Answer:
A complex tissue consist of more than one type of cells
having a common origin which coordinate to perform a common function. Xylem and
phloem are called complex tissues as, they are made up of different types of
cells.
Xylem is composed of four different types of cells
(elements), namely
(i) tracheids (ii)vessels
(iii) xylem parenchyma (iv)
xylem sclerenchyma (or fibre)
Phloem is also composed of four different types of
elements
(i) sieve tubes (ii)
companion cells
(iii) phloem parenchyma (iv)phloem
fibre
The basic difference between xylem and phloem is listed
below
Xylem
Phloem
It
conduct water and minerals.
It
conducts organic solutes or food materials
Conduction is mostly unidirectional, i.e.,
from roots to apical parts of the plant.
In
it conduction may be bidirectional, i.e.,
from
leaves to storage organs or growing parts or from storage organs to growing
parts
of plants.
Conducting
channels or treachery elements are tracheids and vessels.
Conducting
channels are sieve tubes.
Three
of the four elements of xylem are dead (i.e., tracheids, vessels and fibre).
Only xylem parenchyma is the living elements.
Three
of four elements are living i.e., sieve tubes, companion cells and phloem
parenchyma while phloem fibre are dead elements.
In
addition to conduction, xylem provides mechanical strength to the plant.
Phloem
performs no mechanical function for the plants.
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