L:6D throughout the experiment. The reduction in photoperiod per se appeared more important than the magnitude of the reduction in the advancement of the time of spawning with the first fish in groups B, C, and D spawning on September 3, 13, and 24, respectively; spawning of the remaining fish in each group was spread over 6-week periods. In contrast, spawning in group E began on October 24 and was spread over a period of 12 weeks. Spawning in group A was delayed until the following March. Although a long photoperiod earlier in the year was clearly necessary for the advancement of spawning, as evidenced by the delay in maturation under constant short days, no clear increases in E 2, T, and Ca 2+ were detected until after the reduction in photoperiod. Thereafter, the sequence of changes in serum E 2, T, and Ca 2+ levels was similar in all groups although the timings of these alterations were modified in relation to the time of spawning. Thus, peak levels of the three serum parameters were attained earliest in the year by fish in group B followed by those in groups C, D, E, and A, respectively. Collectively, these data support the hypothesis that photoperiod entrains an endogenous rhythm of maturation rather than having a direct, driving influence on the control of reproduction.

Relationship of Dietary Calcium Level During the Prelay Phase of an Induced Molt to Postmolt Performance

Leghorn laying hens were induced to molt by a combination of photoperiod reduction and fasting for 14 days, during which time the hens lost 31.5% of their initial body weight. The hens were then assigned to one of four diets containing 1.0, 1.75, 2.5, or 3.5% calcium until egg production resumed. The 3.5% calcium diet was fed to all treatments from the resumption of 5% egg production.Postmolt egg production and feed conversion were not affected significantly. Egg weight, shell weight, and egg specific gravity were not affected consistently. It was concluded that high dietary calcium levels immediately postfast have no adverse effect on postmolt performance.

Seasonal changes in testicular contents of testosterone and androstenedione and in the metabolic clearance rate of testosterone in the sand rat (Psammomys obesus).

Adult male sand rats (Psammomys obesus) were caught in the Béni-Abbès area. The highest testicular contents of androgens (ng/testis) were observed in autumn and in winter (testosterone: 7.6 +/- 1.1; androstenedione: 0.76 +/- 0.11) and the lowest in early summer (June) (testosterone: 1.5 +/- 0.3; androstenedione: 0.20 +/- 0.05). Values had increased by late July. Annual variations of the testosterone metabolic clearance rate (litres/24 h/100 g body wt) were similar to those of testicular androgens; values were high in winter (6.7 +/- 0.7) and lowest in June (3.2 +/- 0.3). The onset of testicular endocrine activity in sand rats was concomitant both with the highest temperatures and the start of reduction in photoperiod; its regression occurred when temperature and photoperiod were increasing.

Effect of changing photoperiod on peripheral plasma prolactin and progesterone concentrations in the tammar wallaby (Macropus eugenii).

In tammar wallabies kept in normal daylengths between the equinoxes, births occurred at the normal time after the summer solstice and the progesterone profile reflected this cycle. There were no significant changes in plasma prolactin. In tammars placed in a 15L:9D photoperiod and then, 5 weeks later, in 12L:12D, births occurred 29-36 days after the daylength was reduced. A characteristic transient peak of plasma progesterone occurred 8-14 days after the change, indicating a delay of 3-9 days in the resumption of luteal activity. Plasma prolactin levels were significantly higher (greater than 40 ng/ml)(P less than 0 X 01) during the solstitial daylength, declining to less than 30 ng/ml within 14 days of the reduction in photoperiod. Animals kept in 12L:12D and then in 9L:15D gave birth asynchronously after entry into the pens, suggesting that this daylength (12L:12D) is permissive. Changes in plasma progesterone reflected the resumption of luteal activity but no significant changes in plasma prolactin were observed. This study shows that the inhibition of the corpus luteum in seasonal quiescence can be maintained in the presence or absence of elevated prolactin levels, indicating that other factors, perhaps of pineal origin, may also be involved.

Biological Observations of Menochilus sexmaculatus,1 Reared on Schizaphis graminum23

When Menochilus sexmaculatus (F.) was reared upon the greenbug, Schizaphis graminum (Rondani), females laid an average of 11.4 eggs/day with a mean fertility of 70%; mean fecundity was 779.8 eggs. The mean number of days from egg to adult was 12.25 while average longevity for adults was 63.68 days. The amount of CO2 expired for adults was found to increase with age. Males expire more CO2/unit body weight than females and the rate of CO2 expiration increases exponentially with increasing temperatures. Middle aged adults could not be induced to enter diapause by an abrupt reduction in photoperiod. Additionally, the greenbug was found to be a very satisfactory food source.

Curled Toes and Perosis-Like Leg Abnormalities in Cage Reared Broilers

A high incidence of perosis-curled toe type of leg disorder has consistently developed in both cage- and floor pen-reared male broiler chicks of two different genetic strains within 5 to 7 days when fed a nutritionally complete corn-soybean meal diet. Postmortem analysis of affected birds indicate classic perosis as seen in dietary manganese (Mn) deficiency. Ration modifications, such as inclusion of 50 ppm additional Mn or .5 mg/kg vitamin B-2 did not prevent or reduce the development of this leg problem. Birds reared in floor-pens had a reduced incidence (12 to 13%) of perosis-curled toe problem compared with incidence of leg disorders of battery-reared birds (20 to 60%). In most instances, a positive relationship between rate of weight gain and severity of leg abnormalities was apparent. Reduction in photoperiod from 24 hr/day to 12 hr/day substantially reduced incidence of leg disorders; however, growth rate was also reduced. The practical basal diet employed in all experiments promotes satisfactory rate of growth and feed efficiency and may be an excellent assay diet for experimentation into perosis-like broiler leg problems.

Reproductive Development and Response of White Leghorn Pullets Subjected to Increasing Day-Lengths at Different Ages

REPRODUCTIVE responses of birds to increasing and decreasing photoperiods has been the subject of many studies. However, few reports have dealt with reproductive responses to increasing photoperiod changes at various ages.Change in length of the photoperiod had a greater effect on rate of sexual development and egg production than a constant photoperiod (Morris and Fox, 1958; King, 1958; Lert et al., 1960). Increasing light during the rearing period resulted in early sexual maturity, whereas, decreasing day-lengths retarded sexual development (King, 1961; Shutze et al., 1961; Shutze et al., 1961, 1963; Lowe and Heywang, 1964). Pullets reared on decreasing or short day-lengths, then subjected to increasing day-lengths, responded to the light stimulus with increased production and increased egg size (Morris and Fox, 1958; Shutze et al., 1963; Lowe and Heywang, 1964).Preconditioning of pullets by a reduction in photoperiod initiated prior to 14 weeks of age, resulted in increased egg…

Maintenance of Egg Production in Coturnix Following Reduction in Photoperiod

THE rapid degeneration of the ovary which normally occurs when a laying hen is starved can be prevented by injection of mammalian gonadotropins as was demonstrated by Hosoda et al. (1955). Later, Morris and Nalbandov (1961) showed that both avian and mammalian gonadotropins could induce regular daily ovulation for 8 or more days following the removal of food. Taylor et al. (1962) have reported that calcium-deficient hens injected with crude chicken anterior pituitary will continue to lay eggs until the hens collapse from calcium deficiency.To our knowledge, no one has determined how light-starved birds will respond to exogenous hormones. This paper presents the results of three separate experiments concerned with maintaining egg production in corturnix, following an abrupt decrease in the amount of daily light from 14 hours to 8 hours, by injection of avian adenohypophyses and mammalian gonadotropins.3 EXPERIMENTAL PROCEDUREJapanese quail (Coturnix coturnix japonica) from University of…