Oxygen is released as a by-product. This cellular process occurs in all green portions of a plant. The rate of photosynthesis is decreased when the temperature, light intensity, light duration, available water or carbon dioxide are decreased. Food produced by photosynthesis minus the food used by respiration. That means that rate of food produced must be much greater than the amount used - especially since photosynthesis only occurs in light while respiration occurs day and night.
Vegetative growth requires nitrogen which is absorbed from the soil.
The nutrients and some water will be used for growing new cells. When the remaining water reaches the leaves it is lost through the process of transpiration . Changes in pressure within the plant allow it to move water upwards, like soda through a straw. If insufficient water is available to the roots, water is lost from the cells and the plant wilts. Changes in humidity affect transpiration.