honestly I don't understand a lot of it myself, but with plents, because of how much was done to them retroactively to make them as plant-like as possible, we have to assume plant-like traits unless proven otherwise, and then find a way to bend plant-like traits to fit.
Nearly all of Sagan 4's biochemistry is completely unelaborated. Until I pointed out how stupid it was, plents were stated to have sap filled with literal chlorophyll instead of blood.