You're looking for a free PDF of "Plant Physiology" by Pandey and Sinha. Here's what I found:

provide comprehensive, free-to-download PDFs on Plant Physiology and Biochemistry. Uttarakhand Open University Quick Book Summary

Open University Study Materials: Some Indian universities, like Uttarakhand Open University, provide free course-specific study material that covers the same curriculum (Plant Physiology and Biochemistry) often citing Pandey and Sinha as a primary reference .

Academic Previews: You can find significant portions of the book on Google Books.

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