Here is a summary of the article:

## Resolving N Cost Across Simultaneous Uptake Streams

The total cost of nitrogen (N) uptake is calculated based on the assumption that carbon is partitioned to each uptake stream in proportion to the inverse of the cost of uptake. This means that more expensive pathways receive less carbon.

The key steps in this process are:

1. Calculate the "conductance" to N uptake (N_conductance) as the sum of the inverse of the cost for each uptake pathway.

2. Calculate the fraction of carbon allocated to each uptake pathway (C_frac,x) as the inverse of the N cost for that pathway divided by the total N_conductance.

3. Determine the N acquired from each uptake stream per unit C spent (N_exch,x) by dividing the C fraction by the N cost for that pathway.

4. Calculate the total N uptake per unit C spent (N_exch,tot) as the sum of the N_exch,x values.

5. The overall N cost (N_cost,tot) is then calculated as the inverse of the total N uptake per unit C.

Retranslocation of N is determined separately once the total N cost is known.

The key innovation here is the simultaneous consideration of multiple N uptake pathways, rather than just the cheapest one. This provides a more realistic representation of plant nitrogen acquisition.