The Lions series represents a taster for the the senior side's marquee series against India later this month, with Test player Jennings ensuring the trip got off to a strong start with a knock of 154.
After being sent in to bat on a pitch showing tinges of live grass and some hints of dampness, Jennings and Alex Lees took control to shut the home attack out for the entirety of a wicketless first session on Wednesday.
Lees (73) was unable to kick off after lunch, the first of three wickets to fall to Manav Suthar's left-arm spin, but Jennings settled on an increasingly flat track.
He cut and drove well, hitting cleanly down the ground, and finished with 20 fours and two sixes.
Jennings, who has two Test centuries in sub-continental conditions, is among the players who would be considered for a call-up should Ben Stokes' squad require reinforcements in the coming weeks.
His early form will do his claims no harm, but it is unlikely the Test series will see batting conditions as friendly as this.
Captain Josh Bohannon also adapted quickly, reaching 93 not out by the stumps alongside the lively Lions debutant Dan Mouseley (35no).
James Rew was the only batter to miss out, falling victim to a smart slip catch on 17.
England will be looking to crank up the scoreboard pressure on day two and hoping that the pitch begins to spin sharply as the game progresses.
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