Which sentence has an infinitive phrase that functions as the subject?



To convert sunlight and energy into food is the end result of photosynthesis.
After the rain, water travels from the ground to the roots of a plant.
Plants are adapted to take in moisture from the ground.

These sentences contain two infinitive phrases.

http://www.chompchomp.com/terms/infinitive.htm

Which one do you think is functioning as a subject?

plants are adapted to take in moisture from the ground.

To convert sunlight and energy into food is the end result of photosynthesis

To convert sunlight and energy into food is the end result of photosynthesis.