1) Eat animals and plants. Remember the animals you eat also eat plants. This creates maximum suffering and damage.
2) Eat plants only. This creates less suffering and damage than option 1.
To answer your question though, if it's scientifically proven that plants are sentient and feel pain like we do (i.e. suffer) then I would only eat what plants produce (e.g. nuts, legumes, apples, etc) rather than the plant itself (e.g. carrots).
Personally, at least until we can efficiently synthesize arbitrary dietary proteins, fats, and fibers, I'll keep using my computer built from rare earths mined with exploited workers to post about the delicious, factory-slaughtered chicken I just ate.
'If one can't save everything, one must save nothing?'
You should watch the presentation by Ethan Brown, he talks about creating meat using plant protein.
He's a great entrepreneur and 'hacker'. You might enjoy it.
"plants can see hear and respond" http://www.bbc.com/earth/story/20170109-plants-can-see-hear-...
Provided this is true don't they deserve more protection over animals because they can't defend as well as animals
This doesn't imply at all that they are sentient or have feelings, which is what we care about (or should, in any case) when we discuss harming or protecting other living things.
Of course, there are other considerations such as ecological, but that's not what we're discussing here.