Efficient and Inefficient Use of Phosphorus by Sorghum

Abstract Twelve ( Sorghum bicolor L. Moench) genotypes were grown on acid‐Bladen soil (pH 4.3, P stressed or Al toxic), on limed‐Bladen soil (pH 5.2, Cu stressed), and on alkaline Quinlan soil (pH 7.5, Fe stressed) to determine the effect of P efficiency on use of these clements by the plants. Under P‐stress or Al‐toxicity conditions, the most P‐efficient sorghum genotypes absorbed more 32P than the most P‐inefficient lines and grew normally, while the P‐inefficient plants developed P‐deficiency symptoms. Under Fe‐stress conditions, the most P‐efficient genotypes developed Fe chlorosis, while the most P‐inefficient plants remained green. Under Cu‐stress conditions, one of six genotypes developed severe Cu‐deficiency symptoms, characterized by the accumulation of higher P in the lower leaves, and by lower Fe and Ca in upper leaves of Cu‐stressed plants as compared with Cu‐sufficient plants. Thus, P efficiency in plants may be an asset when P availability limits growth, but it may be a liability when these same plants are subjected to Fe or Cu stress.