Phytochrome has 2 forms Red-absorbing phytochrome Far red absorbing phytochrome Interconverted Two forms of the same compound Total amount same Pr Pfr Pr Pfr
In red light Pfr Pr Pfr Pr absorbs red light, changes to Pfr form. Pfr doesn’t absorb red light, stays the same.
In far red light Pr Pr Pfr Pr doesn’t absorb far red light, stays the same. Pfr absorbs far red light, changes to Pr form.
Sunlight Mostly red A little far red
In sunlight In sunlight most P gets converted to Pfr form. Pr Pfr Pfr
Start of night Most P in Pfr form. Pr Pfr Pfr Pr Pfr Pr Pfr Pfr Pr Pfr
In the dark Pfr form changes gradually to Pr form. Pfr Pr Pfr Pr Pfr
After a short night Pfr still left. Pfr Pr Pfr Pr Pfr Pr Pfr Pfr Pfr
Later in the night More Pfr changes to Pr. Pfr Pr Pr Pfr Pfr Pfr Pr
After a long night All the Pfr is gone. Pr Pfr Pr Pr Pfr Pfr Pr Pr Pr
Day dawns Most P gets converted to Pfr form again. Pr Pfr Pfr Pr Pfr