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81.
Transpiration, leaf conductance, net photosynthesis, leaf growth, above-ground biomass and regeneration of new culms were studied in a rapidly subsiding Spartina alterniflora Lois. salt marsh following the addition at 47 and 94 Kg m–2 of new sediment. Plant growth was enhanced in response to sediment addition as was evident by a significant increase in leaf area, above-ground biomass production and regeneration of new culms (p 0.05). Leaf conductance and transpiration rates were significantly greater in sediment treated plants than in control plants (p 0.05). Enhanced production of culms per unit area of marsh resulted in increased leaf area which allowed a greater capacity for net photosynthesis and contributed to increases in above-ground biomass of sediment treated plots. 相似文献
82.
M. Heinz R. Krattenmacher B. Hoffmann W. Clauss 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,161(4):363-370
Summary Transepithelial electrogenic Na+ transport (INa) was investigated in the coprodeum of 20-days-old chicken embryos in Ussing chambers. Short circuit current (Isc) and transepithelial resistance (Rt) were 14.7±4.8 A · cm-2 (n=12) and 0.53±0.09 k · cm-2 (n=12), respectively. INa was calculated from changes in Isc by substitution of mucosal Na+ by (N-methyl-d-glucamine) (NMDG). Isc inversed during Na+ removal, and INa was found to be 27.8±4.7 A · cm-2 (n=12). Amiloride (100 mol · l-1) inhibited only about 60% of INa. Analysis of Isc fluctuations revealed a Lorentzian component in the power density spectrum with a corner frequency of about 57 Hz. This component was not correlated to INa, and its origin is still unclear. Removal of mucosal Ca2+ increased INa about 2.5-fold due to an increase of the amiloride-insensitive component of INa in additionally investigated adult tissues. The results clearly show that this is due to a non-selective cation channel with an apparent order of selectivity Cs+>Na+=K+>Rb+>Li+. The Ca2+ concentration required to block 50% of the Isc was about 18 mol · l-1. The I
sc
Ca
could also be supressed by other divalent cations such as Mg2+ and Ba2+. Additionally, an INa-linked Lorentzian component occurred which dominated the control spectrum with a significantly higher corner frequency (about 88 Hz). The results indicate that Na+ absorption in the coprodeum of the chicken embryo is more complex than in adult hens. However, the Ca2+ sensitivity of INa is similar to comparable effects described for other epithelia. This possibly reflects the existence of two types of amiloride-insensitive apical cation channels as pathways for Na+ absorption, which may be involved to differing degrees in ontogenetic developments of nonselective channels to Na+-specific ion channels.Abbreviations
DPL
direct-linear-plot method
-
slope of the back-ground noise component
-
EGTA
ethylene glycol-bi(2-amino-ethylether)-N,N,N,N-tetraacetic acid
-
f
frequency
-
f
c
corner frequency of the Lorentzian noise component
-
G
t
transepithelial conductance
-
HEPES
N-hydroxyethylpiperazine-N-ethanesulfonic acid
-
I
sc
short-circuit current
-
I
Na
transepithelial sodium current
-
I
sc
Ca
Ca2+-sensitive short-circuit current
-
K
m
Ca
Michaelis-Menten constant for Ca2+
-
K
B
power density of the background noise component at f=1Hz
-
m
mucosal
-
NMDG
N-methyl-D-glucamine
-
R
t
transepithelial resistance
-
s
serosal
-
SEM
standard error of mean
-
S(f)
power density of the Lorentzian noise component
-
S
o
plateau value of the Lorentzian noise component 相似文献
83.
SCE在鹌鹑胚胎细胞间的分布为Poisson分布;在染色体间的分布是非随机的,与染色体的相对长度成正相关(P<0.05),但也不完全按各染色体的相对长度分布。着丝粒区的SCE相对很高,按染色体的相对长度分布。胚胎的不同性别对每个细胞的SCE平均值无显著影响,但对性染色体Z上的SCE是否有影响还不能做出肯定的结论。 相似文献
84.
Summary A single neuronal cell assay of neurite growth was utilized to determine types and domains of neuronal proteoglycans involved in neurite growth on laminin. Perturbations of biosynthesis and processing, enzymatic digestion with specific lyases, and competition with glycosaminoglycan side chains produced complementary data consistent with a molecular model implicating glycosaminoglycan (GAG) residues of heparan sulphate proteoglycans (HSPGs) in neurite growth. The observations suggest that HSPGs promote neurite growth on laminin by bridging between binding domains for HSPGs on laminin and on the neuronal cell surface, and that the bridge is tethered at both ends by noncovalent interactions between the binding domains and GAG side chains. Sulphation of the GAGs of HSPGs appears to be critical to the tethering and/or neurite growth-promoting activity of neuronal HSPGs. 相似文献
85.
Using the developing chick embryo as a model and a very sensitive micromethod for amino acid analysis, a complete analysis is presented of the developmental changes in free amino acid concentration in the blood, in the CSF, and in two different brain regions (optic lobe and frontal lobe) of the chick embryo (from day 4 of incubation, until day 5 post hatching). The developmental profile of Lys is the only one that is almost identical in all three compartments. The developmental profiles of the serum and of the brain are very similar for Arg and Phe, less so for Leu and Gly, and towards the end of the embryonic period, similar also for Val, Ile, Trp, and Met. The amino acid concentrations in the CSF are either much lower than in serum and brain already at the earliest stages, or they progressively decline to levels lower than those in brain and serum, most rapidly between day 6 and 8 of embryonic life. The concentrations of neuroactive amino acids (Gln, Glu, Asp, GABA, Tau, and Gly) in both brain regions begin to increase very early, and continue to rise, except Tau, which goes through a maximum at day 8. Comparative analysis of the developmental profiles of each amino acid in serum, brain, and CSF reveals that the blood supply and the cellular uptake, retention, and metabolism by neural cells are the major determinants of the free amino acid pool of the developing brain. 相似文献
86.
Embryo survival and alevin emergence pattern of brown trout were studied in simulated redds with different homogeneous gravel sizes and different concentrations of peat material. Optimal survival (95%) occurred in 18 mm gravel and survival decreased with decreasing gravel size. High concentrations (40%) of peat material resulted in low survival (65%). The proportion of premature emerging alevins increased in finer gravels and at high peat concentrations. Premature alevins had a large yolk sac and are probably very vulnerable to predators. 相似文献
87.
88.
A burst of CO2 from photosynthesizing leaves after a temperature decrease under constant light conditions 总被引:1,自引:0,他引:1
A transient CO2 burst from seedlings of some plant species was observed after a rapid temperature decrease. The magnitude of the CO2 release depended on initial temperature, oxygen concentration and light intensity. To obtain a maximal value of CO2 release, the temperature had to decrease by more than 8°C. The phenomenon was detected only in the light, and was confined to C3 species. It was inhibited by low oxygen concentration, indicating its possible connection with photorespiration. 相似文献
89.
Mannitol metabolism in cultured plant cells 总被引:3,自引:0,他引:3
Michael R. Thompson Trevor J. Douglas Hamako Obata-Sasamoto Trevor A. Thorpe 《Physiologia plantarum》1986,67(3):365-369
Non-structural storage carbohydrates were measured in 9-day-old barley ( Hordeum vulgare L. cv. Brant) primary leaves. Accumulation rates of starch, sucrose and total non-structural carbohydrates (TNC) were approximately linear when measured between 2- and 12-h of light. Progressively higher TNC accumulation rates were observed at higher irradiance levels (i.e., comparing 250, 550 and 1050 ·mol m−2 s−1 ). Synthesis of a low-molecular-weight fructan also was enhanced by high irradiances. Low irradiance treatments decreased leaf sucrose levels and there was a corresponding increase in the lag period preceding starch synthesis in the light. Increased starch accumulation rates were usually observed when sucrose concentrations were high. These and other results suggested that cytosolic sucrose concentrations affected starch metabolism in the chloroplast. However, sucrose accumulation rates increased and starch storage decreased when barley seedlings were transferred from 20 to 10°C during the light period. Lowering the night temperature from 20 to 10°C for a single dark period 8-days after planting increased the TNC content of barley primary leaves at the beginning of day nine. In this experiment, TNC accumulation rates of treated and untreated leaves were similar. Changes in the accumulation rate of TNC were usually observed within 2- to 4-h after barley seedlings were exposed to altered environmental conditions. Monitoring rapid changes in leaf carbohydrate levels is a sensitive method for assessing the effects of environmental treatments on photosynthetic metabolism. 相似文献
90.
Following a survey of a range of varieties of rye, mainly Secale cereale, for reaction to DDT, the mode of action of the pesticide in a susceptible variety was studied. Two sites of interaction of DDT with the photosynthetic electron transport chain were demonstrated. The first site of inhibition was on the oxidizing side of photosystem 2, between the sites of electron donation from diphenylcarbazide at pH 6.0 and pH 8.0 in Tris-washed chloroplasts. The second site of DDT inhibition was in the intermediate electron transport chain, and was demonstrated by using dichlorophenol-indophenol and phenyldiamines as electron donors in chloroplasts where electron flow from photosystem 2 was inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea. The sites are distinct from those characteristic of herbicides which affect photosynthetic electron flow. 相似文献