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31.
32.
Summary Striated Ciliary Roots (SCRs), about 3 m long, are attached to the basal bodies of branchial crown ciliated epithelial cells ofOwenia. These SCRs appear to consist of 5–7-nm diameter filaments organized in a cross-striation pattern with an apparent variable periodicity of 50 to 80 nm. The most exciting observation emerging from this study is the constant and conspicuous close spatial relationship between SCRs and fairly well developed Golgi apparatus. By enhancing contrast and preservation of cell components, the OsFeCN postfixation-staining of material prefixed in glutaraldehyde in the presence of calcium has revealed some fine-structural details within the SCR-Golgi Association. By means of the calcium precipitation method, with antimonate or oxalate in conjunction with X-ray microanalysis, we have identified calcium within SCR dark bands and SCR-associated Golgi bodies. The ability to bind calcium makes the Golgi apparatus a likely candidate for Ca2+ regulation of putative contraction of the SCRs and/or ciliary motility. The slight period variability measured in the SCRs and cytochemical localization of Mg2+, Ca2+-dependent ATPase activities associated with cross striations support the view that theOwenia SCRs may be contractile organelles.The striking and specific close structural association between the Golgi apparatus and the SCR showing Ca2+-binding capabilities suggests that some sort of Ca2+-mediated functional relationship between these organelles may exist.Abbreviations SCR
striated ciliary root
- OsFeCN method
osmium tetroxide-ferricyanide method
- EDTA
ethylenediamine tetraacetic acid
- EGTA
ethyleneglycol-bis-(-aminoethyl ether) N,N-tetraacetic acid
- ATP
adenosine 5-triphosphoric acid
- ATPase
adenosine triphosphatase
- ASW
artificial sea-water 相似文献
33.
The effect of drought on levels of abscisic acid,cytokinins, gibberellins and ethylene in aeroponically-grown sunflower plants 总被引:7,自引:0,他引:7
Abscisic acid (ABA), cytokinins and gibberellin-like substances (GAs) were extracted from the roots and shoots of 17-day-old sunflower seedlings which had been droughted or were unstressed. Plants were grown in an aeroponic chamber which allowed for good control over degree of water stress and easy access to roots. Following methanolic extraction of lyophilized material, cytokinins were separated from the acidic growth-regulators on a cellulose PO4 cationic exchange column. The cytokinins were analysed by paper chromatography and HPLC and the soybean hypocotyl section assay. Semipurified acidic regulators were chromatographed on SiO2 columns and HPLC and aliquots assayed with the dwarf rice cv. Tan-ginbozu bioassay for GAs. Fractions known to contain ABA were purified by sequential reverse-phase HPLC of the acid and then of the methyl ester forms followed by quantitation as Me-ABA on GLC-EC. ABA losses were measured by using an internal standard [3H]-ABA). Ethylene production was also monitored in stressed and unstressed seedlings.The effect of drought on GAs and ethylene was minimal. The ABA levels were markedly higher in droughted plants. Stressed roots had 32 times more ABA than controls. The levels of cytokinins in the shoots of droughted plants were about half those in unstressed shoots, and qualitative differences occurred in the roots. Under stress a large peak of activity was present similar to zeatin glucoside which was not present in the unstressed condition. The results are discussed in relation to drought-effects on metabolism. 相似文献
34.
Flood tolerant Glyceria maxima and intolerant Pisum sativum were compared in respect of the effects of anoxia and flooding on the maximum catalytic activities of alcohol dehydrogenase in their roots. Small (<73%) increases in enzyme activity occurred when excised roots of both species were incubated in nitrogen for up to 2 days. Further incubation in nitrogen rapidly and permanently damaged the roots of both species. Enzyme activity in flooded roots of Glyceria was about double that in corresponding non-flooded roots. A marginally greater difference was found for roots of Pisum. It was concluded that the two species respond so similarly to the above treatments that variation in the extent of induction of alcohol dehydrogenase is unlikely to be a significant factor in determining their ability to tolerate flooding. 相似文献
35.
Summary Experiments, performed withPinus pinaster cloned shoots submitted to an auxin treatment (NAA 10–6
M, 18 days), demonstrated that rooting abilityin vitro persists over 5 successive induction cycles (through out a 9-month period). Rooting ability needs a permanent synthesis of auxin synergists which activate the metabolism of cell dedifferentiation and root primordium initiation. Agar culture permitted intense meristem initiation, but prevented active root elongation. In the presence of a mycorrhizal fungus,Pisolithus tinctorius orHebeloma cylindrosporum, roots resumed growth and short lateral root formation was stimulated. These two phenomena induced by fungal association improve the quality of the root systems required to facilitate successful transplantation from test-tubes to field conditions. 相似文献
36.
Marie-Pierre Arvy 《Physiologia plantarum》1983,58(1):75-80
After incubation for 3 h with (75 Se) selenate, the selenium distribution in the bean plant (Phaseolus vulgaris L. cv. Contender) through a 29-day period showed an uneven distribution: roots and trifoliate leaves were richer in 75 Se than stem and primary leaves. The high selenium concentration of roots resulted from the retention of selenate by the root cells: at the end of the 29-day period about 60° of the radioactivity was always ethanol-soluble, and when analysed by paper chromatography, proved to be selenate. By contrast, much of the radioactivity of the leaves was ethanol-insoluble, 75 Se being quickly captured in metabolic processes which immobilize it. During plant development, a portion of the total selenium remains mobile and is continually mobilized to the younger organs which display a rapid growth rate. This delivery results from a progressive liberation of selenate retained by mature organs, especially the roots, and from turnover in older leaf tissues, especially the trifoliate leaves. 相似文献
37.
Rice root glutamate synthase activity was assayed with various reducing systems. Ferredoxin-dependent glutamate synthase (EC 1.4.7.1) and pyridine nucleotide-dependent glutamate synthase (NADH, EC 1.4.1.14; or NADPH, EC 1.4.1.13) exhibited a strict specificity for the electron donor. The ferredoxin-dependent glutamate synthase from rice roots could accept electrons from photoreduced ferredoxin in an illuminated reconstituted spinach chloroplast system. Thioredoxin, a potent electron carrier, was not able to provide either ferredoxin-dependent or pyridine nucleotide-dependent glutamate synthase with electrons as no glutamate formation was detected in the presence of reduced thioredoxin f or m. 相似文献
38.
Influence of temperature on root development and phosphate influx in winter wheat grown at different P levels 总被引:1,自引:0,他引:1
Root development was studied in winter wheat ( Triticum aestivum L. cv Starke II) grown at 5,10, 15 and 20°C in nutrient solutions with phosphate concentrations of 10, 100 or 1000 μM . The plants were grown for 38 days (5 and 10°C), 19 days (15°C) or 14 days (20°C). At the end of the cultivation period the phosphate influx in the roots was determined with 32 P-phosphate. Root development (lateral and seminal roof length and number) was monitored throughout the cultivation period on the same individuals by repeated (approximately every second day) photocopying of the roots for measurements with digitizer and appropriate software. The 5°C treatment yielded no laterals, and the seminals were only slightly affected by the different phosphate treatments. The 10 μM phosphate treatment gave high root:shoot dry weight ratio, high average lateral root length and high specific root length [m root (g root fresh weight)-1 ]. The 1000 μM phosphate treatment yielded the highest number of laterals per m seminal root, and usually also the highest absolute numbers. Phosphate influx decreased with increased P status of the roots. It is argued that phosphate influx is dependent on factors such as P status, root geometry and relative root extension rate. 相似文献
39.
Apparent phytotoxicity of mononuclear hydroxy-aluminum to four dicotyledonous species 总被引:3,自引:0,他引:3
It has long been assumed that Al3+ is an important rhizotoxic ion in acid soils around the world, but the toxicity of Al3+ relative to mononuclear hydroxy-Al [AlOH2+ and Al(OH)+ 2 ] has been examined in detail only for an Al-sensitive wheat variety ( Triticum aestivum L. cv. Tyler). That plant appears to be sensitive to Al3+ but not to AlOH2+ and Al(OH)+ 2 . New experiments, and reanalyses of previously published experiments, provide evidence that dicotyledonous species may be sensitive to mononuclear hydroxy-Al and that Al3+ may be nontoxic, or less toxic, to those plants. Despite these consistently measured differences between wheat and the dicotyledons, the determination of relative toxicities (Al3+ vs mononuclear hydroxy-Al) may be an intractable problem. Because of hydrolysis equilibria, (AlOH2+ ) and (Al(OH)+ 2 ) are equivalent to (Al3+ )k1 (H+ )−1 and (l3+ )k2 (H+ )−2 , respectively, in which k1 and k2 are the first and second hydrolysis constants (braces denote activities). Thus, any expression of root elongation as a function of mononuclear hydroxy-Al can be alternatively expressed as a function of (Al3+ ) and (H+ ). Toxicity attributed to mononuclear hydroxy-Al may actually be Al3+ toxicity that increases as pH rises (i.e. Al3+ toxicity ameliorated by H+ ). 相似文献
40.