1. With the exception of flowers, leaves are the most morphologically diverse plant structures. We’d need a lot more than 10 facts to do them justice.
  2. There are more than 60 botanical terms used to describe the structures and forms of leaves.
  3. Leaves are plant organs, usually having two basic parts: the blade (lamina) and the petiole, which is the short “stem” that attaches a leaf to the rest of the plant.
  4. Most photosynthesis takes place in the leaves, although some does occur in green stems.
  5. The principle site of photosynthesis in leaves is inside the mesophyll, a layer of spongy tissue located just below the epidermis on the upper leaf surface.
  6. Mosses and liverworts look like they have leaves, but they don’t. A true leaf is composed of more than one layer of cells, including a cuticle (waxy outer covering), stomata (for gas exchange), xylem (water-conducting tissue), phloem (sap-conducting tissue) and internal air spaces.
  7. The first leaves that appear on a plant after germination are called cotyledons. They all look about the same and do not look like the true leaves of a plant that develop later.
  8. Monocots, which are plants with narrow, sword-like leaves such as grasses, grains, onions, tulips and bananas, produce one cotyledon. Dicots, which are broad-leafed plants like tomatoes, beans, lettuce and oak trees, produce two cotyledons upon germination.
  9. Do conifers have leaves? Yes, needles are leaves that are specialized to resist desiccation.
  10. What about cacti? Yes, they have leaves too, but they are either microscopic or soon fall off after a short growth spurt in the spring.