Biomass accumulation, photochemical efficiency of photosystem II, nutrient contents and nitrate reductase activity in young rosewood plants (Aniba rosaeodora Ducke) submitted to different NO3-:NH4+ ratios

• Published in: Acta amazonica 2007, Vol.37 (4), p.533-541
• Main Authors: Barreto, Denize Caranhas de Sousa(Instituto Nacional de Pesquisas Laboratório de Fisiologia e Bioquímica Vegetal), Gonçalves, José Francisco de Carvalho(Instituto Nacional de Pesquisas), Santos Júnior, Ulysses Moreira dos(Instituto Nacional de Pesquisas Laboratório de Fisiologia e Bioquímica Vegetal), Fernandes, Andreia Varmes(Instituto Nacional de Pesquisas Laboratório de Fisiologia e Bioquímica Vegetal), Bariani, Adriana(Instituto Nacional de Pesquisas Laboratório de Fisiologia e Bioquímica Vegetal), Sampaio, Paulo de Tarso Barbosa(Coordenação de Pesquisas em Silvicultura Tropical)
• Format: Article
• Language: English
• Subjects: Chlorophyll a fluorescence; Chloroplastid pigments; Espécie arbórea; Fluorescência da clorofila a; Pigmentos cloroplastídicos; Tree species
• ISSN: 0044-5967; 0044-5967
• DOI: 10.1590/S0044-59672007000400008

The rosewood (Aniba rosaeodora Ducke) is a native tree species of Amazon rainforest growing naturally in acidic forest soils with reduced redox potential. However, this species can also been found growing in forest gaps containing oxide soils. Variations in the forms of mineral nitrogen (NO3- or NH4+) may be predicted in these different edaphic conditions. Considering that possibility, an experiment was carried out to analyze the effects of different NO3-:NH4+ ratios on the growth performance, mineral composition, chloroplastid pigment contents, photochemical efficiency photosystem II (PSII), and nitrate redutase activity (RN, E.C.1.6.6.1) on A. rosaeodora seedlings. Nine-month-old seedlings were grown in pots with a washed sand capacity of 7.5 kg and submitted to different NO3-:NH4+ ratios (T1 = 0:100%, T2 = 25:75%, T3 = 50:50%, T4 = 75:25%, and T5 = 100:0%). The lowest relative growth rate was observed when the NO3-:NH4+ ratio was equal to 0:100%. In general, high concentrations of NO3- rather than NH4+ favored a greater nutrient accumulation in different parts of the plant. For the chloroplastid pigment, the highest Chl a, Chl b, Chl tot, Chl a/b and Chl tot/Cx+c contents were found in the treatment with 75:25% of NO3-:NH4+, and for Chl b and Cx+c it was observed no difference. In addition, there was a higher photochemical efficiency of PSII (Fv/Fm) when high NO3- concentrations were used. A linear and positive response for the nitrate reductase activity was recorded when the nitrate content increased on the culture substrate. Our results suggest that A. rosaeodora seedlings have a better growth performance when the NO3- concentrations in the culture substrate were higher than the NH4+ concentrations. O pau-rosa (Aniba rosaeodora Ducke) habita, naturalmente, solos florestais ácidos com potencial redox reduzido. No entanto, estas espécies têm sido encontradas também em clareiras que, teoricamente, apresentam solos mais oxidados. Nestas diferentes condições edáficas, pode-se prever variações nas formas do nitrogênio mineral (NO3- ou NH4+). Considerando essa possibilidade foi conduzido experimento com o objetivo de estudar os efeitos de diferentes relações de NO3-:NH4+ sobre o acúmulo de biomassa, a composição mineral, as concentrações de pigmentos cloroplastídicos, a eficiência fotoquímica do fotossistema II e a atividade da enzima redutase do nitrato (RN, E.C.1.6.6.1) em A. rosaeodora. Plantas jovens com nove meses foram cultivadas em vasos com capacidad