Secondary growth occurs in dicots and gymnosperms as a result of cell division in the vascular cambium. The vascular cambium is composed of procambial cells that differentiate into two types of cambium: fasicular cambium, which arises within vascular bundles, and interfasicular cambium, which arises between bundles from parenchyma cells. These two cambiums join to form a continuous cambium ring within the stem that produces secondary xylem and phloem through the activity of fusiform and ray initials.

1. Secondary Plant Body
Definition: The secondary plant body
is composed of the division and
differentiation components of the
fascicular and interfascicular cambia.
• Secondary plant body is the result
of the secondary growth in plant.

2. • Secondary growth: The growth that
results from cell division in the
cambia or lateral meristems and that
causes the stems and roots to thicken.

3. • While primary growth is growth that
occurs as a result of cell division at
the tips of stems and roots, causing
them to elongate, and gives rise to
primary tissue.

4. Q: Which plants undergo secondary
growth?
Ans: Secondary growth is the characteristic
of dicots and gymnosperms. The monocots
and pteridophytes usually complete their
life in primary plant body and do not grow
in thickness by cambial activity.

6. Q: Which cells cause secondary growth?
Ans: A type of cells called “procambial
cells” differentiate in to vascular tissues,
but of these remain meristematic after the
completion of primary growth and
become the cambium of the secondary
body.

8. Q: Where are procambium cells found
in plants?
• Ans: Procambium cells originate
within the vascular bundles, therefore
it is termed as vascular cambium or
fasicular (fasicle= bundle) cambium.

9. Q: What are two types of cambium by origin?
Ans: There are two types:
1- Fasicular Cambium: The cambium that arise
with in the bundles of primary vascular tissue of
the stem is called Fasicular Cambium.
2- Interfasicular Cambium: Cambium arise in
between the vascular bundles. It arises from
parenchyma cells rather than procambial cells.

10. • Both fasicular and interfasicular
cambium join together and form a
continuous hollow cylinder called as
cambium ring. This cambium ring
present throughout the length of the
main plant axis.

14. • Cell types of Cambium
• 1- Fusiform initials: These are elongated
spindle shaped cells arranged in vertical rows
having an appearance like that of bricks. They
help in producing secondary xylem elements
and secondary phloem elements in the vascular
cambium.

15. • 2- Ray Initials: The ray initials are
isodiametric cells—about equal in all
dimensions—and they produce the vascular
rays, which constitute the horizontal system of
secondary tissues; this horizontal system acts
in the translocation and storage of food and
water. The ray initials form the radial system
of the bark and wood.