EXERCISE 21: THE INTERNAL STRUCTURE OF A YOUNG DICOT STEM

Young stems of dicotyledonous Plants

This exhibits structural differences when compared to portions of the same stems or other similar stems that have matured

cross section of Aristolochia elegans

What specimen was prepared for Exercise 21: The internal structure of a young dicot stem

Epidermis, Cortex, Stele, Pericycle, Vascular bundles, Pith rays, Pith

Under the LPO, what are the layers of the cell that should be identified? Starting from the outermost toward the center of the cross-section

Epidermis

This focuses on the outermost part of the specimen. Few trichomes may be seen here. Guard cells may also be seen though rarely

Cortex

Focuses beneath the epidermal cells.

Collenchyma, Parenchyma

What are the two cells found in cortex?

Collenchyma

These cells are outer in the cortex

Parenchyma

These cells are inner in the cortex

Starch sheath

This may be present in the cortex

Stele

This constitutes the rest of the specimen

Pericycle, Vascular bundles, Pith rays, Pith

The stele consists of?

Pericycle

Composed of parenchyma and sclerenchyma cells; the latter may be seen in isolated groups

Vascular bundles

These are seen in a broken ring in the young stem

Cambium

In vascular bundles, the phloem is outer to the xylem, in between is the?

HPO

Vascular bundles are better viewed under?

Pith rays

Parenchyma cells between bundles

Pith

Those bigger than parenchyma cells toward the center

Collenchyma, Sclerenchyma, Xylem, Phloem

Cells in the stem that lend mechanical support

Meristematic tissues

To what type of tissues do cambium cells belong to?

Vascular tissue system (Xylem)

What distinct region occupies the biggest portion of the stem cross section?

Encourages plant growth

Important function of cambium

Yes, presence of chloroplast

Are young stems capable of photosynthesis? Why?