In some species, awns might serve as a feeding deterrent against large
herbivores which might munch up the fruit wholesale, preserving the
fruit for smaller animals or insects which might carry away the fruits
individually and drop or stash some.

M. Reed

Iris Cohen wrote:

I stumbled over the question what primary function the awn of Poaceae might
have.

It is frequently used as a three letter word in crossword puzzles.

Iris,
Central NY, Zone 5a, Sunset Zone 40
"The trouble with people is not that they don't know but that they know so much
that ain't so."
Josh Billings (Henry Wheeler Shaw), 1818-1885