Subramanyan passed away here on June 29.
Solanki met the late artist's daughter Uma Padmanabhan and handed her the letter.
In the letter, Gandhi described Subramanyan as a "brilliant and versatile artist".
"He was a many-splendoured personality: freedom fighter, scholar and creative genius, inspirational teacher to generations of young artists, and a man of boundless warmth, generosity and joie de vivre," she said.
Meanwhile, at a condolence meeting held here today, Shubhanginidevi Raje, chancellor of the Maharaja Sayajirao University, paid tributes to Subramanyan.
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About one thousand people from across the country attended the condolence meeting held on the Fine Arts faculty premises here.
In a career spanning over six decades, the multifaceted artist, who lived in Vadodara, had been a painter, sculptor, muralist and print-maker besides writer of children's books.
He was awarded Padma Vibhushan in 2012.