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During periods of high atmospheric humidity, twigs of Tamarix aphylla (L.) Karst. become covered by an alkaline solution. The pH of that solution fluctuates between 8.0 – 8.5 in the dark and 10.5 during the light hours. Such a solution, produced by the glands, constitutes an efficient trap for atmospheric CO2. Upon the periodic drop in pH, much of the preabsorbed carbon may gradually be released from the solution. This enriches the immediate surroundings of the twigs with CO2 for prolonged periods of time. The expected concentrations of CO2, at the boundary layer between the atmosphere and the surfaces of the twigs, are over 1 000 ppm. As net photosynthesis of T. aphylla reaches maximal rates only at CO2 concentrations of above 500 ppm, the plants may benefit from this extra source of carbon and may exploit it for maximal assimilation during the early morning hours. Thus, the "salt glands'of Tamarix , which are liable for the production of the alkaline recretum, may serve a triple purpose: (a) removal of excess salts out of the twigs, (b) provision of a cover of hygroscopic solutes that moistens the twigs and shortens the duration of transpiration, and (c) providing the plants with an environment enriched in CO2.  相似文献   
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Congenital amusia is a neurogenetic disorder of music processing that is currently ascribed to a deficit in pitch processing. A recent study challenges this view and claims the disorder might arise as a consequence of a general spatial-processing deficit. Here, we assessed spatial processing abilities in two independent samples of individuals with congenital amusia by using line bisection tasks (Experiment 1) and a mental rotation task (Experiment 2). Both amusics and controls showed the classical spatial effects on bisection performance and on mental rotation performance, and amusics and controls did not differ from each other. These results indicate that the neurocognitive impairment of congenital amusia does not affect the processing of space.  相似文献   
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An endogenous circadian rhythm of transpiration in Tamarix aphylla   总被引:1,自引:0,他引:1  
An endogenous circadian rhythm in the transpiration of Tamarix aphylla (L.) Karst. was found for plants grown in continuous light under laboratory conditions. The mean period (±SD) was 21.7±2.3 h (n = 121). No such rhythm was observed in continuous darkness, except for one small hump at the time of the first cycle. The influence of NaCl, Cd(NO3)2 and LiCi on the rhythmic behaviour of young T. aphylla plants was investigated. NaCl concentrations of up to 150 m M reduced the overall transpiration rates of the plants, but did not change the period of the rhythm. The amplitude and the mesor of the oscillations were inversely correlated with the NaCl concentration. A similar influence was found for Cd(NO3)2, but with concentrations that were approximately three orders of magnitude smaller than those of the NaCl treatments. The rhythmic behaviour of the plants was not altered by 10 m M LiCl. It is suggested that the described rhythm of transpiration may have a dual effect: (a) it might cause a partial closure of the stomates during midday hours and (b) it might serve as a possible synchronizer ("master clock") for other rhythmic phenomena in the plants.  相似文献   
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Summary Electrophoretic studies of fumarase and nicotine adenine dinucleotide (NAD)-malate dehydrogenase were carried out in the fumaric acid-accumulating fungus Rhizopus oryzae. The analyses revealed two fumarase isoenzymes, one localised solely in the cytosol and the other found both in the cytosol and in the mitochondrial fraction. The activity of the cytosolic isoenzyme of fumarase was higher during the acid production stage than during growth. Addition of cycloheximide inhibited fumaric acid production and decreased the activity of the cytosolic isoenzyme of fumarase. These results suggested that de novo protein synthesis is required for increase in the activity of the cytosolic isoenzyme and that such an increase in activity is essential for fumaric acid accumulation. Three distinct isoenzymes of NAD-malate dehydrogenase could be detected in R. oryzae. No changes were observed in the isoenzyme pattern of malate dehydrogenase during fumaric acid production.  相似文献   
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The wake and sleep-onset times of a patient with a sleep-wake cycle longer than 24 hr were recorded by the patient for 4 years. During this time, the patient found himself unable to maintain a 24-hr sleep-wake schedule. When treated with 1-2 mg clonazepam, taken nightly, he was able to become entrained to a 24-hr day. Despite entrainment of his sleep-wake cycle, the patient reported depression, lack of motivation and fatigue and chose not to continue taking the drug.  相似文献   
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Enamel hypoplasia was recorded for the primary and permanent teeth of Natufians (terminal Pleistocene Hunter-Gatherers) and Early Arabs (Subsistence farmers). Minimal hypoplasia was found in the primary teeth of the Natufians, but in the Early Arab population, 31% of upper first primary molars showed enamel defects. In the permanent teeth, the Early Arab population again showed a significantly higher frequency of hypoplasia, with all teeth affected. In the Natufians, only later developing teeth showed enamel defects. These findings suggest that health status in the Early Arab population was poor throughout life, affecting pregnant mothers, their foetuses, young infants and children. These results confirm other studies that have shown deterioration in health status of early agriculturalists relative to hunter- gatherers. Comparisons of these findings with those of recent populations indicate that health status in the Natufians was comparable to that of modern populations with subsistence diets and mediocre health care. Health status in the Early Arab population was comparable to that of modern populations suffering from severe malnutrition and chronic disease.  相似文献   
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