Elucidating mechanisms underlying organ abscission.

Abscission consists in the detachment of entire vegetative and reproductive organs due to cell separation processes occurring at the abscission zones (AZs) at specific positions of the plant body. From an evolutionary point of view, abscission is a highly advantageous process resulting into fruit and seed dispersal as well as the shedding of no longer useful organs. In an agricultural context, however, abscission may become a major limiting factor for crop productivity. Domestication of major crops included the selection of plants that did not naturally shed ripe fruits or seeds. The understanding of abscission is of great importance to control seed and fruit production and to improve breeding and harvesting practices. Thus, advances made on model plants and crops are of major importance since they may provide potential candidate genes for further biotechnological applications. Here, we review the current knowledge of the physiological, genetic and genomic aspects related to abscission including the most recently disclosed putative regulators that appear to be implicated in the development and/or activation of the AZs

Functional genomic approaches to understanding abscission activation in citrus

Abscission events in citrus allow the detachment of entire organs, both vegetative (buds, leaves) and reproductive (flowers, ovaries, fruitlets, mature fruits). This is achieved by the modification of cellular adhesion in a discrete group of specialized cells differentiated in predictable positions, known as abscission zones (AZs). Thus, abscission facilitates several key processes for citrus biology that, in an agricultural context, represent a major limiting factor for crop yield. In this regard, understanding the regulation of abscission is an important item for the citrus fruit industry. Several functional genomic approaches are currently being used to gain insights into the regulation of citrus abscission and to provide potential candidate genes for further biotechnological applications. These include: (a) the development of an expressed sequence tag (EST) dataset from abscission activated AZs and the analysis of ESTs distribution in organs to reveal AZ-preferential gene expression during abscission activation, (b) comparative transcriptomic analysis using cDNA microarrays and laser microdissected tissues (AZ cells, petiole and fruit rind cells flanking AZs), and (c) functional characterization of putative abscission-associated citrus genes in Arabidopsis thaliana and rice (Oryza sativa)

Modelling environmental adjustments of production technologies: A literature review: Externalities and environmental studies

This chapter theoretically discusses existing methodologies to model environmental adjustments of technologies. We elaborate on the limitations of treating pollution as an input or weakly disposable output, as commonly occurs in the literature. Moreover, we discuss the drawbacks of models that rely on the materials balance principle. We advocate the use of multi-equation modelling, which explicitly models the subprocesses of the production technology. Applied to the context of pollution, such an approach separately models the conventional technology, on the one hand, and the pollution-generating technology, on the other. Finally, we discuss abatement options as well as the possibility of adjusting for good environmental outputs (e.g. carbon sinks).</p

An Integrated View of Whole-Tree Hydraulic Architecture. Does Stomatal or Hydraulic Conductance Determine Whole Tree Transpiration? - Fig 8

<p>(A) Diameter, (B) density and (C) total lumen area of xylem vessels of taproot and basal stem in cross sections of <i>Poncirus trifoliata</i> (PT) and Cleopatra mandarin (CM) seedlings. Histological data correspond to the mean of six independent plants (n = 6) of each rootstock. The value for each plant is the mean of three visual fields of three sections from three samples per root and stem. Different letters indicate statistically significant differences (P <0.05) (LSD test).</p