Could some genetic engineered plants survive the upper layers of the atmosphere if they where able to fly/float?
http://selenianboondocks.com/2013/12/venus-isru-condenseable...
https://what-if.xkcd.com/30/ (not quite a scientific source, so make what you want of it)
Maybe if your plants can deal with the acid you might be able to do it. (I am not a biologist, chemist or anything relevant to answer this question, this is just my best guess).
[1] "NASA Study Proposes Airships, Cloud Cities for Venus Exploration" http://spectrum.ieee.org/aerospace/space-flight/nasa-study-p...