Thank you for your post.
You've asked a loaded question that is very generalized, so here are some topics that may help you.
You can definitely set up parent child relationships within FileMaker Pro. There needs to be some kind of common link between the two tables. For example, if you have a Sales Order file, you may enter a Product ID. That Product ID may be linked to an Inventory table that then shows the Description, price, quantity on hand, etc. for that particular Product ID.
I'm not sure why you would need a parent child relationship for plant taxonomy, unless you plan to put the Kingdom, Division, Class, Order, Family, Genus (and common name) into separate tables. They may all be related to one another. However, you can set up your database for pop-up menus where the values are defined by a related table. For example, if you select Plantae for the Kingdom, then there will be several choices for Division only associated to Kingdom. Depending on the Division selected, then another pop-up appears that only gives choices for that Division, etc.
This should help point you in the right direction.
If you have more specific questions, feel free to contact me.