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H Photoperiod (h + photoperiod)
Selected AbstractsPRIMARY CARBON AND NITROGEN METABOLIC GENE EXPRESSION IN THE DIATOM THALASSIOSIRA PSEUDONANA (BACILLARIOPHYCEAE): DIEL PERIODICITY AND EFFECTS OF INORGANIC CARBON AND NITROGEN,JOURNAL OF PHYCOLOGY, Issue 5 2009Espen Granum Diel periodicity and effects of inorganic carbon (Ci) and NO3, on the expression of 11 key genes for primary carbon and nitrogen metabolism, including potential C4 photosynthesis, in the marine diatom Thalassiosira pseudonana Hasle et Heimdal were investigated. Target gene transcripts were measured by quantitative reverse transcriptase,PCR, and some of the gene-encoded proteins were analyzed by Western blotting. The diatom was grown with a 12 h photoperiod at two different Ci concentrations maintained by air-equilibration with either 380 ,L · L,1 (near-ambient) or 100 ,L · L,1 (low) CO2. Transcripts of the principal Ci and NO3, assimilatory genes RUBISCO LSU (rbcL) and nitrate reductase displayed very strong diel oscillations with peaks at the end of the scotophase. Considerable diel periodicities were also exhibited by the ,-carboxylase genes phosphoenolpyruvate carboxylase (PEPC1 and PEPC2) and phosphoenolpyruvate carboxykinase (PEPCK), and the Benson,Calvin cycle gene sedoheptulose,bisphosphatase (SBPase), with peaks during mid- to late scotophase. In accordance with the transcripts, there were substantial diel periodicities in PEPC1, PEPC2, PEPCK, and especially rbcL proteins, although they peaked during early to mid-photophase. Inorganic carbon had some transient effects on the ,-carboxylase transcripts, and glycine decarboxylase P subunit was highly up-regulated by low Ci concentration, indicating increased capacity for photorespiration. Nitrogen-starved cells had reduced amounts of carbon metabolic gene transcripts, but the PEPC1, PEPC2, PEPCK, and rbcL transcripts increased rapidly when NO3, was replenished. The results suggest that the ,-carboxylases in T. pseudonana play key anaplerotic roles but show no clear support for C4 photosynthesis. [source] Fecundity, nymphal development and longevity of field-collected tropical bedbugs, Cimex hemipterusMEDICAL AND VETERINARY ENTOMOLOGY, Issue 2 2010Y.-F. HOW This study examined the fecundity, oviposition, nymphal development and longevity of field-collected samples of the tropical bedbug, Cimex hemipterus (Fabricius) (Hemiptera: Cimicidae). Under environmental conditions of 26±2°C, 70 ± 5% relative humidity and a 12-h photoperiod, with bloodmeals provided by a human host, six strains of tropical bedbug had a fecundity of up to 50 eggs per lifetime, over 11,14 oviposition cycles. Increased feeding frequency improved fecundity. After feeding and mating, adult females normally took 2,3 days to produce a first batch of eggs. The oviposition period lasted 2,7 days before cessation of the oviposition cycle. The egg incubation period usually lasted 5,7 days before the emergence of first instars. The nymphs underwent five stadia (the first four of which each took 3,4 days, whereas the last took 4,5 days) before becoming adults at a sex ratio of 1 : 1. More than five bloodmeals were required by the nymphs to ensure a successful moult. Unmated adults lived significantly longer than mated adults (P < 0.05). Unmated females lived up to almost 7 months, but the longevity of mated males and females did not differ significantly (P > 0.05). [source] Photoperiodic and temperature control of nymphal development and induction of reproductive diapause in two predatory Orius bugs: interspecific and geographic differencesPHYSIOLOGICAL ENTOMOLOGY, Issue 4 2008DMITRY L. MUSOLIN Abstract The effects of day-length and temperature on pre-adult growth and induction of reproductive diapause are studied in Orius sauteri and Orius minutus (Heteroptera: Anthocoridae) from northern (43.0°N, 141.4°E) and central (36.1°N, 140.1°E) Japan. In the north, at 20 °C, pre-adult growth is slower under an LD 14 : 10 h photoperiod than under shorter or longer photophases. At 24 and 28 °C, the longer photophases result in shorter pre-adult periods. Acceleration of nymphal growth by short days in autumn appears to be adaptive. In the central region, this response is less pronounced, suggesting that timing of adult emergence is less critical than in the north. Day length also influences the thermal requirements for pre-adult development. The slope of the regression line representing temperature dependence of pre-adult development is significantly smaller and the lower development threshold (LDT) is significantly lower under an LD 12 : 12 h photoperiod than under long-day conditions. The weaker dependence of nymphal growth on temperature and the lower LDT in autumn might be adaptive. In the north, increased temperature shifts the critical day length of diapause induction and suppresses the photoperiodic response in O. sauteri but not in O. minutus. Further south, the incidence of diapause in both species is low even under short-day conditions but the same interspecific difference is observed (i.e. increase of temperature affects the response in O. sauteri but not in O. minutus). This suggests seasonally earlier diapause induction with weaker temperature dependence in O. minutus than in O. sauteri. [source] Effects of relative humidity on cocoon formation and survival in the braconid wasp Cotesia glomerataPHYSIOLOGICAL ENTOMOLOGY, Issue 3 2008JUN TAGAWA Abstract The effects of relative humidity (RH) on cocoon formation and survival in the braconid parasitoid wasp Cotesia glomerata (L.) (Hymenoptera: Braconidae) are investigated under various humidity conditions (50, 75, 90, 95 and 100% RH) at 20 °C and under an LD 16 : 8 h photoperiod. The mortality rate at the time of egression from hosts under 100% RH is significantly higher than for other RHs. Cocoon clusters formed at 100% RH spread significantly more than those formed at 50, 75, or 90% RH. Developmental periods differ significantly among RHs under which wasps developed. The mean period from the egression from hosts to adult emergence is 8.7 days when developed at 50,95% RHs, and 8.0 days at 100% RH. The emergence rates of C. glomerata that are maintained under the same humidity conditions after egression from hosts are not significantly different among RHs. However, emergence rates from cocoons that are transferred from 100% RH to 50 and 75% RH are < 70%, although the rates are > 90% in most cases. Some wasps do not emerge from cocoons: more than 60% die after adult eclosion at all RHs; the relative frequency of adult deaths is approximately 90% at 50% RH. Relative humidity influences the cluster and cocoon status strongly: both good clusters and cocoons are formed at low RHs. Emergence rates from cocoons of different ranks are significantly different: the rates of low-rank cocoons are low at low RHs. The survival of C. glomerata is affected strongly by RH through cocoon formation. [source] Effects of diapause duration on future reproduction in the cabbage beetle, Colaphellus bowringi: positive or negative?PHYSIOLOGICAL ENTOMOLOGY, Issue 2 2006Xiao-Ping Wang Abstract., Cabbage beetles, Colaphellus bowringi, undergoing an imaginal summer and winter diapause in the soil, show a great difference in diapause duration (from several months to more than 3 years) under natural conditions. The effects of diapause duration on future reproduction in the beetle are investigated at 25 °C with an LD 14 : 10 h photoperiod and under natural conditions. The fecundity of postdiapause adults with a short diapause of 5 months and nondiapause adults is similar, showing that a short diapause has no affect on reproduction, whereas the longevity of postdiapause adults with a short diapause of 5 months is significantly shorter than nondiapause adults, showing that a short diapause has a negative affect on longevity. The mean total egg production per female and longevities of postdiapause adults with long diapause periods of 16, 22, 29 and 34 months are similar to nondiapause adults, but the mean daily egg production per female is significantly higher than nondiapause adults, showing that extended diapause has a positive effect on postdiapause reproduction. The offspring of postdiapause parents require a relatively shorter time for egg development compared with the offspring of nondiapause parents, showing that diapause has a positive effect on their offspring's performance. However, there are no significant differences among offspring performance in terms of survival, adult longevity, mean egg production per female and mean daily egg production per female. [source] U.K. winter egg survival in the field and laboratory diapause of Typhlodromips montdorensisPHYSIOLOGICAL ENTOMOLOGY, Issue 1 2005Ian S. Hatherly Abstract.,Typhlodromips montdorensis has potential for release as a glasshouse biological control agent in the U.K. against thrips and spider mites. This study investigates the field survival in the U.K. of T. montdorensis when released as eggs, and the diapause response when reared in a regime related to its location of origin. All acclimated and nonacclimated eggs of T. montdorensis die in the field within 7 days of exposure. It is not possible to induce diapause in T. montdorensis reared at 21 °C under a LD 11 : 13 h photoperiod. The results presented here support the view that T. montdorensis is unlikely to survive a U.K. winter outside of the glasshouse environment, and contribute to the understanding of the biology of this little known species. [source] Effects of red, far-red and blue light in maintaining growth in latitudinal populations of Norway spruce (Picea abies)PLANT CELL & ENVIRONMENT, Issue 2 2006JØRGEN ALEXANDER MØLMANN ABSTRACT Seedlings of trees with a free growth pattern cease growth when night-lengths become shorter than a critical value, and this critical night-length (CNL) decreases with increasing latitude of origin. In northern populations, the light quality also appears to play an important role and a clinal variation in requirement for far-red (FR) light has been documented. In this study we dissected the light quality requirements for maintaining growth in different latitudinal populations of Norway spruce (Picea abies (L.) H. Karst.) using light emitting diodes for red (R), FR and blue (B) light, as 12 h day extension to provide 24 h photoperiod. At equal spectral photon flux, FR light was more effective than R light in maintaining growth, and the requirement of both R and FR increased with northern latitude of origin. One-to-one mixtures of R and FR light were more effective in maintaining growth than either FR or R light alone, indicating a possible interaction between R and FR light maintaining growth. Using the blue light as day extension could not prevent growth cessation in any of the populations, but delayed the bud set slightly in all populations. Our results suggest that phytochrome(s) are the primary photoreceptors in high irradiance responses maintaining growth in Norway spruce seedlings. [source] Clonal variation in morphological and physiological responses to irradiance and photoperiod for the aquatic angiosperm Potamogeton pectinatusJOURNAL OF ECOLOGY, Issue 5 2002Jörn Pilon Summary 1Widely distributed plants are exposed to contrasting gradients in irradiance and photoperiod across latitude. We investigated the relative contribution of local specialization and phenotypic plasticity to variation in plant growth for three clones of the aquatic angiosperm Potamogeton pectinatus L., originating from 42.5 to 68° N. Plants were grown at a factorial combination of two irradiances (50 and 350 µmol m,2 s,1) and three photoperiods (13, 16 and 22 h) and morphology, gas-exchange rate and biomass accumulation were recorded. 2The overall response to variation in irradiance and photoperiod was similar for all three clones. 3Differences in irradiance resulted in strong acclimative changes in morphological and physiological characteristics. At low irradiance, pronounced vertical shoot extension compensated for the limited plasticity in leaf area production, while photosynthetic capacity, apparent quantum yield and total chlorophyll concentration increased. As a result, biomass yield at the end of the experimental period was similar in both treatments. 4A decrease in photoperiod also resulted in plastic changes in morphology (increase of leaf biomass per unit plant biomass) and physiology (increase of photosynthetic capacity). However, these acclimative responses did not fully compensate for differences in photoperiod, since biomass was significantly lower under 13 and 16 h photoperiods than at 22 h. 5P. pectinatus is therefore phenotypically plastic, rather than locally specialized to differences in irradiance and photoperiod. [source] | ||||||||||