Interaction between aluminium and phosphorus in sorghum plants

Abstract

An experiment to test the response of seedlings of the Al-tolerant sorghum (Sorghum bicolor (L.) Moench) genotype SC0283 in culture solutions containing various levels of Al and P was conducted. Aluminium at a low level (0.4 mg L⁻¹) did not affect the biomass production of this genotype. At a high level (1.6 mg L⁻¹), however, Al severely inhibited plant growth mainly by inhibiting root development. Plant dry matter yield was usually enhanced by increasing the P supply. Under high Al stress, however, the positive effect of a high P supply no longer existed, probably because of enhanced accumulation of Al in/on its roots in close association with the P. In general, concentrations of both inorganic and organic P in the plants were increased by improving the P supply, particularly at high Al stress. Phosphorus deficiency differed from Al toxicity in its effect on root morphology, shoot/root ratio and P metabolism. This indicated that there was no Al-induced P deficiency in plants supplied with high Al and suboptimal P. In the absence of Al and at the low level of Al, increasing the P supply usually increased root respiration and nutrient uptake. At the high level of Al, however, only minor effects of P were observed, presumably due to the dominant influence of Al. In general, stress associated with high Al concentration significantly affected plant growth, root morphology and respiration, Al distribution and P metabolism of the Al-tolerant sorghum (genotype SC0283).