photosynthesis help please

Photosynthesis help please:

What happens to electrons after it is used in the light dependent reaction/where is it used up?
What substances affect these electrons if we add them to plants?

Electrons(once have passed down the chloroplasts losing energy, and reach the last stage of photosystem 1) bind with Hydrogen ions and NADP to form reduced NADP which is used later in the light independant reaction.

I'm not sure what you mean with the second question, if this is ISA-related then this site is quite useful
http://www.practicalbiology.org/areas/advanced/energy/photosynthesis/investigating-the-light-dependent-reaction-in-photosynthesis,60,EXP.html