The effects of developmental stage and source leaf position on integration and sectorial patterns of carbohydrate movement in an annual plant, Perilla frutescens (Lamiaceae).

A well-integrated plant shows extensive carbohydrate translocation through the plant body. Even in highly integrated plants, however, translocation patterns will be sectorial if vascular tissue restricts carbon movement to sectors along stems. Both integration and sectorial translocation patterns are sensitive to plant architecture and thus may change as a plant develops. These patterns should vary also with the position of the source leaf because leaves at each node are unique in age and vascular relationship to the rest of the plant. I measured the effects of developmental stage and location of the source leaf on integration and sectoriality in an annual plant, Perilla frutescens, by labeling plants with C at one of three leaves and four developmental stages. Stage and source leaf affected both integration and sectoriality. Most notably, integration declined and sectoriality increased during seed fill, when resource demand at each node was high. Furthermore, translocation was least extensive from the leaf supporting the largest number of seeds on its axillary branch. These results suggest that plants are not homogeneous collections of subunits; rather, the role of each leaf in a plant's carbon budget is a function of its age and location on the plant.

Visual hierarchical analysis of Block Design configural errors.

Patients have been frequently observed to violate the overall configuration on the WAIS-R Block Design subtest. The significance of these configural errors was investigated with hierarchical patterns consisting of large "global" shapes made from smaller "local" shapes. Subjects were administered two similarity judgment tasks in which they were asked to decide which of two hierarchically structured comparison figures most resembled a standard figure. Results indicated that subjects who made configural errors on Block Design were less likely than a matched sample who did not make configural errors to select the comparison figure that resembled the standard figure at the global level. Furthermore, the present findings were obtained from subjects without known right-hemisphere lesions, suggesting that the correlation between Block Design errors and global/local performance is applicable to a broad range of patient and non-patient populations. The data are consistent with the view that errors on Block Design may reflect differences in the perceptual encoding of global/local features.

The premature aging hypothesis: old before its time?

This study tested the hypothesis that alcoholism results in premature aging of memory functioning. It was proposed that support for the premature aging hypothesis must come from qualitative as well as quantitative similarities between younger alcoholics and older controls. The California Verbal Learning Test (CVLT) was administered to young and old alcoholics and to young and old controls. The CVLT provides measures of recall, recognition, learning strategies, and error types. Alcoholism and aging produced similar levels of immediate and delayed free recall. However, poor recognition memory and more frequent intrusion and false positive errors were associated with alcoholism but not with aging. Qualitative differences in error types between alcoholism and aging were also found. Results indicated that alcoholism and aging produce independent verbal learning decrements.