R/constants.R

In PhotoGEA: Photosynthetic Gas Exchange Analysis

# Here we define some constants so they can be used consistently across
# calculations in separate functions.

ISOTOPE_CONSTANTS <- list(
    a_b             = 2.9,       # ppt; isotopic fractionation during diffusion through the laminar boundary layer
    a_s             = 4.4,       # ppt; isotopic fractionation during diffusion through air
    a_m             = 1.8,       # ppt; isotopic fractionation during diffusion through water
    b               = 29,        # ppt; isotopic fractionation during Rubisco carboxylation
    b_prime_4       = -5.7,      # ppt; combined isotopic fractionation during CO2 dissolution, hydration, and PEPc activity at 25 degrees C
    delta_Ca_growth = -8,        # ppt; isotope ratio of ambient air during plant growth
    f_other         = 0.00474,   # dimensionless; fraction of CO2 that is not 13C16O16O or 12C16O16O
    R_VPDB          = 0.0111797, # dimensionless; Vienna Pee Dee Delemnite standard
    s               = 1.8        # ppt; isotopic fractionation during leakage from bundle-sheath cells
)