The ivy plant must have been in sunlight and the number of energy storage molecules would have increased.
Photosynthesis
Plants are generally able to photosynthesize by using carbon dioxide and water to produce energy storage molecules in the form of carbohydrates.
Hence, if the ivy plant has been taking in carbon from the air for several hours, it means that the carbon is being used to synthesize carbohydrates - a process that depends on the products of light reaction of photosynthesis.
More on photosynthesis can be found here: https://brainly.com/question/1388366?referrer=searchResults
