Isoprene emission from aspen leaves : influence of environment and relation to photosynthesis and photorespiration

Isoprene emission rates from quaking aspen (Populus tremuloides Michx.) leaves were measured simultaneously with photosynthesis rate, stomatal conductance, and intercellular CO₂ partial pressure. Isoprene emission required the presence of CO₂ or O₂, but not both. The light response of isoprene emission rate paralleled that of photosynthesis. Isoprene emission was inhibited by decreasing ambient O₂ from 21% to 2%, only when there was oxygen insensitive photosynthesis. Mannose (10 millimolar) fed through cut stems resulted in strong inhibition of isoprene emission rate and is interpreted as evidence that isoprene biosynthesis requires either the export of triose phosphates from the chloroplast, or the continued synthesis of ATP. Light response experiments suggest that photosynthetically generated reductant or ATP is required for isoprene biosynthesis. Isoprene biosynthesis and emission are not directly linked to glycolate production through photorespiration, contrary to previous reports. Isoprene emission rate was inhibited by above-ambient CO₂ partial pressures (640 microbar outside and 425 microbar inside the leaf). The inhibition was not due to stomatal closure. This was established by varying ambient humidity at normal and elevated CO₂ partial pressures to measure isoprene emission rates over a range of stomatal conductances. Isoprene emission rates were inhibited at elevated CO₂ despite no change in stomatal conductance. Addition of abscisic acid to the transpiration stream dramatically inhibited stomatal conductance and photosynthesis rate, with a slight increase in isoprene emission rate. Thus, isoprene emission is independent of stomatal conductance, and may occur through the cuticle. Temperature had an influence on isoprene emission rate, with the Q₁₀ being 1.8 to 2.4 between 35 and 45°C. At these high temperatures the amount of carbon lost through isoprene emission was between 2.5 and 8% of that assimilated through photosynthesis. This represents a significant carbon cost that should be taken into account in determining midsummer carbon budgets for plants that are isoprene emitters.     

Allocation of Photosynthate to Individual Tubers of Solanum tuberosum L.: I. RELATIONSHIP BETWEEN TUBER GROWTH RATE AND ENZYME ACTIVITIES OF THE STARCH METABOLISM

Potato plants (Solanum tuberosum L.) were grown in water culturein a controlled environment. Cooling (+8°C) of individualtubers decreased their growth rates and increased the growthrates of non-cooled tubers of the same plant. The carbohydrateconcentration in non-cooled and cooled tubers did not differsignificantly, but ¹⁴C-import from labelled photosynthate waslower in cooled than in non-cooled tubers. The markedly lowerconversion rate of ethanol-soluble ¹⁴C to starch in cooled,in comparison to non-cooled tubers, was not associated withsignificant differences in the in vitro activities of starchsynthase, ADPG-pyrophosphorylase and starch phosphorylase understandard assay conditions (+30°C). However, the Q₁₀-valuesof the enzymes differed in vitro in the temperature range between30°C and 8°C, leading to a marked decrease in the activityratio of ADPG-pyrophosphorylase/starch phosphorylase in cooledtubers. In tubers differing in growth rates without manipulation, 14d after tuber initiation significant positive correlations werefound between ¹⁴C-concentration of tuber tissue and the in vitroactivities of starch synthase and ADPG-pyrophosphorylase anda significant negative correlation between ¹⁴C-concentrationand starch phosphorylase. In contrast, in tubers which wereanalysed 5 d after initiation, there were only small differencesbetween tubers in growth rate, ¹⁴C import and the activity ratioADPG-pyrophosphorylase/starch phosphorylase. From various directand indirect evidence it is concluded that the growth rate ofindividual tubers, and thus the sink strength, is at least inpart controlled by the activity of starch synthesizing enzymes. Key words: Potato tuber, cooling, starch synthesizing enzymes     

Influences of sea level changes and volcanic eruptions on Holocene vegetation in Tonga

Here, we investigate Mid- to Late-Holocene vegetation changes in low-lying coastal areas in Tonga and how changing sea levels and recurrent volcanic eruptions have influenced vegetation dynamics on four islands of the Tongan archipelago (South Pacific). To investigate past vegetation and environmental change at Ngofe Marsh (‘Uta Vava’u), we examined palynomorphs (pollen and spores), charcoal (fire), and sediment characteristics (volcanic activity) from a 6.7-m-long sediment core. Radiocarbon dating indicated the sediments were deposited over the last 7700 years. We integrated the Ngofe Marsh data with similar previously published data from Avai’o’vuna Swamp on Pangaimotu Island, Lotofoa Swamp on Foa Island, and Finemui Swamp on Ha’afeva Island. Plant taxa were categorized as littoral, mangrove, rainforest, successional/ disturbance, and wetland groups, and linear models were used to examine relationships between vegetation, relative sea level change, and volcanic eruptions (tephra). We found that relative sea level change has impacted vegetation on three of the four islands investigated. Volcanic eruptions were not identified as a driver of vegetation change. Rainforest decline does not appear to be driven by sea level changes or volcanic eruptions. From all sites analyzed, vegetation at Finemui Swamp was most sensitive to changes in relative sea level. While vegetation on low-lying Pacific islands is sensitive to changing sea levels, island characteristics, such as area and elevation, are also likely to be important factors that mediate specific island responses to drivers of change.     

Growth in utero and cognitive function in adult life: follow up study of people born between 1920 and 1943.

OBJECTIVES--To examine the relation between fetal growth and cognitive function in adult life. DESIGN--A follow up study of men and women whose birth weights and other measurements of body size had been recorded at birth. SETTING--Hertfordshire, Preston, and Sheffield. SUBJECTS--1576 men and women born in Hertfordshire, Sheffield, or Preston between 1920 and 1943. MAIN OUTCOME MEASURES--Intelligence quotient as measured by the AH4 test and amount of decline in cognitive function with age as estimated by the difference between score on the Mill Hill vocabulary test and score on the AH4 test. RESULTS--Score on the intelligence test was higher in people who had a large biparietal head diameter at birth, but it was not related to any other measure of body size or proportions. No association was found between decline in cognitive function and any measure of size or proportions at birth. CONCLUSION--Impaired fetal growth was not associated with poorer cognitive performance in adult life. Adaptations made by the fetus in response to conditions that retard its growth seem to be largely successful in maintaining brain development.     

Methanol Emission from Leaves (Enzymatic Detection of Gas-Phase Methanol and Relation of Methanol Fluxes to Stomatal Conductance and Leaf Development)

We recently reported the detection of methanol emissions from leaves (R. MacDonald, R. Fall [1993] Atmos Environ 27A: 1709-1713). This could represent a substantial flux of methanol to the atmosphere. Leaf methanol production and emission have not been investigated in detail, in part because of difficulties in sampling and analyzing methanol. In this study we used an enzymatic method to convert methanol to a fluorescent product and verified that leaves from several species emit methanol. Methanol was emitted almost exclusively from the abaxial surfaces of hypostomatous leaves but from both surfaces of amphistomatous leaves, suggesting that methanol exits leaves via stomates. The role of stomatal conductance was verified in experiments in which stomates were induced to close, resulting in reduced methanol. Free methanol was detected in bean leaf extracts, ranging from 26.8 [mu]g g-1 fresh weight in young leaves to 10.0 [mu]g g-1 fresh weight in older leaves. Methanol emission was related to leaf development, generally declining with increasing leaf age after leaf expansion; this is consistent with volatilization from a cellular pool that declines in older leaves. It is possible that leaf emission could be a major source of methanol found in the atmosphere of forests.     

Active and passive cation transport and L antigen hertogeneity in low potassium sheep red cells

Several lines of experimental evidence are presented suggesting that the L antigens in low potassium (LK) sheep red cells are associated with separate Na(+)K(+) pump flux is distinct from the action of anti-L(l) on K(+) leak flux, implying that K(+) leak transport sites may not be converted into active pumps by the L antiserum. Treatment of LK red cells with trypsin completely abolished both the stimulation of K(+) pump flux and the enhancement of the rate of ouabain binding brought about by anti- L. That this effect is due to a total destruction of the L(p) determinant associated with the LK pump was evident from the complete failure of anti-L(p) to bind to trypsinized LK red cells. The L(p) antigen can be effectively protected against the trypsin attack by prior incubation with anti-L, indicating that the sites for antibody binding and trypsin action may be closely adjacent at the structural level. Trypsin treatment, however, did not interfere with anti-L(l) reducing ouabain insensitive K(+) leak influx, nor did it prevent binding of anti-L(ly), the hemolytically active L antibody which is probably identical with anti-L(l). The functional independence of the L(p) and L(l) sites was documented by the observation that anti-L(l) still reduced K(+) leak influx in LK cells with experimentally induced high potassium concentrations, at which K(+) pump flux is fully suppressed, whether or not anti-L(p) was binding to the L(p) antigen associated with the LK pump.     

Relation of birth weight and childhood respiratory infection to adult lung function and death from chronic obstructive airways disease.

OBJECTIVE--To examine whether birth weight, infant weight, and childhood respiratory infection are associated with adult lung function and death from chronic obstructive airways disease. DESIGN--Follow up study of men born during 1911-30 whose birth weights, weights at 1 year, and childhood illnesses were recorded at the time by health visitors. SETTING--Hertfordshire, England. SUBJECTS--5718 men born in the county during 1911-30 and a subgroup of 825 men born in the county during 1920-30 and still living there. MAIN OUTCOME MEASURES--Death from chronic obstructive airways disease, mean forced expiratory volume in one second (FEV1) and forced vital capacity (FVC), and respiratory symptoms. RESULTS--55 men died of chronic obstructive airways disease. Death rates fell with increasing birth weight and weight at 1 year. Mean FEV1 at age 59 to 70 years, adjusted for height and age, rose by 0.06 litre (95% confidence interval 0.02 to 0.09) with each pound (450 g) increase in birth weight, independently of smoking habit and social class. Bronchitis or pneumonia in infancy was associated with a 0.17 litre (0.02 to 0.32) reduction in adult FEV1 and with an increased odds ratio of wheezing and persistent sputum production in adult life independently of birth weight, smoking habit, and social class. Whooping cough in infancy was associated with a 0.22 litre (0.02 to 0.42) reduction in adult FEV1. CONCLUSIONS--Lower birth weight was associated with worse adult lung function. Intrauterine influences which retard fetal weight gain may irrecoverably constrain the growth of the airways. Bronchitis, pneumonia, or whooping cough in infancy further reduced adult lung function. They also retarded infant weight gain. Consistent with this, death from chronic obstructive airways disease in adult life was associated with lower birth weight and weight at 1 year. Promoting lung growth in fetuses and infants and reducing the incidence of lower respiratory tract infection in infancy may reduce the incidence of chronic obstructive airways disease in the next generation.     

Fetal and infant growth and impaired glucose tolerance at age 64.

OBJECTIVE--To discover whether reduced fetal and infant growth is associated with non-insulin dependent diabetes and impaired glucose tolerance in adult life. DESIGN--Follow up study of men born during 1920-30 whose birth weights and weights at 1 year were known. SETTING--Hertfordshire, England. SUBJECTS--468 men born in east Hertfordshire and still living there. MAIN OUTCOME MEASURES--Fasting plasma glucose, insulin, proinsulin, and 32-33 split pro-insulin concentrations and plasma glucose and insulin concentrations 30 and 120 minutes after a 75 g glucose drink. RESULTS--93 men had impaired glucose tolerance or hitherto undiagnosed diabetes. They had had a lower mean birth weight and a lower weight at 1 year. The proportion of men with impaired glucose tolerance fell progressively from 26% (6/23) among those who had weighted 18 lb (8.16 kg) or less at 1 year to 13% (3/24) among those who had weighed 27 lb (12.25 kg) or more. Corresponding figures for diabetes were 17% (4/23) and nil (0/24). Plasma glucose concentrations at 30 and 120 minutes fell with increasing birth weight and weight at 1 year. Plasma 32-33 split proinsulin concentration fell with increasing weight at 1 year. All these trends were significant and independent of current body mass. Blood pressure was inversely related to birth weight and strongly related to plasma glucose and 32-33 split proinsulin concentrations. CONCLUSIONS--Reduced growth in early life is strongly linked with impaired glucose tolerance and non-insulin dependent diabetes. Reduced early growth is also related to a raised plasma concentration of 32-33 split proinsulin, which is interpreted as a sign of beta cell dysfunction. Reduced intrauterine growth is linked with high blood pressure, which may explain the association between hypertension and impaired glucose tolerance.     

Oviducal Contribution to Alteration of the Vitelline Coat in the Frog, Rana japonica. An Electron Microscopic Study

The vitelline coat (VC) surrounding coelomic eggs of the frog, Rana japonica , comprises bundles of filaments running both parallel and perpendicular to the egg surface. The coat gives little or no staining reaction with PA-CrA-Silver methenamine. In contrast, in the VC of uterine eggs the filament bundles are less conspicuous. and the interstices between the filament bundles stain strongly for carbohydrate. This alteration occurs during passage of the eggs down the first 1/20 th of the oviduct, the pars recta. The epithelium of the p. recta contains secretory cells, which contain electron-dense granules distinct from those in the jelly-secreting cells in more caudal portions of the oviduct. Treatment of coelomic eggs with an extract of p. recta followed by exposure to a sperm suspension resulted in marked swelling and softening of the VC. These results indicate that the contents of the granules secreted from the epithelial cells in the p. recta are deposited in the VC to increase its susceptibility to a fertilizing sperm.