Interaction of plant growth regulators and reactive oxygen species to regulate petal senescence in wallflowers (Erysimum linifolium)

Background In many species floral senescence is coordinated by ethylene. Endogenous levels rise, and exogenous application accelerates senescence. Furthermore, floral senescence is often associated with increased reactive oxygen species, and is delayed by exogenously applied cytokinin. However, how these processes are linked remains largely unresolved. Erysimum linifolium (wallflower) provides an excellent model for understanding these interactions due to its easily staged flowers and close taxonomic relationship to Arabidopsis. This has facilitated microarray analysis of gene expression during petal senescence and provided gene markers for following the effects of treatments on different regulatory pathways. Results In detached Erysimum linifolium (wallflower) flowers ethylene production peaks in open flowers. Furthermore senescence is delayed by treatments with the ethylene signalling inhibitor silver thiosulphate, and accelerated with ethylene released by 2-chloroethylphosphonic acid. Both treatments with exogenous cytokinin, or 6-methyl purine (which is an inhibitor of cytokinin oxidase), delay petal senescence. However, treatment with cytokinin also increases ethylene biosynthesis. Despite the similar effects on senescence, transcript abundance of gene markers is affected differentially by the treatments. A significant rise in transcript abundance of WLS73 (a putative aminocyclopropanecarboxylate oxidase) was abolished by cytokinin or 6-methyl purine treatments. In contrast, WFSAG12 transcript (a senescence marker) continued to accumulate significantly, albeit at a reduced rate. Silver thiosulphate suppressed the increase in transcript abundance both of WFSAG12 and WLS73. Activity of reactive oxygen species scavenging enzymes changed during senescence. Treatments that increased cytokinin levels, or inhibited ethylene action, reduced accumulation of hydrogen peroxide. Furthermore, although auxin levels rose with senescence, treatments that delayed early senescence did not affect transcript abundance of WPS46, an auxin-induced gene. Conclusions A model for the interaction between cytokinins, ethylene, reactive oxygen species and auxin in the regulation of floral senescence in wallflowers is proposed. The combined increase in ethylene and reduction in cytokinin triggers the initiation of senescence and these two plant growth regulators directly or indirectly result in increased reactive oxygen species levels. A fall in conjugated auxin and/or the total auxin pool eventually triggers abscission

Social performance nei pazienti psichiatrici: metodi standardizzati di valutazione

Social performance nei pazienti psichiatrici: metodi standardizzati di valutazion

Post Enumeration Survey of the Population and Housing Census: trends and future perspectives in Italy

The present study focuses on the Post Enumeration Survey (in the following PES) of the Population and Housing Census and is part of a wider project concerning the retrieval and analysis of information related to all past Italian PES. In Italy, the most recent PES was carried out in 2001 with the main purpose of estimating and disseminating coverage errors, in order to give a quality measurement of the 14th Population and Housing Census itself. This research aims to examine all Italian Post Enumeration Surveys in detail, from the very first which took place in 1981, with a particular attention to their evolution over time, providing an elaborated analysis of the specific features characterising the stages of the production cycle: survey plannings, decisions on the sampling design, questionnaire building and changing scenary, monitoring phase during data collection

Standardized assessment of the needs for care in a cohort of patients with schizophrenic psychoses

Standardized assessment of the needs for care in a cohort of patients with schizophrenic psychose