It doesn't look like a full split, so not that bad. If you want to you can put a bit of tape around the stem on the ends and in the middle but cushion that tape with foam or similar so the stem can still expand.

It should heal over just fine.

BTW, the little white things that you see near that split are called adventitious roots or root primorida, are perfectly normal and if that stem were covered with soil roots would grow from those primordia.

Carolyn

Yea...there's something you can do...take it out of that crappy fad topsy turvey tomato thing. Plant it in a normal container, right-side-up, give it a shot of liquid-based fertilizer & in 2-3 days you'll see it "scab up" and start healing. =)

LOL Thanks, both of you. :)