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MICRO - structural bioindications of environmental stress factors


Plants confronted with environmental or anthropogeneous constrains quickly develop modifications in the microscopical cell, tissue and organ structure of the affected plant parts. The symptom morphology, distribution and severity reflect the way the plant physiology is disturbed and vary for different stress factors. Hence, microscopy can be used to understand the mechanistic relationship between stress and injury as well as diagnose the origin of plant health disorders.


Principal objectives in MICRO are to develop analytical tools to assess the structural changes from the sub-cellular to whole organ level and to apply them within the framework of research projects on different environmental issues. Primarily, the effects of abiotic stress factors are studied.

In MICRO, different qualitative and quantitative approaches in transmitted light, fluorescent and electron microscopy are combined. Groups of bioindications and their distribution within cells and tissues are thus characterised in order to decipher the plant’s response to physiological changes caused by the investigated stress factor. Structures, evidenced using specific histochemical stains, can be quantified using image analysis and data compared with physiological, (bio)chemical, morphological or other measurements.


The approaches developed in MICRO are versatile and applied to various research fields. Our science is principally developed through participation within different WSL large experiments (MODOEK) and applied in collaboration projects with WSL or other partners. Our motto is that structural changes are fundamental in the way plants respond to stress and occur simultaneously to modifications in the plant physiology.

Examples of relevant research topics


Compartmentation of soil contaminants in plants

 As a consequence of present and past industrial activities, chemical accidents or careless disposal of waste products, thousand of sites in Switzerland and other developed countries have been contaminated with different organic and anorganic - mostly metal – pollutants. These sites are unfit for crop production and are either spontaneously re-colonized by vegetation or can be remediated, in the case of low contamination, using tolerant or metal accumulating plants to phyto-extract or phytostabilize the soil contaminants and thus avoid their horizontal or vertical diffusion to groundwater.

In MICRO, the soil pollutant allocation at cell, tissue and organ level is analysed using histochemical and microanalytical metal revelation methods. Findings are compared to stress, detoxification and tolerance reactions to characterise plant sensitivity and allocation efficiency. This knowledge can be applied in ecosystem restoration to select the appropriate plant systems.


Tolerance and stress reactions in woody species in response to ongoing climate change

Major changes in the composition of the ecosystem are forecast as a consequence of elevated temperatures and a reduction in precipitation expected during this century. The increase in mortality of sensitive species at the most exposed locations, such as Scots pines in the central alpine valleys, show that ecosystems have already begun to react.

In MICRO, reactions to primarily drought stress are investigated and stress symptoms or phenotypic adaptations (xeromorphic changes) characterised in sensitive and tolerant species. Qualitative and quantitative markers are developed to bioindicate tree reactions in the field and understand the mechanisms in foliage leading to tolerance during drought spells.


Ozone symptoms in foliage of woody species

Present ambient ozone concentrations throughout the northern and parts of southern hemisphere cause specific stress symptoms in a large number of woody broadleaved and conifer species in synergy with photo-oxidative stress. Microscopical symptoms are varying as a function of the ozone dose or plant species.

In MICRO, symptoms in sensitive species are validated and the synergy between the effects of ozone and other stress factor are investigated.