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PubMed2003

Winter bud content according to position in 3-year-old branching systems of 'Granny Smith' apple.

An investigation was made of the number of preformed organs in winter buds of 3-year-old reiterated complexes of the 'Granny Smith' cultivar. Winter bud content was studied with respect to bud position: terminal buds were compared on both long shoots and spurs according to branching order and shoot age, while axillary buds were compared between three zones (distal, median and proximal) along 1-year-old annual shoots in order 1. The percentage of winter buds that differentiated into inflorescences was determined and the flowers in each bud were counted for each bud category. The other organ categories considered were scales and leaf primordia. The results confirmed that a certain number of organs must be initiated before floral differentiation occurred. The minimum limit was estimated at about 15 organs on average, including scales. Total number of lateral organs formed was shown to vary with both bud position and meristem age, increasing from newly formed meristems to 1- and 2-year-old meristems on different shoot types. These differences in bud organogenesis depending on bud position, were consistent with the morphogenetic gradients observed in apple tree architecture. Axillary buds did not contain more than 15 organs on average and this low organogenetic activity of the meristems was related to a low number of flowers per bud. In contrast, the other bud categories contained more than 15 differentiated organs on average and a trade-off was observed between leaf and flower primordia. The ratio between the number of leaf and flower primordia per bud varied with shoot type. When the terminal buds on long shoots and spurs were compared, those on long shoots showed more flowers and a higher ratio of leaf to flower primordia.

Cell Differentiation↗
PubMed1976

Variables associated with the winter camping location of elderly recreational vehical owners in southwestern Arizona.

During the winter of 1973-1974, 580 elderly recreational vehicle campers were interviewed in six private trailer parks and four public camping areas in southwestern Arizona and Southern California. The ten sites represented four different types of camping environment: (1) highly developed, relatively expensive urban private trailer parks, (2) moderately developed, relatively inexpensive, rural private trailer parks, (3) authorized, developed, free federal campgrounds, and (4) unauthorized, undeveloped, free public land camping areas. Analysis of variance was utilized to identify those respondent characteristics most strongly associated with the type of site selected for winter residence. The most important of these variables were per person annual income, woman's age, man's education, woman's total preretirement adult camping experience, value of mobile quarters and tow vehicle, and percentage of the year lived in a recreational vehicle. Several financial indicators and certain noneconomic characteristics of females were strongly associated with winter camping location.

Age Factors↗
PubMed2004

Indoor winter fumigation of Apis mellifera (Hymenoptera: Apidae) colonies infested with Varroa destructor (Acari: Varroidae) with formic acid is a potential control alternative in northern climates.

Formic acid treatment for the control of the ectoparasitic varroa mite, Varroa destructor Anderson & Trueman, infesting honey bee, Apis mellifera L., colonies is usually carried out as an in-hive outdoor treatment. This study examined the use of formic acid on wintered colonies kept indoors at 5 degrees C from 24 November 1999 to 24 March 2000. Colonies were placed in small treatment rooms that were not treated (control) or fumigated at three different concentrations of formic acid: low (mean 11.9 +/- 1.2 ppm), medium (mean 25.8 +/- 1.4 ppm), or high (mean 41.2 +/- 3.3 ppm), for 48 h on 22-24 January 2000. Queen bee, worker bee, and varroa mite mortality were monitored throughout the winter, and tracheal mite, Acarapis woodi (Rennie), prevalence and mean abundance of nosema, Nosema apis Zander, spores were assessed. This study revealed that formic acid fumigation of indoor-wintered honey bees is feasible and effective. The highest concentration significantly reduced the mean abundance of varroa mites and nosema spores without increasing bee mortality. Tracheal mite prevalence did not change significantly at any concentration, although we did not measure mortality directly. The highest concentration treatment killed 33.3% of queens compared with 4.8% loss in the control. Repeated fumigation periods at high concentrations or extended fumigation at low concentrations may increase the efficacy of this treatment method and should be tested in future studies. An understanding of the cause of queen loss and methods to prevent it must be developed for this method to be generally accepted.

Acari↗
PubMed2004

Damage loss assessment and control of the cereal leaf beetle (Coleoptera: Chrysomelidae) in winter wheat.

Cereal leaf beetle, Oulema melanopus (L.), invaded northern Alabama and Georgia more than a decade ago and since has become an economic pest of winter wheat and other cereal crops in the southeastern United States. A series of trials was conducted beginning in 1995 to determine optimal rate and timing of applications of selected foliar insecticides for managing cereal leaf beetle in soft red winter wheat. These trials, cage studies with larvae, and a manual defoliation experiment were used to provide information on cereal leafbeetle yield loss relationships and to develop economic decision rules for cereal leaf beetle in soft red winter wheat. Malathion, methomyl, carbaryl, and spinosad effectively controlled larval infestations when treatments were applied after most eggs had hatched. Encapsulated endotoxin of Bacillus thuringiensis, methyl parathion, and disulfoton applied at the lowest labeled rates were not effective treatments. Organophosphate insecticides generally were not effective when applied before most eggs had hatched. The most effective treatments were the low rates of lambda cyhalothrin when applied early while adults were still laying eggs and before or near 50% egg hatch. These early applications applied at or before spike emergence virtually eliminated cereal leaf beetle injury. The manual defoliation study demonstrated that defoliation before spike emergence has greater impact on grain yield and yield components than defoliation after spike emergence. Furthermore, flag leaf defoliation causes more damage than injury to lower leaves. Grain test weight and kernel weight were not affected by larval injury in most trials. Regression of larval numbers and yield losses calculated a yield loss of 12.65% or 459 kg/ha per larva per stem, which at current application costs suggested an economic threshold of 0.4 larvae per stem during the spike emergence to anthesis stages.

Animals↗
PubMed2006

Molecular genetic studies of the memory of winter.

Many plant species have evolved the ability to flower in the proper season by sensing environmental cues. The prolonged cold of winter is one such cue that certain plants use to acquire competence to flower the following spring. For example, biennials and winter annuals become established in one growing season and often flower quickly in the early spring of the following year to complete their life cycles. The process by which exposure to prolonged cold establishes competence to flower is known as vernalization. Many studies, starting with the classic work of Lang and Melchers, have shown that the vernalized state can be stable; i.e. after exposure to cold has ended, competence to flower, in certain species, can persist for many months and throughout many cell divisions in the shoot apical meristem. Thus, plants can exhibit a 'memory of winter' and vernalization can result in an epigenetic switch in the classic sense of the term: a change that is stable in the absence of the inducing signal. The nature of this epigenetic switch in Arabidopsis thaliana is discussed here.

Amino Acid Sequence↗
PubMed2001

Winter emergency pressures for the NHS: contribution of respiratory disease, experience in North Staffordshire district.

The rise in emergency medical admissions in winter in the NHS hospitals in the United Kingdom has been recognized to reflect respiratory and cardiovascular illness. In our study we looked at the contribution of respiratory disease to the winter pressures in our district. Respiratory disease related emergency admissions increased twofold in the winter months, with obvious implications for workload. An evidence-based National Service Framework for respiratory disease would be useful.

Emergencies↗
PubMed1999

The winter bed crisis--quantifying seasonal effects on hospital bed usage.

Winter bed crises are a common feature in NHS hospitals, and have given rise to great concern. We set out to determine the relative contribution of seasonal effects and other factors to bed occupancy in a large teaching hospital over one year. There were 190,804 occupied bed-days, which we analysed by specialty groupings. There was considerable variability in bed occupancy in each specialty. A significant winter peak occurred for general medicine and orthopaedics together with a significant increase on 'take-in' days. Virtually all specialties showed a significant variation in occupancy between weekdays. Geriatric Medicine had a high and fairly constant occupancy, with some seasonal effect. We conclude that seasonal trends in bed occupancy occur in 'front door' specialties and are predictable. In these specialties, admission policies also make a contribution to bed usage and are amenable to modification. There is no surge in occupancy in the immediate post-Christmas period, except that attributable to the seasonal trend. In the 'elective' specialties, bed occupancy fluctuates widely, with reduced occupancy at weekends and at Christmas. These differences are entirely amenable to modification. More effective bed management would make a very significant contribution to avoiding winter bed crises.

Bed Occupancy↗
PubMed1992

Modeling shoot water contents in high-elevation Picea rubens during winter.

During the winter of 1990-1991, a meteorological tower was established at an 880-m elevation site within the spruce-fir zone on Mt. Moosilauke, New Hampshire, USA. Hourly means of air, needle and trunk temperatures, wind velocity, relative humidity and solar radiation were recorded. On a weekly basis, shoots that had elongated during the preceding growing season were collected from four red spruce (Picea rubens Sarg.) trees and their relative water contents (RWC) determined. Cuticular resistances of needles from these shoots were measured four times during the winter.Measured meteorological parameters were used in a previously developed model to simulate changes in red spruce shoot RWC during the winter. The modeled results were compared to measured shoot RWCs. The predictive power of the model was improved when it was modified to include measured values of cuticular resistance and needle and trunk temperatures. The new version of the model accurately predicted RWC from late December 1990 to the beginning of April 1991, after which spring recharge appeared to occur. We conclude that water lost from foliage was easily replaced by stored reserves and that uptake of water by the roots was not required to maintain an adequate foliar water content during the winter.

Journal Article↗
PubMed1995

Winter photosynthesis of red spruce from three Vermont seed sources.

We evaluated winter (January through March) carbon assimilation of red spruce (Picea rubens Sarg.) from three Vermont seed sources grown in a common garden in northwestern Vermont. Although CO(2) exchange rates were generally low, net photosynthetic rates increased during two prolonged thaws. Significant correlations between CO(2) exchange rates and multiday air temperature means supported our observations of enhanced gas exchange during extended periods of elevated temperature. Increases in photosynthesis during thaws occurred before observed increases in leaf conductance, indicating that initial changes in photosynthesis were probably not associated with changes in stomatal aperture. Results of correlations between photosynthetic rates and PAR suggested that solar irradiance did not have a strong effect on winter carbon capture. Rates of net photosynthesis differed among seed sources. Trees from the Mt. Mansfield source had the highest average rates of photosynthesis and, at times, rates for individual trees from this source approximated those occurring during the growing season. Because seed sources differed in photosynthetic rates but not in leaf conductance, we conclude that differences in winter photosynthesis among seed sources were primarily attributable to factors other than changes in stomatal aperture.

Journal Article↗
PubMed1997

Carbon dioxide gas exchange of cembran pine (Pinus cembra) at the alpine timberline during winter.

Winter CO(2) gas exchange of the last three flushes of cembran pine (Pinus cembra L.) was studied under ambient conditions at the alpine timberline, an ecotone with strong seasonal changes in climate. During the coldest months of the year, December to March, gas exchange was almost completely suppressed and even the highest irradiances and temperatures did not cause a significant increase in net photosynthesis compared to spring and fall. In general, daily CO(2) balance was negative between December and March except during extended warm periods in late winter. However, because twig respiration was also reduced to a minimum during the December-March period, daily carbon losses were minimal. Total measured carbon loss during the winter months was small, equalling the photosynthetic production of one to two warm days in spring or summer when average air temperature was above 6 degrees C.

Journal Article↗
PubMed1998

Photosynthetic capacity of red spruce during winter.

We measured the photosynthetic capacity (P(max)) of plantation-grown red spruce (Picea rubens Sarg.) during two winter seasons (1993-94 and 1994-95) and monitored field photosynthesis of these trees during one winter (1993-94). We also measured P(max) for mature montane trees from January through May 1995. Changes in P(max) and field photosynthesis closely paralleled seasonal changes in outdoor air temperature. However, during thaw periods, field photosynthesis was closely correlated with multiple-day temperature regimes, whereas P(max) was closely correlated with single-day fluctuations in temperature. There was a strong association between short-term changes in ambient temperature and P(max) during the extended thaw of January 1995. Significant increases in P(max) occurred within two days of the start of this thaw. Repeated measurements of cut shoots kept indoors indicated that temperature-induced increases in P(max) can occur within 3 h. Although significant correlations between P(max) and stomatal conductance (g(s)) or intracellular CO(2) concentration (C(i)) raised the possibility that increases in P(max) resulted from increases in stomatal aperture, fluctuations in g(s) or C(i) explained little of the overall variation in P(max). Following both natural and simulated thaws, P(max) increased considerably but plateaued at only 37% of the mean photosynthetic rate reported for red spruce during the growing season. Thus, even though shoots were provided with near-optimal environmental conditions, and despite thaw-induced changes in physiology, significant limitations to winter photosynthesis remained.

Journal Article↗
PubMed2005

Hydraulic conductivity, photosynthesis and leaf water balance in six evergreen woody species from fall to winter.

To confirm that freeze-thaw embolism is a primary stress for evergreen woody species in winter, hydraulic conductivity, photosynthesis and leaf water potential were measured during fall and winter in trees growing in a cool temperate zone (Nikko) and in a warm temperate zone (Tokyo). We examined two evergreen conifers that naturally occur in the cool temperate zone (Abies firma Siebold & Zucc. and Abies homolepis Siebold & Zucc.), and four evergreen broad-leaved woody species that are restricted to the warm temperate zone (Camellia japonica L., Cinnamomum camphora (L.) J. Presl, Ilex crenata Thunb. and Quercus myrsinaefolia Blume). In Tokyo, where no freeze-thaw cycles of xylem sap occurred, hydraulic conductivity, photosynthesis and water balance remained constant during the experimental period. In Nikko, where there were 38 daily freeze-thaw cycles by February, neither of the tracheid-bearing evergreen conifers showed xylem embolism or leaf water deficits. Similarly, the broad-leaved evergreen trees with small-diameter vessels did not exhibit severe embolism or water deficits and maintained CO(2) assimilation even in January. In contrast, the two broad-leaved evergreen trees with large-diameter vessels showed significantly reduced hydraulic conductivity and shoot die-back in winter. We conclude that freeze-thaw embolism restricts evergreen woody species with large-diameter vessels to the warm temperate zone, whereas other stresses limit the distribution of broad-leaved trees, that have small-diameter vessels, but which are restricted to the warm temperate zone.

Abies↗
PubMed1988

Water relations of Eucalyptus pauciflora near the alpine tree line in winter.

Water potential measurements were made, over three winter seasons, on Eucalyptus pauciflora Sieb. ex Spreng. at four elevations extending up to 200 m above the natural tree line in the Snowy Mountains area of southeastern Australia. Shoot water potentials were lowest in winter but never approached lethal levels. Contrary to expectations, there was no gradient of water potential with elevation. This was attributed primarily to the absence of a gradient of soil temperatures once snowpack had developed. Lowest water potentials were observed at air temperatures several degrees above zero, suggesting that transpiration and absorption may be differently affected, with temperatures above and below these values causing higher water potentials. The results suggest that shoot dieback in winter, which is a common phenomenon at alpine tree lines, is not caused by low water potentials in southeastern Australia.

Journal Article↗
PubMed1991

In situ experimental freezing produces symptoms of winter injury in red spruce foliage.

Two mechanisms have been proposed to explain winter injury to needles of red spruce (Picea rubens Sarg.): (1) desiccation, which is characterized by net loss of foliar water from the needle to the environment, with cell injury resulting from dehydration; and (2) freezing, which is characterized by direct injury to cells resulting from intracellular or extracellular ice formation during exposure to low temperature. To compare the separate and combined effects of freezing and desiccation, branches of a mature red spruce at 1160 m were (a) experimentally frozen in situ to -50 degrees C; (b) cut and tied in their original orientation and allowed to desiccate passively; or (c) both frozen in situ and cut and tied in their original orientation. Needle water content, electrolyte leakage (an index of cell injury), and needle color were monitored for 60 days after treatment. Freezing resulted in immediate increases in electrolyte leakage, rapid water loss, and reddening necrosis of needles similar to that of naturally injured needles. Cutting resulted in more gradual water loss, no significant changes in electrolyte loss until severe desiccation had occurred, and a change in the color of the needles to a dull green. Because freezing produced reddening necrosis, a key symptom of winter injury, whereas desiccation did not, we conclude that freezing is probably the primary cause of winter injury in red spruce, and that desiccation is a secondary effect.

Journal Article↗
PubMedDate not supplied

Outdoor winter activities of spinal cord-injured patients. With special reference to outdoor mobility.

Two hundred forty-seven patients with spinal cord injuries living in Hokkaido, the northern part of Japan, were mailed a questionnaire relating to winter outdoor activities. One hundred eight patients responded to the questionnaire, 98 males and 10 females, with ages ranging from 30 to 79 (mean, 53.3) yr. Injury levels of patients were: cervical in 23 patients, thoracic and thoracolumbar in 47, and lumbar in 38. All respondents were unable to walk independently because of quadriplegia or paraplegia. Approximately 90 percent of respondents found it necessary to go outside during the winter season. Eighty-five percent were outside during the coldest period. The most common reasons for outdoor activities were shopping and routine doctor's appointments. The main method of ambulating outside was a manual and/or electrically operated wheelchair, sometimes in conjunction with an automobile. However, there were many problems reported in using wheelchairs; for example, wheels and casters were very slippery on the snow and ice, casters were easily buried in the snow, and wheelchair rims were very cold to handle. It was also pointed out that exposure to cold weather induced physical problems such as muscle spasticity, pain, and numbness of lower extremities. This survey revealed that spinal cord-injured patients would benefit from a wheelchair specifically designed for winter conditions.

Accidental Falls↗
PubMed2006

High prevalence of self-reported depressive mood during the winter season among Swedish senior high school students.

OBJECTIVE: There are few studies regarding the prevalence of seasonal variation in mood among children and adolescents. The main objective of this study was to estimate the prevalence of self-reported depressive mood during the winter season among Swedish adolescents and to investigate gender differences. Another aim was to analyze the factor structure and internal consistency of the Kiddie SPAQ (K-SPAQ), a pediatric version of the Seasonal Pattern Questionnaire (SPAQ). METHOD: All students 17 to 18 years old, registered in the second year of senior high school in Falun, a district in central Sweden, were screened with the K-SPAQ in January 2003 (response rate 87.3%, n = 756). RESULTS: The prevalence of self-reported depressive mood during the winter season was estimated at 20.1% (n = 151/751) and was higher among girls (25.5%) than boys (13.8%). Approximately 8% reported more severe depressive symptoms. Depressive mood during the summer was rare (0.1%, n = 1/751). Factor analysis of the General Seasonal Score items in the K-SPAQ revealed a two-factor structure. A Cronbach's alpha of 0.87 demonstrated a good internal consistency. CONCLUSIONS: Depressive symptoms during autumn and winter were common among Swedish senior high school students, especially among girls. This is probably an underdiagnosed condition among adolescents that ought to receive more attention from the health and school authorities.

Adolescent↗
PubMed2004

Stable isotope ratios indicate that body condition in migrating passerines is influenced by winter habitat.

Although predicted some time ago, there has been little success in demonstrating that the overall fitness of migratory birds depends on the combined influences of their experiences over all seasons. We used stable carbon isotope signatures (delta13C) in the claws of migrating black-throated blue warblers Dendroica caerulescens to infer their wintering habitats and investigated whether winter habitat selection can be linked to condition during migration. Resident bird species with low delta13C corresponded to selection of more mesic habitats, and migrating birds with low delta13C were in better condition than conspecifics with higher delta13C signatures. These findings concur with empirical observations on the wintering grounds, where dominants (mostly males) tend to exclude subordinates from mesic areas (considered to be high-quality habitats). We believe that variation in condition during migration may be one of the key factors determining differences in arrival times and condition at the breeding areas, which in turn have a major influence on reproductive success.

Animal Migration↗
PubMed2005

The relative role of winter and spring conditions: linking climate and landscape-scale plant phenology to alpine reindeer body mass.

The relative importance of winter harshness and early summer foraging conditions are of prime interest when assessing the effect of global warming on Arctic and mountainous ecosystems. We explored how climate and vegetation onset (satellite-derived normalized difference vegetation index data) determined individual performance in three reindeer populations (data on 27814 calves sampled over 11 years). Snow conditions, spring temperatures and topography were the main determinants of the onset of the vegetation. An earlier onset positively affected the body mass of calves born the following autumn, while there was no significant direct negative impact of the previous winter. This study underlines the major impact of winter and spring climatic conditions, determining the spring and summer food availability, and the subsequent growth of calves among alpine herbivores.

Animals↗