Vascular bundles are found in vascular plants and contain two main components: xylem and phloem. Xylem transports water and minerals from the roots to the leaves. It is composed of tracheids, vessels, xylem fibers, and xylem parenchyma cells. Tracheids are the fundamental cell type of xylem - they are elongated tube-like cells that lose their living contents and function to transport water and minerals up the plant. Tracheids exhibit different patterns of secondary thickening on their cell walls.

1. Vascular bundle
• Define
• Vascular plant are also called “Tracheophyta”
(Trachaea=vessel a component of plant and
phyta means =plant).
• Vascular bundle is divided into two
components :
xylem phloem

2. Xylem
• The term xylem was
proposed by the
Nageli(1858).
• He derived the word from a
Greek word
• “Xylos” meaning wood ,The
main function of xylem to
conduct water and minerals
from root to leaves. Xylem
plays an essential
‘supporting’ role providing
strength to tissues

3. Components of
Xylem
1. Tracheides
2. Vessles
3. Xylem fibres
4. Xylem paranchyma
• Tracheides
• These are fundamental
cells of xylem .These are
elongated tube like cells
with tapering ends. the cells
are non living at their
maturity and mature cells
are empty without
protoplast.

4. Patterns of secondary
thickening in tracheids:
(a). Annular thickening:
(b). Spiral thickening (helical thickening):
(c). Scalariform thickening (ladder like
thickening):.
(d). Reticulate thickening (net-like
thickening):
(e). Pitted thickening:

5. Types