Characteristics of Acacia mangium shoot apical meristems in natural and in vitro conditions in relation to heteroblasty

PDF version of the authors can be published in January 2013International audienceMorphological and histocytological characteristics of Acacia mangium shoot apical meristems (SAMs) were assessed in natural and in vitro conditions in relation to heteroblasty. In the natural environment, SAMs with a mature-phyllode morphology were much bigger, contained more cells with larger vacuolated area, or vacuome, and lower nucleoplasmic ratios than those from the juvenile type (Juv). In these latter, nuclei appeared more voluminous, evenly and lightly stained, with clearly distinguishable nucleolei and less abundant chromocenters. In vitro, where reversions from mature to juvenile morphological traits do occur unpredictably, heteroblasty was less obvious in the SAM characteristics examined. In vitro SAMs corresponding to the juvenile and mature types showed similarities with outdoor Juv SAMs, but could be distinguished from these latter by a much larger vacuome that might be induced by the culture conditions. These findings encourage pursuing the investigations at the chromatin and nucleolus level in SAM zones where heteroblasty-related differences have been detected

Executive self, self-esteem, and negative affectivity: Relations at the phenotypic and genotypic level

Complementary approaches examined the relations among executive self, self-esteem, and negative affectivity. A cross-sectional (N = 4,242) and a longitudinal (N = 158) study established that self-esteem mediated the relation between executive self and negative affectivity. A 3rd study (N = 878 twin pairs) replicated this pattern and examined genetic and environmental influences underlying all 3 phenotypes. Covariation among the 3 phenotypes reflected largely common genetic influences, although unique genetic effects explained variability in both executive self and negative affectivity. Executive self was influenced by shared environmental influences unique from those affecting self-esteem and negative affectivity. Nonshared environmental influences accounted for the majority of variance in each construct and were primarily unique to each. The unique genetic and nonshared environmental influences support the proposition that the executive self, self-esteem, and negative affectivity capture distinct and important differences between people