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191.
Herman Yeger Diane Forget Jennifer Alami Bryan R. G. Williams 《In vitro cellular & developmental biology. Animal》1996,32(8):496-504
Summary The temporal and spatial expression patterns of the Wilms tumor gene, WT1, were studied during the organogenesis of the mouse
kidneyin vitro. In situ hybridization and immunocytochemistry localized cellular expression of WT1 in whole kidney organ cultures to the induced
metanephric mesenchyme and developing podocytes. Organ cultures were further characterized immunocytochemically with antibodies
that specifically labeled the different tubular epithelial components and supporting mesenchyme of the developing nephrons.
In organ cultures, the WT1 expression pattern could be visualized in induced metanephric mesenchyme and entire cell cohorts
of differentiating podocytes. Expression of WT1 and cell specific markers were retained in short-term monolayer cultures of
dissociated kidneys. The development of the metanephric kidneyin vitro involves a highly restricted temporal and spatial cellular expression pattern of WT1 which closely follows that observed
in tissue sections from gestational kidney isolated during organogenesis in the mouse. 相似文献
192.
Vera V. Lozovaya Ximing Luo Jack M. Widholm 《In vitro cellular & developmental biology. Plant》1996,32(4):295-298
Summary Seven suspension-cultured lines of five different species (Amaranthus powellii Datura innoxia, Glycine max, Gossypium hirsutum, andNicotiana tabacum × Nicotiana glutinosa fusion hybrid), which had been grown under photomixotrophic conditions, were placed under heterotrophic conditions (darkness
and media with 3% sucrose or starch) where the chlorophyll levels declined to near zero. After three transfers over a 70-d
period, the cells were placed back into photomixotrophic or photoautotrophic conditions where regreening occurred rapidly
and continued growth was observed. This rapid adaptation to photosynthetic conditions contrasts with the original initiation
process for these cultures, which required many months and an apparent selection since many of the original cells died. Thus,
these seven photosynthetic cell suspension cultures appear to be different from the original cultures due possible to genetic
or adaptive changes. 相似文献
193.
旱地玉米农田棵间蒸发研究 总被引:3,自引:0,他引:3
采用中子微区模拟装置测量旱地玉农田棵间蒸发,实验表明,本实验装置实用可行。晋西棵间蒸发量占降水量(510nm)的55%以上,棵间蒸发与蒸散的比值同时叶面积指数呈反相关,玉米产量与作物蒸腾呈正相关。 相似文献
194.
Marianne V. Nielsen 《Journal of phycology》1995,31(5):715-719
Light-saturated photosynthesis (Pmax) of Emiliania huxleyi (Lohmann) Hay et Mohler is known to be carbonlimited at natural concentrations of dissolved inorganic carbon (DIC). In the present study, light-limited and light-saturated photosynthetic rates of E. huxleyi were studied at three concentrations of DIC (2.4, 7.4, and 12.4 mM) for high-calcite (Cin/Ctot=0.48) and low-calcite (Cin/Ctot=0.08) cells of the same strain. The photosynthetic efficiency (α) and the maximum quantum yield (θmax)A increased by more than a factor of 2 from the lowest to the highest DIC level. Pmax a, and θmax were always higher for the high-calcite than for the low-calcite cells at identical DIC levels. This may indicate that the calcifcation process acts as an extra supplier of CO2 for photosynthesis making the CO2 shortage at natural DIC levels a little smaller for high-calcite than for low-calcite E. huxleyi. A dependency of θmax on DIC has not previously been shown for marine phytoplankton. θmax is a key parameter in recent biooptical models of phytoplankton productivity, and the results from the present study are therefore important for modeling the productivity of E. huxleyi. 相似文献
195.
Root to shoot ratio of crops as influenced by CO2 总被引:1,自引:0,他引:1
Hugo H. Rogers Stephen A. Prior G. Brett Runion Robert J. Mitchell 《Plant and Soil》1995,187(2):229-248
Crops of tomorrow are likely to grow under higher levels of atmospheric CO2. Fundamental crop growth processes will be affected and chief among these is carbon allocation. The root to shoot ratio (R:S, defined as dry weight of root biomass divided by dry weight of shoot biomass) depends upon the partitioning of photosynthate which may be influenced by environmental stimuli. Exposure of plant canopies to high CO2 concentration often stimulates the growth of both shoot and root, but the question remains whether elevated atmospheric CO2 concentration will affect roots and shoots of crop plants proportionally. Since elevated CO2 can induce changes in plant structure and function, there may be differences in allocation between root and shoot, at least under some conditions. The effect of elevated atmospheric CO2 on carbon allocation has yet to be fully elucidated, especially in the context of changing resource availability. Herein we review root to shoot allocation as affected by increased concentrations of atmospheric CO2 and provide recommendations for further research. Review of the available literature shows substantial variation in R:S response for crop plants. In many cases (59.5%) R:S increased, in a very few (3.0%) remained unchanged, and in others (37.5%) decreased. The explanation for these differences probably resides in crop type, resource supply, and other experimental factors. Efforts to understand allocation under CO2 enrichment will add substantially to the global change response data base.Abbreviations R:S
root to shoot ratio, dry weight basis 相似文献
196.
Root and leaf attributes accounting for the performance of fast- and slow-growing grasses at different nutrient supply 总被引:18,自引:1,他引:17
Despite their difference in potential growth rate, the slow-growing Brachypodium pinnatum and the fast-growing Dactylis glomerata co-occur in many nutrient-poor calcareous grasslands. They are known to respond differently to increasing levels of N and
P. An experiment was designed to measure which characteristics are affected by nutrient supply and contribute to the ecological
performance of these species. Nutrient acquisition and root and shoot traits of these grasses were studied in a garden experiment
with nine nutrient treatments in a factorial design of 3 N and 3 P levels each.
D. glomerata was superior to B. pinnatum in nutrient acquisition and growth in all treatments. B. pinnatum was especially poor in P acquisition. Both species responded to increasing N supply and to a lesser extent to increasing
P supply by decreasing their root length and increasing their leaf area per total plant weight. D. glomerata showed a higher plasticity. In most treatments, the root length ratio (RLR) and the leaf area ratio (LAR) were higher for
D. glomerata. A factorization of these parameters into components expressing biomass allocation, form (root fineness or leaf thickness)
and density (dry matter content) shows that the low density of the biomass of D. glomerata was the main cause for the higher RLR and LAR. The biomass allocation to the roots showed a considerable plasticity but did
not differ between the species. B. pinnatum had the highest leaf weight ratio. Root fineness was highly plastic in D. glomerata, the difference with B. pinnatum being mainly due to the thick roots of D. glomerata at high nutrient supply. The leaf area/leaf fresh weight ratio did not show any plasticity and was slightly higher for B. pinnatum.
It is concluded, that the low density of the biomass of D. glomerata is the pivotal trait responsible for its faster growth at all nutrient levels. It enables simultaneously a good nutrient
acquisition capacity by the roots as well as a superior carbon acquisition by the leaves. The high biomass density of B. pinnatum will then result in a lower nutrient requirement due to a slower turnover, which in the long term is advantageous under nutrient-poor
conditions. 相似文献
197.
Pigment analysis was performed by means of normal phase HPLC on a number of bacteriochlorophyll a and b containing species of purple bacteria that contain a core antenna only. At least 99% of the bacteriochlorophyll in Rhodobacter sphaeroides R26, Rhodopseudomonas viridis and Thiocapsa pfennigii was esterified with phytol (BChl a
p and BChl b
p, respectively). Rhodospirillum rubrum contained only BChl a esterified with geranyl-geraniol (BChl a
GG). Rhodospirillum sodomense and Rhodopseudomonas marina contained, in addition to BChl a
p, small amounts of BChl a
GG, and presumably also of BChl a esterified with dihydro and tetrahydro geranyl-geraniol (2,10,14-phytatrienol and probably 2,14-phytadienol). In all species bacteriopheophytin (BPhe) esterified with phytol was present. The BChl/BPhe ratio indicated that in these species a constant number of 25 ± 3 antenna BChls is present per reaction centre. This number supports a model in which the core antenna consists of 12 - heterodimers surrounding the reaction centre. Determination of the in vivo extinction coefficient of BChl in the core-reaction centre complex yielded a value of ca. 140 mM–1 cm–1 for BChl a containing species and of 130 mM–1 cm–1 for Rhodopseudomonas viridis.Abbreviations BChl
bacteriochlorophyll
- BPhe
bacteriopheophytin
- GG
geranyl-geraniol
- LHI and LHII
core and peripheral antenna complexes
- P
phytol
- RC
reaction centre
Dedicated to the memory of Professor D.I. Arnon. 相似文献
198.
Each cryptomonad strain contains only a single spectroscopic type of biliprotein. These biliproteins are isolated as 50000 kDa '2 complexes which carry one bilin on the and three on the subunit. Six different bilins are present on the cryptomonad biliproteins, two of which (phycocyanobilin and phycoerythrobilin) also occur in cyanobacterial and rhodophytan biliproteins, while four are known only in the cryptomonads. The subunit is encoded on the chloroplast genome, whereas the subunits are encoded by a small nuclear multigene family. The subunits of all cryptomonad biliproteins, regardless of spectroscopic type, have highly conserved amino acid sequences, which show > 80% identity with those of rhodophytan phycoerythrin subunits. In contrast, cyanobacteria and red algal chloroplasts each contain several spectroscopically distinct biliproteins organized into macromolecular complexes (phycobilisomes). The data on biliproteins, as well as several other lines of evidence, indicate that the cryptomonad biliprotein antenna system is primitive and antedates that of the cyanobacteria. It is proposed that the gene encoding the cryptomonad biliprotein subunit is the ancestral gene of the gene family encoding cyanobacterial and rhodophytan biliprotein and subunits.Abbreviations Chl
chlorophyll
- CER
chloroplast endoplasmic reticulum
- SSU rRNA
small subunit ribosomal RNA 相似文献
199.
Elevated CO2 (ambient + 35 Pa) increased shoot dry mass production in Avena fatua by 68% at maturity. This increase in shoot biomass was paralleled by an 81% increase in average net CO2 uptake (A) per unit of leaf area and a 65% increase in average A at the ecosystem level per unit of ground area. Elevated CO2 also increased ecosystem A per unit of biomass. However, the products of total leaf area and light-saturated leaf A divided by the ground surface area over time appeared to lie on a single response curve for both CO2 treatments. The approximate slope of the response suggests that the integrated light saturated capacity for leaf photosynthesis is 10-fold greater than the ecosystem rate. Ecosystem respiration (night) per unit of ground area, which includes soil and plant respiration, ranged from-20 (at day 19) to-18 (at day 40) mol m-2 s-1 for both elevated and ambient CO2
Avena. Ecosystem below-ground respiration at the time of seedling emergence was -10 mol m-2 s-1, while that occuring after shoot removal at the termination of the experiment ranged from -5 to-6 mol m-2 s-1. Hence, no significant differences between elevated and ambient CO2 treatments were found in any respiration measure on a ground area basis, though ecosystem respiration on a shoot biomass basis was clearly reduced by elevated CO2. Significant differences existed between leaf and ecosystem water flux. In general, leaf transpiration (E) decreased over the course of the experiment, possibly in response to leaf aging, while ecosystem rates of evapotranspiration (ET) remained constant, probably because falling leaf rates were offset by an increasing total leaf biomass. Transpiration was lower in plants grown at elevated CO2, though variation was high because of variability in leaf age and ambient light conditions and differences were not significant. In contrast, ecosystem evapotranspiration (ET) was significantly decreased by elevated CO2 on 5 out of 8 measurement dates. Photosynthetic water use efficiencies (A/E at the leaf level, A/ET at the ecosystem level) were increased by elevated CO2. Increases were due to both increased A at leaf and ecosystem level and decreased leaf E and ecosystem ET. 相似文献
200.
The morphology and function of one tropical and 25 temperate reservoirs are examined in relation to their effect upon the nature of the land/water interface and, further, to what extent the features of these ecotones satisfy the ecological requirements of the reservoir fish species throughout their life cycle during spawning, larval, juvenile and adult stages. The two main conclusions are that (1) reservoir fish species are especially dependent upon land/water ecotones during their early life history and (2) there exists a strong relationship between the extent of the littoral area and the nature of the fish stocks. Several examples are given to show that manipulation of the land/water ecotone is a major tool for the management of reservoirs advantageously for their major functions. 相似文献