smoke can kill plants as much as it can kill a human,
heres how
basicly, as mentioned above by another user " smoke can clog the cells of the plant)
now heres another terrible fact of science,
nicotene is a healthy plant killer ( fact !!)
it can murder germinating or un-germinated seeds,
from a single touch or the seed with ur hand , nicotene is transfered to the seeds and poisons it,
excess nicotene from the tobbaco in your joint ( exhaled in the smoke ) will travel in the smoke and cling to the plant , there by posioning it.
Do you wan to smoke in your grow room ?