Tuesday, November 14, 2006

Linking Leaf Expansion and Senescence with Allocation of Carbon Resources on a Per-Leaf Basis in Maize.

Jon I. Lizaso1, Kenneth J. Boote2, and James W. Jones2. (1) Univ of Florida, Dept of Agronomy, PO Box 110500, Gainesville, FL 32611, (2) Univ of Florida, Dept of Agronomy, PO Box 110500, Gainesville, FL 32611

In previous work, we developed a maize (Zea mays L.) leaf area simulation model calculating expansion and senescence on a per-leaf basis. We also developed a layered leaf-to-canopy photosynthesis and respiration model calculating the daily assimilate contributions of each leaf. To continue model development we wanted to simulate nitrogen dynamics on a per-leaf basis and to link N and photosynthesis processes. To do that, we needed to simulate individual leaf biomass. In the present work we linked the daily allocation of carbon resources with leaf area expansion and senescence processes for each individual leaf.  The above-mentioned leaf area model was linked to an in-house new maize model adapted from the CSM-CERES distributed with DSSAT 4.0. Specific leaf area (SLA) per-leaf was calculated considering the effects of irradiance and temperature. Individual leaf demand for assimilates in growing leaves was then obtained by dividing the leaf area growth rate by the specific leaf area. When the daily supply of assimilates is not enough to provide the potential demand of organs, carbon allocation is limited to the actual supply and leaf expansion is reduced to maintain the calculated SLA. The model also has functions to increase carbon partitioning to roots under water or nitrogen stresses. The model was tested using field measurements of individual leaves in experiments where population densities were varied in the range 7-22 plant m-2. Our results showed reasonable accuracy when the simulated leaf area and leaf dry weights were compared against individual leaves and against whole canopies.