Effects of Silicon on the Availability of Boron:

Abstract

Silicon (Si) and boron (B) are elements with many similar chemical properties, both are weak, undissociated acids in aqueous solution and Si can complex readily with polyhydroxy compounds just as B (Brown et al., 1999; Kinrade et al., 1999). However, little is known about possible interactions between these elements in higher plants. Interestingly, dicotyledonous and graminaceous species differ not only in their capacity for Si uptake but also in their B and Ca requirement, which is inversely related (Loomis and Durst, 1992). On the other hand, there are positive correlations between Si and B uptake within different barley genotypes. Thus, genotypes with a lower Si uptake showed also a lower B uptake and were therefore more tolerant to high B supply (Loomis and Durst, 1992). However, there are no reports on a direct Si-B interaction within these barley genotypes as shown for oilseed rape (Liang and Shen, 1994). These authors found that Si supply increased the range between critical deficiency and toxicity concentration for B in rape. Since it is well known that B plays an important role in phenol pathway and ascorbic acid synthesis, we measured the effect of Si on growth, B concentration and B compartmentation. In addition, free peroxidase (POD), ionically and covalently bound POD were investigated because of the well documented effect of B on POD binding (Goldbach, 1991).