The ideal percentage of light intensity that maximizes the rate of photosynthesis can vary based on several factors, including the type of plant, its growth stage, and environmental conditions such as temperature and CO2 availability. However, in general terms, studies suggest that the rate of photosynthesis typically increases with light intensity up to a certain point, known as the light saturation point.
For many plants, light saturation occurs at about 60% to 100% of full sunlight (which is around 1000 to 2000 µmol photons m^-2 s^-1 for photosynthetically active radiation). Beyond this intensity, the rate of photosynthesis can plateaus and may even decline due to factors like photoinhibition.
To optimize photosynthesis, a light intensity in the range of 70% to 80% of full sunlight is often considered ideal for many crops in controlled environments. However, for specific species or under certain growth conditions, optimal light levels can vary. It's important to monitor the specific responses of the plants being grown to determine the best intensity for maximizing photosynthesis.