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991.
992.
21-day old plants ofChenopodium rubrum L. ecotype 374 were used. Organ relationships in the shoots were investigated by32P distribution, which indicated different organ correlations in plants grown in continuous light and in plants treated with
flower-inducing and non-inducing dark periods. Dark periods were associated with a low32P distribution in young leaves and a high one in axillary buds. In the following light period the high32P distribution in axillary buds continued whereas the32P distribution in the leaves on the main axis increased and was similar to that in plants grown in continuous light. The high32P distribution in axillary buds was brought about by both, flower-inducing and non-inducing dark treatments. Decapitation
resulted in a high32P distribution in buds, in continuous light an increased32P distribution was also found in leaves. These effects were not fully cancelled by IAA application.
The results are discussed with respect to an assumption that decrease of apical dominance represents a step in a sequence
of events leading to flowering. 相似文献
993.
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
994.
Plasticity of the tobacco genome was studied by testing the DNAs of protoplast-derived regenerants with three different repetitive
DNA sequences by the method of quantitative DNA/DNA hybridizations. A large population of 91 regenerants belonging to 35 different
protoclones was analysed and a high degree of heterogeneity in the contents of the different DNA repeats was detected. The
contents of middle repetitive sequences of two types were more stable or changed in the same direction, while the highly repetitive
sequence varied independently and displayed a significant reduction in comparison with the two other sequences. Comparing
the variation within the subpopulations of plants of the same clonal origin and the variation among the protoclones led to
a conclusion that the pre-existing DNA variability in the starting plant material and/or thein vitro stress during the very early stages of protoclone regeneration played a decisive role in the formation of modified genomes
in regenerants. 相似文献
995.
An improved method for the isolation of leaf mesophyll protoplasts ofSolanum tuberosum L. cvs. Xenia and Bintje, their culture and regeneration to plants is described. The improvements involve the culture of nodal stem explants on Schenk and Hildebrandt (SH) medium supplemented with AgNO3 (7.5 mg 11) and Alar 85 (5 mg 1?1), and the pre-treatment of donor plants for 2–3 weeks at a short photoperiod (6 h), a low irradiance (17 (μmol m?2s?1) and a low temperature (20 °C). Regeneration of cell wals was observed within 2–3 d and cell divisions within 7–12 d after resuspending freshly isolated protoplasts in Sidorov et al. (SW) medium. The resulting microcalli were cultured on solid media containing zeatin (1–2,5 mg 1?1) and/or NAA (0.1 and/or 0.01 mg 1?1) and subsequently on medium with BAR (0.25 mg1?1) and GA?3 (0.1 mg 11) for shoot regeneration. 相似文献
996.
Functionally-stabilized proteins--a review 总被引:1,自引:0,他引:1
The maintenance or stabilization of protein or enzyme function is of vital importance in Biotechnology. Investigations of thermophilic organisms, studies of denaturation and the use of enzymes in organic solvents have each contributed to an understanding of protein stability. Enzymes can reliably and reproducibly be stabilized by variety of means including immobilization, use of additives, chemical modification in solution and protein engineering. Examples of each of these are discussed. With these recent advances it appears that a rational strategy for achieving a particular stabilized enzyme or protein may be within reach. 相似文献
997.
N Macková P Fedorocko P Brezáni 《Physiological research / Academia Scientiarum Bohemoslovaca》1991,40(5):503-512
The culture medium administered to C57Bl/6 mice 18 h and 8 h before a single irradiation (9 Gy) had a radioprotective effect and clearly influenced postirradiation changes in haemopoiesis. Haemopoiesis recovery appeared to be faster in culture medium-pretreated animals than in those irradiated without such pretreatment. By 12-15 days after irradiation, the thymus cortex appeared to be repaired, on day 21 a multiple increase in extramedullary erythropoiesis, myelopoiesis and megakaryocytopoiesis in the red pulp was found and later, on day 28, the lymphopoiesis in the white pulp of spleen was restored. The rate of haemopoiesis proliferation of predominantly myeloid cells which reached a control level on day 28 following irradiation. Consequently, the regenerative processes in blood-forming organs were accompanied by considerable reticulocytosis and complete recovery of neutrophil and platelet counts in the peripheral blood as seen on day 21. Despite a slower rate complete recovery of the total leukocyte count was reached by day 180 after irradiation. 相似文献
998.
M Pospísil J Sandula I Pipalová M Hofer S Viklická 《Physiological research / Academia Scientiarum Bohemoslovaca》1991,40(4):377-380
Carboxymethylglucan, a novel soluble derivative of beta-1,3-glucan, was found to enhance hemopoietic recovery in sublethally gamma-irradiated mice and to increase survival in lethally irradiated animals when given 24 hours prior to irradiation. Postirradiation treatment with carboxymethylglucan also induced favourable effects in terms of survival when used in combination with preirradiation cystamine administration. 相似文献
999.
Racemization of the aqua-{N-salicylidene-(S)-alaninato}copper(II) by reaction with potassium cyanate
Copper(II) N-salicylidene-(S)-alaninate trihydrate reacting as the S-enantiomeric parent compound with KOCN in hot diluted methanol yielded by slow crystallisation from the cooled reaction mixture (in the course of 1 day) the racemic product K[Cu{sal-(RS)-ala}(NCO)]. The parameters of the axial type EPR spectrum in X-band region and the LF band position in the electronic spectrum are typical of an axially distorted square pyramidal coordination of the Cu(II) atom in this complex. The spectral properties of the complex cuprate prepared and its basal crystallographic data are consistent with those of the earlier studied15 K2[Cu2{sal-(RS)-ala}2(μ-NCO)2] synthetized by using [Cu{sal-(RS)-ala}(H2O)].H2O as the racemic parent complex in the reaction mixture with KOCN. 相似文献
1000.
In the present work we have studied the organization of melano-macrophage centres (MMCs) in the peripheral lymphoid organs, including spleen, pro- and mesonephros, of the goldfish, Carassius auratus, in an attempt to clarify their cellular composition, origins and functional relationships. Histological analysis demonstrated a similar organization in the three organs on the basis of closely packed phagocytic cells containing abundant pigment. The MMCs of Carassius auratus are found throughout the parenchyma of spleen and kidney and show a close association with the vascular system, i.e. splenic ellipsoids, sinusoids of red pulp and renal blood sinuses. They exhibit distinct degree of development from small groups of actively phagocytic macrophages to large, totally or partially encapsulated centres, where effete phagocytic cells are filled by cell debris. Ultrastructural and histochemical data suggest that the main inclusion observed in the MMCs of Carassius auratus is lipofuscin. Haemosiderin occurs in lesser amounts and melanin is almost restricted to kidney MMCs,--mainly mesonephros--. Our results suggest various non-specific physiological roles for the teleost MMCs, including tissue breakdown and erythrocyte catabolism. 相似文献