DIFFERENTIAL RESPONSE OF 2 TARO CULTIVARS TO ALUMINUM .2. PLANT MINERAL CONCENTRATIONS

One proposed mechanism of aluminum (Al)-tolerance involves the ability of plants to maintain uptake of essential mineral elements in the pre sence of Al. To examine this hypothesis, taro [Colocasia esculenta (L. ) Schott] cultivars (cv.) Lehua maoli and Bun long were grown in hydro ponic solution at six initial Al levels (0, 110, 220, 440, 890, and 13 30 muM Al), and plant mineral concentrations were determined after 27 days. Increasing Al levels significantly increased Al concentrations i n taro leaf blades, petioles, and roots. This increase in Al concentra tions in the leaf blades as solution Al levels increased was greater f or Al-sensitive cv. Bun long compared to cv. Lehua maoli, resulting in significant interaction between Al and cultivar effects. However, no significant cultivar differences were found for Al concentrations in t he petioles or roots. Increasing Al levels in solution significantly d epressed concentrations of calcium (Ca), magnesium (Mg), manganese (Mn ), and iron (Fe) in taro leaf blades, and significantly depressed conc entrations of Ca, Mg, copper (Cu), and zinc (Zn) in taro roots. Alumin um-induced Ca deficiency appeared to be one possible mechanism of Al p hototoxicity in taro, becvasue Ca concentrations in the leaf blades an d roots at the higher Al levels were within the critical deficiency ra nge reported for taro. Significant cultivar differences were found, in which Al-tolerant cv. Lehua maoli had significantly greater Ca and Cu concentrations in the roots, and significantly greater potassium (K) concentrations in the leaf blades across all Al levels. Our results sh ow that Al-tolerance in taro cultivars is associated with the ability to maintain uptake of essential mineral nutrients, particularly Ca and K, in the presence of Al.