Answer:
Light photons or packets of light excite the pigments in the photosystem but get from plastocyanin of photosystem 2.
Explanation:
Photosystem I discovered first but it is the second photosystem. When light absorbed by the pigments in the reaction center of the photosystem 2, electrons get excited.
This electron or energy is transferred along from pigment to pigment until electron reaches a special chlorophyll molecules that send their electrons to the final electron acceptor.
These electrons come from the photosystem 2 the directly proceeding Photosystem I, which is the electron transport chain from small protein plastocyanin.
Thus, Light excites the pigments in the photosystem but get from plastocyanin of photosystem 2.