Morphology of Roots

Longitudinal Section of Onion Root Tip

Corn Root

Ranunculus (Buttercup) root x.s.

Ranunculus (Buttercup) root x.s.• There are four xylem

lobes in this "typical dicot root" similar to roots illustrated in most biology textbooks.

• Purple staining structures are starch containing leucoplasts in cells of the cortex.

Young dicot root x.s.

Young dicot root x.s.

• with 3 xylem lobes in the central vascular cylinder. The purple structures are starch storing leucoplasts in parenchyma cells of the root cortex.

Protoxylem and phloem in young dicot root

Protoxylem and phloem in young dicot root

• You can see staining red two of the three protoxyem lobes of this root.

• Primary phloem (arrow) and vascular cambia are visible.

• The metaxylem cells in the center have not yet developed secondary cell walls and thus stain green.

• Later in the development of this root the metaxylem cells will form a secondary cell wall.

Ranunculus root vascular cylinder

Ranunculus root vascular cylinder

• the metaxylem (central last maturing xylem) has fully formed lignified secondary cell walls. From the top center down you can see the cortex, endodermis, pericycle, phloem, vascular cambium, and xylem.

Young Monocot Root

Young Monocot Root

• a pith surrounded by a vascular cylinder, cortex, and a root hair-bearing epidermis.

• A branch root originates at the outer part of the vascular cylindar.

• The large white circular areas are tube-shaped holes in the root that function like vessels in water conduction.

Monocot Root Vascular Tissue

Monocot Root Vascular Tissue

• Moving from the top down you can see the cortex, endodermis, 3 groups of red staining protoxylem with phloem inbetween each group, and pith.

• The hole in the outer pith is tube-shaped and functions like a vesses in water conduction.