Subsequent Growth Period Research Articles

Annual growth of the spring ephemeral Erythronium americanum as a function of temperature and mycorrhizal status

The capacity of the spring ephemeral Erythronium americanum L. to grow and absorb nutrient either as nonmycorrhizal (NM) or mycorrhizal (M) plants under the low temperature regime characteristic of its growth period was investigated. Specimens of E. americanum were collected in the field as either NM (early September) or as M plants (late October). Both groups of plants were submitted to different nutrient regimes during the hypogeous growth period at 5 °C, and during the subsequent epigeous growth period conducted at temperature regimes of either 12 °C day : 10 °C night or 17 °C day : 15 °C night. Nutrient regime influenced bulb nutrient content only during the epigeous growth period. The presence of mycorrhizas did not influence nutrient content, but favoured a greater bulb biomass at the final harvest (epigeous growth period), as did the lower temperature regime. Net nutrient uptake was not reduced at lower temperatures and appeared to follow plant demand. These findings confirm that E. americanum is adapted to perform better under a low temperature regime and that mineral nutrition in this species occurs mainly in spring in response to active growth. Arbuscular mycorrhizal fungi benefit E. americanum maybe through less expensive nutrient uptake or sustained carbon sink demand.

Founding Swarms in a Tropical Social Wasp: Adult Mortality, Emigration Distance, and Swarm Size

When colonies of swarm-founding wasps lose their nests to predation or accident, the entire adult population escapes, emigrates as an absconding swarm, and renests elsewhere. Such an event causes a reduction in the adult population due to losses during the emigration itself and to adult attrition without replacement during the subsequent preemergence growth period in the new nest. We addressed the first of these sources of mortality for 27 absconding swarms of Polybia occidentalis in Costa Rica. Adult mortality over the day that included swarm emigration averaged 0.044 ± 0.039 (SD) of the original population and was a weak positive function of distance moved, but not of swarm size. A larger data set showed that emigration distance increased with swarm size. This is the first study to measure mortality rates during emigration in a swarm-founding social insect.

Ozone biomonitoring with clover clones: yield loss and carryover effect under high ambient ozone levels in northern Italy

Two clones of white clover ( Trifolium repens L. cv. Regal), NC-R (O 3-resistant) and NC-S (O 3-sensitive) were used to assess the effects of ambient ozone at two sites located in the Po plain of Italy. The experiments were carried out as part of the UNECE ICP Vegetation, an international programme within the convention on long-range transboundary air pollution. Clover clones were exposed at Redecesio di Segrate (an urban site near Milan) during 1996 and at Isola Serafini (a rural site near Piacenza) from 1997 to 1999. Each year, the plants were grown in pots according to a standard protocol and exposed to ambient air from May to September. The plants were harvested five times each season by cutting leaves, stolons and flowers, and the dry weight per pot was determined. Ozone concentration was continuously monitored and the total AOT40 (in ppb h) for the 3 months from harvest 1 to harvest 4 was 13985 in 1996, 18275 in 1997, 27815 in 1998 and 18378 in 1999. These ozone levels always affected the growth of the NC-S clone, with biomass reduction of up to 60% (relative to NC-R) recorded at harvests. Linear regression was conducted after pooling the AOT40 and NC-S/NC-R values for harvests 2–5 and year ( r 2=0.026). Moreover, the same analysis was carried out by correlating the AOT40 value of a certain growth period to NC-S/NC-R ratio of the following growth period ( r 2=0.61). These results suggest a carryover effect of ozone doses during one growth period to the subsequent growth period. Finally, data processing was refined by considering only harvests 2–4 of the Isola Serafini experiments and including the carryover effect. The function thus obtained explained an even bigger part of the statistical variability, having an r 2 of 0.91. Carryover effect and site characteristics seem to be important factors to understanding the ozone dose–response relationships.

Seasonal changes in biomass of charophytes in shallow lakes in the northwest of Spain

Seasonal changes in aboveground biomass of submerged macrophytes were recorded in three shallow lakes in northwest Spain from May 1996 to June 1997. The biomass of a monospecific community ( Chara globularis) and of several communities with high charophyte coverage ( C. globularis–Myriophyllum alterniflorum, C. globularis–Potamogeton gramineus and Nitella translucens–Potamogeton natans) were studied monthly. The weather and hydrological regime had a strong influence on the seasonal biomass patterns and on between-the-year differences in the biomass of macrophytes. The biomass in the monospecific C. globularis community showed a bimodal pattern, with maximum in mid-July (128 g DW m −2) and late autumn (165 g DW m −2). Chara overwintered as a green plant and during the subsequent growth period, characterised by high temperature and low rainfall, reached a maximum of 305 g DW m −2 (June 1997). The highest biomass of C. globularis in the Chara–Myriophyllum community was reached in July (Sentiz: 160 g m −2, Redos: 204 g m −2), while the minimum (Sentiz: 10 g m −2; Redos: 3 g m −2) was recorded in February or March. M. alterniflorum (average biomass: 95 g m −2) was a better competitor than C. globularis in Redos lake and appeared to be favoured by the early beginning of the growing season in 1997 and by the later increase in the water level. The biomass of N. translucens (average biomass: 64 g m −2) showed a high stability during the study period, but lacked a well-defined seasonal biomass pattern. P. natans had a marked maximum biomass in August (426 g m −2). Although the stability of the Potamogeton population was low, shading did not have a significant influence on the development of Nitella biomass.

Morphological Development of Alfalfa Cultivars Selected for Higher Quality

Alfalfa (Medicago sativa L.) maturity at the time of harvest greatly influences forage quality. The objective of this research was to determine if observed quality differences between high quality and other alfalfa cultivars were due to differences in morphological development. Two high‐quality cultivars (‘WL 252HQ’, ‘WL 322HQ’) and two check cultivars (‘5262’, ‘5454’) with similar fall dormancy ratings were established on a Murrill silt loam (fine‐loamy, mixed, mesic Typic Hapludult) in the spring of 1996. During 1997, 1998, and 1999, each cultivar was hand‐sampled weekly for 4 consecutive wk during the spring growth period and for 3 consecutive wk during the three subsequent growth periods. Morphological development and forage quality were determined for each alfalfa cultivar at each sampling. There were no interactions between growth period or sampling times and alfalfa cultivars for either alfalfa maturity or forage quality. Morphological development of the cultivars was not different at any of the sampling times. Averaged across all growth periods and sampling times, crude protein (CP) concentrations and in vitro dry matter digestibility (IVDMD) were 14 and 13 g kg−1, respectively, higher for the high‐quality cultivars (ADF) and neutral‐detergent fiber (NDF) concentrations were 16 and 15 g kg−1, respectively, lower. The data from this research indicates that the difference in quality between the high quality and traditional alfalfa cultivars is not due to differences in morphological development. Selecting for higher‐quality alfalfa was successful and is not an artifact of inadvertently selecting for delayed development.

EFFECTS OF INTERMITTENT LIGHTING ON BREEDER CHICKS PROVIDED WITH “IN-TRANSIT” NUTRIENTS

In-transit supply of nutrients and water supplement is essential to maintaining good chick quality and well-being during long, international shipments. Although chicks require light to promote ingestion of nutrients, supply of continuous in-transit lighting is impractical. This study compared four intermittent lighting regimens of 1L:5D, 5L:10D,10L:10D, and 5L:15D applied to a three-day simulated transport period with regard to chick performance and energetics during the treatment period and a four-day subsequent growth period. The four lighting regimens produced similar seven-day chick performance, although chicks under 10L:10D had a somewhat higher body mass loss and metabolic rate than birds in other regimens during the three-day treatment period (P < 0.05). The results suggest the existence of flexibility in providing in-transit lighting for shipping chicks. Significant differences in the heat and moisture production rate of the chicks were observed between light and dark periods, with the response values being 21 to 27% lower in the dark period than in the light period. The results further suggest that chicks in transit would benefit the most from sufficient lighting to ingest necessary nutrients but then remaining in darkness to conserve body energy.

Enhancement of myeloid cell growth by benzene metabolites via the production of active oxygen species

In low concentrations, benzene and its metabolite hydroquinone are known to have diverse biological effects on cells, including the synergistic stimulation with GM-CSF of hematopoietic colony formation in vitro, stimulation of granulocytic differentiation in vitro and in vivo, and general suppression of hematopoiesis in vivo. These chemicals are also known to be active in the induction of active oxygen species. We used several assays to determine the effects of benzene metabolites (hydroquinone, benzenetriol, benzoquinone) and active oxygen species (xanthine/xanthine oxidase) on cell growth and cell cycle kinetics of the human myeloid cell line HL-60. HL-60 cells treated with these chemicals for 2 h in PBS showed increased growth over untreated controls in a subsequent 18h growth period in complete media. Incorporation of 3H-thymidine was also increased proportionately by these treatments. Catalase treatment abrogated the increased cell growth of all chemicals, suggesting an oxidative mechanism for the effect of all treatments alike. Cell cycle kinetics assays showed that the growth increase was caused by an increased recruitment of cells from G0/G1 to S-phase for both hydroquinone and active oxygen, rather than a decrease in the length of the cell cycle. Benzene metabolite's enhancement of growth of myeloid cells through an active oxygen mechanism may be involved in a number of aspects of benzene toxicity, including enhanced granulocytic growth and differentiation, stimulation of GM-CSF-induced colony formation, apoptosis inhibition, and stimulation of progenitor cell mitogenesis in the bone marrow. These effects in sum may be involved in the benzene-induced “promotion” of a clonal cell population to the fully leukemic state.

Estudo de desenvolvimento de Viguiera robusta Gardn., uma Asteraceae do cerrado

RESUMO - (Estudos de desenvolvimento de Viguiera robusta Gardn., uma Asteraceae do cerrado). Com o objetivo de se conhecer alguns aspectos da fisiologia de plantas do componente herbáceo da vegetação de cerrado, foram estudados aspectos do desenvolvimento de Viguiera robusta. As plantas, obtidas a partir de sementes (aquênios), foram mantidas sob condições fotoperiódicas controladas, acompanhando-se seu crescimento vegetativo e floração, no subseqüente período de crescimento. Os aquênios germinaram melhor sob luz constantes e às temperaturas de 30ºC e 20/30ºC permanecendo viáveis após 12 meses de armazenamento a 5ºC em frascos de vidro fechados. Sob fotoperíodo de 8 h houve menor crescimento vegetativo. A floração ocorre inicialmente nos fotoperíodos mais curtos e, no decorrer do tempo, também nos fotoperíodos mais longos; sob dias longos-curtos a floração também foi constatada. Plantas em fotoperíodo de 8 h apresentaram maior número de capítulos desenvolvidos. Plantas jovens têm folhas opostas, havendo depois o aparecimento de folhas alternas, não estando esta alteração na filotaxia relacionada com a indução da floração. A ocorrência da floração provoca a liberação de gemas laterais, que formam novos ramos, especialmente nas plantas sob tratamento fotoperiódico de 8 h. Após a senescência da parte aérea, ocorre nova brotação, independente do tratamento fotoperiódico aplicado, estando esse processo provavelmente mais relacionados às condições bioquímicas e fisiológicas do órgão subterrâneo de reserva do que às condições fotoperiódicas de crescimento.

ENERGETICS, MORTALITY, AND BODY MASS CHANGE OF BREEDER CHICKS SUBJECTED TO DIFFERENT POST-HATCH FEED DOSAGES

Newly hatched leghorn breeder chicks (averaging 38.5 g body mass) housed in shipping containers were subjected to four limited feeding regimens for a three-day (3-d) period. The chicks were then raised for five days with adlibitum access to feed and nipple drinkers. For the 3-d treatment, the chicks received an average of 2.0, 2.5, 3.0, or 3.5 g starter feed (20.5% protein and 12,754 kJ/kg ME) and twice as much Aqua-Jel® (a water supplement) (AJ) placed directly on the honeycomb bedding of the containers. Air temperature at the chick level was maintained at 29.1 ± 0.2°C. Relative humidity was 28 to 37% during the treatment and 31 to 55% during the subsequent growth period. A photoperiod of 12L:12D cycle was provided throughout the experimental period. The 3-d mortality rate (1.0 to 1.7%) and body mass loss (15.4 to 16.8% initial value) showed no significant difference (P > 0.05) among the treatments. Metabolic rate was also not significantly different (P > 0.05) among the treatments, although it was generally proportional to the level of nutrient supply. Lighting conditions had a major impact on the chick energetics. Specifically, moisture production (MP) averaged 5.6 to 7.2 g/(kgyh) during the light period, but 3.8 to 5.1 g/(kgyh) during the dark period (P < 0.05). Total heat production (THP) averaged 8.3 to 9.2 W/kg during the light period and 6.0 to 6.8 W/kg during the dark period. The reduced metabolic rate in the darkness could be a useful avenue for conserving energy and, thus, body mass loss of fasting chicks during prolonged overseas shipment. The 8-d mortality (2.4 to 3.1%) and the 5-d subsequent body mass gain (42.4 to 45.8% of the initial value) of the chicks also showed no significant difference (P > 0.05) among the treatments. Thus a supply of up to 3.5 g feed and 7 g AJ per chick during 72-h post-hatch shipments seems insufficient to achieve a “normal”, postshipment chick performance. Energetic responses during the 5-d subsequent growth period were similar for all the treatments. Specifically, THP averaged 21.3 W/kg during the light period and 14.9 W/kg during the dark period (P < 0.05). The corresponding MP was 23.6 g/(kgyh) and 15.0 g/(kgyh) (P < 0.05), respectively.

Investigation of the nucleation mechanism in bias-enhanced diamond deposition

Polycrystalline diamond films were deposited in a MW-PECVD reactor employing bias-enhanced nucleation as pretreatment to promote the subsequent diamond nucleation. The substrate temperature during the bias-enhanced nucleation was varied between 600° and 760 °C by external heating, while the other deposition parameters namely the microwave input power were kept constant. Likewise, the deposition parameters were not changed in the subsequent diamond growth period throughout the experiment. The films formed during the bias-enhanced nucleation were analyzed employing electron energy loss spectroscopy (EELS) and scanning electron microscopy (SEM). The nuclei density (ND) obtained for good quality diamond crystals after the nucleation step and an additional growth period increases considerably from 1×106 cm−2 or less to 1×1010 cm−2 in a narrow temperature range between 670 and 700 °C. For temperatures exceeding 700 °C continuous films are formed. The structure of the pretreatment deposit also undergoes considerable changes: the intensity of the diamond plasmon increases with the substrate temperature, which is indicative of an increase in the concentration of diamond crystallites embedded in an otherwise amorphous carbon matrix. Our experiments suggest that diamond crystallites formed during the pretreatment serve as nucleation centers for the subsequent diamond growth. We can also conclude that the variation in the substrate temperature rather than the changes in the microwave input power or, respectively, plasma chemistry, drive the observed structural changes and increase in ND.

Effects of Different Photoperiods and Chilling Treatments on Growth and Reproduction of Cardamine flexuosa With. and Its Ecological Implications

Abstract Phenotypic variability of Cardamine flexuosa (Cruciferae) was examined in response to different lengths of exposure to low temperature (5°C) at the juvenile stage, and to two photoperiod regimes (8 and 16 hrs day‐lengths) in the subsequent growth period. The results indicated that this species had a facultative chilling or long‐day requirement for flowering. The long‐day and chilling treatments both caused an earlier onset of stem internode elongation. Longer chilling treatments reduced the number of nodes and increased internode length under both long and short photoperiod regimes. Prolonged chilling treatments followed by long‐day photoperiod remarkably induced more numerous basal branches and inflorescences, as a result producing more siliques. Remarkable rosette leaves Were formed at the base of the main stem when partial chilling and the short‐day treatment suppressed stem internode elongation. The responses to chilling and long‐day treatment closely resembled the synchronized flowering of this species in spring in the field. Delayed flowering under the short‐day treatment resembled size‐ or age‐dependent flowering in late summer to autumn in the field populations.

Regulation of cytosolic carbon metabolism in germinating Ricinus communis cotyledons

The activity, concentration, and molecular structure of the ATP- and pyrophosphate-dependent phosphofructokinases (PFK and PFP, EC 2.7.1.11 and 2.7.1.90, respectively), phosphoenolpyruvate carboxylase (PEPCase, EC 4.1.1.31) and cytosolic pyruvate kinase (PKc, EC 2.7.1.40) from castor seed (Ricinus communis L.) cotyledons were investigated over 20 d of germination. The activities of the four enzymes rapidly increased to maximal values by day 5, and then significantly declined over the subsequent 15-d growth period. The activity of PFK consistently exceeded that of any of the other enzymes, whereas PKc activity always surpassed that of PEPCase. The PEPCase activity was undetectable by day 10. Laser-densitometric quantification of immunoblots probed with polyclonal antibodies against the four enzymes revealed that the developmental changes in enzymatic activity arose from alterations in the relative concentration of each respective protein. There were progressive increases and decreases in the ratio of the α (68-kDa)∶β (64-kDa) subunits of PFP over the first 5 d and subsequent 15 d of germination, respectively. The α∶β subunit ratio of PFP was positively correlated with the extent of activation of the enzyme by 2 μM fructose-2,6-bisphosphate. There was also an apparent alteration in the subunit composition of PEPCase during germination. The PEPCase from cotyledons of imbibed castor seeds consists of a single immunoreactive 100-kDa subunit, whereas immunologically related 100- and 110-kDa polypeptides were observed on immunoblots of extracts prepared from cotyledons of 2- to 18-d germinated seeds. By contrast, over 20 d of seedling growth the cytosolic isoenzymes of cotyledonary PFK and PK appeared to be uniformly composed of a single type of subunit of approximately 61.5 and 56 kDa, respectively. This study provides a first insight into changes at the molecular level that accompany the surge in cotyledon glycolysis during castor seed germination, and suggests that the synthesis of four key glycolytic enzymes is highly regulated in this tissue and that this regulation follows a preset developmental program.

Modeling the effect of daily ration and feeding frequency on growth of redtail shrimp Penaeus penicillatus (Alock) at controlled temperatures

Obtaining optimal growth of redtail shrimp at an economic production cost is essential. An experiment was conducted to evaluate simultaneous effects of daily ration and feeding frequency on growth of redtail shrimp at controlled temperatures. Two series were operated contemporarily, one at 25°C and the other at 30°C. the three daily rations were 5, 15, and 25% of fresh body weight in association with three levels of daily feeding frequency: one, three, and five times. Each series lasted for 80 days. The growth rate and the combined effects were studied on day 40 and day 80 for each series. Response surface analyses showed that, at 25°C, two quadratic polynomial equations could describe the daily growth rates (G1 and G2) during growth periods 1 (day 1-day 40) and 2 (day 41-day 80). The optimal daily ration and feeding frequency in terms of maximum growth rate were found at 25°C to be 22.38% of fresh body weight with three feedings/day for growth period 1 and 22.68% of fresh body weight with three feedings/day for growth period 2. At 30°C, two dynamic models were derived for each growth period that included growth optimums of 21.94% and four feedings/day for the first growth period, and 21.27% and four feedings/day for the subsequent growth period.

Cell substratum modulates responses of preosteoblasts to retinoic acid.

The aim of this study was to determine the role of ECM components of bone in regulating the differentiation and function of cells of the osteoblast lineage. Rat UMR 201 cells, phenotypically preosteoblast, were plated onto plastic tissue culture dishes or dishes coated with gelled type I collagen or reconstituted basement membrane (matrigel). Acute cell attachment assays showed that cells adhered to substrates in the following order: collagen > matrigel >> plastic. Proliferation rate up to 96 hr were similar on each substrate. However, if cells were treated with 10(-6) M retinoic acid (RA), proliferation rates were reduced compared with control for cells grown on collagen and matrigel but not on plastic. Morphological changes were matrix-specific; in subconfluent cultures, long thin processes were seen with cells grown on collagen and a pattern of interconnecting cell processes formed when cells were plated on matrigel. Striking differences were observed in the constitutive or RA-induced gene expression of cells grown on the different substrates. When cells plated on collagen were treated with RA, induction of mRNA for alkaline phosphatase (ALP) as well as ALP enzyme activity were much less than with cells grown on plastic. In contrast, RA treatment induced osteopontin (OP) mRNA expression more strongly in cells plated on collagen compared with plastic within 24 hr and this was maintained for 72 hr. RA treatment produced a two fold increase of pro-alpha 1(I) collagen mRNA in cells grown on plastic and matrigel but not in cells grown on collagen. Growth on collagen produced changes in the way UMR 201 cells responded to RA from which they did not fully recover in subsequent 48-hr growth periods on plastic. These results indicate that ECM components regulate the function of and are capable of modulating RA-induced differentiation of preosteoblasts.

Primate population studies at Polonnaruwa. III. Somatometric growth in a natural population of toque macaques ( Macaca sinica)

Growth studies of non-human primates in natural populations are rare due to difficulties in obtaining measurements on animals of known age. We report a cross-sectional analysis of growth in the natural population of toque macaques ( Macaca sinica) from Polonnaruwa, Sri Lanka, including the timing of growth and physical maturation and the developmental basis of sexual dimorphism. Twenty-eight measurements were collected from 274 macaques aged 2 weeks to 34 years. Non-parametric spline curves were fit to the distribution of measurement values over age separately by sex. The spline curves suggest four age intervals in which linear regressions of trait on age and analysis of covariance of measurement value with age, sex, and their interaction, can be used to parametrically test specific hypotheses about growth and sexual dimorphism. Most growth had ceased for both sexes in the adult phase. Prior to this, females had two and males three distict growth phases. There was little sexual dimorphism in growth rates among infants and young juveniles (birth to 2·5 years). The age limits for subsequent growth periods differed by sex and trait. Thus, skeletal limb growth ceased in juvenile females by about 5·5 years, but continued into an additional subadult phase in males reaching completion by about 7·5 years, whereas muscle mass and weight reached maturity by about 8 and 12 years in females and males, respectively. An adolescent growth spurt was evident only for body weight in males, but cannot be ruled out for other traits. These macaques grow for one and a half to twice as long as macaques from other species in laboratory colonies. Much of the sexual dimorphism among adults arises from bimaturism, although sex differences in growth rates among older juveniles are also responsible for a significant portion of adult dimorphism.

Comparative leaf development ofOsmunda lancea andO. japonica (osmundaceae): Heterochronic origin of rheophytic stenophylly

Comparative development of the narrow pinnules of rheophyticOsmunda lancea and of the broad pinnules of a related dryland species,O. japonica, was examined and the origin of rheophytic stenophylly was discussed. The mature leaves and their various parts ofO. lancea are smaller and narrower than those ofO. japonica. The young pinnules ofO. lancea at the initiation of cell expansion are smaller than those ofO. japonica. The growth pattern of the pinnules is fundamentally the same in the two species, but pinnule growth period is shorter inO. lancea than inO. japonica. While the largest growth rate in pinnule length is quite similar, inO. lancea the pinnules are less elongated and much less broadened during ontogeny. Cell expansion in the mesophyll and epidermis proceeds acropetally and toward the margin along the axes of costules and veins. Although the numbers of mesophyll and epidermal cells between two adjacent veinlets are almost the same inO. lancea andO. japonica, during the subsequent growth period inO. lancea, the cells expand to a smaller extent and the veinlets become more narrowly oblique to the costule. This oblique distortion of laminar segments framed by veins causes stenophylly, an allometric modification. The stenophylly ofO. lancea is believed to have arisen by heterochronic evolution, in particular, progenesis.

Localization, cellular morphology and respiratory capacity of “brown” adipose tissue in newborn reindeer

1. 1. The localization and cellular morphology of adipose tissue was studied by light, fluorescence and electron microscopy in reindeer between 2 weeks pre partum and 4.5 months post partum during calving, and the subsequent growth period. The respiratory capacity of the adipose tissue was examined in terms of morphometric mitochondrial volume and cytochrome- c oxidase or succinate dehydrogenase activity. 2. 2. Adipose tissue was located at specific anatomical sites in the newborn reindeer (from 0 to 2 days of age). The perirenal-abdominal depot was the largest location (32%) followed by the inter(pre)scapular (18%) and sternal (12%) depots. Internal depots dominated over external or peripheral depots (66-34%). The locations of adipose tissue were largely similar in foetal, newborn and young reindeer. 3. 3. The adipose tissue of the newborn reindeer had all the typical cell morphological characteristics of brown adipose tissue: abundant mitochondria, multilocular fat, high vascularization and a dense spot-like sympathetic innervation between the adipocytes. In the young reindeer, however, it resembled white adipose tissue, being almost totally unilocular with few mitochondria. 4. 4. There was a significant correlation between morphometric mitochondrial volume and cytochrome-c oxidase activity ( r = 0.848) in the adipose tissue. Mitochondrial volume, cytochrome- c oxidase and succinate dehydrogenase activity were highest after birth and decreased to almost an undetectable level during the first month. A parallel decrease occurred in the amount of brown adipose tissue from birth (1–2%) to the age of about one month (0.3%). 5. 5. It is concluded that the distinct cell morphological features and high respiratory capacity of the adipose tissue indicate the presence of brown adipose tissue at specific anatomical locations in newborn reindeer. A marked progression towards the characteristics of white adipose tissue then takes place at the same locations during the first month. The results suggest the fundamental significance of brown adipose tissue for non-shivering thennogenesis in newborn reindeer.

The effect of spectral composition on growth and smolting in Atlantic salmon ( Salmo salar) and subsequent growth in sea cages

Groups of Atlantic salmon ( Salmo salar) parr were reared under indoor light sources of different spectral composition. A control group was reared under outdoor light conditions. Growth rate was not significantly different among the indoor groups, whereas the outdoor group had a significantly lower growth rate. All groups developed the external appearance and experienced the reduced condition factor and increased salinity tolerance normally associated with the parr-smolt transformation. Fish from all groups were successfully acclimated to seawater in early May. The subsequent 6-month growth period in seawater did not reveal any differences in growth potential of fish from the different experimental groups. It was concluded that the parr-smolt transformation was completed under light sources of different spectral composition.

Influence of Extent and Timing of Colorado Potato Beetle (Coleoptera: Chrysomelidae) Defoliation on Potato Tuber Production in Eastern Virginia

A 2-yr field study was done to evaluate tuber production of ‘Superior’ variety potatoes, Solanum tuberosum L., following various levels of defoliation by the Colorado potato beetle, Leptinotarsa decemlineata (Say). Plants were subjected to defoliation during five consecutive plant growth periods, and tuber weights were measured at the end of each period. Additional plants subjected to defoliation were marked with a visual defoliation rating at the end of each period and maintained free of Colorado potato beetle infestation during subsequent growth periods. Tuber weights of these plants were recorded at the end of growth period five. plants were most sensitive to beetle defoliation during the early stages of plant growth up to 60 d after planting. Tuber yield was least affected by beetle feeding damage during later plant growth stages. Up to 100%defoliation during the last plant growth period (75-89 d after planting) did not result in significant reduction in tuber weights, compared with undefoliated plants. Colorado potato beetle counts indicated that plants could tolerate beetle populations well above published threshold levels without a decrease in tuber production, particularly after initiation of bloom.

Serum ferritin in Danish children and adolescents.

Serum ferritin concentrations were measured in 909 urban Danish schoolchildren (451 boys, 458 girls) 6 to 17 years old. The children had been randomly selected and served as an urban reference population. Geometric mean ferritin values were identical in boys and girls 6 to 15 years old, while 16- and 17-year-old boys had higher values than girls (P less than 0.01). There was a slight rise in mean ferritin values from 6 to 11 years, followed by a temporary fall during the subsequent adolescent growth period. Geometric mean ferritin values and significant differences were as follows: Children 6 to 11 years old (n = 335), 29 micrograms/l and adolescents 12 to 15 years old (n = 417), 26 micrograms (P less than 0.01): Adolescent boys 16 to 17 years old (n = 76), 32 micrograms/l and adolescent girls same age (n = 81), 24 micrograms/l (P less than 0.01). The frequencies of low ferritin values less than 10 micrograms/l (i.e. exhausted iron stores) were: Children 6 to 11 years old, 2.1%: Adolescents 12 to 15 years old, 5.0%: Adolescent boys 16 to 17 years old, 0.0%: Adolescent girls 16 to 17 years old, 11.1%. High ferritin values greater than 60 micrograms/l (i.e. large iron reserves) were observed in 6.2% of boys and 6.9% of girls.