Sunlight!!!
Although the above answer is correct, I guess there could be some explaining. You see, sunlight powers and starts the photosynthesis. Plants absorb carbon dioxide and release oxygen. Here's something that will help, sunlight is the source for all energy. Even us. We need to breath to live. Plants give us oxygen to breath. Plants use sunlight to give us oxygen. So, the answer to any question involving the source of anything is always sunlight.
Photosynthesis uses sunlight as a source to package energy into glucose, and essentially all energy from the sunlight is factored into the monosaccharide, so in a sense glucose is part sunlight.
Light energy
Light energy
the energy source is sun. Photosynthesis need sun as a energy source.
It is the energy source. It is using as the energy source.
Sunlight is the main energy source for photosynthesis.
The sun is the source of radiant energy in Photosynthesis photosynthesis - synthesis of compounds with the aid of radiant energy (especially in plants)
the energy source for Photosynthesis is light.
The Sun is the primary source of energy for most living organisms on Earth. Solar energy is converted into chemical energy through processes like photosynthesis, which then fuels the food chain.
The Sun
Sun
sunlight