Effects of different nitrogen sources on growth, chlorophyll concentration, nitrate reductase activity and carbon and nitrogen distribution in Araucaria angustifolia

Abstract

The southern Brazilian highland plateau is a mosaic of two contrasting plant communities, Araucaria forests and grasslands, both differing in the relative abundances and spatial patterns of soil nitrate and ammonium. However, we still do not know the inorganic N preferences of one key species in this mosaic, Araucaria angustifolia, the dominant tree species in the Araucaria forests and an important tree species invading the adjacent grasslands. Growth responses measured in a greenhouse study demonstrated that the species prefers NH 4 + over NO 3 -as an inorganic N source. When provided alone, NO 3 -induced N deficiency symptoms: increases in root: shoot ratio, root branching and leaf mass per area, thickening of the shoot apexes and decreased mass-based chlorophyll and N concentrations of the young leaves. Nitrate-based nutrition also affected the whole plant N and carbon (C) distribution: young leaves accumulated less N and showed a larger C:N ratio than mature leaves. The nitrate reductase activity (NRA) followed the pattern of root: shoot partitioning expected for temperate climate conifers, i.e. activity concentrated in roots. However, the presence of NRA even under sole NH 4 + nutrition indicates that plants may show constitutive levels of the enzyme, or that low levels of NO 3 -(possibly formed by contamination of the growth media) can induce leaf NRA. We suggest that A. angustifolia uses ammonium as a preferential inorganic N source, and that this preference may favor a more successful establishment in grassland than in forest areas.Key Words: Araucariaceae, ammonium, inorganic nitrogen, nitrate, nitrogen deficiency. efeitos de diferentes fontes de nitrogênio no crescimento, concentração de clorofila, atividade de nitrato redutase e distribuição de carbono e nitrogênio em Araucaria angustifolia: o planalto sul-brasileiro apresenta um mosaico de duas comunidades vegetais contrastantes, florestas com Araucaria e campos, que diferem em suas abundâncias relativas e nos padrões espaciais de nitrato e amônio no solo. Entretanto, ainda não se conhecem as preferências quanto ao N inorgânico de uma espécie-chave neste mosaico, Araucaria angustifolia, a espécie arbórea dominante nas florestas com Araucaria e uma importante espécie florestal que invade os campos adjacentes. Respostas de crescimento medidas em um estudo em casa de vegetação demonstraram que a espécie prefere o NH 4 + ao NO 3 -, como fonte de N inorgânico. Quando fornecido isoladamente, o NO 3 -induziu sintomas de deficiência de N: aumentos na razão raiz:parte aérea, ramificação radicular e massa foliar por área, espessamento dos ápices caulinares e redução nas concentrações por unidade de massa de clorofila e N, nas folhas jovens. Uma nutrição baseada em nitrato também afetou a distribuição de N e C na planta como um todo: as folhas jovens acumularam menos N e mostraram uma maior razão C:N do que as folhas maduras. A atividade da redutase do nitrato (ARN) seguiu o padrão de partição entre raiz e parte aérea esperado para coníferas de clima temperado ...

Effects of soil water availability on foliar water uptake of Araucaria angustifolia

“…Despite important advances in the understanding of the ecophysiology of A. angustifolia (e.g., Inoue et al 1978;Duarte and Dillenburg 2000;Mósena and Dillenburg 2004;Korndörfer et al 2008;Garbin and Dillenburg 2008), very few studies examined the species' responses to variations in the availability of water in the environment. The study by Mósena and Dillenburg (2004) reported the expected growth reductions in response to water withdrawal, but the main focus of their study was on the interactive effects of soil compaction and drought.…”

Effects of Different NH4:NO3 Ratios on Growth and Nutrition Uptake in Iris germanica ‘Immortality’

“…In prairie gentian (Eustoma grandiflorum), the dry weight of leaf, stem, and shoot increased linearly with increasing NH 4 :NO 3 ratios (Mendoza-Villarreal et al, 2015). In addition, if available N form was not the one preferred by plants, then it may cause N-deficiency symptoms, such as lower dry biomass and larger root-to-shoot ratio (Garbin and Dillenburg, 2008). Thus, no changes of dry weight using different NH 4 :NO 3 ratios indicate TB iris may not have a preference for either ammonium or nitrate N form.…”

SLUDGE FROM RICE PARBOILING WASTEWATER TREATMENT PLANT AS ALTERNATIVE SUBSTRATE FOR THE PRODUCTION OF Araucaria angustifolia SEEDLINGS

“…Although nitrogen levels in the substrate mixtures were not measured in this work, the sludge chemical characterization (Table 1) shows that nitrate is present, which may have contributed for A. angustifolia seedlings growth. Nevertheless, Garbin and Dillenburg (2008) attested that this species assimilates inorganic nitrogen preferentially as ammonium. Vieira et al (2011) noticed that the sludge from rice parboiling wastewater treatment is rich in nitrogen (23.5 g kg -1 ) and phosphorus (42.4 g kg -1 ), which may support plant growth.…”