SHORT-TERM EFFECTS OF PH AND ALUMINUM ON MINERAL-NUTRITION IN MAIZE VARIETIES DIFFERING IN PROTON AND ALUMINUM TOLERANCE

In short-term (24 h) nutrient solution experiments, the influence of d ifferent proton (pH 6.0 and pH 4.3) and aluminium (Al) (0, 20, and 50 mu M) concentrations on root and coleoptile elongation, dry weight, an d the uptake of selected mineral nutrients was studied in maize (Zea m ays L.) varieties that differ in acid soil tolerance under field condi tions. The acid-soil-tolerant maize varieties, Adour 250 and C525M, pr oved to be hydrogen (H+) ion sensitive, but Al tolerant, while the aci d soil tolerant variety BR201F was H+ tolerant but Al sensitive. The a cid soil sensitive variety HS 7777 was affected by both H+ and Al toxi city. The proton-induced inhibition of root elongation was closely rel ated to the proton-induced decrease of the specific absorption rates ( SAR) of boron (B), iron (Fe), magnesium (Mg), calcium (Ca), and phosph orus (P). In contrast, only the specific absorption rate of B (SARB) w as significantly correlated to the Al-induced inhibition of root elong ation. It is concluded, that alterations of nutrient uptake may play a n important role in H+ toxicity, while at least after short-term expos ure to Al, alterations of Ca, Fe, Mg, or P uptake do not seem to be re sponsible for Al-induced inhibition of root elongation. Further attent ion deserves the Al-B interaction, moreover taking into account that a highly significant correlation between Al-induced increase of callose concentration in root tips and Al-induced decrease of SARB could be e stablished.