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1.
Osteoporos Int ; 31(5): 857-866, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31844906

RESUMO

We conducted a randomized controlled trial to compare the efficacy of adding a video tool to a printed booklet on osteoporosis. Both strategies were effective in increasing knowledge and decreasing decisional conflict. There was no difference in the measured outcomes between the intervention and control groups. Patient preferences and learning styles are key factors in deciding a presentation format when educating patients with osteoporosis. INTRODUCTION: Innovative approaches to patient education about self-management in osteoporosis may improve outcomes. METHODS: We conducted a randomized controlled trial to compare the efficacy of adding a multimedia patient education tool involving video modeling to a printed educational booklet on osteoporosis. Participants were post-menopausal women with osteoporosis. We assessed osteoporosis knowledge, decisional conflict, self-efficacy, and effectiveness in disease management at baseline, immediately post-intervention, and at 3 and 6 months. Linear regression models were used to explore changes in outcomes at 6 months with respect to baseline characteristics. RESULTS: Two hundred and twenty-five women were randomized, 111 to receive the multimedia tool in addition to the booklet and 114 to receive the booklet alone. Knowledge and decisional conflict scores significantly improved in both groups at all post-intervention assessment points, but with no significant differences in score changes between the groups. Self-efficacy and disease management effectiveness showed no significant changes from baseline. In the entire cohort, younger age was associated with better effectiveness in disease management and Hispanic women had greater gains in knowledge at 6 months compared to White women. Women with limited health literacy who had received the multimedia tool in addition to the printed materials had higher decisional conflict than those who received printed materials alone. CONCLUSION: Both multimedia and printed tools increased knowledge and decreased decisional conflict to the same extent, neither of the educational materials proved to be better than the other. For women with limited health literacy, receiving the booklet alone was more effective in reducing decisional conflict after 6 months, than adding the multimedia tool.


Assuntos
Multimídia , Osteoporose , Feminino , Conhecimentos, Atitudes e Prática em Saúde , Humanos , Lactente , Osteoporose/terapia , Folhetos , Educação de Pacientes como Assunto , Preferência do Paciente
2.
Science ; 206(4416): 333-5, 1979 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-17733682

RESUMO

The sorption rate and metabolic fate of nitrogen dioxide, a major air pollutant, have been determined for Phaseolus vulgaris (L.). Sorption was determined kinetically by chemiluminescent monitoring of (15)NO(2) removal from the test atmosphere and directly by mass spectrometric analysis of nitrogen derived from the plant tissue. Sorptive processes were first order with respect to (15)NO(2) concentration. Virtually all of the (15)NO(2) taken up was metabolized.

3.
New Phytol ; 122(3): 439-446, 1992 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33874224

RESUMO

Initial (0-1 h) net rates of nitrate and ammonium uptake from 200 µM NH4 NO3 were progressively increased as 8-d-old maize (Zea mays L.) seedlings, grown on 5 mM nitrate, were exposed to nitrogen-free solutions for up to 48 h. Further nitrogen deprivation to 72 h resulted in a decline in the nitrate uptake rate. Nitrate uptake rates of plants at all stages of nitrogen deprivation increased steadily during an 8 h exposure to 200 µM NH4 NO3 . The pattern of the response of ammonium uptake during the 8 h adaptation period was considerably different. In nitrogen-replete plants the ammonium uptake rate increased steadily, but deprivation of nitrogen for 12 h and longer resulted in complex responses in which the initial rate was followed by a decline, a subsequent increase, and another decline. The responses of the nitrate uptake system are considered to reflect a lifting of the suppressive effects of nitrate and a product of nitrate assimilation during nitrogen deprivation, a concomitant degradation of an induced component of the nitrate uptake system during that time, and reinduction of the uptake system during the adaptation period. The responses of the ammonium uptake system are considered to reflect the interplay of suppression by a product of ammonium assimilation, the accumulation of root ammonium and associated ammonium efflux, and a stimulation by ammonium of its own uptake. As a consequence of the differential responses of the two uptake systems, nitrate and ammonium uptake rates were positively correlated, largely independent, or negatively correlated as the plants progressed through the 8 h adaptation period.

4.
Arch Pediatr Adolesc Med ; 155(7): 822-30, 2001 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-11434851

RESUMO

OBJECTIVE: To investigate behavioral risks and life circumstances of adolescent mothers with older (> or =5 years) adult (> or =20 years old) vs. similar-aged (+/-2 years) male partners at 12 months' postpartum. METHODS: Nine hundred thirty-one adolescent females were interviewed after delivery and were mailed surveys to complete at 12 months' postpartum. Analysis by chi(2) and t test was used to identify differences in behavioral risks (planned repeated pregnancy, substance use, and intimate partner violence) and life circumstances (financial status, school enrollment, and social support) for adolescent mothers with older adult vs similar-aged partners. Additional stratified analyses were conducted to evaluate the extent to which living with an adult authority figure or being with the father of her infant born 12 months previously might alter observed relationships. RESULTS: At 12 months following delivery, 184 adolescent mothers (20%) reported having an older adult partner, whereas 312 (34%) had a similar-aged partner. The remaining adolescent mothers (n = 239) were excluded from further analyses. Adolescent mothers with older adult partners were significantly less likely to be employed or enrolled in school and were more likely to report planned repeated pregnancies. These adolescent mothers also received less social support. No differences were observed in intimate partner violence or the mother's substance use. Adolescent mothers with older adult partners who did not live with an adult authority figure seemed to be at greatest risk. CONCLUSIONS: The negative educational and financial impact of coupling with an older vs. similar-aged partner seems greater for those mothers who no longer reside with an adult authority figure. These adolescent mothers are also at greater risk of planned rapid repeated pregnancy. Given their limited educational attainment and family support, a subsequent pregnancy may place these young women at considerable financial and educational disadvantage.


Assuntos
Comportamento do Adolescente , Fatores Etários , Mães/psicologia , Assunção de Riscos , Cônjuges , Adolescente , Adulto , Violência Doméstica , Feminino , Humanos , Masculino , Gravidez , Medicina Reprodutiva , Isolamento Social , Apoio Social , Transtornos Relacionados ao Uso de Substâncias , Texas , Estados Unidos
5.
Addiction ; 92(2): 197-206, 1997 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-9158231

RESUMO

This study examined the operating characteristics of the Alcohol Use Disorders Identification Test (AUDIT) as a screen for "at-risk" drinking in a multi-ethnic sample of primary care patients, from a family practice center located in the southwestern United States. A probability sample of 1,333 family medicine patients, stratified by gender and racial/ethnic background (white, African-American and Mexican-American) completed the AUDIT, followed by the Alcohol Use Disorders and Associated Disabilities Interview Schedule (AUDADIS) to determine ICD-10 diagnoses. Indicators of hazardous alcohol use and alcohol-related problems were included as measures of "at-risk" drinking. Despite differences in the spectrum of alcohol problems across patient subgroups, there was no evidence of gender or racial/ethnic bias in the AUDIT as indicated by Receiver Operating Characteristic Curve analysis. Excluding abstainers from the analysis and little impact on screening efficacy. In this population, the AUDIT appears to be an unbiased measure of "at-risk" drinking.


Assuntos
Alcoolismo/diagnóstico , Programas de Rastreamento/métodos , Adulto , Negro ou Afro-Americano , Fatores Etários , Alcoolismo/etnologia , Feminino , Humanos , Masculino , Americanos Mexicanos , Pessoa de Meia-Idade , Valor Preditivo dos Testes , Prevalência , Assunção de Riscos , Sensibilidade e Especificidade , Fatores Sexuais , Texas/epidemiologia
6.
J Stud Alcohol ; 57(2): 203-9, 1996 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-8683970

RESUMO

OBJECTIVE: To identify patient factors associated with primary care physicians asking about alcohol consumption, warning of harmful ethanol effects, and advising modification of alcohol use in their patients. METHOD: A cross-sectional design was used, with a probability sample of 1,333 adult family medicine patients, stratified by sex and racial/ethnic background, drawn from a university-based, family medicine clinic. Patients completed self-report screens for alcohol-related problems (including the CAGE) and questionnaires on their experiences with the primary care provider. RESULTS: Over 64% of male and female patients indicated their physician had asked them at some time about their alcohol consumption. Logistic regression models indicated that male patients were 1.5 times as likely to have been warned about alcohol and three times as likely to have been told to stop or modify their consumption compared to female patients. Patients with lower educational attainment were more likely to have been warned, while the likelihood of ever being told to stop or modify consumption increased with age. These associations were significant after controlling for patient race/ethnicity, cigarette use and CAGE scores. CONCLUSIONS: Patient factors including sex, educational attainment, age, cigarette use and problem alcohol use appear to explain some of the variation in the use of preventive interventions for alcohol abuse by primary care providers. Yet, different patient factors appear to be related to the use of different preventive interventions. The role of patient factors, and in particular sex of patient, in the use of preventive intervention strategies for alcohol abuse by primary care physicians should be further explored.


Assuntos
Alcoolismo/prevenção & controle , Educação de Pacientes como Assunto , Relações Médico-Paciente , Adulto , Alcoolismo/diagnóstico , Alcoolismo/reabilitação , Estudos Transversais , Feminino , Comportamentos Relacionados com a Saúde , Conhecimentos, Atitudes e Prática em Saúde , Humanos , Estilo de Vida , Masculino , Pessoa de Meia-Idade , Atenção Primária à Saúde
7.
Fam Med ; 30(6): 421-3, 1998 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-9624520

RESUMO

BACKGROUND AND OBJECTIVES: The processes of teaching outpatient procedures in the training of primary care physicians have not been widely studied or standardized. This study identified the most widely used teaching settings, methods of evaluation, and barriers to teaching several key procedures in US family practice residencies. METHODS: A survey was sent to directors of family practice residency programs. Key issues identified in phone survey data of published experts in procedural training were used in developing the survey. RESULTS: Of the 464 residency directors contacted, 342 (73.7%) returned completed surveys. Results showed that the family practice center (FPC) was the most common setting for this teaching. Faculty observation was used as a principal evaluation method in most programs for all procedures. Several barriers to training were identified as "very" or "moderately" important. CONCLUSIONS: While the FPC is the most frequently used setting for training in procedures, significant limitations include problems of low volume, limited methods of evaluation, scheduling difficulties, and lack of faculty interest and skill. Several internal and external strategies may be used to alleviate these problems.


Assuntos
Assistência Ambulatorial , Medicina de Família e Comunidade/educação , Internato e Residência/métodos , Avaliação de Programas e Projetos de Saúde/métodos , Ensino/métodos , Competência Clínica , Docentes de Medicina , Seguimentos , Humanos , Relações Interpessoais , Inquéritos e Questionários , Estados Unidos
8.
J Fam Pract ; 48(10): 769-77, 1999 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-12224674

RESUMO

BACKGROUND: Traditional diagnostic criteria for depression and anxiety fail to account for symptom severity. We previously evaluated a severity-based classification system of mood and anxiety symptoms. This study examines whether those severity groups are predictive of differences in health care utilization. METHODS: We used a cohort design to compare the health care utilization of 1232 subjects classified into 4 groups according to symptom severity. Health care billing data were evaluated for each subject for a 15-month period around the index visit. Multiple linear regression models were used to examine relative contributions of individual variables to differences in health care utilization. Analysis of variance procedures were used to compare charges among the severity groups after adjusting for demographic and medical comorbidity variables. RESULTS: After adjustment, significant differences in health care utilization between groups were seen in all but 3 of the 15 months studied. Also, after adjustment, the presence of a mood or anxiety disorder influenced utilization for only a 6-month period. At 9 to 12 months, subjects in the high-severity group showed a more than twofold difference in adjusted charges compared with the low-severity group ($225.36 vs $94.37). CONCLUSIONS: Our severity-based classification predicts statistically and clinically significant differences in health care utilization over most of a 15-month period. Differences in utilization persist even after adjustment for medical comorbidity and significant demographic covariates. Our work lends additional evidence that beyond screening for the presence of mood and anxiety disorders, it is important to assess symptom severity in primary care patients. Further study directed toward developing effective methods of identifying patients with high levels of mood and anxiety symptom severity could result in significant cost savings.


Assuntos
Afeto/classificação , Ansiedade/classificação , Atenção à Saúde/estatística & dados numéricos , Adulto , Consumo de Bebidas Alcoólicas/epidemiologia , Consumo de Bebidas Alcoólicas/psicologia , Ansiedade/epidemiologia , Análise por Conglomerados , Estudos de Coortes , Comorbidade , Atenção à Saúde/economia , Feminino , Custos de Cuidados de Saúde/classificação , Humanos , Masculino , Análise de Regressão , Índice de Gravidade de Doença , Texas/epidemiologia
9.
J Fam Pract ; 41(1): 33-41, 1995 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-7798064

RESUMO

BACKGROUND: The issue of whether to screen men for prostate cancer is controversial. No randomized clinical trials have been completed to confirm the efficacy of screening for prostate cancer. We created a mathematical model of the clinical risks and benefits of screening for prostate cancer. METHODS: A Markov decision-analytic model evaluated the outcomes of annually screening asymptomatic men for prostate cancer beginning at age 50 years. The screening and testing algorithm included the digital rectal examination, transrectal ultrasound, and prostate-specific antigen test. A sample of 10 male patients with no history of prostate disease were interviewed to assess their utilities (preferences) regarding the various adverse outcomes of prostate cancer treatment. RESULTS: The model indicated that no screening was preferred to screening when patients' utilities were considered (24.14 vs 23.47 quality-adjusted life years expected). The optimal decision was sensitive to the utilities of impotence and urethral stricture, the most common adverse outcomes for patients under the age of 65 years. When adverse outcomes of treatment were ignored, screening was favored (24.86 vs 24.22 years of life expectancy. CONCLUSIONS: When quality-of-life preferences of men are considered, the annual screening of asymptomatic patients for prostate cancer is not recommended.


Assuntos
Técnicas de Apoio para a Decisão , Programas de Rastreamento , Neoplasias da Próstata/prevenção & controle , Idoso , Disfunção Erétil/etiologia , Humanos , Masculino , Cadeias de Markov , Pessoa de Meia-Idade , Prostatectomia/efeitos adversos , Neoplasias da Próstata/terapia , Qualidade de Vida , Radioterapia/efeitos adversos , Resultado do Tratamento , Estreitamento Uretral/etiologia
10.
J Fam Pract ; 48(9): 682-8, 1999 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-10498074

RESUMO

BACKGROUND: The benefits of early detection of prostate cancer are uncertain, and the American College of Physicians and the American Academy of Family Physicians recommend individual decision making in prostate cancer screening. This study reports the knowledge of male primary care patients about prostate cancer and prostate-specific antigen (PSA) testing and examines how that knowledge is related to PSA testing, preferences for testing in the future, and desire for involvement in physician-patient decision making. METHODS: The sample included 160 men aged 45 to 70 years with no history of prostate cancer who presented for care at a university-based family medicine clinic. Before scheduled office visits, patients completed a questionnaire developed for this study that included a 10-question measure of prostate cancer knowledge, the Deber-Kraestchmer Problem-Solving Decision-Making Scale, sociodemographic indicators, and questions on PSA testing. RESULTS: In general, patients who were college graduates were more knowledgeable about prostate cancer and early detection than those with a high school education or less. Aside from college graduates, most patients could not identify the principle advantages and disadvantages of PSA testing. Patients indicating previous or future plans for PSA testing demonstrated greater knowledge than other patients. Desire for involvement in decision making varied by patient education but was not related to past PSA testing. CONCLUSIONS: Patients lack knowledge about prostate cancer and early detection. This knowledge deficit may impede the early detection of prostate cancer and is a barrier to making an informed decision about undergoing PSA testing.


Assuntos
Tomada de Decisões , Medicina de Família e Comunidade , Conhecimentos, Atitudes e Prática em Saúde , Consentimento Livre e Esclarecido , Programas de Rastreamento , Participação do Paciente , Antígeno Prostático Específico/sangue , Neoplasias da Próstata/diagnóstico , Adulto , Idoso , Escolaridade , Humanos , Conhecimento , Masculino , Pessoa de Meia-Idade , Educação de Pacientes como Assunto , Neoplasias da Próstata/sangue , Neoplasias da Próstata/psicologia , Fatores de Risco , Fatores Socioeconômicos , Texas
12.
Fam Med ; 23(6): 419, 1991 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-1936712
15.
16.
Plant Physiol ; 49(2): 218-23, 1972 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-16657928

RESUMO

Concurrent O(2) evolution, O(2) uptake, and CO(2) uptake by illuminated maize (Zea mays) leaves were measured using (13)CO(2) and (18)O(2). Considerable O(2) uptake occurred during active photosynthesis. At CO(2) compensation, O(2) uptake increased. Associated with this increase was a decrease in O(2) release such that a stoichiometric exchange of O(2) occurred. The rate of O(2) exchange at CO(2) compensation was directly related to O(2) concentration in the atmosphere at least up to 8% (v/v).When illuminated maize leaves were exposed to saturating CO(2) concentrations containing approximately equal amounts of (12)CO(2) and (13)CO(2), the latter was taken up more rapidly, thus depressing the atom% (13)C in the atmosphere. Moreover, upon exposure to CO(2) containing 96 atom% (13)C, there occurred a directly measurable efflux of (12)CO(2) from the leaves for at least 15 minutes. During this period an equimolar evolution of (16)O(2) and uptake of (13)CO(2) was observed. Thereafter, although the rate of (16)O(2) evolution remained unchanged, the rate of (13)CO(2) uptake declined markedly, suggesting continual (13)C enrichment of the photorespiratory substrate.It is concluded that a finite photorespiratory process occurs in maize and that the CO(2) generated thereby is efficiently recycled. Recycling maintains the internal CO(2) concentration at a level difficult to detect by most photorespiratory assays.

17.
Plant Physiol ; 84(4): 1416-20, 1987 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-16665619

RESUMO

Potassium influx into roots of dark-grown decapitated maize seedling (Zea mays L., cv Pioneer 3369A) was examined in presence and absence of ambient ammonium and at various root potassium concentrations. Six-day old seedlings which were dependent on the endosperm reserves for their energy source were exposed to KCl (labeled with (86)Rb) ranging from 5 to 200 micromolar. At both low (13 micromoles per gram fresh weight) and high (100 micromoles per gram fresh weight) root potassium concentration, isotherms indicated two potassium influx systems, one approaching saturation at 50 to 100 micromolar potassium and an additional one tentatively considered to be linear. A mixed-type inhibition by ammonium for the low-concentration saturable system was indicated by a concomitant decrease in V(max) and increase in K(m). High root potassium concentration decreased V(max) but had little effect on K(m) of this system. The rate constant for the second quasilinear system was decreased by ambient ammonium and by high root potassium status. Transfer of high potassium roots to potassium-free solutions resulted in an increase in influx within 2 hours; by 24 hours influx significantly exceeded that of roots not previously exposed to potassium. In roots of both low and high root potassium concentrations, potassium influx was restricted progressively as ambient ammonium increased to about 100 micromolar, but there was little further inhibition as ammonium concentrations increased beyond that to 500 micromolar. The data imply that potassium influx has two components, one subject to inhibition by ambient ammonium and one relatively resistant.

18.
Plant Physiol ; 84(4): 1421-6, 1987 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-16665620

RESUMO

An experiment was conducted to investigate the reduction of endogenous NO(3) (-), which had been taken up by plants in darkness, during the course of the subsequent light period. Vegetative, nonnodulated soybean plants (Glycine max [L]. Merrill, ;Ransom') were exposed to 1.0 millimolar (15)NO(3) (-) for 12 hours in darkness and then returned to a solution containing 1.0 millimolar (14)NO(3) (-) for the 12 hours ;chase' period in the light. Another set of plants was exposed to (15)NO(3) (-) during the light period to allow a direct comparison of contributions of substrate from the endogenous and exogenous sources. At the end of the (15)NO(3) (-) exposure in the dark, 70% of the absorbed (15)NO(3) (-) remained unreduced, and 83% of this unreduced NO(3) (-) was retained in roots. The pool of endogenous (15)NO(3) (-) in roots was depleted at a steady rate during the initial 9 hours of light and was utilized almost exclusively in the formation of insoluble reduced-N in leaves. Unlabeled endogenous NO(3) (-), which had accumulated in the root prior to the previous dark period, also was depleted in the light. When exogenous (15)NO(3) (-) was supplied during the light period, the rate of assimilation progressively increased, reflecting an increased rate of uptake and decreased accumulation of NO(3) (-) in the root tissue. The dark-absorbed endogenous NO(3) (-) in the root was the primary source of substrate for whole-plant NO(3) (-) reduction in the first 6 hours of the light period, and exogenous NO(3) (-) was the primary source of substrate thereafter. It is concluded that retention of NO(3) (-) in roots in darkness and its release in the following light period is an important whole-plant regulatory mechanism which serves to coordinate delivery of substrate with the maximal potential for NO(3) (-) assimilation in photosynthetic tissues.

19.
Plant Physiol ; 88(3): 725-30, 1988 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-16666374

RESUMO

A series of experiments was conducted to characterize alterations in carbohydrate utilization in leaves of nitrogen stressed plants. Two-week-old, nonnodulated soybean plants (Glycine max [L.] Merrill, ;Ransom'), grown previously on complete nutrient solutions with 1.0 millimolar NO(3) (-), were transferred to solutions without a nitrogen source at the beginning of a dark period. Daily changes in starch and sucrose levels of leaves were monitored over the following 5 to 8 days in three experiments. Starch accumulation increased relative to controls throughout the leaf canopy during the initial two light periods after plant exposure to N-free solutions, but not after that time as photosynthesis declined. The additional increments of carbon incorporated into starch appeared to be quantitatively similar to the amounts of carbon diverted from amino acid synthesis in the same tissues. Since additional accumulated starch was not degraded in darkness, starch levels at the beginning of light periods also were elevated. In contrast to the starch effects, leaf sucrose concentration was markedly higher than controls at the beginning of the first light period after the N-limitation was imposed. In the days which followed, diurnal turnover patterns were similar to controls. In source leaves, the activity of sucrose-P synthase did not decrease until after day 3 of the N-limitation treatment, whereas the concentration of fructose-2,6-bisphosphate was decreased on day 2. Restricted growth of sink leaves was evident with N-limited plants within 2 days, having been preceeded by a sharp decline in levels of fructose-2,6 bisphosphate on the first day of treatment. The results suggest that changes in photosynthate partitioning in source leaves of N-stressed plants resulted largely from a stable but limited capacity for sucrose formation, and that decreased sucrose utilization in sink leaves contributed to the whole-plant diversion of carbohydrate from the shoot to the root.

20.
Plant Physiol ; 89(2): 457-63, 1989 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-16666565

RESUMO

An experiment was conducted to investigate the relative changes in NO(3) (-) assimilatory processes which occurred in response to decreasing carbohydrate availability. Young tobacco plants (Nicotiana tabacum [L.], cv NC 2326) growing in solution culture were exposed to 1.0 millimolar (15)NO(3) (-) for 6 hour intervals during a normal 12 hour light period and a subsequent period of darkness lasting 42 hours. Uptake of (15)NO(3) (-) decreased to 71 to 83% of the uptake rate in the light during the initial 18 hours of darkness; uptake then decreased sharply over the next 12 hours of darkness to 11 to 17% of the light rate, coincident with depletion of tissue carbohydrate reserves and a marked decline in root respiration. Changes also occurred in endogenous (15)NO(3) (-) assimilation processes, which were distinctly different than those in (15)NO(3) (-) uptake. During the extended dark period, translocation of absorbed (15)N out of the root to the shoot varied rhythmically. The adjustments were independent of (15)NO(3) (-) uptake rate and carbohydrate status, but were reciprocally related to rhythmic adjustments in stomatal resistance and, presumably, water movement through the root system. Whole plant reduction of (15)NO(3) (-) always was limited more than uptake. The assimilation of (15)N into insoluble reduced-N in roots remained a constant proportion of uptake throughout, while assimilation in the shoot declined markedly in the first 18 hours of darkness before stabilizing at a low level. The plants clearly retained a capacity for (15)NO(3) (-) reduction and synthesis of insoluble reduced-(15)N even when (15)NO(3) (-) uptake was severely restricted and minimal carbohydrate reserves remained in the tissue.

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