The results indicated that the synergistic or additive interactions among the components of the tripartite symbiotic association (Rhizobium-AMF-broad bean) increased plant productivity.

The influence of phosphorus (P) and nitrogen (N) supply on biomass, leaf area, photon saturated photosynthetic rate (P max ), quantum yield efficiency (α), intercellular CO 2 concentration (C i ), and carboxylation efficiency (CE) was investigated in Vicia faba. The influence of P on N accumulation, biomass, and leaf area production was also investigated. An increase in P supply was consistently associated with an increase in N accumulation and N productivity in terms of biomass and leaf area production. Furthermore, P increased the photosynthetic N use efficiency (NUE) in terms of P max and α. An increase in P supply was also associated with an increase in CE and a decrease in C i. Under variable daily meteorological conditions specific leaf nitrogen content (N L ), specific leaf phosphorus content (P L ), specific leaf area (δ L ), root mass fraction (R f ), P max , and α remained constant for a given N and P supply. A monotonic decline in the steady-state value of R f occurred with increasing N supply. δ L increased with increasing N supply or with increasing N L . We tested also the hypothesis that P supply positively affects both N demand and photosynthetic NUE by influencing the upper limit of the asymptotic values for P max and CE, and the lower limit for C i in response to increasing N.Additional key words: carboxylation efficiency; intercellular CO 2 concentration; leaf area; nitrogen use efficiency; photon saturated photosynthetic rate; quantum yield efficiency; root; stem.

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

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