Altered stomatal dynamics of two Euramerican poplar genotypes submitted to successive ozone exposure and water deficit.

The impact of ozone (O) pollution events on the plant drought response needs special attention because spring O episodes are often followed by summer drought. By causing stomatal sluggishness, O could affect the stomatal dynamic during a subsequent drought event. In this context, we studied the impact of O exposure and water deficit (in the presence or in the absence of O episode) on the stomatal closure/opening mechanisms relative to irradiance or vapour pressure deficit (VPD) variation.

Integrated analysis of the detoxification responses of two Euramerican poplar genotypes exposed to ozone and water deficit: Focus on the ascorbate-glutathione cycle.

Ozone (O) and drought increase tree oxidative stress. To protect forest health, we need to improve risk assessment, using metric model such as the phytotoxic O dose above a threshold of y nmol·m·s (PODy), while taking into account detoxification mechanisms and interacting stresses. The impact of drought events on the effect of O pollution deserves special attention.

Antioxidative responses of three oak species under ozone and water stress conditions.

Plants are frequently exposed to adverse environmental conditions such as drought and ozone (O). Under these conditions, plants can survive due to their ability to adjust their metabolism. The aim of the present study was to compare the detoxification mechanisms of three oak species showing different O sensitivity and water use strategy.

Both gravistimulation onset and removal trigger an increase of cytoplasmic free calcium in statocytes of roots grown in microgravity.

Gravity is a permanent environmental signal guiding plant growth and development. Gravity sensing in plants starts with the displacement of starch-filled plastids called statoliths, ultimately leading to auxin redistribution and organ curvature. While the involvement in gravity sensing of several actors such as calcium is known, the effect of statolith displacement on calcium changes remains enigmatic.

Ozone exposure and flux-based response functions for photosynthetic traits in wheat, maize and poplar.

Ozone exposure- and dose-response relationships based on photosynthetic leaf traits (CO2 assimilation, chlorophyll content, Rubisco and PEPc activities) were established for wheat, maize and poplar plants grown in identical controlled conditions, providing a comparison between crop and tree species, as well as between C3 and C4 plants. Intra-specific variability was addressed by comparing two wheat cultivars with contrasting ozone tolerance. Depending on plant models and ozone levels, first-order, second-order and segmented linear regression models were used to derive ozone response functions.

Distinct responses to ozone of abaxial and adaxial stomata in three Euramerican poplar genotypes.

Ozone induces stomatal sluggishness, which impacts photosynthesis and transpiration. Stomatal responses to variation of environmental parameters are slowed and reduced by ozone and may be linked to difference of ozone sensitivity. Here we determine the ozone effects on stomatal conductance of each leaf surface.

The CHAP domain of Cse functions as an endopeptidase that acts at mature septa to promote Streptococcus thermophilus cell separation.

Cell separation is dependent on cell wall hydrolases that cleave the peptidoglycan shared between daughter cells. In Streptococcus thermophilus, this step is performed by the Cse protein whose depletion resulted in the formation of extremely long chains of cells. Cse, a natural chimeric enzyme created by domain shuffling, carries at least two important domains for its activity: the LysM expected to be responsible for the cell wall-binding and the CHAP domain predicted to contain the active centre.

Ozone-induced changes in photosynthesis and photorespiration of hybrid poplar in relation to the developmental stage of the leaves.

Young poplar trees (Populus tremula Michx. x Populus alba L. clone INRA 717-1B4) were subjected to 120 ppb of ozone for 35 days in phytotronic chambers.

A specific form of thioredoxin h occurs in plant mitochondria and regulates the alternative oxidase.

The plant mitochondrial thioredoxin (Trx) system has been described as containing an NADPH-dependent Trx reductase and Trx o. In addition to the mitochondrial isoform, Trx o, plants are known to contain several chloroplastic Trx isoforms and the cytosolic Trx h isoforms. We report here the presence in plant mitochondria of a Trx isoform (PtTrxh2) belonging to the Trx h group.