Effects Of Short Days Research Articles

Effect of Short Day and Low Temperature at the Nursery Stage on the Inflorescence and Yield of Six Different Strawberry (Fragaria ananassa Dutch.) Cultivars in a Soilless Culture System

In Korea, the majority of strawberry cultivation follows a forcing culture, where planting occurs in mid-September after the flower differentiation, and harvesting begins at the end of November. October and November constitute off-season, resulting in higher prices. The accelerated forcing culture involves artificially promoting flower differentiation to expedite strawberry harvest. This study aimed to identify the most suitable schedule for strawberry cultivation using the short-day and low-temperature treatments through greenhouse environmental control during the nursery stage. The selection of the most suitable cultivars for accelerated forcing culture among Korean breeding cultivars (‘Sulhyang’, ‘Kuemsil’, ‘Kingsberry’, ‘Vitaberry’, ‘Jukhyang’, and ‘Altaking’) was also part of the objectives. The nursery treatments were initiated on 4 July, 14 July, and 25 July. After approximately 5 weeks of treatment, transplanting was carried out. The control group was transplanted on 15 September. When night-chilling nursery treatment was applied on 4 July, followed by transplanting on 11 August, all six cultivars exhibited flowering earlier compared to the control group, leading to increased early yield. Particularly, the ‘Sulhyang’ cultivar showed the highest marketable yield at 68.6 g per plant in October. This research contributes to identifying the nursery cultivation schedule for off-season strawberry production and selecting suitable cultivars, and is expected to contribute to increased farm income.

Effects of short day and temperature on growth and flowering of Vanda hybrid

Effects of short day and temperature on growth and flowering of <i>Vanda</i> hybrid

Effect of artificial short-days on morphological characterization of standard chrysanthemum (Chrysanthemum morifolium Ramat) genotypes

Effect of artificial short-days on morphological characterization of standard chrysanthemum (Chrysanthemum morifolium Ramat) genotypes

Long juvenility trait: A vehicle for commercial utilization of soybean (Glycine max) in lower latitudes

AbstractSoybean, a short‐day plant, has its origin in higher latitudes of China, and its commercial cultivation remained confined to areas &gt;22°N till 1970s due to precocious flowering accompanied with reduced biomass in lower latitudes. This review summarizes the effect of short days on soybean phenology, discovery of a novel long juvenile (LJ) trait, its role in breaking the latitudinal boundary for soybean production, identification of genes and impact of LJ trait on world soybean production. E6, J and E9 major genes governing the trait have been characterized and cloned. LJ varieties are late in flowering and maturity and successful in long rainfall regime of Brazil. Availability of vast vacant fallows of Cerrado has been another factor for utilization of this trait in Brazil. Recent advances for developing short‐duration LJ varieties, for limited rainfall areas and its suitability to existing cropping systems by combining it with photoinsensitivity, have been reviewed. Based on the available data from lower latitudes of Brazil, the contribution of the LJ trait is estimated to 23.7% of the total world production.

Effect of melatonin from slow-release implants on aquaporins (AQP1 and AQP4) in the ovine choroid plexus

Aquaporins (AQPs) play important role in the cerebrospinal fluid (CSF) secretion and AQP1 and AQP4 are localized in the choroid plexus (CP), which is the main place of CSF production. In ewes, seasonally breeding animals, the turnover rate (TOR) of CSF is photoperiodically modulated and melatonin, a biochemical signal about changing photoperiod, is used to advance the onset of the breeding season by mimicking the stimulatory effect of short days (SD). This study evaluates the effect of melatonin implantation during long days (LD) on AQPs expression in the ovine CP. Studies were performed on ovariectomized, estradiol implanted ewes treated with placebo (n = 6) or with melatonin (n = 6) during LD. Ewes were sacrificed 40 days after melatonin/placebo implantation and CPs from the lateral/third brain ventricles were collected for Real-time and Western blot analyses. Additionally, for immunohistochemical analysis, CP samples were collected from ewes (n = 3) sacrificed during LD. We demonstrated an apical membrane localization of AQP1 and a diffused distribution of AQP4 in the epithelial cells of CP. The mRNA expression of AQP1 was 20 times higher than the expression of all AQP4 isoforms, and among them AQP4 isoforms containing exon 2 constituted approximately 38%. The melatonin implantation significantly (P &amp;lt; 0.05) increased the mRNA expression of AQP1 and AQP4 and the protein level of AQP4 isoforms (33 and 28 kDa). For AQP1 we observed a significant (P &amp;lt; 0.05) decrease of glycosylated (33 kDa) and a significant (P &amp;lt; 0.05) increase of unglycosylated (23 kDa) predominant protein form. Therefore it can be suggested that at least AQP1, which is involved in CSF production and has been demonstrated to be modulated by melatonin implantation, is linked with the photoperiodic modulation of the CSF production in ewes.

Circadian clock regulates photoperiodic responses governed by distinct output pathways in the bean bug, Riptortus pedestris

Effects of RNA interference (RNAi) targeted against circadian clock genes on two distinct types of photoperiodic responses – ovarian development and lipid accumulation – were investigated in a bean bug Riptortus pedestris, to explore which physiological process in the photoperiodic response involved the circadian clock. Ovarian development and lipid accumulation are known to be regulated by distinct output pathways. Control insects showed clear photoperiodic responses; i.e. induction of ovarian development and suppression of lipid accumulation under long-day conditions, whereas opposite characteristics under short-day conditions. We found that RNAi directed against period, a negative element of the circadian clock, produced a long-day effect for both the ovarian development and lipid accumulation, while RNAi directed against Clock, a positive element of the circadian clock, produced a short-day effect for both, irrespective of photoperiod. These results indicate that the circadian clock comprised of these genes regulates a process governing both distinct photoperiodic responses.

Low temperature-induced circulating triiodothyronine accelerates seasonal testicular regression.

In temperate zones, animals restrict breeding to specific seasons to maximize the survival of their offspring. Birds have evolved highly sophisticated mechanisms of seasonal regulation, and their testicular mass can change 100-fold within a few weeks. Recent studies on Japanese quail revealed that seasonal gonadal development is regulated by central thyroid hormone activation within the hypothalamus, depending on the photoperiodic changes. By contrast, the mechanisms underlying seasonal testicular regression remain unclear. Here we show the effects of short day and low temperature on testicular regression in quail. Low temperature stimulus accelerated short day-induced testicular regression by shutting down the hypothalamus-pituitary-gonadal axis and inducing meiotic arrest and germ cell apoptosis. Induction of T3 coincided with the climax of testicular regression. Temporal gene expression analysis over the course of apoptosis revealed the suppression of LH response genes and activation of T3 response genes involved in amphibian metamorphosis within the testis. Daily ip administration of T3 mimicked the effects of low temperature stimulus on germ cell apoptosis and testicular mass. Although type 2 deiodinase, a thyroid hormone-activating enzyme, in the brown adipose tissue generates circulating T3 under low-temperature conditions in mammals, there is no distinct brown adipose tissue in birds. In birds, type 2 deiodinase is induced by low temperature exclusively in the liver, which appears to be caused by increased food consumption. We conclude that birds use low temperature-induced circulating T3 not only for adaptive thermoregulation but also to trigger apoptosis to accelerate seasonal testicular regression.

Dorsomedial Hypothalamic Lesions Block Syrian Hamster Testicular Regression in Short Day Lengths Without Diminishing Increased Testosterone Negative-Feedback Sensitivity1

The dorsomedial nucleus (DMN) of the hypothalamus, the only site within the mediobasal hypothalamus of Syrian hamsters that both binds melatonin and has abundant concentrations of androgen receptors, has been proposed as a target tissue for induction of seasonal changes in brain sensitivity to steroid negative feedback. We tested whether DMN ablation, which does not interfere with pineal gland secretion of melatonin in short day lengths, prevents testicular regression by altering sensitivity to steroid negative feedback. Hamsters with DMN lesions, unlike control hamsters, failed to undergo testicular regression after transfer from a long (14 h light/day) to a short day length (8 h light/day); however, increased negative-feedback inhibition of follicle-stimulating hormone by testosterone was not compromised by ablation of the DMN, indicating that this tissue is not an essential mediator of seasonal changes in feedback sensitivity. We propose a redundant neural network comprised of multiple structures, each of which contributes to neuroendocrine mechanisms, that determines the effect of short days on gonadal function.

Exogenous melatonin reproduces the effects of short day lengths on hippocampal function in male white-footed mice, Peromyscus leucopus

Photoperiodism is a biological phenomenon, common among organisms living outside of the tropics, by which environmental day length is used to ascertain the time of year to engage in seasonally-appropriate adaptations. White-footed mice (Peromyscus leucopus) are small photoperiodic rodents which display a suite of adaptive winter responses to short day lengths mediated by the extended duration of nightly melatonin secretion. Exposure to short days alters hippocampal dendritic morphology, impairs spatial learning and memory, and impairs hippocampal long-term potentiation (LTP). To determine the role of melatonin in these photoperiod-induced alterations of behavioral, neuroanatomical, and neurophysiological processes in this species, we implanted male mice subcutaneously with melatonin or empty Silastic capsules and exposed them to long or short day lengths. After 10weeks, mice were assessed for hippocampal LTP, tested for spatial learning and memory in the Barnes maze, and morphometric analysis of neurons in the hippocampus using Golgi staining. Extending the duration of melatonin exposure, by short-day exposure or via melatonin implants, impaired both Schaffer collateral LTP in the CA1 region of the hippocampus and spatial learning and memory, and altered neuronal morphology in all hippocampal regions. The current results demonstrate that chronic melatonin implants reproduce the effects of short days on the hippocampus and implicate melatonin signaling as a critical factor in day-length-induced changes in the structure and function of the hippocampus in a photoperiodic rodent.

Effects of Short Day Conditioning, Chilling and GA3 Treatments to Yield and Fruit Quality in Strawberry Plug Transplants Aiming Early Fruit Production

In this study, we tested the effects of short day (SD), chilling (Ch) and gibberalic acid (GA3) treatments on the yield and fruit characteristics of ‘Camarosa’ and ‘Sweet Charlie’ plug plants under a freeze-protected greenhouse in Mediterranean conditions for two growing seasons in 2006-2007 and 2007-2008. The treatments included control (ambient day length and temperature); SD (8 h days) and ambient temperature; SD + Chilling (Ch) (18/12°C day/night temperatures); SD + Ch (10°C); SD + Ch (2°C); and, GA3 (10 ppm applied to the plants in November). In each growing season, the plug plants were planted in mid-August using bag culture. Yield, fruit weight, firmness, total soluble solids (SS), titratable acidity (TA), and SS/TA ratio were investigated. Considerable amounts of early yield (March and April) were recovered from ‘Sweet Charlie’; 116 and 72 g/plant in the first and second growing seasons, respectively. ‘Sweet Charlie’ also had consistently higher total yield than ‘Camarosa’ (457 vs. 400 g/plant in the 2006-2007 season and 446 vs. 406 g/plant in the 2007-2008 season). Treatment did not have a consistent effect on the fruit quality traits measured. The results indicated that although SD conditioning, Ch and GA3 treatments may have an effect on the total and early yield of strawberries, these effects may be cultivar-dependent and further regulated by environmental factors. Therefore, we propose that low-chilling varieties be utilized for early fruit production that can initiate flower buds in warmer, longer days.

Seasonal Variation in Sensitivity of the Photoperiodic Response System in the Subtropical Tree Sparrow (Passer montanus)

We investigated seasonal variations in response to photoperiods in subtropical tree sparrow (Passer montanus), by examining the effects of long and short days on stimulation of response and termination of refractoriness, respectively. We also assessed whether photoperiodic effects were sex dependent. In one study, wild sparrows were transferred in each month of the year to artificial long days (14L/10D) for 12 weeks. Birds transferred from November to March (female) or April (male) showed gradual increase in gonadal growth and darkening of bill color, while those transferred from April (female) or May (male) to July underwent gradual regression in the above responses. Moult in the wing primaries and body feathers progressed with gonadal regression and the birds transferred from April/May to October exhibited gradual increase and decrease in feathers moult. In another study, 6 weeks of short day (9L/15D) exposure could recover responsivity to long days in refractory birds. Male and female birds responded almost in similar fashion with some variations. Overall, our results show a gradual change over seasons in responsiveness of the endogenous response system to stimulatory effects of long day length. They suggest roles of both long and short day lengths in regulation of seasonal cycles in subtropical tree sparrows.

Can advance of first lambing induced by melatonin implants influence the next lambing time in Sarda breed sheep?

Carcangiu, V., Mura, M. C., Bini, P. P., Vacca, G. M., Daga, C. and Luridiana, S. 2012. Can advance of first lambing induced by melatonin implants influence the next lambing time in Sarda breed sheep? Can. J. Anim. Sci. 92: 67–71. In adult sheep, exogenously administered melatonin from continuous slow-release implants has been shown to advance the onset of the breeding season by mimicking the stimulatory effect of short days. The aim of this study was to verify if treatment with one or two melatonin implants was effective in advancing the first conception in Sarda ewe lambs, and if this advance would also be seen in the second lambing too. In the first year, 600 ewe lambs were randomly assigned to groups M, M+M and C, each with 200 animals. On Jun. 30, group M received a single implant while group M+M received two implants. Group C was untreated. On Aug. 04, 25 rams were introduced in the groups and removed after 70 d. From these 600 animals the 420 head that lambed prior to Mar. 12 were chosen for the second year. These ewes were subdivided into two groups T1 (ewes who lambed between 2007 Jan. 01 and Feb. 10) and T2 (ewes which lambed between 2007 Feb. 11 and Mar. 12). Both in T1 and T2 the distribution of the animals in M, M+M and C group was maintained. In the first year, the treated animals lambed earlier (P&lt;0.05) and showed higher numbers of lambed ewes at Feb. 10 (P&lt;0.01) and at March 12 (P&lt;0.05) compared with untreated control animals. The animals that showed an advance in the period of their first conception, also showed, in the second breeding year, an advance in the lambing time (P&lt;0.001). This study provides evidence that the advance of first conception, obtained with melatonin treatment also influenced the reproductive activity in the following breeding season.

The effect of melatonin treatment in rams on seasonal variation of testicular size and semen production parameters

The administration of exogenous melatonin can mimic the stimulatory effect of short days in advancing the onset of maximum reproductive parameters in seasonal rams. However, the animals need to be previously exposed to natural or artificial long days before responding to the melatonin treatment. The objective of this study was to test the effect of melatonin treatment on rams, initiated in mid May (end of spring) – when rams have already been exposed to some months of increasing day length, but not to artificial long day treatment on testicular size and semen characteristics. Sixteen rams (8 Texel and 8 Charollais) were treated with melatonin subcutaneous implants (REGULIN®) on 22 May and 20 June (spring/summer) (n=8) or remained untreated (n=8). Blood samples were taken from all rams over a 24-h period to determine the plasma melatonin concentration profile. The ram's testes were all measured four times at 2-week intervals, and testicular volume and scrotal circumference determined. Semen was collected using the artificial vagina at two occasions (end of June and end of August), when 5 ejaculates were obtained from each ram and analysed for semen volume and sperm concentration. The plasma melatonin levels in the melatonin-treated rams were significantly higher than for the untreated rams (P<0.01). During the dark phase of the day, the plasma melatonin concentrations were elevated (P<0.01) in the control, but not in the melatonin-treated rams. Scrotal circumference and testicular volume increased (P<0.001) from May to July (late spring to mid-summer) in both groups of rams, with no significant difference being detected between groups. Semen volume and sperm concentration increased (P<0.01) from June (summer) to July/September (summer/autumn) in both treatment groups. Melatonin treatment of the rams did not affect the semen volume or sperm concentration during any of the collection periods. Data suggest that the treatment of rams with melatonin implants initiated in late spring, without a priming period of long days preceding the treatment, is not sufficient stimulus to increase testis growth and sperm production.

Effects of photoperiod on gluconeogenic activity and total lipid concentration in organs of crabs, Neohelice granulata, challenged by salinity changes

Abstract. This study assessed the effects of long (LD) or short (SD) days on the conversion of [14C]‐glycerol to [14C]‐glucose and total lipid concentration in organs of the crab Neohelice granulata challenged by a change in external salinity. In the 20‰‐acclimated crabs, no difference was found in the concentration of total lipids in the muscle, hepatopancreas, gills, or hemolymph between crabs acclimated to SD or LD. In SD crabs, the total lipid levels in the anterior and posterior gills did not decrease during an osmotic challenge. Only in the posterior gills did the total lipid levels decrease during acclimation to the 34‰ medium in LD animals. The total lipid concentration in the hemolymph decreased after 1 d of osmotic stress in SD, and increased in the hepatopancreas. In LD crabs, the lipid contents decreased gradually in muscle, and in the hepatopancreas on day 3 after transfer to 34‰ medium. In 20‰‐acclimated crabs, the gluconeogenesis activity in both sets of gills was higher in LD than in SD animals. The gluconeogenesis capacity decreased in both sets of gills on the first day of osmotic challenge in SD, and in the posterior gills on the third day in LD crabs. These results suggest that in organs of N. granulata, photoperiod affects the metabolic adjustments to an osmotic challenge.

Temperature and photoperiodic control of diapase induction in the ant Lepisiota semenovi (Hymenoptera, formicidae) from Turkmenistan

The ant L. semenovi has been found to belong to species with endogenous-heterodynamic seasonal life cycles with the obligate diapause induced predominantly by factors internal for a colony, whereas external ecological factors (photoperiods and temperature) produce merely modifying effects by accelerating or delaying the diapause onset. The photoperiodic and temperature regulation of diapause induction in larvae and queens is shown. Under effect of short days and low temperature the periods of larval pupation and queen oviposition in a colony are shortened markedly, i. e., the periods of larvae and queens occurs earlier. The daily rhythms of temperature 15/25 degrees C and particularly 20/30 degrees C as compared with constant temperatures 20 and 25 degrees C that correspond to the mean daily temperatures of the thermorhythm, inhibit manifestations of the short day effects by stimulating the non-diapause development and increasing duration of the seasonal development cycle of ant colonies. The L. semenovi photoperiodic reaction is quantitative, as development and pupation of larvae and egg-laying of queens cease sooner or later under both the short and the long days, but in the latter case significantly later. Thus, L. semenovi is one more example among very rare ant species that are revealed to have the photoperiodic regulation of the colony development seasonal cycle.

A circadian system is involved in photoperiodic entrainment of the circannual rhythm of Anthrenus verbasci

In the circannual pupation rhythm of the varied carpet beetle, Anthrenus verbasci, entrainment to annual cycles is achieved by phase resetting of the circannual oscillator in response to photoperiodic changes. In order to examine whether a circadian system is involved in expression of the periodic pattern and phase resetting of the circannual rhythm as photoperiodic responses, we exposed larvae to light–dark cycles with a short photophase followed by a variable scotophase (the Nanda–Hamner protocol). When the cycle length ( T) was a multiple of 24 h, i.e., 24, 48, or 72 h, short-day effects were clearer than when T was far from a multiple of 24 h, i.e., 36 or 60 h. Exposure to light–dark cycles of T = 36 h had effects similar to exposure to long-day cycles of T = 24 h. The magnitude of phase shifts depended on the duration and the phase of exposure to the cycles of T = 36 or 60 h. It was therefore concluded that a circadian system is involved in photoperiodic time measurement for phase resetting of the circannual oscillator of A. verbasci.

Responses to stepwise photoperiodic changes for the larval diapause of the Indian meal moth Plodia interpunctella

Abstract The Indian meal moth Plodia interpunctella Hübner (Lepidoptera: Pyralidae) diapauses as a last‐instar (fifth) larva. At 30 °C, no larvae enter diapause under any photoperiodic conditions; at 25 °C, the photoperiodic response curve is a long‐day type with a critical length of approximately 13 h light; at 20 °C, diapause is induced moderately even under long days (&gt; 13 h). Cumulative effects of short days or long days on diapause induction are determined by alternate, stepwise and gradually changing regimes of photoperiod at 25 °C. When the larvae are repeatedly exposed to LD 16 : 8 h and LD 12 : 12 h photoperiods every other day, the incidence of diapause is 37%. When the larvae are placed under an LD 16 : 8 h photoperiod for 2 days and then under an LD 12 : 12 h photoperiod for 1 day, it is 38 %. Exposure to an LD 16 : 8 h photoperiod for 1 day and then to an LD 12 : 12 h photoperiod for 2 days induces only 15% diapause. This may indicate that the photoperiodic information is not accumulated in a simple fashion despite the generally accepted hypothesis (i.e. photoperiodic counter). Larvae exposed to an LD 16 : 8 h photoperiod for 5 days after oviposition express a very high incidence of diapause even under short days between an LD 2 : 22 h and LD 12 : 12 h photoperiod. After 10 days exposure to an LD 16 : 8 h photoperiod, however, the short day does not induce diapause strongly. On the other hand, an LD 12 : 12 h photoperiod in the early larval life is highly effective in the induction of diapause. A gradual increase or decrease of photoperiod (2 min day−1) shows that the direction of photoperiodic change does not affect the diapause determination.

The Effects of Crown Removal, Short Days and Polyethylene Mulch Color on Fruit Yield Parameters and Quality Compounds, in Tunnel-Grown ‘Korona’ Strawberry (Fragaria × ananassa Duch.)

The effects of exposing strawberry plants to a short-day treatment (10 h day-1) from August 10 to September 17, and reducing the crown number per plant in the following spring were examined on fruit yield and quality in Haygrow® (UK) tunnel-grown strawberries. Reducing the number of crowns per plant increased °Brix level and reduced fruit yield. The yield reduction was lower than the reduction in crown number should account for, mainly because the number of fruits per crown was higher on plants with reduced crown number than on multicrown (MC) plants. Short-day treatment increased yield by 10% in MC plants compared with plants grown under ambient light, but the length of the photoperiod had no effect on quality compounds irrespective of crown number. However, for fruit size there was a significant interaction between day-length and crown number, expressed as increased fruit size of plants under ambient light conditions and no effect on short-day plants owing to reduced crown number. There were no interactions between other experimental factors on the characters in question here.

Melatonin mediates photoperiod control of endocrine adaptations and humoral immunity in male Siberian hamsters

Effects of photoperiod are mediated by the pineal gland in male Siberian hamsters. The hypothesis that the pineal hormone melatonin mediates the effects of short days (SD) to blunt select humoral and endocrine functions was tested. In the first study, regressed testes were found in pineal-intact controls transferred from long days (LD) to SDs (16 hr to 8 hr light/day); the rise in antigen-induced serum immunoglobulin (Ig) M was blunted and serum cortisol concentrations elevated compared with long-day controls. These effects of short-day were blocked in pinealectomized males moved from long to SDs, but restored by melatonin treatments. In a second study, males in LD were exposed to constant light (LL) to abolish the nighttime melatonin rhythm. In hamsters in LL, melatonin induced testicular regression as in males in SDs. Large testes were present in vehicle-treated controls in LL and in males that remained in LDs. Antigen-induced increases in serum IgM in vehicle and melatonin treatment males in LL were intermediate between concentrations in long- or short-day controls and not significantly different from each other. However, serum cortisol was again elevated in hamsters in SDs or in LL when treated with melatonin compared with males in LL or LDs. These findings indicate that melatonin treatments mimicked the effects of SDs to regulate adaptive physiologic functions in hamsters lacking the nocturnal melatonin rhythm. Thus, the photoneuroendocrine mechanism regulating reproductive responses to photoperiod also mediates short-day effects on T cell-dependent B-cell antibody production and processes that regulate cortisol in circulation.

Diapause dynamics, seasonal phenology, and pupal color dimorphism of Papilio polyxenes in southern Florida, USA

AbstractThe seasonal phenology, pupal diapause, and pupal color dimorphism of a Papilio polyxenes Fabr. (Lepidoptera: Papilionidae: Papilionini) population from subtropical southern Florida, USA, were studied. Adult eclosion from field‐collected individuals indicated that this population is primarily active from the late dry season through the wet season (March–September). Most pupae entering diapause in April eclosed the same year but one pupa eclosed the following February. In laboratory tests, larval rearing under short days (L10:D14) induced 88.6% pupal diapause. Diapause responses to relatively longer (L12:D12–L16:D8) photoperiods ranged from 35.1–51.5%, and were statistically equivalent. These results indicate greater variability in the photoresponse of subtropical P. polyxenes compared to temperate populations that generally show little diapause under long‐day conditions and complete diapause under short days. The proportions of diapause pupae and brown pupal color, among broods reared at photoperiods ≥L12:D12, were both normally distributed. Diapause pupae were sensitive to photoperiods from L10:D14 to L16:D8. Diapause duration was inversely related to the photophase length to which the pupae were continuously exposed. Four generations of selection, at L10:D14, for non‐diapause reduced pupal diapause from 88.6 to 20.6%, indicating the existence of considerable additive genetic variance for this trait. Selection for non‐diapause increased the percentage of green pupae from 21.8 to 58.8% and decreased the incidence of diapause in both green and brown pupae. Brown pupal color and liability to diapause are linked, but this linkage is weaker than that documented in temperate populations. The overriding effect of short days (L10:D14) inducing only brown diapause pupae did not occur in southern Florida P. polyxenes.