Yes, STOMATA is a Scrabble word!

Letter values in Scrabble US: S 1, T 1, O 1, M 3, A 1, T 1, A 1.

Is it a valid word?

STOMATA is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a minute epidermal pore in a leaf or stem through which gases and water vapor can pass
a mouth or mouthlike opening (especially one created by surgery on the surface of the body to create an opening to an internal organ)