Aluminum Accumulation and Tolerance of Triticale and Wheat in Relation to Root Cation Exchange Capacity1

Since plant characteristics associated with Al tolerance vary from one species to another, the objective this study was to relate Al tolerance, Al accumulation, root Cation Exchange Capacity (CEC), and exchangeable Al in triticale (X Triticosecale, Witt Mack) and wheat (Triticum aestivum L.). Ten cultivars of the two species were grown in nutrient solutions with 0 or 6 ppm Al added. The solutions were adjusted to pH 4.8 either at transplanting or daily during plant growth. Aluminum accumulation and displacement by Ca and K from roots exposed to Al for up to 24 hours were also determined. With the solution pH adjusted only at transplanting, the relative root lengths (Al/no Al) indicated that the order of Al tolerance was 6TA 298 and 6TA 131 > 6TA 385 > 6TA 203 triticale and Atlas 66 > Thorne and Seneca > Monon > Redcoat and Arthur wheats. Similar Al tolerance ratings were obtained when solutions were adjusted daily to pH 4.8. Correlation coefficients between relative root lengths and root Al concentrations were −0.93** and −0.90** for triticale and −0.85** and −0.063 for wheat, respectively with pH unadjusted and pH adjusted. Correlation coefficients between plant-induced pH values and root Al concentrations were −0.19 for triticale and −0.79** for wheat. The root CEC values were generally lower in Al-tolerant than Al-sensitive cultivars. The results also suggested that the CEC of roots may be a factor in controlling Al absorption in the first 6 hr of plant exposure before the exchange sites are Al-saturated at longer periods.