Senescence of maize plants: evolution of flowering to harvest

In monocarpic species such as corn, senescence of leaves is coordinated with that of the whole plant and influenced by the reproductive function. The objective of the present study was to describe the evolution of corn senescence along two axes: (1) the whole-plant axis, where all foliar stages were each considered as an entity, and (2) the foliar axis, where the dynamics of three macroscopic symptoms of senescence was considered on each leaf taken individually, according to zones from the apex to the base of the leaf lamina. From a corn field culture, leaves were sampled or whole plants were submitted to a follow-up, from flowering to harvest. Dynamics of water, dry matter, and chlorophyll contents were different along the leaf as well as between ranking of leaves. Moreover, plant chlorophyll content followed a more complex dynamics than that of water and dry matter. From a follow-up of discoloration along leaves of 15 stems from top to bottom, authors have established functional relationships describing the advance of the senescence front for each foliar rank from 7 to top (rank 15 or 16). This quantitative description can be used directly in crop models as well as structure-function plant models. This would allow estimation of leaf-senescence impact on light-radiation interception and, therefore, on photosynthesis and productivity. Results can also be used for interpretation of reflectance measurements on corn canopies by remote sensing.