Differential Response of Two Corn Inbreds to Varying Root Temperature 1

Root temperature is a factor which greatly affects corn ( Zea mays L.) growth. However, little information is available concerning the relative responses of different genotypes to changes in temperature. Two experiments were done to gather this information. The purpose of the first experiment was to compare the growth of 12 inbreds in nutrient solutions maintained at 14.8, 19.4, 23.9, and 28.2 C. Air temperature ranged from 23.9 to 32.2 C. Several lines developed an abnormality in growth that resembled Ca deficiency as the root temperature was increased. The ND33 line was most severely affected by root temperature. The abnormality developed first and was most severe at 28.2 C, was least severe at 19.4 C, and did not occur at 14.8 C. The ND203 line grew normally but its growth was greatly stimulated by increasing root temperature. The objective of a second experiment was to learn the cause of the root‐temperature dependent abnormality. The ND33 and ND203 lines were grown in nutrient solutions maintained at 14.8 and 28.2 C. The ratios of top growth at 28.2 C to that at 14.8 C for ND203 and ND33 after 4 weeks were 7.8 and 1.7. Percentage Ca in the tips of the youngest three unfurled blades of both inbreds at 2 weeks was less at 28.2 C. The ND33 line contained lower concentrations of leaf‐tip Ca than ND203. In contrast, whole plant Ca percentage were larger at 28.2 C and ND33 contained higher concentrations than ND203. We hypothesize that the rapidly growing, newly emerging leaves of ND33 were affected by Ca deficiency at the higher root temperature. The results suggest that attention should be paid to genotype when corn‐root temperature studies are being planned.