Ante- and post-mortem cellular injury dynamics in hybrid poplar foliage as a function of phytotoxic O3 dose.

After reaching phytotoxic levels during the last century, tropospheric ozone (O3) pollution is likely to remain a major concern in the coming decades. Despite similar injury processes, there is astounding interspecific-and sometimes intraspecific-foliar symptom variability, which may be related to spatial and temporal variation in injury dynamics. After characterizing the dynamics of physiological responses and O3 injury in the foliage of hybrid poplar in an earlier study, here we investigated the dynamics of changes in the cell structure occurring in the mesophyll as a function of O3 treatment, time, phytotoxic O3 dose (POD0), leaf developmental stage, and mesophyll layer.

Dynamics of Foliar Responses to O Stress as a Function of Phytotoxic O Dose in Hybrid Poplar.

With background concentrations having reached phytotoxic levels during the last century, tropospheric ozone (O) has become a key climate change agent, counteracting carbon sequestration by forest ecosystems. One of the main knowledge gaps for implementing the recent O flux-based critical levels (CLs) concerns the assessment of effective O dose leading to adverse effects in plants. In this study, we investigate the dynamics of physiological, structural, and morphological responses induced by two levels of O exposure (80 and 100 ppb) in the foliage of hybrid poplar, as a function of phytotoxic O dose (POD) and foliar developmental stage.

Elevated CO2 and/or ozone modify lignification in the wood of poplars (Populus tremula x alba).

Trees will have to cope with increasing levels of CO(2) and ozone in the atmosphere. The purpose of this work was to assess whether the lignification process could be altered in the wood of poplars under elevated CO(2) and/or ozone. Young poplars were exposed either to charcoal-filtered air (control), to elevated CO(2) (800 μl l(-1)), to ozone (200 nl l(-1)) or to a combination of elevated CO(2) and ozone in controlled chambers.

The response to daylight or continuous ozone of phenylpropanoid and lignin biosynthesis pathways in poplar differs between leaves and wood.

Ozone induces a stimulation of the phenylpropanoid and lignin biosynthesis pathways in leaves but the response of wood, the main lignin-producing tissue, is not well documented. The purpose of this study was to compare the responses of phenylpropanoid and lignin pathways in leaves and stem wood by a simultaneous analysis of both organs. Young poplars (Populus tremula×alba) were subjected either to daylight ozone (200 nL L(-1) during light period) or continuous ozone (200 nL L(-1) during light and dark periods) in controlled chambers.

Cellulose and lignin biosynthesis is altered by ozone in wood of hybrid poplar (Populus tremula × alba).

Wood formation in trees is a dynamic process that is strongly affected by environmental factors. However, the impact of ozone on wood is poorly documented. The objective of this study was to assess the effects of ozone on wood formation by focusing on the two major wood components, cellulose and lignin, and analysing any anatomical modifications.

Condensed lignins are synthesized in poplar leaves exposed to ozone.

Poplar (Populus tremula x alba) trees (clone INRA 717-1-B4) were cultivated for 1 month in phytotronic chambers with two different levels of ozone (60 and 120 nL L(-1)). Foliar activities of shikimate dehydrogenase (EC 1.1.

Regulation of phosphoenolpyruvate carboxylase in Pinus halepensis needles submitted to ozone and water stress.

Effects of ozone and/or drought stresses on phosphoenolpyruvate carboxylase (PEPc, EC 4.1.1.