Untersuchungen zur Translokation von Magnesium (28Mg) in Sonnenblumenpflanzen

Abstract

Investigations on translocation of magnesium (28Mg) in sunflower plants.1. The translocation and retranslocation of Mg respectively 28Mg in sunflower plants of different age have been investigated. The focus of this investigation was on the influence of the composition of the uptake solution and the age of plants on the uptake of Mg respectively 28Mg through the roots or through the leaves and on Mg translocation (distribution).2. After sunflower plants were grown in Mg‐deficient 1/2‐Hoagland solution Mg in the plants were redistributed. The Mg in the roots, stems, cotyledons, primary and secondary leaves was retranslocated to the youngest leaves.3. In isolated, secondary‐rooted sunflower shoots grown in Mg‐deficient solution, plant Mg was retranslocated into the new roots and into the youngest shoots.4. The 28Mg‐uptake from the 0,2 mM MgSO4 solution was usually higher than from the 1/10‐Hoagland solution. The composition of the uptake solution had little influence on the distribution of 28Mg. Independent of the age plants had the highest 28Mg content in the young and the lowest in the old leaves.5. Root uptake of 28Mg resulted in a more uniform distribution in the plant than leaf uptake. The old leaves had a higher 28Mg content by root uptake than by leaf uptake of 28Mg. This is probably influenced by transpiration, in combination with the xylem transport of 28Mg after root uptake, which differs from leaf uptake and translocation in basipetal direction.6. With increased age of plants, the content of 28Mg/10 gr. fresh weight decreased and the difference in content between the parts of plant was higher. The decrease of Mg content in the oldest leaves was the highest.7. The results showed that Mg was transportable in the phloem. The magnitude and the direction of Mg transport was determined as primarily through the assimilation stream, which is coupled with Mg transport in plants.