If photosynthesis is to occur at all, the plant must be able to intercept light. The better a plant is in intercepting the light, the greater opportunities the plant has to produce food. Why have so many plants developed broad, flattened leaves? What is heliotropism, and how does it make plants more efficient? What are sleep movements? Describe the model for leaf orientation in the upper, middle, and lower levels of a leaf canopy. prepare a 200 word essay.