There might be a whimsical reason why Exoplants seem to be a typo error of Exoplanets. Extrasolar Plants, or Exoplants would be a likely constituent of habitable exoplanets or habitables (habs).
An exoplanet that happens to support life would likely host an organism that can harness the energy of it's closest star to support the processes of life.
Although not all forms of life are dependent on a star for it's energy source--as exemplified by extremophiles that thrive in the dark deep-sea trenches, it's worth investigating the possibilities of how other forms of life might utilize the light from their host star.
Our ultimate prize is the detection of bio-signatures given off via the metabolism of exoplants with their own kind of photosynthesis. That'll be the day when our interest in exoplants will bloom.