On the mechanism of rejuvenation of ageing detached bean leaves by low-concentration stressors.

The effect of low concentrations of some stress-inducing compounds of different toxicity and chemical nature, such as Cd and Pb salts or DCMU, was investigated on the senescence of chloroplasts in detached primary leaves of bean (Phaseolus vulgaris L.). After 1 week of senescence followed by root development from the petiole, these agents stimulated chlorophyll accumulation and photosynthetic activity ((14)CO(2) fixation) as compared to the control, thus inducing rejuvenation. Low-concentration stressors increased the level of active cytokinins in roots and leaves during the treatment, as monitored by the Amaranthus betacyanin bioassay and high-pressure liquid chromatography. The lithium ion, an inhibitor of the PIP(2)-IP(3)/DAG signal transduction pathway, abolished the stimulating effect of stressors, both in roots (retarding cytokinin synthesis) and consequently also in leaves (reducing cytokinin-dependent chlorophyll accumulation). This suggests the involvement of the PIP(2)-IP(3)/DAG signal transduction pathway in generation of these consecutive organ-specific responses.

Involvement of the phosphoinositide signaling pathway in the anti-senescence effect of low-concentration stressors on detached barley leaves.

The effect of low concentration of some stress-inducing compounds of different toxicity and chemical nature like Pb and Ti salts or DCMU on the senescence of chloroplasts was investigated in detached primary leaves of barley (Hordeum vulgare cv. Omega). These agents stimulated chlorophyll accumulation, photosynthetic activity ((14)CO (2) fixation), and decreased the number of plastoglobuli in chloroplasts compared to the control, thus delaying senescence. Low-concentration stressors did not increase the level of active cytokinins of leaves during the treatment. Lithium and stearoylcarnitine chloride inhibited the stimulating effect of stressors. This points to the involvement of the PIP (2)-IP (3)/DAG signal transduction pathway in generation of the specific responses.

Reference concentrations of trace elements in urine of the Budapestian population.

Reference values in biological specimens are crucial to estimate the type and magnitude of environmental and occupational exposure: Because of its importance in the excretion of noxious substances and to the noninvasive mode of its collection, urine is a useful specimen for monitoring studies. Thus, the concentrations of six trace elements (Al, Co, Mo, Nb, Ni, and Ti) were determined in 100 urine samples of the Budapestian population by inductively coupled plasma-mass spectrometry. The obtained creatinine adjusted concentrations (medians) are (in microg/g) 9.9, 0.6, 53.5, 0.4, 1.5, and 8.5 for Al, Co, Mo, Nb, Ni, and Ti, respectively.

Speciation of beryllium, nickel, and vanadium in soil samples from Csepel Island, Hungary.

Sequential leaching methods have been used for the speciation of Be, Ni, and V in five soil samples from Csepel Island on the Danube river located near an oil-fired power plant. The concentrations of the elements of the extracts were determined by inductively coupled plasma mass spectrometry. The total efficiency (the sum of the extracted metals divided by metal fraction which is soluble in aqua regia) of the five-step method was always higher. The difference for Ni was considerable, because of the high abundance of Ni found in the moderately reducible fraction, which is absent from the three-step method. The sum of the mobile species (exchangeable, carbonatic, and easily reducible) determined by both methods, were in reasonable agreement; this was not so for the individual fractions. There were greater differences between the non-mobile fractions (moderately reducible and oxidizable), because of the presence or absence of the moderately reducible fraction. For both methods there was good correlation between the oxidizable fraction and the organic matter content of the soils.