Ecophysiological responses of Araucaria angustifolia seedlings to different irradiance levels.

Abstract

Brazilian pine (Araucaria angustifolia [Bert.] O.Ktze.) is an indigenous conifer of the southern region of South America, typically regarded as a sun-loving species. However, there is insufficient information on the species’ behaviour under different irradiances to characterise its plasticity to light. The purpose of this work was to measure some ecophysiological responses of Brazilian pine seedlings to three irradiance levels: 100, 45 and 10% full sunlight. Thirty seedlings were grown under each of the irradiance treatments and, after 5 months, growth parameters, leaf chlorophyll concentration and in vivo nitrate reductase activity, in both leaves and roots, were analysed. There was no increase in shoot biomass allocation in response to shading, in contrast to results from other experiments. Only low-light seedlings showed significant increase in specific leaf area, as well as in the ratio of height to shoot biomass. Chlorophyll content and the ratio of chlorophyll a to chlorophyll b did not vary among treatments. Nitrate reductase activity was detected only in roots and was reduced in the low-light treatment. An overall analysis of the results points to a normal growth of Brazilian pine seedlings at both high- and medium-light sites, at least in their initial stages of development.

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

“…These results support the suggestions made by Franco et al (2005) that most of the N taken up from the soil is metabolized in the roots, and is consistent with the results of Duarte and Dillenburg (2000), who detected NRA only in the roots of A. angustifolia. Our study to the best of our knowledge, presents the first evidence of leaf NRA in this species.…”

“…Nitrate reductase activity: The in vivo NRA was measured 2 d after the last nutrient solution application, according to Klumpp et al (1989) and Duarte and Dillenburg (2000). Light conditions prior to analysis were the same for all sample units.…”

“…angustifolia, and Franco et al (2005) quantified carbon (C) and N in leaves, roots and stems of young and mature individuals and showed that, particularly for young plants, roots are important reservoirs of these elements. Duarte and Dillenburg (2000) detected very low NRA in young plants and found that the activity was concentrated in the roots, suggesting a NH 4 + -N preference by the species. These studies indicate an important role of roots in the C and N metabolism of the species.…”

THE SIZE OF Araucaria angustifolia (Bertol.) Kuntze ENTERING INTO REPRODUCTIVE STAGES AS A BASIS FOR SEED MANAGEMENT PROJECTS

“…Despite the great amount of studies on various ecological and biological aspects of A. angustifolia, including symbiotic associations (ZANDAVALLI et al, 2004), animal interactions (IOB;VIEIRA, 2008), demographics (SOLÓRZANO-FILHO, 2001;PUCHALSKY et al, 2006;SOUZA, 2007;SOUZA et al, 2008), dendrochronology (OLIVEIRA et al, 2009), and physiological development DILLENBURG, 2000), and in many other fields, many basic ecological questions regarding their population remain unanswered. For example, the creation of a production area for araucaria nuts demands basic ecological understanding on growth, sexual maturity and seed production of such individuals to establish adequate planting techniques.…”

Trade-offs among ecosystem services under different pinion harvesting intensities in Brazilian Araucaria Forests

“…The maintenance of A. angustifolia populations depend on its seedlings, which are shade-tolerant in the early development stages (Duarte, & Dillenburg 2000) but require light in the subsequent stages (Reitz, & Klein 1966). This behaviour normally results in a J-inverted distribution pattern, i.e., a high concentration of individuals in the smaller diameter classes and a sharp reduction towards larger classes (Paludo, et al 2009).…”