After 4 years of service, Maheshwari obtained a Fulbright Smith Mundt Fellowship in 1959 and traveled to the US to where he continued his research at Yale University and California Institute of Technology.
[6] One of the first significant contributions of Maheswari was the discovery of RNA polymerase activity in chloroplasts which he accomplished during his early stint at California Institute of Technology while working with Robert S. Bandurski and their researches revealed the presence of DNA in organelle.
[6][8] Maheshwari's researches on plant growth hormones returned new protocols for the isolation of cytokinins and gibberellins and elucidated the function of salicylic acid during the flowering period.
[3] Maheshwari's researches have been detailed in over 200 articles and in a book, Signal Transduction in Plants: Current Advances, co-edited with Sudhir Kumar Sopory and Ralf Oelmüller.
[4] Maheshwari's project, Survey and Synthesis the information in the area of molecular Biology of Plant Development and Differentiation, was selected for the Jawaharlal Nehru Fellowship in 1981[12] and the University of Hyderabad awarded him the Doctor of Science degree (honoris causa) in 2013.