How to produce correct epithet of a species named in the honor of a person?
You should check the article 60 of ICN: http://www.iapt-taxon.org/nomen/main.php?page=art60

See in particular Recommendation 60C about specific epithet, and in the specific case, the rule 60C.1 (specific epithet derived from a person name).


You can use the genitive case (as Plant of Vodyanitskiy) as in rule (a), which is independent of generic name, so  if the professor is male: X. vodyanitskiyi, and she is female: X. vodyanitskiyae.
or as adjective (so inflected according the genera), in rule (c): X. vodyanitskiyana, X. vodyanitskiyanus, X. vodyanitskiyanum


Note: there are other rules to have a valid published name, and it is recommended to explain why you choose such name. In additional to the ICN code, there is the companion book: The code decoded. A user's guide to the International Code of Nomenclature for algae, fungi, and plants(Regnum Vegetabile 155), by Nicolas Turland