Distribution of 14C-activity after 14CO2 application of the non structural carbohydrate in broad leaved dock (Rumex-Obtusifolis L), wild chervil (Anthriscus-Silvestris Cv Hoffmann) and cow parsnip (Heracleum-Spondylium L), at different growth stage

In the present work was intended to test and provide guidance on the successful utilization of herbicides. At the time of sprouting of broad leaved dock the fraction of 14C mono- and disaccharides immediately after treatment with 14CO2, in the roots and shoot parts of the plant sometimes makes up more than 50% of the total sugars. This relates obviously with an accelerated starch accumulation at this stage of growth in the root system. However, it was not shown to be the case that the sensitivity of broad leaved dock towards systemic herbicides increases at the same time. The basipetal translocation of assimilates does not seem to be the only prerequisite for an effective attack on this type of weed. At all growth stages only of wild chervil on small fraction of the 14C is present in the mono- and disaccharide fractions. At the time of flowering when the use of herbicides can be recommended, the composition of the 14C carbohydrate fraction does not give an addition or better explanation for the sensitivity of the plants towards herbicides at this stage of growth. The experimental results were influenced by the fact that at the time of flowering no basic rosette had been formed and the 14C application had to be applied at a higher inserted leaf on the shoot. The main fraction of 14C activity in mono- and disaccharide immediately after 14CO2 application occurs in the roots of cow parsnip at the time of seed ripening when new basic leaves are formed. After seven days the major fractions of the 14C applied occur in the starch fraction of the root. The assumed close relationship between the transport of herbicides in the assimilate stream and the actual herbicide sensitivity of cow parsnip is additionally explained by these results. (orig./MG)