MINERAL ACQUISITION OF ALUMINUM-TOLERANT AND ALUMINUM-SENSITIVE SORGHUM GENOTYPES GROWN WITH VARIED ALUMINUM

A constraint to plants grown on acid soils is commonly aluminum (Al) t oxicity. Plants grown with excess Al normally have imbalanced minerals compared to plants grown without Al. This study was conducted to dete rmine differences among 25 sorghum [Sorghum bicolor (L.) Moench] genot ypes with broad ,genetic backgrounds for Al, phosphorus (P), sulfur (S ), potassium (K), calcium (Ca), magnesium (Mg), manganese (Mn), iron ( Fe), zinc (Zn), and copper (Cu) acquisition when grown with 0, 200, 40 0, 600, and 800 mu M Al in nutrient solutions (pH 4.0). Genotypes were categorized into ''Al tolerant'', ''Al sensitive'', ''intermediate Al tolerant'', and SC 283 (an Al-tolerant standard) according to net mai n axis root length (NMARL) of plants grown with 400 mu M Al. Shoot and root concentrations of minerals were generally lower as Al increased, and some minerals changed more than others. The Al-tolerant genotypes generally had higher concentrations of Mn in shoots and K in roots, l ower concentrations of Ca in shoots and roots, and lower concentration s of P, Mg, and Mn in roots than Al-sensitive genotypes. Except for Zn concentrations in shoots, concentrations of minerals in the intermedi ate Al-tolerant group generally appeared between the Al-tolerant and A l-sensitive groups. Mineral concentrations in SC 283 generally followe d the Al-tolerant group, except for shoot P concentration (lower) and root S concentration (higher) than the other genotypic groups. Mineral acquisition in shoots and roots of the sorghum genotypes used was not a good indicator for distinguishing tolerance to Al toxicity.