Photoperiodic response and heritability of the pre-flowering interval of two red clover (Trifolium pratense) populations

The reaction to 12, 14, and 16 h photoperiods of two medium-maturing red clover (Trifolium pratense) populations (cv. Kenland and Cycle 6 of a selection for long stems) under controlled environment conditions was studied. Under both 14 and 16 h photoperiods, Kenland flowered sooner and had shorter stems, more stems per plant, and greater herbage yield per plant but had a similar number of internodes compared to the long stem Cycle 6 population. A daylength between 12 and 14 h was critical for flower initiation in both populations. The critical daylength to induce stem initiation was shorter than the daylength to induce flowering in some genotypes. From half-sib analyses, the narrow–sense heritability of the pre-flowering interval in Kenland ranged from 15 to 23%. The expected response to one cycle of selection (5% selection intensity) for lengthening or shortening the pre-flower interval was 2.3 to 2.4 days at the 16 h photoperiod and 3.0 days at the 14 h photoperiod. Low correlation between pre-flowering interval, stem length, and stem number indicated that it may be possible to change one character without affecting the other two. The need for further studies of the genetic nature of the control of flowering in red clover was indicated.     

Effect of photoperiod on metabolic rate in a subtropical population of Drosophila melanogaster.

1. Descendents of a Florida, U.S.A. population of Drosophila melanogaster were reared under short (8 hr light: 16 hr dark) and long (16 hr light: 8 hr dark) photoperiods. 2. Flies reared under short photoperiods had higher rates of metabolism at 21 degrees C. 3. Because genetic background (iso-female line) affects metabolic rates, statistical control through analysis of covariance was necessary to isolate the effects of photoperiod on metabolic rates. 4. These results on a subtropical population of D. melanogaster are similar to those found on a temperate population of the same species.     

Photoperiod and Temperature Interactions in Growth and Flowering of Strawberry

Growth and flowering of strawberry cultivars were studied in controlled environments. Early cultivars adapted to marginal growing areas in Scandinavia initiated flower buds in all photoperiods including continuous light at temperatures of 12 and 18°C. At 24°C they remained vegetative in photoperiods above 14 or 16 h. The later cultivars ‘Senga Sengana’ and ‘Abundance’ did not initiate flower buds in 24-h photoperiods at any of these temperatures. Their critical photoperiod changed from above 16 h at 12°C to about 14 and 13 h at 18 and 24°C, respectively. It is concluded that at high latitudes temperature is as important as photoperiod in controlling flowering in the strawberry. Stolon formation, petiole elongation, and leaf area growth were stimulated by high temperature and long days, usually with optima at 16 h and 18°C for petiole elongation and 16 h and 24°C for stolon formation. Although growth and flowering responses in general were opposite, the results indicate that they are to some extent independent. The photoperiodic growth responses were mainly of morphogenetic nature. Dry weight of stem and leaves was little influenced by photoperiod when the irradiance was kept constant.     

Vegetative Response of Saltcedar (Tamarix pentandra Pall.) to Photoperiod

Saltcedar (Tamarix pentandra Pall.) stem cuttings responded vegetatively to various photoperiods of 11-, 14-, 17-, and 8 + 1-hour duration. Total stem length, average stem length, cuticle thickness, and xylem vessel member outside diameter were significantly maximal under a 14-hour photoperiod and less under photoperiods above and below this level. Numbers of stems and roots produced were significantly less in an 11-hour than under a 14-hour photoperiod; but neither was significantly different from responses under 17- and 8 + 1-hour photoperiods. Vegetative photoperiodic responses, except for cuticle thickness, were affected by a photoperiodic after-effect produced by cuttings collected on various dates. Average stem length, total stem length, and number of stems produced were significantly correlated with field photoperiods from November to May.     

THE DEPENDENCE OF FLOWERING IN SEVERAL LONG-DAY PLANTS ON THE SPECTRAL COMPOSITION OF LIGHT EXTENDING THE PHOTOPERIOD

The results of experiments in which the length, time, and spectral composition of photoperiod extensions and light breaks were varied are presented. The plants used included Hyoscyamus niger L. (annual henbane); Beta vulgaris L. (annual sugar beet); Hordeum vulgare L. (barley); Anethum graveolens L. (dill); Lolium temulentum L. (darnel); and Petunia hybrida Vilm. (petunia). Brief light breaks in the middle of each night failed to cause flower induction. Extended breaks and 8-hr extensions of the photoperiod were effective, particularly those with light from BCJ, rubyred, or incandescent lamps. For all lamp types and species, 8-hr extensions prior to each daylight period were more effective than those given at the end of each day. Four-hour light breaks were most effective when given in the middle of each night. The flowering caused by 4-hr breaks with BCJ light from 8 pm to 12 pm was suppressed when the BCJ light was preceded by 4 hr of fluorescent light. When light from BCJ or fluorescent lamps was interpolated for 2 hr at various times during 8-hr extensions with light from the other type of lamp, BCJ light stimulated flowering the most, and fluorescent light inhibited it the most, when interpolated at the end of the daylight period. These results are discussed, and a model of how phytochrome participates in the flowering of long-day plants is presented.     

Two-step photoperiodic and hormonal control of reproduction in the female beetle, Pterostichus nigrita

The carabid P. nigrita is a short-day/long-day insect. Short days with less than 15.0 hr of light per day induce pre-vitellogenesis. Vitellogenesis only takes place in subsequent long days with more than 13,1 hr of light. In the range from ld 13:11 to ld 16:8 egg production is possible without a change in photoperiod. Pre-vitellogenesis is induced by the corpus allatum hormone. Implantation of active corpora allata or injection of juvenile hormone substitutes for short-day photoperiods. Histological investigations and implantation experiments revealed that for vitellogenesis some neurosecretion is necessary. Ecdysterone cannot replace this neurosecretion.     

THE LIFE CYCLE OF BANGIA FUSCOPURPUREA IN CULTURE. I. EFFECTS OF TEMPERATURE AND PHOTOPERIOD ON THE MORPHOLOGY AND REPRODUCTION OF THE BANGIA PHASE12

The Bangia phase of Bangia fuscopurpurea was grown in laboratory culture in a variety of photoperiod and temperature regimes. Plants of the Bangia phase grown from 2 types of asexual spores, monospores and conchospores, exhibited growth differences under similar growing conditions. Plants derived from monospores grew more rapidly and matured earlier than those derived from carpospores. Day length and temperature were found to significantly influence growth rule, maturation, and plant size. Long day lengths resulted in more rapid growth in filament length and diameter and earlier spore formation and spore release. Maximum filament length was observed in a 12/12 hr light-dark cycle at 15 C. Spore formation and release were delayed by decreasing day length or temperature. Temperature and photoperiod were also found to influence the type of spores produced by the Bangia phase. When grown at 22 C, the Bangia phase produced only monospores, which reproduced the Bangia phase. At 9 C, with photoperiods of 11 hr or more of light, the Bangia phase produced carpospores which gave rise to the alternating Conchocelis phase. The conditions under which sporogenesis occurred determined the spore type differentiated.     

Effect of photoperiod on slow and fast developing individuals in aphidophagous ladybirds,Menochilus sexmaculatus and Propylea dissecta (Coleoptera: Coccinellidae)

The effects of environmental parameters on insect development have been studied extensively. But the reasons for 2 differential developmental rates within same cohort under varying environmental factors have not been explored. For the purpose, in this study the existence and stability of slow and fast development under 5 photoperiods (i.e., 8L: 16D, 10L : 14D, 12L : 12D, 14L : 10D and 16L : 8D; light and dark hours per day) and its effect on body mass and reproductive attributes in 2 aphidophagous ladybirds, Menochilus sexmaculatus (Fabricius) and Propylea dissecta (Mulsant) was examined on Aphis craccivora Koch at 27 ± 1 °C temperature. A clear bimodal (2 peaks, where the first peak represented the fast developing and the 2nd peak slow developing individuals) pattern of distribution at each photoperiod was found. The proportion of slow and fast developing individuals in a cohort differed with photoperiods. The slow developing individuals were more in numbers at 8L : 16D, in equal numbers at 14L : 10D and in less numbers at 16L: 8D, indicating that the variation in emergence was owing to exogenous cues influenced differential rates of mortality. Slow developing individuals had female biased sex ratio, higher longevity and lower body mass than fast developing individuals. Fast developing females laid higher numbers of eggs with higher egg viability than slow developing females. Study of such variations in development at different photoperiods is helpful to understand its role in the development of insects particularly ladybirds and permits the selection of fast developing bioagents for their use in biocontrol of pest species.     

Daily changes in concentrations of prolactin in serum of prepubertal bulls exposed to short- or long-day photoperiods

Early temporal changes in concentrations of prolactin (PRL) in serum after a sudden change in photoperiod and daily responsiveness to PRL-releasing and inhibiting factors were investigated in prepubertal Holstein bull calves exposed to different photoperiods. In calves switched from 8-hr light: 16-hr dark to 16-hr light:8-hr dark, there was no observable change in the daily pattern of serum concentrations of PRL after 1, 2, or 4 days. On the other hand, in animals switched from 16-hr light:8-hr dark to 8-hr light:16-hr dark, there was a consistent increase in serum PRL from 33.4 ng/ml on Day 0 to maximum values of 57.3, 62.7, and 78.9 ng/ml between 14 and 18 hr after onset of light on Days 1, 2, and 4, respectively. Thus, absence of light allowed expression of a daily rhythm in serum concentrations of PRL that persisted for at least 4 days after the photoperiod switch. There were no differences in L-dopa inhibition of PRL release in animals exposed to 16-hr light:8-hr dark at 3 or 15 hr after onset of light. However, thyrotropin-releasing hormone-induced release of PRL was greater 3 hr after onset of light (11 hr after onset of dark) compared with release at 9, 15, and 21 hr after onset of light in animals exposed to 16-hr light:8-hr dark, but not in bulls exposed to 8-hr light:16-hr dark. The results provide evidence that the cue for the putative photosensitive period of PRL secretion in cattle may be more closely associated with onset of dark, not onset of light.     

EFFECT OF TEMPERATURE AND PHOTOPERIOD ON GROWTH AND DORMANCY OF BETULA PAPYRIFERA

The effects of day/night temperatures and photoperiod on the growth and dormancy of paper birch (Betula papyrifera) were studied in seedlings from different geographic origins. The response of Alaskan plants to temperature and photoperiod was distinctly different from other seed sources. Alaskan plants required very long days to prevent cessation of growth while plants from southern seed sources grew on photoperiods as short as 14 hr. Low night temperature (14 C) antagonized the promotive action of long photoperiods in Alaskan plants but had little effect in other seed sources. High day temperatures offset the inhibitory effect of the cool night to a lesser degree in Alaskan plants than in plants from other locations. Dormancy induced by short photoperiods was antagonized (relieved ?) to a lesser degree by high night temperatures in Alaskan birch than in other seed sources. Betula papyrifera var. humilis from Alaska may be an incipient species since its morphological traits are accompanied by adaptive physiological responses to its environment. These responses are as distinct as its morphological characteristics.     

PHOTOCONTROL OF GROWTH AND FLOWERING OF CARYOPTERIS

Piringer , A. A., R. J. Downs , and H. A. Borthwick . (U. S. Dept. of Agriculture, ARS, Belts ville, Md.) Photocontrol of growth and flowering of Caryopteris . Amer. Jour. Bot. 50(1): 86–90. Illus. 1963.—Flower buds were initiated on plants of Caryopteris × clandonensis A. Simmonds (C. incana [Houtt.] Miq. × C. mongholica Bunge) on all photopcriods but developed to anthesis only when daily dark periods exceeded 8 hr. Anthesis occurred in not less than 22 days after the beginning of 11 or more short photoperiods. Treatments with short days could be interrupted by as many as 30 non-inductive long days without significant increase in the minimum number of short days required for anthesis. Anthesis, like floral initiation of many plants, was reversibly controlled by red and far-red radiation acting through phytochrome. The inductive effectiveness of long dark periods was nullified by 1 min of red light or about 1 hr of far red. It was modified by night temperature in the range 45–70.F and filament lengths of stamens were shorter at night temperatures of 60 than at 70 F.     

Circadian rhythm of sex pheromone-releasing behaviour in females of the dermestid beetle,Trogoderma glabrum: Regulation by photoperiod

The effects on sex pheromone-releasing, or calling behaviour, of diel photoperiods of varying daylength, of light cycle phase shifts, and of continuous illumination were investigated in Trogoderma glabrum females. On light régimes with 8 to 20 hr daylengths, calling maxima tended to centre close to photophase midpoints. Although influencing the time of day at which calling occurred, daylength had little effect on the amount of activity or the length of the calling period. When 16 : 8 LD light cycles were advanced or delayed by 4 hr, the time of day at which calling peaks were observed shifted within 2 to 4 cycles so that a constant phase relationship with photoperiod was maintained. Daily calling peaks were evident in groups of females exposed to between 1 and 5 days of continuous illumination, but mean calling time occurred earlier in the day as light exposures were lengthened. It was concluded that a circadian rhythm of calling behaviour exists in T. glabrum females. and that the rhythm can be entrained to 24 hr periodicity by photoperiod.     

The influence of breed,season and photoperiod on semen characteristics,testicular size,libido and plasma hormone concentrations in rams

Twenty-seven adult rams (9 Suffolk, 9 Texel and 9 Dorset Horn) were raised under natural photoperiod and were trained to serve into an artificial vagina. On 1 April they were abruptly exposed to 3 different photoperiods as follows: (i) 8 hours light and 16 hours darkness (8L : 16D); (ii) 16 hours light and 8 hours darkness (16L : 8D); (iii) natural photoperiod. All rams were kept at pasture daily between 09.30 h and 16.00 h except when required indoors for experimental work. Rams on artificial photoperiod had appropriate supplemental lighting in an environmental chamber. Semen collection was attempted from each ram on alternate weeks during the experiment which lasted for 6 months. Semen was evaluated for volume, density, motility and abnormalities. Testicular length and circumference were recorded at 2-week intervals and libido was recorded at 4-week intervals. Three blood samples were collected from each ram at 30-min intervals on a weekly basis and the plasma was stored at ?20°C until assayed for testosterone and prolactin.Photoperiod had no significant effect on semen volume, motility and percentage dead or abnormal cells. Breed of ram had a significant effect on semen motility (P < 0.05) with Dorset Horn rams producing semen with the highest motility. Volume and motility scores both increased as the breeding season approached (P < 0.05), while the percentage of abnormal cells decreased (P < 0.01). Breed or photoperiod did not significantly affect scrotal measurements although animals exposed to 8L : 16D had the highest measurements. Month affected testicular measurements which generally increased from April to September. Suffolk rams had higher testosterone concentrations, and this breed also completed the highest number of mounts within an allocated test time (P < 0.05). Dorset Horn rams reached a peak in testosterone concentrations in June/ July whereas Suffolks and Texels reached a similar peak in August. Prolactin concentrations decreased from a maximum at the start and rams on natural photoperiod tended to have highest levels. These results show that month can have a bigger influence on semen characteristics than imposed artificial photoperiods in rams which have been exposed to increasing natural daylength for some months.     

The interactive effects of irradiance and photoperiod on Chara vulgaris L.: concerted responses in morphology, physiology, and reproduction

Both the single and interactive effects of irradiance and photoperiod on a worldwide charophyte species, Chara vulgaris L., were investigated in a greenhouse experiment. Under high light intensity, plants exhibited shortened shoot, compact canopy and low Chl a/Caro. In contrast, elongated shoot, expanded canopy and low Chl a/Chl b corresponded to low light intensity. In addition, both ash mass ratio and relative growth rate (RGR) were positively related to light intensity. The effect of photoperiod on plants was relatively complex. Although photoperiod did not affect morphological characters, an increased photoperiod significantly decreased Chl a/Chl b and Chl a/Caro ratios. Two-way analysis of variance (ANOVA) analysis indicated that significant interaction of irradiance and photoperiod was present on ash mass ratio, RGR, Chl a/Chl b, Chl a/Caro and Chl (a + b)/Caro ratios. The high RGR found for 50% sunlight, L:D 16:8 (50/16) conditions along with the significant interaction of irradiance and photoperiod on RGR indicated that the effect of irradiance was more important than photoperiod for plant growth. And finally, both irradiance and photoperiod had positive effects on the emergence of sex organs (♂♀) and the maturation of oospores, except that increased photoperiod did not accelerate the maturation of oospores. In summary, for both plant growth and reproduction, C. vulgaris was able to acclimate morphologically and physiologically to different irradiance levels and photoperiods. This study can partly explain the broad geographic distribution of C. vulgaris. Handling editor: S. M. Thomaz     

EFFECTS OF LIGHT AND HORMONES ON REGENERATION OF CRASSULA ARGENTEA FROM LEAVES

Plantlet regeneration from leaf segments of Crassula argentea was studied under variable light and hormone treatments. The effects of two hormones (indole 3-acetic acid and isopentenyl adenine at 10⁻⁴ to 10⁻¹⁰ m ) and photoperiods of 8 (short days) or 16 hr of light (long days) were examined. Exogenously applied hormones had little stimulating effect on regeneration but were consistently inhibitory at 10⁻⁴ m . Short days and continuous darkness caused the greatest promotion of regeneration. Prolonged short-day growth periods prior to culturing caused an increasingly greater regeneration response.     

Effects of different photoperiods and wavelengths of light on the life-history traits of an aphidophagous ladybird, Coelophora saucia (Mulsant)

Abstract:  The influence of three photoperiods, viz. short day [8 : 16 h; light : dark (L : D)], long day (16 : 8 h; L : D) and continuous light (24 : 0 h; L : D) and four wavelengths of light, viz. white (control), yellow, blue and red on pre-imaginal development and reproductive performance of a ladybird, Coelophora (= Lemnia ) saucia (Mulsant) (Col., Coccinellidae) have been investigated under laboratory conditions. Long-day photoperiod and white light resulted in low immature stage mortality. Total larval period was longest under short-day and red-light conditions. Females kept at long-day photoperiod and under white light showed better reproductive performance than those placed under other photoperiods and wavelengths.     

The influence of multiple photoperiods and pinealectomy on gonads, pelage and body weight in male meadow voles, Microtus pennsylvanicus

1. Chronic exposure of male Microtus pennsylvanicus to photoperiods with 8, 10 and 12 hr of light per day results in gonadal regression, molt to winter pelage and significant reductions in body weight and food consumption relative to voles kept on photoperiods with 13 and 14 hr of light per day. 2. A precise critical daylength is observed in this species as exposure to photoperiods with 12 or fewer hours of light per day results in complete gonadal involution, seasonal molt and loss of body weight. 3. Pinealectomy abolishes all short-photoperiod induced responses in this species.     

Long day photoperiods and temperature of 20 degrees C induce spermatogenesis in blinded and non-blinded marbled newts during the period of testicular quiescence

Adult male marbled newts (Triturus marmoratus) were collected at the end of the spermatogenesis period and exposed to different photoperiods (natural-daylength-simulated photoperiod, total darkness, 8L:16D, 12L:12D, 16L:8D, and continuous light) for 3 mo. Temperature was maintained at 20 degrees C. Two additional groups of newts were blinded and exposed to either the natural-simulated photoperiod and to 16 h of light per day respectively. Quantitative histologic studies on testicular development and germ cell volume per testis were performed. The newts captured in the field at the beginning (initial controls) or at the end of the experiments (final controls) were in the period of testicular quiescence. Newts kept in total darkness or exposed to a short photoperiod (8L:16D) showed germ cell development up to primary spermatocytes, whereas germ cell development in the newts exposed to long photoperiods (12L:12D or 16L:8D) progressed to elongated spermatids. The newts exposed either to intermediate photoperiods (natural-simulated photoperiod) or to constant light showed an intermediate degree of germ cell development (up to round spermatids). No significant differences between non-blinded and blinded animals were found. These results suggest that (1) mild temperature initiates testicular development in the period of testicular quiescence, (2) long photoperiods associated with mild temperatures produce spermatogenesis in this period, (3) complete darkness or constant light are less effective than some intermediate photoperiod, and (4) the effect of photoperiod on testicular function in newts is not related to ocular photoreception.     

Ultraviolet Radiation on Innate Immunity and Growth of Broad-Snouted Caiman (Caiman latirostris): Implications for Facilities Design

Sunlight is a key environmental factor in almost all ecosystems, and it is necessary for many physiological functions. Many vertebrates require ultraviolet (UV) radiation to perform different physiological processes. Artificial light is used to supplement UV in captive animals, through appropriate photoperiods and UV wavelengths. Previous studies reported that repeated exposure to artificial UV radiation may cause damage to the immune system. Taking into account the importance of UV effects and the serum complement system, the relationship between them was investigated. The study lasted 90 days and was carried out in plastic chambers. Ninety six broad‐snouted caiman (C. latirostris) were assigned to four treatment groups with two replicates each: total darkness (TD), 8 hr per day (8 hr) and 16 hr per day (16 hr) of artificial UV/visible light exposure, and normal photoperiod of natural light (NP). Snout–vent length was measured to determine animal growth. Hemolytic assays were performed to evaluate the effects of artificial UV/visible light, TD, and NP on the serum complement system. Results showed that animals grew more in the NP group. The capacity of C. latirostris serum to hemolyze sheep red blood cells was higher in the NP group than when they are maintained in constant light–dark cycles (8 and 16 hr) or in TD. These data demonstrate that artificial UV should be considered as a potential hazard for captive crocodilians if it is not properly managed, and this should be taken into account in the general design of facilities for reptilian husbandry. Zoo Biol 31:523‐533, 2012. © 2011 Wiley Periodicals, Inc.