Use the Trefle app to look for plant information. Will include functionality for advanced searches.
Refer to Trefle API here: https://docs.trefle.io/
Use the WGSRPD Github repository for all levels, 1-4. https://github.com/tdwg/wgsrpd/tree/master/109-488-1-ED/2nd%20Edition
Level 1: 1-9 Level 2: 10-92 Level 3: Use L3 Code Ex: ALB Level 4: Use L4 Code Ex: ALA-OO however to query if OO is present you need to drop the value and use L3 code