The interior tissues of a leaf are called mesophyll. In most leaves, there is an upper layer of columnar cells called the ______________________ ___________________ and a lower portion of _____________ ______________ open, loose aerenchyma. In Box 6-2, “Botany and Beyond: Leaf Structure, Layer by Layer,” Figure (A) shows the upper layer of columnar cells, but they do not look columnar. Why not? Figure (E) in the box shows the lower aerenchymatous layer. Can you tell what the shape of the intercellular spaces is from this two-dimensional micrograph (look at Figure 6-21 before you answer)?

BOX 6-2 Leaf Structure, Layer by Layer

The internal organization of ordinary leaves is not very complicated but it can be difficult to visualize from looking only at transverse sections. A series of sections through a leaf of privet (Ligustrum) is presented here. These are paradermal sections; that is, they are parallel to the epidermis. The first is at the level of the palisade parenchyma, and each successive section is deeper in the leaf. Try to imagine the appearance of the leaf from the perspective of a carbon dioxide molecule.

Figure (A) & (E)

Figure 6-21

Transcribed Image Text:

(A) PCS A