Glutathione peroxidase (GPX), superoxide dismutase (SOD) and catalase are the most important enzymes of the cell antioxidant defense system, how can i link this enzymes with stress tolerance or resistance in plant.
In each papers i found that when plants are exposed to stressful environmental conditions, the production of Reactive Oxygen Species (ROS) increases and can cause significant damage to the cells.
To add to the above comment, you should also consider photoinhbition.
Under abiotic stress, in particular salt and hydric, the rate of photoinhibition (decrease of the photosynthetic activity) increases radically. This mean you have much more inhibition. This is because the absorption of light induces side reactions that produce ROS. This type of photoinduced ROS are quite damaging for the repair mechanism of the chloroplast, suppressing for example the expression of subunits of PSII.
The enzymes listed above are hypothesized to control the ROS during stress.
NOTE that photoinhibition is not exclusive of high light and at any irradiance you will have certain level of photoinhibition.
I recommend you to read the papers of Takahashi, Murata and Nishiyama, just write in google scholar their names and photoinhbition for more info.
Cheers,
Alonso
Alonso thank you for pointing out the role of photo-inhibition.
If the research is going to conducted in greenhouse the rate of photo inhibition can be reduced?
The short answer is no.
As mention above photoinhibition is a process that is always occurring in the background. The only way to decrease its rate is by decreasing the light intensity. In a green house the only think you do is control other environmental variables such as humidity, temperature, etc.
If you stress a plant many things in its physiology will change. One of them is the photoinhbition rate (kpi). If you induce salt stress, kpi would increase, therefore the photosynthetic activity would decrease.This will happen in a biotron, open top chamber, green house, field or your garden.For example singlet oxygen it is generated linearly proportional to irradience.
Going back to your original question about enzymes and stress. Under stress, It is likely that ROS scavenging processes would be express more and compensate the amount of ROS originated in the photosynthesis. Of course this is only one of the many possibles sites of production of ROS in the plant cell. However, it has been reported by Song et al 2004 that SOD will prevent photoinhibition of PSII.
Why this is important? well, most of the time the plant fitness is measured with techniques that measure photosynthesis. Can you reduce photo-inhibition? No, just keep that in mind at the moment you analyze and interpret your data. Stress responses are very complicated to understand, each plant is different. Even stuff measuered in Arabidopisis can not always be extrapolated to other plants.
I answered you for the same question about relationship between temperature stress and antioxidant enzymes(another question in research gate). Now about salt stress the story is the same. In most stresses (biotic or abiotic) reactive Oxygen Species (ROS) increases and can cause significant damage to the cells and we have not forget this increasing of ROS will damage different organs in the cells like membrane, Proteins and DNA. The product of this damages are MDA, Di-tyrozin and Di hydroxy guanozin respectively. The balance of enzymatic and non-enzymatic antioxidant enzymes with the cells damage biomarkers is important. for example the ratio of SOD/MDA shows the health of cells. Besides, most of these biochemical changes shows their impact on yield(or dry matter). So, the weight of plant or yield(for example seed yield) shows the impact of specific stress on plant. Of course some researchers(Fisher and Maurer) believe yield stability is important than yield itself. Briefly talking, I think it is better we measure most of the antioxidants and biomarkers and then their ratio and then calculate correlation analysis between SSI(Fisher and maurer formula ) and our previous finding ratio. The result will help us to find salt resistant varieties.
cheers
Fischer, R.A. and R. Maurer, 1978. Drought resistance in spring wheat cultivars. I. Grain yield response. Aust. J. Agric. Res., 29: 897–907.
Davood Sir your answer is very helpful and explanatory, it would help me in the research and ill try to estimate MDA, Di-tyrozin and Di hydroxy guanozin.
Thank you
Dear Vikas
Please see attachment for measurement of MDA. Any problem please contact me.([email protected])
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