Oxidating a plant
Since plants are sessile organisms and have only limited mechanisms for stress avoidance, they need flexible means for acclimation to changing environmental conditions.In order to improve a plant's protection, it is important to understand the mechanisms contributing to stress tolerance.
Cadmium and some other metals caused a transient depletion of GSH and an inhibition of antioxidative enzymes, especially of glutathione reductase.These observations suggest that although changes in rhizospheric conditions were perceived by the root part of the symbiosis, the typical Cd‐induced stress responses of phenolics were buffered.It is not known whether mycorrhization protected roots from Cd‐induced injury by preventing access of cadmium to sensitive extra‐ or intracellular sites, or by excreted or intrinsic metal‐chelators, or by other defence systems.In addition, plants are exposed to natural climatic or edaphic stresses, for example, high irradiation, heat, chilling, late frost, drought, flooding, and nutrient imbalances.Some of these stress factors may fluctuate significantly in intensity and duration on time scales of hours, days, seasons, or years; others may change slowly and gradually affect plant growth conditions.The present results indicate that mycorrhization stimulated the phenolic defence system in the mycorrhizal symbiosis.
Cadmium‐induced changes in mycorrhizal roots were absent or smaller than those in non‐mycorrhizal roots.
In order to devise new strategies for phytoremediation and improved tolerance, it is important to understand the basic principles as to how the pollutants are taken up and act at the cellular and tissue level.
In the present study the occurrence and mode of action of metal pollutants will be briefly reviewed, and the role of antioxidants as defence systems will be discussed.
To date an unprecedented, rapid change in environmental conditions is observed, which is likely to override the adaptive potential of plants, especially that of tree species with their long reproductive cycles.
These environmental changes mainly originate from anthropogenic activities, which have caused air and soil pollution, acid precipitation, soil degradation, salinity, increasing UV‐B radiation, climate change, etc.
Available data suggest that cadmium, when not detoxified rapidly enough, may trigger, via the disturbance of the redox control of the cell, a sequence of reactions leading to growth inhibition, stimulation of secondary metabolism, lignification, and finally cell death.