Modeling cassava root system architecture and the underlying dynamics in shoot–root carbon allocation during the early storage root bulking stage

Background and aims

Plants store carbohydrates for later use during, e.g., night, drought, and recovery after stress. Carbon allocation presents the plant with tradeoffs, notably between growth and storage. We asked how this tradeoff works for cassava (Manihot esculenta) pre- and post-storage root (SR) formation and if manipulation of the number of storage organs and leaf growth rate might increase yield.

Methods

We developed a functional-structural plant model, called MeOSR, to simulate carbon partitioning underlying cassava growth and SR formation in conjunction with the root system’s three-dimensional (3D) architecture (RSA). We compared the model results to experimental data and simulated phenotypes varying in the number of SR and leaf growth rate.

Results

The simulated 3D RSA and the root mass closely represented those of field-grown plants. The model simulated root growth and associated carbon allocation across developmental stages. Substantial accumulation of non-structural carbohydrates (NSC) preceded SR formation, suggesting sink-limited growth. SR mass and canopy photosynthesis might be increased by both increasing the number of SR and the leaf growth rate.

Conclusion

MeOSR offers a valuable tool for simulating plant growth, its associated carbon economy, and 3D RSA over time. In the first month, the specific root length increased due to root branching, but in the third month, it decreased due to secondary root growth. The accumulation of NSC might initiate SR development in cassava. Cassava growth is relatively slow during the first 3 months, and a faster crop establishment combined with a greater SR growth might increase yield.