ALUMINUM TOXICITY EFFECTS ON DURUM-WHEAT CULTIVARS

The effects of aluminum on biomass, nutrients and kinases were studied in two durum wheat cultivars (Triticum durum Desf. cvs Sapfo, Capeiti 82) grown in nutrient solutions (pH 4.5) at seven Al levels (0, 9.3, 18.5, 37.1, 74.1, 148, and 297-mu-M). The most evident Al toxicity symptom was a reduction in root growth. Sapfo showed greater Al tolerance than Capeiti 82. However, both cultivars must be characterized as Al-sensitives. Aluminum in the nutrient solution above 74.1-mu-M significantly (P<0.05) reduced root growth of both durum wheat cultivars. The concentration of 74.1-mu-M Al can be suggested for screening of durum wheats on the basis of tolerance to Al. The concentrations of the nutrients Ca, Mg, K, and Fe in the plant tissues of both cultivars decreased even at low Al levels. The decrease of Ca+2 content in leaves and roots of the two durum wheat cultivars was almost the same while the less sensitive cultivar Sapfo retained larger amounts of Mg+2 in roots and leaves compared with the more sensitive cultivar Capeiti 82. Yet, Sapfo retained at 297-mu-M Al larger amounts of Fe in roots and leaves as a percentage of the control (-Al) compared with Capeiti. The uptake of K+ in both cultivars tended to decrease under Al treatment. An indication is mentioned that protein kinases participate in plant responses to Al stress.