Phosphorus deficiency is responsible for biomass reduction of triticale in nutrient solution with aluminum

Plants of triticale (X Triticosecale, Wittmack) cultivars Arabian, Beagle, and TTE 9201 were submitted to aluminum (Al) treatments applied as Al(SO4)(3) . 16H(2)O in a nutrient solution adjusted to pH 4, in concentrations of 0, 370, 555, and 740 muM. The plants were harvested at the end of the biological cycle showing stronger dry matter inhibition in the shoot than in the root. The increasing order of tolerance among cultivars was Arabian, Beagle, and TTE 9201. The concentration of phosphorus (P), calcium (Ca), and magnesium (Mg) decreased in the leaves whereas manganese (Mn) and zinc (Zn) increased. The Al in the shoot represents 0.5% of the root concentration. The translocation of P and nitrogen (N) was also affected because the fraction of these minerals found in the root or shoot (respectively, for P and N) was higher in the Al-treated plants. The relationship between biomass produced and a range of P, Ca, and Mn concentrations in leaves was obtained from another set of experiments designed to define critical foliar concentrations of these elements associated with biomass inhibition. These critical concentrations were 3 mg g(-1) dw for P in young plants and 1.5 mg g(-1) dw in mature plants, 1-2 mg g(-1) dw for Ca, and 2.5 mg g(-1) dw for Mn toxicity. Such concentrations are valuable for diagnosis of the mineral element which probably is limiting growth in acid soils which currently have problems with excess Al and Mn and low Ca and P, Phosphorus deficiency was probably the most important limiting factor in acid nutrient solutions with Al that have been used in previous and present experiments with triticale.