Seasonal Patterns and Genotypic Differences in Phosphofructokinase Activity in Corn (Zea mays L.) Leaf Blades1

Abstract

Phosphofructokinase (ATP: D‐Fructose‐6‐phosphate‐lphosphotransferase, E. C. 2.7.1.11) activity was assayed in a four‐parent diallel cross of corn (Zea mays L.) to determine if there were seasonal changes and genotypic differences in enzymatic activity in leaf blade tissue. Tissue was assayed every week from 2 weeks after seedling emergence until 5 weeks after silking. Seasonal patterns of phosphofructokinase (PFK) activity were found to be similar for all genotypes. A split‐plot‐in‐time statistical analysis showed the effect of time to be highly significant. There was a rapid increase in activity during the first few weeks after seedling emergence, a drop in activity near silking, and a slight increase in activity during the period when starch accumulation in kernels was initiated. When PFK activity was compared at each weekly sampling, the genotype effect was nonsignificant. However, some significant differences were observed when seasonal means for PFK activity in each genotype were compared, even though the range in seasonal means was small.