I feel , 850C is too high a temperature for proline estimation, it  will be more prudent to use 50-600C....  . Find some literature dealing with protocols for proline determination ...

Methods for Determination of Proline in Plants,Plant Stress Tolerance pp 317-331,Part of the Methods in Molecular Biology book series (MIMB, volume 639)

Abstract

Accumulation of proline in higher plants is an indication of disturbed physiological condition, triggered by biotic or abiotic stress condition. Free proline content can increase upon exposure of plants to drought, salinity, cold, heavy metals, or certain pathogens. Determination of free proline levels is a useful assay to monitor physiological status and to assess stress tolerance of higher plants. Here we describe three methods suitable for determination of free proline content. The isatin paper assay is simple and is suitable to assay proline content in large number of samples. The colorimetric measurement is quantitative and provides reliable data about proline content. The HPLC-based amino acid analysis can be employed when concentration of all amino acids has to be compared.

Dear Prof. Anoop,

Thank you very much for all of these valuable details about proline in the attached files. I really appreciate your help.

With kind and best regards,

Heba

Please see the attached file the attached file

Dear Prof. Alhayany,

Thank you for sending me this attachment. Actually, I found something new and interesting to learn in this article. In the method, the authors did 2 steps:

1) they quantified the free proline content and the free amino acids in fresh leaf materials (0.5 gm)

2) they calculated The equivalent dry weight by drying an identical leaf quantity at 80 °C to be able to show the results of proline [µmol/g DM]

** In my experiment, I also want to measure free proline content (as a response to drought stress), but immediately in the plant dry materials (not in the fresh materials at all). The plants have been dried at 85°C for 2 days.

Is it possible to use the same protocol in the attached article with the dry materials?

I have found one Video in the link below shows "Proline Analysis with Dry Material- Full Method". But it is not clear to me which temperature has been used for drying the plant materials and for how long?

I need an exact answer to know that I still able to analyze the free proline content in my dry materials.

https://www.youtube.com/watch?v=M-1pmx0JCEI

Thank you very much once again. I really appreciate your help.

With kind and best regards,

Heba