Books for learning how plants function
I wanted to comment because I don't think my answer will be the best, but I can't because of my low reputation... Anyway, here are two suggestions:


Plant Physiology and Development, by Lincoln Taiz, Eduardo Zeiger &amp; al.
Biochemistry and molecular biology of plants, edited by Bob B. Buchanan, Wilhelm Gruissem and Russell L.Jones


These are the two main books we are using in my university (I'm studying biology) and I think that together they cover a lot of topics. You can probably buy the pdf versions online as well. I hope it helps!