How do antioxidant enzymes like Catalase, SOD, APX and GR behave in plants during heavy metal and salinity stress? Is there any significant relationship among the activity of these enzymes in plants which are in salinity and heavy metal stress. Are they directly or inversely proportional to each other during stress in plants?
@Zhiquan Sir....How can we differentiate between low level and high level stress. Is there any supporting research for plants?
Kirti Pandita
In our rice experiment with pot method, 1 mg Selenium / kg of soil application decreased grain yield with declined SOD and CAT activity and moreover first three panicles early flowered as compared to no Selenium application.
The highest grain yield was observed under combined Selenium and Zinc application with high CAT but SOD decreased.
Generally, we observe an increase in activity of most of these antioxidant enzymes under both heavy metal as well as salt stress. In some systems you may find increase in either catalase or guaicol peroxidase. In general, plants exposed to any stress (especially abiotic stress) show [i] increase in reduced to oxidized states of reducing power [NAD(P)+/NAD(P)H]; and [ii] acceleration in Ascorbate-Glutathione cycle [which use ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase and glutione reductase]. Accordingly, we expect an increase in the activities of these enzymes.
Usually the HM generated ROS and oxidative stress in plants but the level of metals greatly influence the activity of enzymes and plant functional response. At low level some of the specific trace-elements aids the plant in HM mediated stress mitigation but at elevated levels the same metal can have inverse effect on the functional response of plant.
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