Photosynthetic parameters of young Brazil nut (Bertholletia excelsa H. B.) plants subjected to fertilization in a degraded area in Central Amazonia

In an experimental site for reforestation of degraded area, three-year-old plants of Bertholletia excelsa Humb. & Bonpl. were subjected to different fertilization treatments: T0 = unfertilized control, T1 = green fertilization (branches and leaves) and T2 = chemical fertilization. Higher net photosynthetic rates (P (N)) were observed in T1 [13.2 +/- 1.0 mu mol(CO2) m(-2) s(-1)] compared to T2 [8.0 +/- 1.8 mu mol(CO2) m(-2) s(-1)] and T0 [4.8 +/- 1.3 mu mol(CO2) m(-2) s(-1)]. Stomatal conductance (g (s)), transpiration rate (E) and water use efficiency (WUE) of individuals of T1 and T2 did not differ significantly, however, they were by 88, 55 and 63%, respectively, higher in T1 than in the control. The mean values of variable fluorescence (F-v), performance index (P.I.) and total chlorophyll [Chl (a+b)] were higher in T1. Our results indicate that green fertilization improves photosynthetic structure and function in plants of B. excelsa in young phase.