No abstract

In a pot experiment (culture substrate: perlite with a granulometric composition 0-3 mm) with peas (Pisum sativum L.) we studied the influence of sulphur supply on S and N concentrations, yield formation, symbiotic N 2 fixation and available amounts of glucose and sucrose. Under S deficiency conditions S and N concentrations as well as the amounts of glucose and sucrose in shoots and nodules were significantly reduced. We assume that the reduced amounts of available photosynthate with suboptimal S supply could become limiting to energy production and as carbon skeletons for ammonia assimilation, and therefore cause a lower N 2 fixation and a reduced yield formation.

Benzoxazolinone detoxification is similar in plants grown under sulfur deficiency conditions and in control plants grown with an optimal S supply. However, when S-deficient plants were treated with metolachlor before benzoxazolin-2(3H)-one (BOA) incubation, detoxification was reduced, as indicated by a lower accumulation of the detoxification products BOA-6-O-glucoside and glucoside carbamate and by a loss of BOA-6-OH glucosyltransfease activity. Root colonizing microorganisms and the endophytic fungus Fusarium verticillioides participated in benzoxazolinone detoxification by converting the compound to 2-acetamidophenol (AAP) or O-hydroxyphenyl malonamic acid (OHPMA), a process accompanied by the appearance of phenoxazinone. Maize roots, however, absorbed AAP and OHPMA only in traces. Absorbed traces of OHPMA stimulated maize radicle growth, and traces of AAP stimulated cress. Phenoxazinone inhibited the growth of cress radicles at concentrations higher than 500 microM, whereas maize radicles were hardly affected. F. verticillioides did not convert benzoxazolinone to any known microbial degradation product when the medium of maize seedlings was inoculated with the fungus under sterile condition. Plant-fungus interactions seem to be important in plant survival of allelopathic attacks. This study points to a complicated network of allelopathic interactions that are influenced by biotic and abiotic factors, including herbicides.

No abstract

No abstract