THE DYNAMICS OF CORN CANOPY DEVELOPMENT: PHYTOMER ONTOGENY*

Abstract

Quantitative heat-sum relationships are needed for predicting, with most existing corn (Zea mays L.) models, leaf area expansion, sheath and internode extension, and the associated accumulation of dry matter. Plants taken from two experiments were dissected over time for measurements of such processes; values relative to maximum ones attained plotted well vs. plant growth stage (V-stage, or node of the youngest leaf showing a collar). Using such plots, it was possible to derive the V-stage units required for a new primordium to produce a new leaf tip or collar, as well as that for 5 percent of the total leaf area, emerged area, extended sheath and internode or dry matter to attain 50 or 95-100% of the final value. Internode weights, the area of the largest leaf, and the leaf blade weight/area ratio at silking were also tabulated for leave as is for several experiments involving different locations, planting dates, cultivars, and plant densities. The measured association between growth and developmental processes and V-stages and that measured or reported between V-stages and degree days will allow the use of degree day models for predicting these processes for a maize crop.