Describe how the broad leaf of a typical dicot is so well adapted for its job as the photosynthetic organ of a plant. In your answer make sure to assess the ways plants evolved to deal with potential problems the broad leaf might cause

Question

What will be an ideal response?

Answer 1

The broad leaf exposes a great deal of surface area to sunlight but also creates problems that must be solved. That surface area also allows more opportunity for water loss. Although some water loss is actually desirable in order to power movement of water through xylem, too much would be lost if the leaf did not have an epidermis, which is typically associated with a waxy cuticle, to prevent water loss. However, a cuticle that prevents water vapor loss also prevents most gas exchange. That would also prevent much-needed carbon dioxide from entering the leaf for use by photosynthetic cells. To solve this problem, stomata provide entrance for carbon dioxide. However, stomata also let water vapor escape. Guard cells are adapted to keep stomata closed unless photosynthesis is actively occurring during daylight hours.