Plants use two different networks to transport resources throughout their body: the xylem for water transport from the roots to the shoots; and the phloem mainly for transportation of photosynthesis products. Whereas xylem transportation is only upward, phloem is less isotropic. Sieve movements in the phloem are powered by turgor pressure differences between parts of the plants body. One important solute to create turgor pressure is sucrose. Sites of sucrose production (sources) such as leaves, load the phloem with sucrose increasing in turn its turgor pressure. Sucrose consumption sites (sinks) such as shoots, fruits or roots, unload the phloem decreasing its turgor pressure. Due to that sieve flows naturally from sources to sinks.

We applied mathematical modeling to sucrose transportation in trees. In the case of trees it is of particular interest as they can have very diverse size and complexity and so the phloem has to fulfill its task properly despite the very different constraints.

In this talk I explain how we formalize a tree as a binary branching network and study the effect of its size and complexity on the transport of sucrose using computer simulations.