MODELING CARBOHYDRATE PRODUCTION, STORAGE, AND EXPORT IN LEAFY AND NORMAL MAIZE (ZEA-MAYS L)

The structure of maize (Zea mays L.) canopies influences light interce ption, photosynthesis, and yield. A recently developed corn phenotype termed Leafy, which has additional leaves above the ear compared with normal phenotypes of the same maturity, is thought to provide a greate r source of photosynthates. The objective of this study was to develop a mathematical model to compare hybrid light interception, photosynth esis, carbohydrate storage, and export of carbohydrates from the leave s, based on measured leaf area distribution, leaf photosynthesis, and diurnal changes in leaf sugars and starches. Model simulations were ru n for two Leafy hybrids and a normal check hybrid, all grown at 6.5 an d 3.25 plants m(-2). A series of differential equations described how photosynthate was stored as leaf sugar and starch and then exported to stems. Rate coefficients were used to characterize diurnal changes in leaf carbohydrate concentration during early grain filling for differ ent hybrids and planting densities, Model fits to leaf sugar and starc h data were good (0.64 less than or equal to r less than or equal to 0 .89). Model calculations showed that storage of carbohydrates in leave s was relatively small compared with the total amount of leaf photosyn thate produced; more than 90% of the photosynthate was exported direct ly to the stem. Hybrid and planting density comparisons indicated that rate coefficients for the export of photosynthate from leaves increas ed with total plant dry matter, Leafy hybrids and hybrids grown at the lower plant density had greater plant dry weights, photosynthetic rat es, and leaf export rates than the check or hybrids grown at the highe r plant density.