Arabidopsis thaliana leaves with altered chloroplast numbers and chloroplast movement exhibit impaired adjustments to both low and high light

The effects of chloroplast number and size on the capacity for blue light-dependent chloroplast movement, the ability to increase light absorption under low light, and the susceptibility to photoinhibition were investigated in Arabidopsis thaliana. Leaves of wild-type and chloroplast number mutants with mean chloroplast numbers ranging from 120 to two per mesophyll cell were analysed. Chloroplast movement was monitored as changes in light transmission through the leaves. Light transmission was used as an indicator of the ability of leaves to optimize light absorption. The ability of leaves to deal with 3 h of high light stress at 10 °C and their capacity to recover in low light was determined by measuring photochemical efficiencies of PSII using chlorophyll a fluorescence. Chloroplast movement was comparable in leaves ranging in chloroplast numbers from 120 to 30 per mesophyll cell: the final light transmission levels after exposure to 0.1 (accumulation response) and 100 μmol photons m−2 s−1 (avoidance response) were indistinguishable, the chloroplasts responded quickly to small increases in light intensity and the kinetics of movement were similar. However, when chloroplast numbers per mesophyll cell decreased to 18 or below, the accumulation response was significantly reduced. The avoidance response was only impaired in mutants with nine or fewer chloroplasts, both in terms of final transmission levels and the speed of movement. Only mutants lacking both blue light receptors (phot1/phot2) or those with drastically reduced chloroplast numbers and severely impacted avoidance responses showed a reduced ability to recover from high light stress

Flows and cohesion: balancing capabilities across an expanded union

The dynamics of physical relocation of intellectual capital is seen in the flow of skilled workers across international boundaries and the internal movements within the increasingly integrated economy of the European Union. This article describes a research framework developed within the context of a globalised economy and its potential application to issues within the boundaries of the European Unio

Implementing natural capital credit risk assessment in agricultural lending

Agriculture has critical impacts and dependencies on natural capital, and agriculturallenders are therefore exposed to natural capital credit risk through their loans tofarmers. Currently, however, lenders lack any detailed guidance for assessing naturalcapital credit risk in agriculture and are challenged by the fact that the relevant material risks vary considerably by agricultural sector and geography. This paper developsa natural capital credit risk assessment framework based on a bottom‐up review ofthe material risks associated with natural capital impacts and dependencies forAustralian beef production. It demonstrates that implementing natural capital creditrisk assessment is feasible in agricultural lending, using a combination of quantitativeand qualitative inputs. Implementation challenges include the complexity and interconnectedness of natural capital processes, data availability and cost, spatial data analytical capacity, and the need for transformational change, both within lendingorganisations and across the banking sector

The percentage transmission at the end of a given light exposure (A, accumulation at 0

1 μmol photons m s; B, avoidance at 100 μmol photons m s) relative to the value at the end of the 4 h dark treatment () was plotted against chloroplast number per mesophyll cell (). All data for wild-type and mutant plants of ecotypes Columbia, Landsberg , and Wassilewskija (see ) were included except those for , , and the / double mutant. Regression lines were fitted through the data (accumulation: =–5.98–0.58; avoidance: =15.36 + 0.093). All regressions were highly significant ( <p><b>Copyright information:</b></p><p>Taken from " leaves with altered chloroplast numbers and chloroplast movement exhibit impaired adjustments to both low and high light"</p><p></p><p>Journal of Experimental Botany 2008;59(9):2285-2297.</p><p>Published online 8 May 2008</p><p>PMCID:PMC2423661.</p><p></p