I am planning to design an experiment to study PS1 and PS2 activity of cyanobacteria in response to salt stress. How do I select various NaCl concentration levels to study salt stress? Kindly help me out.
the following steps may be useful :
1) select the high and low levels of the input variable (salt stress) based on the subject domain.knowledge
2) choose sufficient no. of levels for the input factor, it is better to have equally spaced intervals between these factor settings, this helps in applying a polynomial regression model with mutually orthogonal contrasts, which increases the ease of data analysis and interpretation.
3) Collect data on PS1 and PS2 activity at the factor settings chosen in your design and fit separate polynomial models for each, or you can go for Multivariate Regression if you feel that the two responses (PS1 and PS2) are strongly or reasonably correlated.
4) fit the polynomial Regression model , test for Statistical significance of overall regression and lack of fit to ensure there is no significant model bias.
4) apply variables subset selection methods, e.g forward selection or backward elimination to remove insignificant regressors from the model.
5) the reduced model, obtained after removing insignificant regressor terms can be used to predict the response behavior over the experimental space encompassed by the experimental design you have chosen.
6) last comes the validation part, study the agreement of predicted mean response at one or more factor settings not actually part of the design but encompassed by it, and the experimentally observed mean value at these settings, if they are in good agreement, the model is appropriate for your purpose.
you can look into the Applied Regression Analysis book By Draper and Smith for more information in this regard, and the topic of Multivariate Regression analysis from the Multivariate Statistics book by Johnson and Wichern.
You can use concentration from 50mM to 200 mM and check photosynthetic efficiency for stress impact.
You can use concentration from 50mM to 200 mM and check photosynthetic efficiency for stress impact.
good morning
Yes You can use firstly through preliminary tests using increasing concentrations of NaCl from 50 to 300 mM. This will allow you to determine the optimal NaCl concentrations to use in your experiment to study their impact on photosynthetic activity.
In our works, I use for the halophytic plants the NaCl beyond de 100 mM till 600 mM
good luck
Sincerely yours
Pr Belkhodja Moulay
University of Oran 1 Algeria