Silicon interactions with manganese and aluminum toxicity in sorghum

Abstract

Silicon fertilization has been shown to alleviate Mn and Al toxicities in some plants. Experiments were conducted to assess the role of different Si levels on the alleviation of Mn and Al toxicity symptoms and on dry matter yields of sorghum [Sorghum bicolor (L.) Moench] grown in nutrient solutions with toxic levels of Mn and Al. Silicon concentration as high as 1780 μM had no detrimental effects on dry matter yields. At high Si levels (2670 and 3560 μM), shoot dry matter yields decreased, but root dry matter yields did not. Plants grown with 3600, 5400, and 7200 μM Mn showed marked visual toxicity symptoms in shoots but no effects on roots, even though root dry matter yield decreased more than shoot dry matter yield. The toxicity symptoms and the dry matter yield reductions caused by 3600 and 5400 μM Mn were partially alleviated by 1780 and 3560 μM Si, whereas no Si level overcame the severe effects induced by 7200 μM Mn. Plants grown with high Al (296 μM) had reduced root dry matter yields. Silicon at 1068 and 3560 μM were required to overcome the Al effect on NB9040 and Martin root dry matter yields respectively. Dry matter shoot/root ratios of plants grown with toxic Mn and Al were high and decreased with added Si. Silicon effects were not sufficient to completely overcome the Mn and Al toxic effects on sorghum.