Complex permanent tissue of plants

1. Manoj Das

2. 2.Complex permanent tissues
Tissues which are composed of two or more
than two types of cells but contribute to a
common functions are called complex tissues.
Types-
1.Xylem (xylon -wood): It is a conducting Tissue
which conducts water and minerals upward
from the root to the leaves . Xylem consists of
four types of cells-
A . Tracheids - These are elongated and
pointed having tapering at both ends, dead
cells with highly lignified walls and wide lumen.
The end walls are imperforate.

4. Depending upon the thickening pattern of
lignin, tracheids are as
i. Annular- The lignin deposition occurs in
form of rings
ii. Spiral- The lignin is deposited in form of
helical in shape
iii. Reticulate – The thickening occurs in
form of net like in structure.
iv. Scalariform – The thickening occurs in
form of ladder like in structure.
v. Pitted- In this type, lignin is uniformly
present except for small unthickened
areas called as pits.

5. B. Vessels
Distribution-Vesssels are foundin the wood of
angiosperms except order Ranales. They are
absent
In pteridophytes except Selaginella and
gymnosperms except order Gnetales.
Structure- A vessel is made a large number of
vessel members which are joined in end to end
manner to produce tubular channel. Each
vessel members are characterized d by the
presence of perforation plate at its both ends.

7. C. Xylem parenchyma
It is made of small living and thin walled
cells and associated with xylem.
Intercellular spaces are well defined.
D. Xylem sclerenchyma
They are thick walled dead fiber type of
sclerenchyma present in xylem.
Functions
i. Tracheids and vessels collectively
known as trachery elements that help
in conduction of sap from roots to the
aerial part of plant body.

8. ii. The xylem parenchyma helps in storage of
food materials as well as slow conduction of
sap.
iii. The xylem sclerenchyma provides
mechanical support to the plant body
Type
The xylem can be classified as
A. On the basis of origin, the xylem is as
a. Primary xylem- It originates from the
procambium during the development of
plants
b. Secondary xylem-It develops by the

9. B. On the basis of development, xylem is as
a. Protoxylem- It is the first formed xylem. It
has small tracheids and vessels.
b. Metaxylem – It is the later formed xylem. It is
made up of large tracheids and vessels.
C. On the basis of relative position of
protoxylem and metaxylem, xylem is as
a. Endarch- In this type metaxylem lies toward
the outer side and protoxylem lies toward the
inner side of axis. It occurs in stems and
leaves.
b. Exarch- In this type, metaxylem lies inner

10. and protoxlem is located at outer side of
axis and occurs in roots.
c. Mesarch- In this type protoxlem lies
between metaxylem or vice versa. It
occurs in dorsiventral leaves.
d. Centrach- When the protoxylem lies at
the centre of metaxylem. and occurs in
ferns

12. 2. Phloem bast or leptome
The phloem is a living and non lignified tissue which
conducts synthesized organic food materials from
photosynthetic areas to the rest part of plant body.
Type
On the basis of development, phloem is grouped as
a. Primary phloem- It is produced from the
procambium during embryonic development. It
includes
i. Protophloem- Early formed phloem is called as
protophloem
ii. Metaphloem- Later formed phloem is called as
metaphloem.

13. Difference between Protophloem and Metaphloem.
Sl. No. Protophloem
Metaphloem
i. Companion cells usually absent Companion
cells are present
ii In stem protophloem is arranged towards the
periphery In stem metaphloem is
arranged towards the inner side

14. b. Secondary phloem- It is produced by the activity of
vascular cambium during the secondary growth.
Structure- The phloem is made up of following
elements-
a. Sieve elements- These include
i. Sieve tubes- They are made up of a large number
of sieve tube members which are joined together
by end to end manner. The sieve tube member is
elongated and tubular in structure. It is
characterized by the presence of sieve plate at
both ends. The cell wall is thin and cells are living.
But the nucleus is absent.
ii. Sieve cells- They are elongated narrow cells with
tapering ends. In these cells sieve areas occur all

15. Distribution- In angiosperms both sieve cells and
sieve tubes are present. But in case of
pteridophytes and gymnosperms, only sieve cells
are present.
b. Companion cells- They occur only in
angiosperms. The companion cells are narrow,
elongated and thin walled living cells. Cells have
well defined nucleus and cytoplasm. They occur
both lateral sides of sieve tubes
c. Phloem parenchyma- The living parenchymatous
cells associated with phloem is called as phloem
parenchyma. It is absent in most of the monocots
and some herbaceous dicots.

16. Functions-
i. The sieve elements help in conduction of food
materials.
ii. The companion cells control all cellular activities
of sieve tubes.
iii. The phloem parenchyma store food material and
also help in slow conduction of food materials.
iv. The phloem sclerenchyma provides mechanical
support to the plant body