The blade is the expanded part of the leaf. It is the most conspicuous part, what most of people identify and understand as a leaf when such a noun is mentioned.
Different types of blade
Inside the blade the following parts can be distinguished:
- Theveins: are a like wrinkles or pipes running along the blade. They are really the vascular bundles coming from the stem throughout the petiole into the the surface of the blade. The central vein is called Midrib. The different patters they draw in different species is a trait used by botanists to distinguish a plant from the other.
- The marginis the rim or final limit of the blade. It can offer different forms:
Different types of margin
- The petioleis the connexion of the stem to the blade. It is the channel for the vascular bundles to arrive to it. It can be short or long. Those leaves having a petiole, no matter how long it may be, are called petiolated. There are some leaves without petiole. In this case they are called stalkless or sessile.
A petiolated leaf and a stalkless one
Test what you have learned about the leaf, clicking what you think is the correct answer among the three different possibilities.