Comparative tolerance of sugarcane, navybean, soybean and maize to aluminium toxicity

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Abstract
The aluminium (Al) tolerance of three sugarcane (Saccharum spp.) cultivars was compared with one cultivar each of navybean (Phaseolus vulgaris), soybean (Glycine max), and maize (Zea mays) in a short-term solution culture experiment. The experiment was conducted under closely controlled conditions of pH (adjusted daily to 4.2 .+-. 0.02) and root temperature (28.degree. C) over a wide range of Al levels expressed as the sum of activities of monomeric Al species (mean .SIGMA.aAl mono 0, 4, 14, 54, and 222 .mu.M). The three sugarcane cultivars, Q77, Q113 and Q117, were found to be considerably more tolerant of Al in solution than were the other three species. At 14 .mu.M .SIGMA.aAl mono, toxicity symptoms on the sugarcane roots were slight, but were well developed on the roots of the other three species. At 220 .mu.M .SIGMA.aAl mono, the distance from the root tip to the first visible lateral was reduced by 9-30% in the sugarcane cultivars compared with 79% in maize and navybean, and 91% in soybean. Interpolation of curves fitted to root length data indicated critical (i.e., 10% total root length reduction) .SIGMA.aAl mono of 11-21 .mu.M for the sugarcane cultivars compared with 2.0 .mu.M, 1.8 .mu.M and 1.0 .mu.M for soybean, maize, and navybean, respectively. Implications for the management of sugarcane land are discussed briefly.