The perk allocation screen right now is at the Collections screen and shows up when you select a crop type, here you also get more info about the crop, and the info will update as you choose perks.
It is still incomplete, it is not reading the new perks from the xml file yet and most of them are not fully implemented, but it is progress regardless.
In case you haven't seen our previous posts on how the new perk system will work, each crop now have a skill assigned to it, as you harvest the crops you gain exp, at certain thresholds you gain a perk point (max 9 perks at skill lv100).
There are 3 perk columns, the left column are the exclusive perks, they are unique to this plant, the middle column have generic perks, once unlocked they can be used on any other compatible plant, and the right column have generic perk slots, here you can apply generic perks from other plants.
The stars on the left are the seed tier, to access perks on the higher tiers you need a seed with the correct level of stars, otherwise the plant will not gain the perks even if you have them assigned in the UI.
I made some progress on Nina, but can't show it yet, you will understand why when she is in the game.