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Leaf senescence results in the recycling of nutrients, thereby providing resources required for growth and reproduction. In this study, the effect of day-length on leaf senescence in eight differentArabidopsis thalianaecotypes was determined and the relationship between senescence and other morphological and life history traits was analysed. A significant variation in the start and extent of leaf senescence depending on the genetic background and the response to day-length was found. Whereas senescence of early flowering ecotypes was accelerated by long days, no effect of day-length on senescence could be found in late flowering Kas-1 plants. Senescence in the different ecotypes was associated with other traits, such as floral transition, the total number of fruits, the total number of leaves and the maximum chlorophyll content. Plants that bolted early also senesced early, produced fewer leaves, accumulated less chlorophyll, but produced more fruits. The present results indicate that senescence may be a key component in the trade-off between investment in photosynthetic capacity and reproduction. The relationship between senescence and other traits was maintained independent of whether differences in senescence were caused by genetic (ecotype) or environmental (day-length) variation, suggesting that genetic and environmental factors affect these traits through common regulatory pathways. [ABSTRACT FROM AUTHOR]

Small-area differences in hospital use were examined using hospitaldischarge abstract data for the populations of seven small service areas in Iowa that exhibited substantial variation in admission rates during 1980. The results indicate (1) a marked difference in the age composition of the patient populations with older patients being more common among residents of high-use areas, (2) higher ageand sexadjusted discharge rates per 1000 in the high-use areas across many diagnostic categories, (3) frequently higher average lengths of stay in high-use areas, (4) a lack of conformity between discharge patterns for selected surgical procedures and diagnoses, and (5) more readmissions to the same hospital during a 12-month period for residents of high-use areas. This data set comprises one part of a study of smallarea differences that also employed household surveys, physician surveys, and other existing data sets. The findings illustrate the potential and limitations of hospital discharge abstracts as a data base for evaluating hospital discharge abstracts as a data base for evaluating hospital utilization differentials. [ABSTRACT FROM PUBLISHER]