Definition: Photosynthesis is the process by which plants prepare their own food using sunlight and carbon dioxide giving out oxygen and sugar molecules.
Photosynthesis is effectively carried out during the day.
It is not advisable to sleep under the tree at night since the plants do not carry out photosynthesis and oxygen is not produced as the end product.
The continuous respiration by the tree at night reduces the oxygen from its atmosphere and increases carbon dioxide.
This can lead to suffocation or breathing problems due to the unavailability of oxygen.