A living being has self awareness, and as such is the subject of his or her own life. Plants react to stimuli, but they are not self aware. They cannot make choices about themselves or their environment. Plants are not beings.

Instead of making rash assumptions, think about it. As the subject of one's own life, one should not be made into an object for others. Rather than put cows on life support or give chickens every advantage of modern medicine, they should not be owned, bred, commodified, and sold. Human and non-human beings should be free to experience their lives on their own terms, unless they are causing harm to others.

Got it? If not, try reading animal rights theory as explained by Lee Hall and Joan Dunayer, and see if you can dispute it. (I don't mean PeTA and all that other nonsense that really has nothing to do with animal rights theory.)

As for 'quality of life', I think that's a decision you have a right to make for yourself, and under some circumstances, for dependents. Outside of that, the decision should be one's own.