Published in:
Journal of Plant Nutrition and Soil Science, 170 (2007) 1, Seite 14-23
Language:
English
DOI:
10.1002/jpln.200625057
ISSN:
1436-8730;
1522-2624
Origination:
Footnote:
Description:
AbstractThe plant nutrient phosphorus (P) is spread throughout the plant within the transpiration stream after uptake in the form of phosphate via the roots. Short‐term distribution is therefore strongly dependent on transpiration rather than on sinks, so that P mainly enters adult leaves. The objective of this work was to investigate the transport of phosphate in leaf veins and its distribution within the leaf. Experiments were performed with broad bean (Vicia faba L. var. Scirocco) using radioactively labeled phosphate. In a relatively new approach, the tracer was monitored by a sensitive imaging plate using Fujifilm's Bioimaging Analyzer System. Radioactive label could be monitored in fresh leaves (without fixing) using exposure times of only 5–20 min. For this reason, the method offered the possibility to obtain several subsequent autoradiographic images of the same sample after different feeding times. Phosphate tracer quickly reached small veins, which were then more intensely labeled than the tissue between them. Within the first 15 min, intercostal fields were only slightly stained. After application of phosphate tracer onto the leaf blade, export from the leaf was pronounced and started within 30 min. Phosphorus is effectively redistributed from adult leaves to sinks such as the terminal bud or growing root tips. Using the imaging method, an impression of the high velocity and effectiveness of this process was obtained. The results furthermore imply that leaf veins may be one of the most important locations where exchange between xylem and phloem transport takes place, although exchange between xylem and phloem was also observed in the shoot axis and in the petioles.