EFFECTS OF EXCESS MANGANESE ON MINERAL UPTAKE IN MYCORRHIZAL SORGHUM

Associations between vesicular-arbuscular mycorrhizal (VAM) fungi and manganese (Mn) nutrition/toxicity are not clear. This study was conducted to determine the effects of excess levels of Mn on mineral nutrient uptake in shoots and roots of mycorrhizal (+VAM) and non-mycorrhizal (-VAM) sorghum [Sorghum bicolor (L) Moench, cv. NB9040]. Plants colonized with and without two VAM isolates [Glomus intraradices UT143-2 (UT1 43) and Gl. etunicatum UT316A-2 (UT316)] were grown in sand irrigated with nutrient solution at pH 4.8 containing 0, 270, 540, and 1080 mu M of added Mn (as manganese chloride) above the basal solution (18 mu M) Shoot and root dry matter followed the sequence of UT316 > UT143 > -VAM, and shoots had greater differences than roots. Shoot and root concentrations and contents of Mn, phosphorus (P), sulfur (S), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), and copper (Cu were determined. The +VAM plants generally had higher mineral nutrient concentrations and contents than -VAM plants, although -VAM plants had higher concentrations and contents of some minerals than +VAM plants at some Mn levels. Plants colonized with UT143 had higher concentrations of shoot P, Ca, Zn, and Cu and higher root Mg, Zn, and Cu than UT316 colonized plants, while UT316 colonized plants had higher shoot and root K concentrations than UT143 colonized plants. These results showed that VAM isolates differ in enhancement of mineral nutrient uptake by sorghum.