Heitor Monteiro Duarte

Hypersensitivity of Fagus sylvatica L. against leaf galling insects

Hypersensitivity is known as a localized resistance of plants against pathogens. It also can be detected in response to galling insects, i.e., in the area immediately adjacent to the site of oviposition and attempted penetration by the galling larva. This host response includes morphological and histological changes that cause the death of the attacked tissue. It is observed as a rounded dark brown halo around the gall induction site. We provide the first observation on the occurrence and possible relevance of this induced mechanism by which one of the most common tree species in Germany, Fagus sylvatica L., resists attack by two of its most common galling insects, Mikiola fagi and Hartigiola annulipes (Diptera: Cecidomyiidae). Galls induced by these cecidomyiids were extremely common in the studied area in beech forests around Darmstadt, Germany. The availability of resources (leaves on a stem) was a poor predictor of attack by the galling insects as well as for gall abundance (galls successfully formed). Hypersensitive reaction was the most important factor acting against the galling population studied. More than 77% of the attempts of the insects to induce galls on F. sylvatica resulted in failure and consequently the death of the galling larvae. Therefore, few live galls remained to be found and destroyed by natural enemies. This corroborates the view that in galling insect–host plant system interactions plant-driven factors may play a major role in determining herbivore failure and success, and perhaps the resulting community structure.

Ecophysiology of selected tree species in different plant communities at the periphery of the Atlantic Forest of SE Brazil I. Performance of three different species of Clusia in an array of plant communities

Three species of Clusia, namely two CAM-species (C. hilariana Schlecht. and C. fluminensis Planch. et Triana) and a C3-species (C. parviflora Saldanha et Engl.) were studied in different plant communities at the periphery of the Atlantic Forest in the state of Rio de Janeiro, Brazil. The sites chosen were an inselberg (C. parviflora), a range of wet restinga – dry restinga – semideciduous dry forest (C. fluminensis), and a gradient from the sea shore inland with a first sand dune beach ridge – a dry forest – a second beach ridge (C. hilariana). Analyses comprised C and N contents, soluble carbohydrates, soluble nonprotein N compounds and carbon isotope ratios (δ13C) in leaves, roots, phloem and wood. Photosynthetic performance was assessed by chlorophyll fluorescence with measurements of instant photosynthetic yield as well as light dependence and potential quantum-use efficiency of photosystem II.The data allow, first, to discuss differences between the ecophysiological performance of C3- and CAM-species of Clusia. The C3-species, C. parvifolia, had an overall weaker performance than the two CAM-species, where, however, the effects of mode of photosynthesis may have been overlaid by site conditions. Second, it was studied whether ecophysiological performance relates to patterns of local abundance, which was confirmed by showing that the dominant Clusia species of the restingas, C. hilariana, showed the strongest performance overall.Finally, it was studied whether the ecophysiological performance varied in response to site-dependent gradients of environmental water relations, which was confirmed for functions such as photosynthetic capacity, photoinhibition and solute accumulation of C. hilariana and C. fluminensis in relation to moisture of sites.

In situ measurements of carbon and nitrogen distribution and composition, photochemical efficiency and stable isotope ratios in Araucaria angustifolia

Araucaria angustifolia (Bertol.) Kuntze is an indigenous conifer restricted to the southern region of South America. In this on-site field study, we provide a detailed description of the nitrogen compounds and sugars allocated to the different plant compartments in tall adult trees, young trees about 2–3 m tall and small seedlings at its northernmost occurrence in the mountains of Itatiaia (20°25′S; 44°50′W; 2,000 m a.s.l.), SE Brazil. We determined C and N contents, soluble sugars, soluble non-protein N-compounds and δ15 N-signatures in leaves, roots, wood of stems, xylem- and phloem- sap. We also measured chlorophyll a fluorescence of photosystem II and carbon isotope discrimination reflecting photosynthetic activity and water-use efficiency. The high C and N concentrations in fine roots suggest that they are important reservoirs of N and C. Most nitrogen taken up from the soil was metabolised in the roots. The only inorganic nitrogen form detectable in the xylem sap was a small amount of ammonium. Glutamine was the dominant transport form of nitrogen in the xylem, while glutamate and the amides glutamine and asparagine were the most abundant soluble N compounds in the phloem. Total soluble non-protein N and sugar concentrations were significantly higher in the phloem of adult trees. In this particular site, A. angustifolia was apparently not exposed to water stress, as indicated by the high values of carbon isotope discrimination. The three developmental stages were clearly separated in terms of photosynthetic performance. Indeed, effective quantum yield of photosystem II increased from seedlings to adult trees under ambient irradiance.

Physiological synecology of tree species in relation to geographic distribution and ecophysiological parameters at the Atlantic forest periphery in Brazil: an overview

This paper provides a synthesis of the three papers published in the series “Ecophysiology of selected tree species in different plant communities at the periphery of the Atlantic forest of SE – Brazil” (Trees, this issue). We reviewed data obtained for seven tree species, belonging to the legume family and the genus Clusia of the Clusiaceae. These groups were chosen because legumes are the most abundant tree species in the Atlantic forest complex (except in the open restingas), and the genus Clusia is reportedly of utmost ecological importance as nurse plants in several habitats of the complex. These species were surveyed along one or more of several forest and open habitats at the margin of the Atlantic rain forest (open restingas, restinga dry forest, inselberg, semideciduous dry forest) and indicated the following general patterns: (1) at the intraspecific level, ecophysiological performance often (but not always) varied largely in both time and space; (2) at the interspecific level, ecophysiological performance was often (but not always) related positively to species dominance in the community; and (3) at both levels, ecophysiological performance was not related to the geographic distribution patterns, i.e., generalists and specialists did not form groups of similarly behaving plants in regard to ecophysiology. We discuss the implications of these findings, compare them with earlier studies, and suggest that ecophysiological research in the Atlantic rain forest complex could enhance its explanatory power by increasing spatial and temporal scales of observation.

Expression of crassulacean acid metabolism in Clusia hilariana Schlechtendal in different stages of development in the field

Expression of crassulacean acid metabolism (CAM) in the obligate CAM-tree Clusia hilariana SCHLTDL. was studied in the restinga of Jurubatiba National Park, on the Atlantic coast of Rio de Janeiro state, Brazil, comparing plants at different developmental stages. Between young and mature plants there were trends of differences in six parameters, which are all related to CAM expression. From young to mature plants there were tendencies for a decrease of (1) the degree of succulence, (2) the degree of day/night changes of malic acid levels, (3) titratable acidity with nocturnal acid accumulation, (4) the degree of day/night changes of free hexoses with nocturnal break down, (5) effective quantum use efficiency of photosystem II at high photosynthetic photon flux density, and (6) protection from photoinhibition. These tendencies form a clear pattern which suggests that CAM was somewhat more pronounced in leaves of young plants than in leaves of mature plants. A developmental regulation may be involved. However, the observations are probably best explained by stress, since in the dry soils of the restinga young plants have no access to the ground water table while adult trees develop extensive root systems.

Morphology, Anatomy, Life Forms and Hydraulic Architecture

The 300 to 400 woody species of Clusia all display one typical morphotype (Luttge 2000). Clusias are branched shrubs and trees with dichasial cymes and opposite leaves (see also Sect. 6.1). Among the various species leaves vary in absolute size. However, the leaves of all species are morphologically and anatomically very similar, always entire, leathery and somewhat succulent (Fig. 2.1). In view of the important effects of leaf form and structure on photosynthesis and ecophysiological performance (Niinemets and Sack 2005), this is remarkable particularly with respect to the large photosynthetic flexibility of some species of Clusia. However, this has not been much explored for Clusia. On the other hand, floral morphology of Clusias is rather variable (Sect. 6.5).

Geographic Distribution of Natural Products Produced by the Red Alga Laurencia dendroidea J. Agardh

In order to evaluate the chemical diversity of Laurencia dendroidea J. Agardh, a widely distributed seaweed in Brazilian coast, a phytochemical study was carried out with algae collected from six different locations along the Southeast Brazilian coast. Purified compounds were identified by MS and NMR techniques. The chemical profiles of lipophilic extracts were obtained by GC/MS for each population. In total, 15 compounds were described. The sesquiterpene composition accounted for 49 – 63% of the GC/MS chromatogram area. The discrimination of three chemotypes was done by the use of HCA on GC/MS chromatograms. They were also analyzed by the PCA and, together with peak area analysis, it was possible to discriminate all populations by the main variation of elatol, obtusol, rogiolol, and triquinane. The results revealed the high diversity of sesquiterpene composition among populations of L. dendroidea. Curiously, the within and among population variation of elatol and obtusol suggested a biochemical interplay on the content of these compounds. More studies are necessary to understand the patterns of chemical diversity and compound variation within and among populations of L. dendroidea.