Final answer:
Plants require sunlight for photosynthesis, a critical process for growth. Controlled variables like sunlight amount, soil type, and water availability are essential in plant experiments.
Explanation:
Light quantity refers to the intensity or concentration of sunlight and varies with the season of the year. Plants need sunlight to undergo photosynthesis, a process vital for their growth. It is crucial to maintain controlled variables like the amount of sunlight, type of soil, and water availability to conduct a valid plant experiment.
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