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81.
82.
83.
A study was made of the changes in the content of essential oil and its components (farnesene, (-)-α-bisabolol, (-)-α-bisabololoxide
A, (-)-α-bisabololoxide B and spathulenol, α-bisabolonoxide A, chamazulene, cis en-in-dicycloether) and of the number of secretory
canals in the receptacles during the beginning of flowering, full flowering and the termination of flowering of camomile anthodia.
The total content of the essential oil was highest during the beginning of flowering and lowest during its termination. The
proportion of the individual sesquiterpenes in the essential oil underwent changes mostly during the beginning and termination
of flowering. The number of secretory canals in the basal and middle anthodial parts increased during the beginning of flowering
and the full flowering. 相似文献
84.
Sucrose was markedly superior to fructose and glucose in promoting growth of plantlets from immature maize embryos. The elongation
of roots is shown to be more sucrose dependent than that of shoots. On the other hand, the exogenous sucrose was less effective
than fructose as substrate for carbohydrate catabolism and for the synthesis of alcohol-insoluble compounds at the beginning
of embryo cultivation. The absorbed fructose was found to be rapidly converted to sucrose and the level of endogenous sucrose
derived from sugar supplied to the medium was higher in fructosethan in sucrose-fed embryos. The preferential utilization
of fructose over sucrose, however, declined with the progress of germination which may be related to the decrease in proportion
of scutellum in total mass and physiological activity of the embryo. 相似文献
85.
Summary LW13K2 cells, a clone of a spontaneously in vitro transformed derivative of embryonic Lewis rat fibroblastic cells, were studied by phase contrast cine-light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The ruffles found at the advancing edge of cells grown on glass substrates in vitro form and recede in a period of less than one min if they do not make an attachment of the substrate. If they fail to make an attachment they may form pinocytotic channels near the leading edge as described by Price (1972) and/or collapse, generally backwards, towards the cell body. The spines which appear to reinforce the membranous ruffles are the last structures to disappear, and accumulate in an irregular array behind the ruffling edge; this area is behind that in which pinocytosis occurs. In comparison with the sparse numbers of ribosomes found in the trailing edge, they are present in notable concentrations near the leading, ruffling edge of the cell. No membrane vesicles have been found in or near the ruffling edges at the ruffle-spine concentration zone. 相似文献
86.
The capacity of pollen tubes to utilize exogenous uridine during 8 h of cultivation in shaken suspension in a sugar-mineral
medium was examined by continuous and pulse labelling with3H-uridine. The increase of uptake with increasing concentration of the nucleoside indicated a saturable transport system with
an approximate Km of 9.4 × 10−6 M and 12.5 × 10−6M as determined in 1-h and 6-h cultures, respectively. Maximal uptake took place at the beginning of germination reaching
a rate of about 2 nmol h−1 per 1 mg of dry pollen at 0.1 mM external uridine. The uptake activity decreased with the time of pollen tube growth to less
than one third during the 8-h cultivation period. Moreover, the level of radioactivity taken up initially decreased later
on during continuous cultivation in the presence of3H-uridine. The uptake took place against a concentration difference and the onset and rate of uridine release depended on
its exogenous concentration.
The activity of the nucleoside incorporation into RNA increased during the first 4 h of cultivation, decreasing later on.
The proportion of RNA radioactivity in continuously labelled pollen tubes grew steadily during 6 h and reached 2.5% with respect
to soluble pool at 0.4 μM uridine. The time course of RNA labelling was independent of uridine concentration within the range
of 0.4 μM to 40 μM but this concentration rise resulted in an about fiftyfold increase of the total amount of external uridine
incorporated. 相似文献
87.
88.
A method for the preparation and regeneration of protoplasts of Streptomyces lincolnensis is described. Mycelium in the early exponential phase appeared to be most suitable for this purpose and yielded up to 25% regenerated intact cells. Transformation of S. lincolnensis protoplasts was achieved using broad-host-range streptomycete plasmid vectors pIJ622, pMP66, pRS410 and pIJ943 constructed from replicons pIJ101, pSLG33 and SCP2. The efficiency of transformation was 3.10(3) transformants per micrograms plasmid DNA when (2-5).10(7) recipient protoplasts were used. Interspecific transformations showed that there is no efficient restriction system in S. lincolnensis that would limit the transfer of genetic information from S. lividans or E. coli. 相似文献
89.
The rat NMDAR1 (N-methyl-D-aspartate receptor) was expressed transiently in human embryonic kidney cells. Transfected cell homogenates showed saturable [3H]MK-801 binding activity that was best fit by a single high-affinity site with a KD of 9 nM and a Bmax of 113 fmol of binding sites/mg of protein. Antibodies raised against the peptide sequence NMDAR1 (929-938) coupled to keyhole limpet haemocyanin specifically recognised a single band with M(r) 117,000 in immunoblots from adult rat brain. In the transfected cells, the antibody recognised two bands: one with M(r) 117,000, which was coincident with that from brain membranes, and one with M(r) 97,000, which was identified as nonglycosylated NMDAR1 subunit. These results identify the NMDAR1 of rat brain and further show that the homooligomer binds MK-801, albeit at low efficiency. 相似文献
90.
Spring barley seedling were grown in the dark for 21 d and respiration rates of the whole plant (including the seed), of the
shoots, and of the roots were determined. A function describing the growth and maintenance components of respiration was interpolated
through the experimental points and its parameters in plants under different mineral nutrition were compared. The plants grown
in a complete nutrient solution showed the highest growth rate in the initial phase of development and thus reached the maximum
respiration rate earlier than plants in the other variants. The highest proportion of substrate was respired in the shoot.
Plants grown under deficiency of phosphorus and magnesium had a slower respiration rate than plants grown in the complete
nutrient solution (NP), whereas the amount of respired substrate in plant parts was similar to that recorded in the NP plants.
Plants grown in distilled water showed the lowest growth efficiency and respirated the highest proportion of substrate in
the root. 相似文献