What process involves gradually increasing light and temperature exposure for seedlings?

The process of gradually increasing light and temperature exposure for seedlings is known as hardening off. This technique is crucial for preparing young plants to adapt to outdoor conditions after being started indoors or in a controlled environment.

During the hardening off process, seedlings are gradually exposed to outdoor elements, which helps them acclimatize and reduces the shock they might experience when moved permanently outside. This gradual transition allows seedlings to develop stronger stems, thicker leaves, and improved resistance to environmental stressors such as wind, direct sunlight, and temperature fluctuations.

In contrast, watering focuses on providing moisture to the plants; transplanting involves moving plants from one location to another; and fertilizing is about supplying essential nutrients for growth. While these are all important aspects of plant care, they do not specifically address the acclimatization process required for seedlings to thrive outside, making hardening off the correct choice.