Seasonal patterns in the phytochemistry of three Populus species

HOST PREFERENCE AND ALLOZYME DIFFERENTIATION IN SHOOT GALLING SAWFLY,EUURA ATRA

“…Salicaceae species are characterized by the existence of lower-molecular weight phenolic glucosides; each willow species appears to contain a characteristic total amount and composition of these glucosides (Julkunen-Tiitto 1989a, 1989b. There is a lot of evidence that phenolic glucosides ofSalicaceae species constitute a multifunctional role in plant-herbivore interactions (Markham, 1971;Smiley et al, 1985;Tahvanainen et al, 1985aTahvanainen et al, , 1985bLindroth et al, 1987;Rowell-Rahier and Pasteels, 1986;Clausen et al, 1989). Since phenolic glucosides are ecologically important secondary metabolites we selected them for screening of chemical similarity of willows.…”

Age-Related Shifts in Leaf Chemistry of Clonal Aspen (Populus tremuloides)

“…Samples were collected as described above, i.e., 5-10 leaves from at least three locations within the canopy. To avoid the potentially confounding effect of within year variation in chemistry (Lindroth et al, 1987;Riipi et al, 2002), only fully expanded source leaves were used in chemical analyses. Ramet age was determined by counting annual growth rings on cut ends or, for larger ramets, by averaging ring counts from two tree cores made with an increment borer.…”

“…Within-plant differences in chemical defense can occur as a result of induction (Karban and Baldwin, 1997), leaf maturation (Lindroth et al, 1987;Riipi et al, 2002), somatic mutations in meristematic tissues (Suomela and Ayres, 1994;Gill et al, 1995;Tuskan et al, 1996), and through the process of ontogenetic maturation from juvenile to adult phase (Bryant and Julkunen-Tiitto, 1995;Karban and Thaler, 1999;Erwin et al, 2001;Boege and Marquis, 2005;Laitinen et al, 2005. Within-species variation in plant chemistry can affect ecological interactions and ecosystem processes. For example, primary plant compounds such as protein and water are critical for herbivore growth and development (Awmack and Leather, 2002), and qualitative or quantitative variation in phytochemical defenses within a species also strongly influences herbivore behavior and performance (Crawley, 1983;Schultz, 1988;Shelton, 2000).…”

Plantas medicinais: fatores de influência no conteúdo de metabólitos secundários

“…Os carrascos gregos, por ex., coletavam suas amostras do veneno cicuta (Conium maculatum) pela manhã, quando os níveis de coniina são maiores 1,2 . Variações temporais e espaciais no conteúdo total, bem como as proporções relativas de metabólitos secundários em plantas ocorrem em diferentes níveis (sazonais e diárias; intraplanta, inter-e intraespecífica) e, apesar da existência de um controle genético, a expressão pode sofrer modificações resultantes da interação de processos bioquímicos, fisiológicos, ecológicos e evolutivos [3][4][5][6][7] . De fato, os metabólitos secundários representam uma interface química entre as plantas e o ambiente circundante, portanto, sua síntese é freqüentemente afetada por condições ambientais 8 .…”