When I read your question all I could say to myself is, "What the heck is 'a standard graph of IAA'"? I wondered if you meant a graph of absorbance vs. wavelength. Or maybe it was something more esoteric. But I think that you are referring to the sentence in "Isolation and characterization of indole acetic acid (IAA) producing Klebsiella pneumoniae strains from rhizosphere of wheat (Triticum aestivum) and their effect on plant growth" by Sachdev et al. That states, "After incubation, IAA production was determined using Salkowski method as described earlier. Standard graph of IAA was constructed using standard IAA..."

So nobody can give you a "Standard graph" (more commonly called a "standard curve"). It is something that you need to construct by running known concentrations of IAA through the Salkowski technique (preferably with the background that you have in your experiments). To make your life a little easier, I have attached a paper by Glickmann and Dessaux that goes through the procedure.

Dear professor, that's exactly what I meant, the standard curve (sorry). Unfortunately, IAA is not available here in Algeria, I've been searching for long time. Thank you so much for your help.

I am sorry to hear that. IAA is quite inexpensive in the US and in Europe. Sigma lists it at $27.00 for 5 g and there are many other places that offer it for even less. I suppose that you could synthesize it. Even though the synthesis is relatively easy, it would cost more to synthesize it than to buy it. But see my attachment. IAA is sometimes sold as a plant growth auxin under the name Heteroauxin. Maybe it is available in Algeria under that name through a garden nursery or through some plant biochemists. I take it that you are not allowed to order the material from Europe, China or the US.

In any case, nobody can really run a good standard curve of the colored product made from IAA and send that to you. Your standard curve would look different due to impurities in the phenol, the sulfuric acid, the background sample and even the water you use. The results might be close or they might be significantly different. That is why you need to run the curve yourself.