Sometimes, different research articles show huge variations in the number of reported species of a plant genus. How and from where to get the updated and correct information related to this fact?
Usually, most of the information is stored in online databases.
There were probably a certain amount of known plant species in 2000 so there is a report with a different number of plant species in 2000 vs in the year 2020. Maybe less plant species in 2020 vs in 2000 because of things like deforestation, or maybe there is more because advanced genomics led to the discovery of new species scientists were previously not aware of. The numbers in 2020 were right and the numbers in 2000 were right at the time.
Usually go to the right scientific database, click a few buttons and you will find the answer as of today.