Longer Photoperiods Research Articles

The synchronization of neuronal oscillators determined by the directed network structure of the suprachiasmatic nucleus under different photoperiods.

The main function of the principal clock located in the suprachiasmatic nucleus (SCN) of mammals is synchronizing the body rhythms to the 24 h light-dark cycle. Additionally, the SCN is able to adapt to the photoperiod of the cycle which varies among seasons. Under the long photoperiod (LP), the synchronization degree of the SCN neurons is lower than that under the photoperiod (SP). In the present study, a potential explanation is given for this phenomenon. We propose that the asymmetrical coupling between the light-signal-sensitive part (the ventralateral part, abbreviation: VL) and the light-signal-insensitive part (the dorsalmedial part, abbreviation: DM) of the SCN plays a role in the synchronization degree, which is reflected by the ratio of the number of the directed links from the VL neurons to the DM neurons to the total links of both directions between the VL and the DM. The ratio is assumed to characterize the directed network structure under different photoperiods, which is larger under the SP and smaller under the LP. We found that with the larger ratio in the situation of the SP, the synchronization degree is higher. Our finding may shed new light on the asymmetrical coupling between the VL and the DM, and the network structure of the SCN.

고온, 일장 및 저일사 조건이 감자 생육 및 수량에 미치는 영향

지구 온난화에 의한 미래의 기후변화는 감자의 생물 계절, 생육 및 수량에 지대한 영향을 미칠 것으로 예상되므로 그 영향을 평가하여 적응대책을 수립하여야 한다. 본 연구에서는 고온조건을 포함한 다양한 기상 조건에서 감자의 생육과 수량 변화를 확인하고자 하였다. 작기 이동 실험은 2014년과 2015년, 수원의 서울대학교 부속 실험농장에서 실시되었으며, 봄 실험에서는 조생종인 남작과 수미 그리고 중만생종인 대서를 세 번의 파종기에 걸쳐 재배하였다. 가을 실험에서는 수미와 대서를 두번의 파종기에 걸쳐 2014년에만 재배하였다. 괴경형성기는 품종과 파종기에 따라 출아 후 11일부터 22일까지 다양한 시기에 나타났다. 기상요인들이 괴경형성기에 미치는 영향을 분석한 결과, 현재 기후조건에서 괴경형성기는 기온 상승과 단일조건하에서 촉진되었다. 반면에 고온과 장일 조건에서 적은 일사량은 역시 괴경형성기를 지연시켰다. 공시 품종 모두 괴경형성 적온은 <TEX>$22-24^{\circ}C$</TEX> 내외로 추정되었으며, 기온, 일장 및 일사는 괴경형성에 상승적으로 상호작용하였다. 재배기간, 괴경 형성기와 기상요인이 수량에 미치는 영향을 확인하기 위한 능형회귀 결과 가장 큰 영향은 재배기간으로 나타났다. 남한에서 감자의 생육기간은 봄철의 장마와 늦가을의 서리로 제한된다. 이는 봄 작기 동안의 수원의 평균 기온이 감자 수량의 최적온도와 큰 차이를 보이지 않고 2014~2015년 마른장마로 인해 생육시기 동안 충분한 일사량이 확보되어 제한요인으로 작용하지 못하였기 때문이다. 앞당겨진 괴경형성기와 최저기온의 상승은 수량을 감소시켰다. <TEX>$17-22^{\circ}C$</TEX> 범위의 평균기온에서는 일교차만이 수량에 큰 영향을 주었다. 고온반응 실험은 2015년에 서울대학교 부속실험농장의 플라스틱 하우스 4개동에서 수행되었다. 대표 품종으로 수미가 이용되었으며, 4월 29일과 9월 17일에 외기온 프라스틱하우스와 외기온보다 <TEX>$1.5^{\circ}C$</TEX>, <TEX>$3.0^{\circ}C$</TEX>, <TEX>$5.0^{\circ}C$</TEX> 높게 조절되는 프라스틱 하우스에 각각 80주씩 파종하였다. 가을실험에서는 출아기와 괴경형성기만을 관측하였다. 괴경형성기는 장일효과로 인해 봄 실험에서 가을 실험에 비해 14일 가량 늦어졌으며, <TEX>$5.0^{\circ}C$</TEX> 온실에서는 고온, 저일사와 장일효과로 인해 괴경이 형성되지 않았다. 온도 상승에 따라 괴경 형성 초기의 괴경 숫자가 감소하여, 괴경으로 전류되는 동화산물과 수확기 괴경의 평균 생서중이 감소하였다. 잉여동화산물은 주로 줄기로 집적되어 왕성한 줄기신장을 보였다. 본 실험 결과에 따르면 이미 수원의 현재 기후는 감자재배의 적온 범위를 벗어나기 시작하였으며, 미래기후에서 고온피해는 더 심각하게 나타날 것이다. 하지만, 감자의 괴경 형성 및 비대에 대한 이해는 아직까지도 부족한 상태이므로 미래 기후 변화 영향을 평가하기 위해서는 고온 하에서 감자의 생리적 반응에 대한 구체적인 연구가 필요할 것으로 사료된다. Potato phenology, growth, and yield are projected to be highly affected by global warming in the future. The objective of this study was to examine the responses of potato growth and yield to environmental elements like temperature, solar radiation, and daylength. Planting date experiments under open field condition were conducted using three cultivars differing in maturity group (Irish Cobbler and Superior as early; Atlantic as mid-late maturing) at eight different planting dates. In addition, elevated temperature experiment was conducted in four plastic houses controlled to target temperatures of ambient temperature (AT), <TEX>$AT+1.5^{\circ}C$</TEX>, <TEX>$AT+3^{\circ}C$</TEX>, and <TEX>$AT+5^{\circ}C$</TEX> using cv. Superior. Tuber initiation onset was found to be hastened curve-linearly with increasing temperature, showing optimum temperature around <TEX>$22-24^{\circ}C$</TEX>, while delayed by longer photoperiod and lower solar radiation in Superior and Atlantic. In the planting date experiments where the average temperature is near optimal and solar radiation, rainfall, pest, and disease are not limiting factor for tuber yield, the most important determinant was growth duration, which is limited by the beginning of rainy season in summer and frost in the late fall. Yield tended to increase along with delayed tuber initiation. Within the optimum temperature range (<TEX>$17^{\circ}-22^{\circ}C$</TEX>), larger diurnal range of temperature increased the tuber yield. In an elevated temperature treatment of <TEX>$AT+5.0^{\circ}C$</TEX>, plants failed to form tubers as affected by high temperature, low irradiance, and long daylength. Tuber number at early growth stage was reduced by higher temperature, resulting in the decrease of assimilates allocated to tuber and the reduction of average tuber weight. Stem growth was enhanced by elevated temperature at the expense of tuber growth. Consequently, tuber yield decreased with elevated temperature above ambient and drop to almost nil at <TEX>$AT+5.0^{\circ}C$</TEX>.

Comparative Proteomic Analysis of the Response of Maize (Zea mays L.) Leaves to Long Photoperiod Condition.

Maize (Zea mays L.), an important industrial material and food source, shows an astonishing environmental adaptation. A remarkable feature of its post-domestication adaptation from tropical to temperate environments is adaptation to a long photoperiod (LP). Many photoperiod-related genes have been identified in previous transcriptomics analysis, but proteomics shows less evidence for this mechanism of photoperiod response. In this study, we sampled newly expanded leaves of maize at the three- and six-leaf stages from an LP-sensitive introgression line H496, the donor CML288, LP-insensitive inbred line, and recurrent parent Huangzao4 (HZ4) grown under long days (15 h light and 9 h dark). To characterize the proteomic changes in response to LP, the iTRAQ-labeling method was used to determine the proteome profiles of plants exposed to LP. A total of 943 proteins differentially expressed at the three- and six-leaf stages in HZ4 and H496 were identified. Functional analysis was performed by which the proteins were classified into stress defense, signal transduction, carbohydrate metabolism, protein metabolism, energy production, and transport functional groups using the WEGO online tool. The enriched gene ontology categories among the identified proteins were identified statistically with the Cytoscape plugin ClueGO + Cluepedia. Twenty Gene Ontology terms showed the highest significance, including those associated with protein processing in the endoplasmic reticulum, splicesome, ribosome, glyoxylate, dicarboxylate metabolism, L-malate dehydrogenase activity, and RNA transport. In addition, for subcellular location, all proteins showed significant enrichment of the mitochondrial outer membrane. The sugars producted by photosynthesis in plants are also a pivotal metabolic output in the circadian regulation. The results permit the prediction of several crucial proteins to photoperiod response and provide a foundation for further study of the influence of LP treatments on the circadian response in short-day plants.

Seasonal change in xylem growth of Pinus densiflora in central Japan

This study investigated the seasonal change in xylem growth of Japanese red pine (Pinus densiflora). Wood cores were sampled at 2-week intervals from April to November in 2012 using the microcoring method. Daily increment rates of tracheid number and tree-ring width were compared with seasonal changes in daily mean temperature and photoperiod. Xylem growth started in early to late May and stopped in late October to early November. The maximum daily increment rates of tracheid number and tree-ring width were in early July. The 95 % confidence intervals of the timing of the maximum daily increment rates included the summer solstice (23 June) with the longest photoperiod, but not the warmest day (30 July). The maximum daily increment rate of xylem growth is thought to be controlled by the photoperiod rather than by temperature. The daily mean temperature exceeded 20 °C after the summer solstice, indicating that temperature is not a limiting factor for xylem growth. This study suggests that the timing of maximum daily increment rates of xylem growth of P. densiflora is controlled by the photoperiod.

Responses of Flowering Time to Elevated Carbon Dioxide among Soybean Photoperiod Isolines

Changes in the phenology of flowering in soybeans caused by long-term growth at elevated CO2 may be important to the responses of seed yield to elevated CO2. Here we utilized near-isogenic lines of soybeans differing in three genes influencing photoperiod sensitivity to determine whether these genes affected the response of flowering time to elevated CO2. Six isolines of Harosoy 63 were grown at ambient (380 μmol∙mol−1) and elevated (560 μmol∙mol−1) CO2 concentrations in the field using free-air CO2 enrichment systems, in air-conditioned glasshouses with natural summer photoperiods, and in indoor chambers with day lengths of 11, 13, 15, and 17 hours. The effect of CO2 concentration on flowering time varied with genotype, and there was also an interaction between CO2 and photoperiod in all genotypes, as indicated by ANOVA. Elevated CO2 accelerated flowering in some cases, and delayed it in other cases. For all three of the isolines with single dominant genes, elevated CO2 decreased the days to first open flower at the longest photoperiod. At the shortest photoperiod, elevated CO2 delayed flowering in all but one isoline. The all-recessive isoline had slower flowering at elevated CO2 at both the shortest and the longest photoperiods, and also in the field and in the glasshouse. Delayed flowering at elevated CO2 in the field and glasshouse was associated with an increased final number of main stem nodes. It is concluded that the E1, E3, and E4 genes each influenced how the time to first flowering was affected by CO2 concentration at long photoperiods.

Growth and essential oil production by Martianthus leucocephalus grown under the edaphoclimatic conditions of Feira de Santana, Bahia, Brazil

ABSTRACT: The semiarid region of Brazil holds a great richness of medicinal and aromatic plants with considerable potential for pharmaceutical, food, cosmetic and biopesticide industries. Martianthus leucocephalus (Mart. Ex Benth.) J. F. B. Pastore is endemic to this region, and its essential oils contain a principle compound, isobornyl formate, which demonstrates antimicrobial activity against Bacilus cereus, Staphylococcus aureus and Candida albicans. In spite of its significant pharmacological potential, little is known about its growth. In light of the influence of seasonality on plant growth, development, and secondary metabolism, the present study evaluated the growth and essential oil content of M. leucocephalus grown and harvested during different months of the year in the edaphoclimatic conditions of Feira de Santana, Bahia State, Brazil. The experimental design was entirely randomized, with twelve harvesting periods and five replicates. The study acquired monthly data of mean temperatures, relative humidity, rainfall, irradiance, and photoperiod from the National Institute of Meteorology (INMET) and quantified the fresh and dry weights of leaves, flowers and branches, as well as leaf area, and essential oil content. The data were submitted to Spearman correlation analysis and the means were compared using the Scott-Knott test. Total leaf masses and oil contents were higher during periods with longer photoperiods and higher solar irradiance. Rainfall and relative humidity reduced plant growth and essential oil content. Higher total mean dry masses were recorded from September to January (except October), while oil content was higher in March.

Effect of Light Intensity and Photoperiod on Growth and Biochemical Composition of a Local Isolate of Nostoc calcicola

A study was conducted to investigate the effect of light intensity (21, 42, and 63μmol photons m(-2)s(-1)) and photoperiod (8:16, 12:12, and 16:8h light/dark) on the biomass production and its biochemical composition (total carotenoids, chlorophyll a, phycoerythrin (PE), phycocyanin (PC) and allophycocyanin (APC), total protein, and carbohydrates) of a local isolate of Nostoc calcicola. The results revealed that N. calcicola prefers dim light; however, the most of the levels of light intensity and photoperiod investigated did not have a significant impact on biomass production. Increasing light intensity biomass content of chlorophyll a, PE, PC, APC, and total protein decreased, while total carotenoids and carbohydrate increased. The same behavior was observed also when light duration (photoperiod) increased. The interaction effect of increasing light intensity and photoperiod resulted in an increase of carbohydrate and total carotenoids, and to the decrease of chlorophyll a, PE, PC, APC, and total protein content. The results indicate that varying the light regime, it is capable to manipulate the biochemical composition of the local isolate of N. calcicola, producing either valuable phycobiliproteins or proteins under low light intensity and shorter photoperiods, or producing carbohydrates and carotenoids under higher light intensities and longer photoperiods.

Plasticity of the thermal developmental reaction norms in the european peacock butterfly Inachis io (Lepidoptera, Nymphalidae)

The goal of the study was to analyze the plasticity of the developmental thermal reaction norms in the peacock butterfly Inachis io as affected by different photoperiodic conditions and group versus individual keeping. Overwintered imagoes were collected in Stariy Peterhof (Saint-Petersburg, Russia) in May 2010 and 2012–2013. Twelve experimental regimes were used: 4 thermal (16, 18, 20 and 22°C) and 3 photoperiodic (12, 18 and 22 h of light per day). Under short-daylight conditions (12 h), the larvae were shown to develop a little faster than under long-day conditions (22 h), although the thermal developmental thresholds were invariable in both cases. The linear regression coefficient characterizing developmental thermolability was significantly higher only in males more affected during their development by the short-day photoperiod than females. Under the 18-h daylight regime, larval development was less thermolabile and characterized by a lower thermal threshold than under the shorter or longer photoperiod. The influence of the short-day photoperiod on the larval development manifested itself most distinctly in the body mass changes in emerging pupae: under all thermal regimes, the pupae were lighter under the short-than long-day photoperiod. The pupal body mass grew with the rise in temperature, contrary to the temperature–size rule. Individual keeping led to the longer duration and lower thermolability of larval and pupal development, as well as to a reduced pupal body mass. Individual keeping exerted a stronger influence on females than on males.

Seasonal variation in the populations of Polyphagotarsonemus latus and Tetranychus bastosi in physic nut (Jatropha curcas) plantations.

Studies on the seasonal variation of agricultural pest species are important for the establishment of integrated pest control programs. The seasonality of pest attacks on crops is affected by biotic and abiotic factors, for example, climate and natural enemies. Besides that, characteristics of the host plant, crop management, location and the pests' bioecology also affect this seasonality. The mites Polyphagotarsonemus latus (Prostigmata: Tarsonemidae) and Tetranychus bastosi (Prostigmata: Tetranychidae) are the most important pests in the cultivation of physic nut, Jatropha curcas (Euphorbiaceae). All parts of J. curcas can be used for a wide range of purposes. In addition many researchers have studied its potential for use as neat oil, as transesterified oil (biodiesel), or as a blend with diesel. However studies about physic nut pests have been little known. The objective of this study was to assess the seasonal variation of P. latus and T. bastosi in physic nut. This study was conducted at three sites in the state of Tocantins, Brazil. We monitored climatic elements and the densities of the two mite species and of their natural enemies for a period of 2years. Attack by P. latus occurred during rainy seasons, when the photoperiod was short and the physic nut had new leaves. In contrast, attack by T. bastosi occurred during warmer seasons with longer photoperiods and stronger winds. Populations of both mites and their natural enemies were greater in sites with greater plant diversity adjacent to the plantations. The predators found in association with P. latus and T. bastosi were Euseius concordis (Acari: Phytoseiidae), spiders, Stethorus sp. (Coleoptera: Coccinellidae) and Chrysoperla sp. (Neuroptera: Chrysopidae).

Diurnal vertical migration rhythms and their photoresponse in four phytoflagellates causing harmful algal blooms

AbstractWe observed diurnal vertical migrations (DVMs) of four noxious phytoflagellates: Chattonella antiqua, Heterosigma akashiwo (raphidophyte), Karenia mikimotoi, and Heterocapsa circularisquama (dinoflagellate) under various light conditions such as fluence rate, day length, light regime, and wavelength in the laboratory. For all flagellates cyclic DVMs were observed at an irradiance of 30 μmol quanta m−2 s−1 on a 12 h : 12 h light : dark (L : D) cycle. Start times of upward and downward migrations under the light condition differed among species, indicating that each flagellate has its own original DVM cycle. The ascent period of C. antiqua during the photoperiod was much longer than the other flagellates, whereas K. mikimotoi remained submerged longer. No flagellate displayed cyclic DVM in the dark, and only K. mikimotoi did even under weak light of 1 μmol quanta m−2 s−1. C. antiqua and K. mikimotoi extended their surface‐accumulation periods at longer photoperiods, but the other species scarcely changed theirs. For all the flagellates, a DVM rhythm was entrained by shifting the L : D cycle; this occurred under white or blue light, but not under red light. These results indicate that all flagellates require (blue) light for maintenance and adjustment of DVM cycle but responses to change in light intensity and day length differ among species. The present study suggests that the species‐specific DVM cycle and its photoresponse property can change time staying in surface or bottom layers in the natural environment, and therefore, may affect photosynthesis and nutrient uptake for survival and growth in four phytoflagellates.

Reducing Cannibalism of Narrow Clawed Crayfish Astacus leptodactylus Eschscholtz 1823 Through Management of Photoperiod and Stocking Density

In crayfish hatcheries, one of the main factors affecting reproduction operation is survival and cannibalism of brood stock. One of the main problems for expansion of Astacus leptodactylus Eschscholtz 1823 production is high mortality and cannibalism of broodstock during the reproduction operation. The effect of photoperiod and stocking density on cannibalism, moulting and survival of A. leptodactylus was examined in the context of broodstock husbandry. Cannibalism was lowest and survival highest when crayfish were housed at low density (10.m -2 ) and with longer photoperiod. The longest photoperiod, 18 h light (L): 6 h dark (D) conditions resulted in high survival with minor cannibalism. Longest photoperiod also had the undesirable outcome of lower frequency of moulting, suggesting possible impacts on growth.

Evaluación del cambio en la concentración de dióxido de carbono en una corriente de gas mediante el uso de Chlorella vulgaris

&lt;p&gt;Chlorella vulgaris tiene una eficiencia de 38% en la remoción de dióxido de carbono presente una corriente de gas, el estudio se fundamento en la experimentación con especies de microalgas nativas de Colombia para su uso potencial como tratamiento en procesos industriales de combustión. El trabajo se inició con una revisión bibliográfica para identificar las condiciones de cultivo adecuadas de la microalga Chlorella vulgaris, posterior a esto se realizó el diseño básico de un biorreactor para llevar a cabo el cultivo y determinar la cinética de crecimiento de la microalga, después se propuso el diseño de experimentos que incluye dos factores: Concentración de dióxido de carbono [%CO2 v/v] y duración del fotoperíodo; se realizaron cuatro tratamientos para verificar el comportamiento de las variables por acción de la microalga en diferentes condiciones. Finalmente se analizaron los resultados y se determinó el tratamiento más eficiente. Los resultados muestran que el tratamiento más eficiente es aquel en el que los factores tienen los mayores valores, es decir, el fotoperíodo mas largo y la mayor concentración de CO2.&lt;/p&gt;

Growth and lignan accumulation of Phyllanthus amarus (Schum. &amp; Thonn.) cultured in vitro photoautotrophically as affected by light intensity and photoperiod

Light intensity and photoperiod are two important factors to the growth and secondary metabolite accumulation of in vitro plants, especially under photoautotrophic micropropagation. Internodal segments carrying 1 leaf of in vitro Phyllanthus amarus plants were used as explants. Four explants were put on MS medium with half strength macro elements and without sugar and vitamins, in a Magenta box-type vessel (V = 370 ml). There were two holes (Ф = 1 cm) covered by Millipore membranes (Ф = 0.45 µm) on the vessel lid. Perlite was used as supporting material. The experiment was carried out with 3 different light intensities (80, 120 or 160 µmol m-2 s-1) in combination with 3 levels of photoperiod (8, 12 or 16 hours per day), under room temperature of 25 ± 2oC and relative humidity of 50%. On day 40, Phyllanthus amarus plants grew better under higher PPF and longer photoperiod. Increased fresh weight and dry weight, stem diameter and shoot lenght of in vitro plants were the highest under the PPF of 160 μmol m-2 s-1 and the photoperiod of 16 hours per day. Phyllanthin, hypophyllanthin and niranthin contents were the largest when plants were cultured under the PPF of 80 µmol m-2 s-1 and the photoperiod of 12 hours per day.

Do protocols for the intensive production of Coreopsis grandiflora affect its garden performance?

Scheduled production of ornamentals has facilitated the development of novel crop lines that can be sold in flower over an extended period, thereby maximising sales potential. Research activities have aided the development of protocols for these ‘forced’ crops, but little attention has been given to knowledge of how such protocols affect subsequent garden performance. The aim of this study therefore, was to investigate the influence of different production factors (cutting size, temperature, photoperiod and time of propagation) on flower induction both with respect to the main marketing stage, but also in terms of ‘after-sales’ performance. The short-lived herbaceous perennial Coreopsis grandiflora cv. Flying Saucers was used as a model subject. When exposed to five diurnal temperatures (14, 20, 24, 27 and 31°C) and grown at four photoperiods (8, 11, 14 and 17h), time to first open flower was optimal at 27°C (42 days). Speed of flowering was aided by longer photoperiod (approximately 5 days earlier at 17h than at 14h). Greatest numbers of flowers produced overall though was associated with the 14°C/14h regime. Comparisons based on original cutting size demonstrated that large cuttings, rooted under long-day photoperiods produced plants with greater flower numbers than other cutting treatments. Once planted out, however, plants from all treatment combinations had similar floral performance (mean of 160 flowers per plant). Time of propagation/planting-out also had no overall effect on the numbers of flowers produced within the lifespan of the plant. It was concluded that conditions during production and planting time did not influence garden performance over the longer term.

An insight into the sensitivity of maize to photoperiod changes under controlled conditions

Response of maize to photoperiods affects adaption of this crop to environments. We characterize the phenotypes of four temperate-adapted maize foundation parents, Huangzao 4, Chang 7-2, Ye 478 and Zheng 58, and two tropically adapted maize foundation parents, M9 and Shuang M9 throughout the growth stage under three constant photoperiod regimes in a daily cycle of 24 h at 28 °C, and analysed expression of 48 photoperiod response-associated genes. Consequently, long photoperiod (LP) repressed development of the tassels of photoperiod-sensitive maize lines at V9 stage, and caused subsequent failure in flowering; failure of photoperiod-sensitive maize lines in flowering under LP was associated with lower expression of flowering-related genes; photoperiod changes could make a marked impact on spatial layout of maize inflorescence. The larger oscillation amplitude of expression of photoperiod-responsive genes occurred in LP-sensitive maize lines. In conclusion, failure in development of tassels at V9 stage under LP is an early indicator for judging photoperiod sensitivity. The adaptation of temperate-adapted maize lines to LP is due to the better coordination of expression among photoperiod-sensing genes instead of the loss of the genes. High photoperiod sensitivity of maize is due to high expression of circadian rhythm-responding genes improperly early in the light.

Photoperiod and Temperature Effects on Rhizome Production and Tillering Rate in Tall Fescue [Lolium arundinaceum (Schreb.) Darby.

ABSTRACTTemperature and photoperiod are key factors regulating plant growth and development. The objective of this study was to investigate the effects of temperature and photoperiod on tillering and rhizome formation in tall fescue [Lolium arundinaceum (Schreb.) Darby.]. Different genotypes were selected based on tillering ability and/or rhizome production. Plants were grown in growth chambers with a combination of different photoperiods and day/night temperatures: short photoperiod (9 h) and low temperature (day/night at 15/10°C) (SL), long photoperiod (18 h) and low temperature (LL), short photoperiod and high temperature (day/night at 25/15°C) (SH), and long photoperiod and high temperature (LH). The SL treatment resulted in significant increases in the number of tillers in the experiment and Genotype 1109 produced the maximum number of tillers. The number of rhizomes was increased under LL and LH conditions in three clonal lines. Our results suggested that the responses of tiller and rhizome development to temperature and photoperiod varied with genotypes; in addition, longer photoperiod appeared to promote rhizome formation, regardless of temperature, whereas lower temperature stimulated rapid tiller production in some genotypes of tall fescue. This study will help to determine the performance of tall fescue under the longer/shorter photoperiod and variable temperature conditions in different parts of United States.

Functional characterization of duplicated Suppressor of Overexpression of Constans 1-like genes in petunia.

Flowering time is strictly controlled by a combination of internal and external signals that match seed set with favorable environmental conditions. In the model plant species Arabidopsis thaliana (Brassicaceae), many of the genes underlying development and evolution of flowering have been discovered. However, much remains unknown about how conserved the flowering gene networks are in plants with different growth habits, gene duplication histories, and distributions. Here we functionally characterize three homologs of the flowering gene SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) in the short-lived perennial Petunia hybrida (petunia, Solanaceae). Similar to A. thaliana soc1 mutants, co-silencing of duplicated petunia SOC1-like genes results in late flowering. This phenotype is most severe when all three SOC1-like genes are silenced. Furthermore, expression levels of the SOC1-like genes UNSHAVEN (UNS) and FLORAL BINDING PROTEIN 21 (FBP21), but not FBP28, are positively correlated with developmental age. In contrast to A. thaliana, petunia SOC1-like gene expression did not increase with longer photoperiods, and FBP28 transcripts were actually more abundant under short days. Despite evidence of functional redundancy, differential spatio-temporal expression data suggest that SOC1-like genes might fine-tune petunia flowering in response to photoperiod and developmental stage. This likely resulted from modification of SOC1-like gene regulatory elements following recent duplication, and is a possible mechanism to ensure flowering under both inductive and non-inductive photoperiods.

Effect of exponential fertilization on growth and nutritional status in Buddhist pine (Podocarpus macrophyllus [Thunb.] D. Don) seedlings cultured in natural and prolonged photoperiods

Slow growth rate limits the development of seedlings from the Podocarpaceae family. The extended photoperiod (EP) is well known to promote tree seedling growth, but it may also cause the possibility of nutrient dilution without a proper nutrient supply regime. Exponential fertilization (EF) has been proven to counter nutrient dilution within tree seedlings efficiently. However, no study has determined the response of Podocarpus seedlings to the interaction of EF and photoperiod. We fed 13-month old Buddhist pine (Podocarpus macrophyllus [Thunb.] D. Don) seedlings using EF applied at rates of 0 (control), 50 (E50), 100 (E100), and 150 (E150) mg nitrogen (N) seedling−1 for 5 months, during which half of all seedlings were cultured in the natural photoperiod (NP) with the others exposed to EP. The longer photoperiod resulted in greater seedling height and biomass accumulation of Buddhist pine seedlings. Relative to NP, EP increased N content at the whole-plant level but decreased N concentration in the stem and root, which indicated the symptom of N dilution. However, both phosphorus (P) content and P concentration increased in response to the longer photoperiod. EF rates in the E100 and E150 treatments were evaluated to be the ‘sufficiency’ ones for both N and P in EP and NP, respectively. In conclusion, EP could stimulate the growth of Buddhist pine seedlings but caused N dilution within them at the same time, and photoperiod would change the nutritional response of these seedlings to EF.

Anti-Müllerian hormone (AMH), inhibin-α, growth differentiation factor 9 (GDF9), and bone morphogenic protein-15 (BMP15) mRNA and protein are influenced by photoperiod-induced ovarian regression and recrudescence in Siberian hamster ovaries.

Exposure of Siberian hamsters to short photoperiod (SD) inhibits ovarian function, including folliculogenesis, whereas function is restored with their transfer to long photoperiods (LD). To investigate the mechanism of photo-stimulated recrudescence, we assessed key folliculogenic factors-anti-Müllerian hormone (AMH), inhibin-α, growth differentiation factor-9 (GDF9), and bone morphogenic protein-15 (BMP15)-across the estrus cycle and in photo-regressed and recrudescing ovaries. Adult hamsters were exposed to either LD or SD for 14 weeks, which respectively represent functional and regressed ovaries. Select regressed hamsters were transferred back to LD for 2 (post-transfer week 2; PTw2) or 8 weeks (PTw8). Ovaries were collected and fixed in formalin for immunohistochemistry or frozen in liquid nitrogen for real-time PCR. AMH, inhibin-α, GDF9, and BMP15 mRNA and protein were detected in all stages of the estrus cycle. Fourteen weeks of SD exposure increased (P < 0.05) ovarian AMH, GDF9, and BMP15, but not inhibin-α mRNA levels as compared to LD. Transfer of regressed hamsters to stimulatory long photoperiod for 8 weeks returned AMH and GDF9 mRNA levels to LD-treated levels, and further increased mRNA levels for inhibin-α and BMP15. Immunostaining for AMH, inhibin-α, GDF9, and BMP15 proteins was most intense in preantral/antral follicles and oocytes. The overall immunostaining extent for AMH and inhibin-α generally mirrored the mRNA data, though no changes were observed for GDF9 or BMP15 immunostaining. Shifts in mRNA and protein levels across photoperiod conditions suggest possible syncretic roles for these folliculogenic factors in photo-stimulated recrudescence via potential regulation of follicle recruitment, preservation, and development.

Continuous melatonin attenuates the regressing activities of short photoperiod in male golden hamsters.

Golden hamsters reproduce in a limited time of a year. Their sexual activities are active in summer but inactive in winter during which day length does not exceed night time and environmental conditions are severe to them. The reproductive activities are determined by the length of light in a day (photoperiod). Melatonin is synthesized and secreted only at night time from the pineal gland. Duration of elevated melatonin is longer in winter than summer, resulting in gonadal regression. The present study aimed at the influences of continuous melatonin treatments impinging on the gonadal function in male golden hamsters. Animals received empty or melatonin-filled capsules for 10 weeks. They were divided into long photoperiod (LP) and short photoperiod (SP). All the animals maintained in LP (either empty or melatonin-filled capsules) showed large testes, implying that melatonin had no effects on testicular functions. Animals housed in SP displayed completely regressed testes. But animals kept in SP and implanted with melatonin capsules exhibited blockage of full regression by SP. These results suggest that constant release of melatonin prohibits the regressing influence of SP.