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1.
2.
Does transpiration have an essential function in long-distance ion transport in plants? 总被引:6,自引:3,他引:3
Abstract. Long-term effects of transpiration on growth and on long-distance ion transport were investigated in maize over a whole growth cycle. Maize plants were grown with nutrients supplied at adequate levels in hydroculture or in soil at 50–60% and at >95% relative humidity. Although the amount of water lost by the plants under these conditions differed by a factor 2 to 3, there was neither a decrease in growth (fresh weight and dry weight) nor in ash content of the 'humid'plants. This was also found when the upper part of the shoot (70–150 cm) was tested separately. It is suggested that transpiration is not essential for long-distance transport of mineral elements in plants. Alternatives are discussed. 相似文献
3.
Synchronously growing cells of nitrogen-fixing Synechococcus sp. Miami BG 043511 were harvested periodically and the capability for hydrogen photoproduction in closed vessels was measured under hydrogen production conditions. The capability for hydrogen photoproduction in cells was correlated with that of cellular carbohydrate content. Cells with a high carbohydrate content exhibited a high capacity for hydrogen production and those with low carbohydrate content exhibited low capacity for hydrogen production. Nitrogenase activity at the onset of incubation did not coincide with a capability for the cells to produce hydrogen during the subsequent incubation period. Interestingly, when cells with a high capacity for hydrogen photoaccumulation were incubated, alternate periods of hydrogen and oxygen accumulation were observed at 12 hour intervals. About 0.5 ml of hydrogen per ml of cell suspension was accumulated in flasks during the initial 12-h incubation period. These observations indicate that the use of synchronous culture can be one of the ways of provide materials suitable not only for basic studies but also for applied aspects of hydrogen photoproduction. 相似文献
4.
Abstract Little information exists about nitrogen losses through microbial activity during treatment of solid urban waste (SUW) by processes such as composting. In the present study, in addition to evaluating the pattern of nitrogen losses by denitrification at different stages of the process, a comparison between the method of Pochon and Tardieux, and an improved gas chromatographic method for estimating denitrifying populations was undertaken, Though the MPN (Most Probable Number) enumerations were higher using the colorimetric method than the gas chromatographic one, the patterns of the two graphs showing numbers of denitrifiers during composing were the same. The highest numbers were revealed immediately after loading the reactor (107 –108 /g d.w.), lower numbers of denitrifiers were found in the second sampling corresponding to the thermophilic phase (103 –104 /g d.w.). These numbers increased gradually as the waste material stabilized (10th to 123rd day of composting) to again reach values of 107 –108 /g d.w. 相似文献
5.
6.
Summary Video-densitometric DNA measurements of Feulgenstained tissues of 42 day old eggs of the corn snake,Elaphe g. guttata (Columbridae, Serpentes), revealed a basic DNA content of 2C=2.17 pg, with somatic polyploidy in the allantois, the chorioallontois, the yolk sac, and other extraembryonic membranes. The maximum value determined was 128C (in binucleate cells 2×128C) at the distal pole of the egg. This is the first report of somatic polyploidy in a snake, and one of the first in reptiles in general. 相似文献
7.
Birgit Dittrich 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,161(4):441-449
Summary
Hyperia galba was collected in the waters around Helgoland and in the Weser-Elbe-estuary during autumn. Its mode of life is a temporary but obligatory parasitism. The basal biochemical composition of the adults was analyzed in detail and related to the fresh, dry, and ash-free dry weight as well as sex and body length. Hyperia galba (males/females) consists of 85/86% water; the dry matter contains approximately 64/61% protein, 10/11% lipid, 1.2/1.5% carbohydrate, 10/8% chitin, and 23/23% ash. The analyses of basal elemental composition yielded approximately 38% C, 9% N and 6% H. Under natural conditions, individuals may encounter at least two periods of food shortage during their lives. Therefore, the analyses were carried out on individuals of different developmental stages also under food deprivation. The data are discussed with respect to the special mode of life of the species and compared with those found by other authors in several related crustacean species.Abbreviations
AFDW
ash-free dry weight
-
BL
body length
-
DW
dry weight
-
SD
standard deviation
-
WW
wet weight 相似文献
8.
Six to seven week old red clover plants (Trifolium pratense L. cv Merviot) were used to investigate the time-course of root senescence following complete and permanent excision from
the shoot. Plants were grown in sand culture watered with nutrient solution. After excision of the shoots, roots were left
in situ and sampled over a period of up to 42 days. Respiration rate began to decrease immediately after excision, reaching
50% of its initial value after 24 h. The decline involved a reduction in the capacity of the respiratory pathways as measured
in the presence of an uncoupler (FCCP) and exogenous glucose. The reduction in respiration could be prevented by supplying
100 mM sucrose to excised roots incubated in nutrient solution at the time of excision, but not 4–5 days after excision. There
was a steady reduction in the protein and soluble sugar concentrations from the time of excision and a smaller reduction in
starch. Free amino acid concentrations increased immediately after excision, but the temporal dynamics differed between individual
amino acids. The total concentration of free amino acids rose to a maximum value 6–13 days after excision, before declining.
Under these conditions roots survived for a remarkably long period of time. Depending on the experiment, cell viability, measured
as the percentage of cells with positive turgor, was unchanged for at least 20 days, and complete loss of viability was not
observed until 34–42 days after excision. There was no appreciable loss of N from the roots until cell viability declined
significantly. The potential implications of these results for modelling and management of N cycling in cropping systems is
discussed briefly. 相似文献
9.
The effect of iron deprivation on the expression of outer membrane proteins and the ability to use heme as an iron source by uropathogenic Proteus mirabilis , Pr 6515, was studied. Examination of iron-restricted bacteria showed three outer membrane proteins ranging from 66 to 75 kDa to be affected by iron restriction, as well as a newly expressed 64-kDa protein. These proteins were induced within 15 minutes of iron-deprivation. The strain grew in the presence of ferric citrate, hemin and hemoglobin as iron sources, but could not use transferrin, lactoferrin or siderophores from exogenous sources. The 64- and 66-kDa proteins showed hemin-binding activity by affinity chromatography, and both reacted in Western blots with sera from mice transurethrally infected with the same strain. We suggest that P. mirabilis expresses iron-regulated outer membrane proteins that could be involved in heme uptake and may have a role in pathogenesis. 相似文献
10.