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The effects of anion channel blockers, 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS) and anthracene-9-carboxylic acid (A-9-C), on the uptake and xylem transport of nitrate were investigated in intact barley (Hordeum vulgare L.) seedlings using 13NO3 − and 15NO3 − as tracers. The seedling roots were pretreated with either blocker for 1 h and then 13NO3 − or 15NO3 − was supplied to the medium. Real-time images of 13N accumulation in shoots were monitored during the first 30 min using Positron Emitting Tracer Imaging Systems (PETIS). The radioactivity in the shoots of the plants treated with either blocker was about half of that in the shoots of the control plants. Analysis of the distribution of 13N in whole seedlings using a Bioimaging Analyzer System (BAS) showed a 13N-accumulation in both shoots and roots of the control plants but reduced 13N-levels in the shoots of the plants treated with either blocker. Nitrate concentrations in the xylem sap were significantly reduced by the appli...

15P-water flow from the roots to the top in tomato (Lycopersicon esculentum Mill.) and rice (Oryza sativa L.) plants was visualized with time using a positron-emitting tracer imaging system (PETIS). The 15O-water flow was switched on by light and completely stopped in the dark. The flow rate in the stem of tomato and the shoot of rice at a light intensity of 500 μmol·m−2·s−1 was 1.9 and 0.4 cm min−1, respectively.

The positron emitting tracer-imaging system (PETIS) was used to determine whether it was possible to obtain on image of 13N-distribution in common bean in which a single root was fed with a liquid medium containing nitrate at different concentrations with different 13N specific activities. The distribution of the images of the 13N atoms in the root could be obtained over a wide range of nitrate concentrations and 13N specific activities in the medium. As for nitrate stress on leguminous root nodulation, the positional relationship between the nitrate uptake sites and root hair just elongating area, where rhizobia capably initiate their infection, was studied in common bean and soybean. PETIS gave direct evidence that single roots of both common bean and soybean showed one or two dense 13N-distribution areas after 2 min pulse-feeding of 13N03 -. These areas remained stable over 30 min, and the first dense site, which was common in all the examined roots, extended over ca. 1 cm above the root apex....

The Positron-Emitting Tracer Imaging System (PETIS) is introduced for monitoring the distribution of (11)C-labelled photoassimilates in Sorghum. The obtained two-dimensional image data were quantitatively analysed using a transfer function analysis approach. While one half of a Sorghum root in a split root system was treated with either 0, 100, or 500 mM NaCl dissolved in the nutrient solution, tracer images of the root halves and the lower stem section were recorded using PETIS. From the observed tracer levels, parameters were estimated, from which the mean speed of tracer transport and the proportion of tracer moved between specified image positions were deduced. Transport speed varied between 0.7 and 1.8 cm min(-1) with the difference depending on which part of the stem was involved. When data were collected in the lowest 0.5-1 cm of the stem, which included the point where the roots emerge, transport speed was less. Rapid changes in NaCl concentration, from 0 to 100 mM, resulted in short-term increases of assimilate import into the treated root. This response represented a transient osmotic effect, that was compensated for in the medium-term by osmotic adaptation. Higher concentrations of NaCl (500 mM) resulted in distinctly less photoassimilate transport into the treated root half. The present results agree with earlier observations, showing that transport of (11)C-labelled photoassimilates measured with the PETIS detector system can be quantified using the method of input-output analysis. It is worth noting that with the PETIS detector system, areas of interest do not need to be defined until after data collection. This means that unexpected behaviour of a plant organ will be seen, which is not necessarily the case with conventional detector systems looking at predefined areas of interest.

[11C]Methionine was supplied through barley roots and the 11C signal was followed for 90 min using a real-time imaging system (PETIS), with subsequent development of autoradiographic images of the whole plant. In all cases, [11C]methionine was first translocated to the 'discrimination center', the basal part of the shoot, and this part was most strongly labeled. Methionine absorbed by the roots of the plants was subsequently translocated to other parts of the plant. In Fe-deficient barley plants, a drastic reduction in [11C]methionine translocation from the roots to the shoot was observed, while a greater amount of 11C was found in the leaves of Fe-sufficient or methionine-pretreated Fe-deficient plants. Treatment of Fe-deficient plants with aminooxyacetic acid, an inhibitor of nicotianamine aminotransferase, increased the translocation of [11C]methionine to the shoot. The retention of exogenously supplied [11C]methionine in the roots of Fe-deficient barley indicates that the methionine is used in the biosynthesis of mugineic acid phytosiderophores in barley roots. This and the absence of methionine movement from shoots to the roots suggest that the mugineic acid precursor methionine originates in the roots of plants.

[ 11 C]methionine was supplied to Fe-deficient and Fe-sufficient barley plants through a single leaf, and real time 11 C movement was monitored using a Positron Emitting Tracer Imaging System (PETIS). In Fe-deficient plants, [ 11 C]methionine was translocated from the tip of the absorbing leaf to the 'discrimination centre' located at the base of the shoot, and then retranslocated to all the chlorotic leaves within 60 min, while a negligible amount was retranslocated to the roots. In Fe-sufficient plants, methionine was translocated to the discrimination centre and then only to the newest leaf on the main shoot within 60 min. A negligible amount was also retranslocated to the roots. In conclusion, methionine from the above-ground parts of a plant is not a precursor of mugineic acid under Fe-deficiency. The discrimination centre is suggested to play a vital role in the distribution of mineral elements and metabolites in gramin-aceous monocots.