Answer: endothermic
Explanation: An endothermic reaction is a type of of chemical reaction in which energy is absorbed from the surrounding. The temperature of the surrounding decreases.
An Exothermic reaction is a type of chemical reaction in which energy is released into the surrounding. The temperature of the surrounding increases.

Thus as photosynthesis is taking place, it absorbs energy from surroundings in the form of sunlight and thus is considered as endothermic reaction.