Dynamics of the Elongation of Internodes in Maize (Zea mays L.). Effects of Shade Treatment on Elongation Patterns

Abstract

The dynamics of elongation of individual maize internodes have previously been characterized under standard agronomic conditions. In this paper these dynamics are compared with those under a shading treatment. Shading was applied after the tip appearance of leaf 6, using a black net that transmitted 20% of light, without altering spectral composition. Internode length was determined as a function of thermal time by measuring the vertical displacement of individual leaf collars. Shading slowed plant development and caused significant reductions in internode length. The onset of the linear phase of elongation was delayed by shading, but its duration was not affected. The reduction in the linear elongation rate was almost totally responsible for the reduction in the final length of phytomers in the shade treatment. The co-ordination between collar emergence and the onset of linear elongation remained. These results support the contention that the kinetics of internode elongation are controlled by the emergence of leaf collars.