This is very useful for your research. (Look at the attached file page 8)
1. Antonelli A., Smith R. J., Fry C., Simmonds M. S., Kersey P. J., Pritchard H. W., ... & Qi Y. D. (2020). State of the World’s Plants and Fungi (Doctoral dissertation, Royal Botanic Gardens (Kew); Sfumato Foundation).
The World Checklist of Vascular Plants, the most comprehensive and regularly updated species list of its kind, records around 350,000 accepted species, of which 325,000 are flowering plants.
Scientists have estimated that there are around 8.7 million species of plants and animals in existence. However, only around 1.2 million species have been identified and described so far, most of which are insects and still new variety have been described,
and they are much which is not identified by the scientist.