In the context of this page, a plant is defined as photosynthetic and not constituting a tree or shrub. It is understood that this definition is open to some interpretation, which will be done loosely.

Diversity

The following is an edited extract from Wikipedia under a Creative Commons Licence:

About 350,000 species of plants, defined as seed plants, bryophytes, ferns and fern allies, are estimated to exist currently. As of 2004, some 287,655 species had been identified, of which 258,650 are flowering plants, 16,000 bryophytes, 11,000 ferns and 8,000 green algae.

The naming of plants is governed by the International Code of Botanical Nomenclature and International Code of Nomenclature for Cultivated Plants (see the Wikipedia article on cultivated plant taxonomy).

According to one source, there are a "couple of thousand plant species" on the island from all the above divisions. Personally, I think this figure is remarkably pessimistic, even discounting introduced species. Another reference states, "The flora of the Mediterranean region is floristically rich in comparison with adjacent temperate and desert regions. As a whole it comprises approximately 24-25 000 species (or approximately 29-30 500 taxa including subspecies) (Greuter 1991; Heywood 1995; QuCzel 1985,1995 )."  It would seem unlikely that the island would have only about 6.7 percent of the regional taxa, particularly when neighbouring countries all seem to have more than the cited 2 000 (approx.).