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# Maximum Electron Transport Rate

## Key Points:

1. The LUNA model simulates the maximum electron transport rate (Jmax) based on nitrogen allocation, photosynthetically active radiation (PAR), day length, and air humidity.

2. The baseline electron transport rate (Jmax0) is calculated using the baseline proportion of nitrogen allocated for electron transport (Jmaxb0), the nitrogen use efficiency of Jmax (NUEJmax), and the fraction of nitrogen allocated to aboveground plant parts (FNCa).

3. The model includes functions to account for the impacts of day length (f(day length)) and relative humidity (f(humidity)) on Jmax.

4. The efficiency of light energy absorption (α) is calculated based on the amount of nitrogen allocated for light capture (Nlc) and the conversion factor from nitrogen to chlorophyll (Cb).

5. The actual electron transport rate (Jx) is calculated using the empirical expression of Leuning (1937), which incorporates the maximum photosynthetically active radiation (PARmax) and the maximum electron transport rate (Jmax).

## Equations:

1. Jmax = Jmax0 + Jmaxb1 f(day length) f(humidity) α PAR
2. Jmax0 = Jmaxb0 FNCa NUEJmax
3. f(day length) = (day length/12)^2
4. f(humidity) = (1 - exp(-H max(RH - RH0, 0) / (1 - RH0)))
5. α = 0.292 / (1 + 0.076 / (Nlc Cb))
6. Jx = (α PARmax) / ((1 + (α^2 PARmax^2 / Jmax^2))^0.5)