Interrelationships Between Nitrogen Supply and Photosynthetic Parameters in Vicia faba L

We determined for Vicia faba L the influence of nitrogen uptake and accumulation on the values of photon saturated net photosynthetic rate (PNmax), quantum yield efficiency (α), intercellular CO2 concentration (Ci), and carboxylation efficiency (Ce). As leaf nitrogen content (NL) increased, the α converged onto a maximum asymptotic value of 0.0664±0.0049 μmol(CO2) μmol(quantum)−1. Also, as NL increased the Ci value fell to an asymptotic minimum of 115.80±1.59 μmol mol−1, and Ce converged onto a maximum asymptotic value of 1.645±0.054 μmol(CO2) m−2 s−1 Pa−1 and declined to zero at a NL-intercept equal to 0.596±0.096 g(N) m−2. α fell to zero for an NL-intercept of 0.660±0.052 g(N) m−2. As NL increased, the value of PNmax converged onto a maximum asymptotic value of 33.400±2.563 μmol(CO2) m−2 s−1. PN fell to zero for an NL-intercept of 0.710±0.035 g(N) m−2. Under variable daily meteorological conditions the values for NL, specific leaf area (δL), root mass fraction (Rf), PNmax, and α remained constant for a given N supply. A monotonic decline in the steady-state value of Rf occurred with increasing N supply. δL increased with increasing N supply or with increasing NL.