Relationships between internode elongation, plant height and leaf appearance in maize

Abstract

Abstract Two field studies were undertaken to formulate relationships between leaf appearance, leaf height and plant height in maize which could be used in models of light competition in intercropping systems. In the first study a single hybrid was subjected to three water-stress treatments: mild stress, severe stress and well-watered conditions. Leaf appearance and length of individual internodes, sheaths and leaves were measured at frequent intervals. The aim was to describe the underlying growth processes linking plant height with leaf appearance. The study showed that for the upper two-thirds of the nodes on the plants, the duration of elongation of sheaths and internodes was 4.1 and 5.8 phyllochron (defined as the time interval between the appearance of successive leaves), respectively. Water stress had little impact on the duration of elongation. The increase in leaf height (the apparent insertion point of the laminae) attained after full expansion was due to continued elongation of internodes below it. In the second study seven genotypes, ranging in final leaf number from 16 to 20, were measured for leaf appearance, leaf height and plant height. The aim was to develop, across genotypes, relationships to predict leaf height as a function of leaf appearance and final leaf number. Across all genotypes a consistent relationship was found between plant height increase and leaf appearance, with height increasing at a slow initial rate until the appearance of leaf 7, afterwards height increased at 5 times the initial rate until appearance of the flag leaf. A consistent relationship was also found to describe further increase in leaf height after full expansion. This study showed that height of individual leaves in maize can be related throughout growth to leaf appearance and final leaf number. Therefore, vertical distribution of maize leaf area can be predicted in crop growth models relatively easily from leaf appearance, final leaf number and additional information of leaf sizes and angles.