Vascularization refers to the development of vascular tissues in plants. During primary growth, procambium develops and differentiates into primary xylem and phloem. During secondary growth, the vascular cambium develops more xylem and phloem. The vascular bundles contain conducting tissues that transport water, minerals and organic compounds throughout the plant. Vascular bundles are organized into steles of various types depending on the plant. Angiosperm flowers also exhibit patterns of vascularization that provide clues about floral evolution.
2. ADVANCE ANATOMY OF PLANT
BS BOTANY 8TH EA
SUBMITTED TO
MAM SADIA
SUBMITTED BY
FARWA TARIQ
GOVERNMENT COLLEGE WOMEN UNIVERSITY FAISALABAD
3.
4. Vascularization definition
• The gradual sequence of development and arrangement of xylem phloem and
cambium in plant is called vascularization.
• Evolution of vascular tissues in plants was one of the essential adaptations to terrestrial
habitats. Vascular tissues are the specialized conducting tissues, xylem and phloem.
Plants with vascular tissues are grouped as the Tracheophyta and
include Pteridophyta, Gymnosperms and Angiosperms.
5.
6. Xylem:
• It is a specialized tissue for conduction of water and minerals from roots to all other
parts of the plant.
• Xylem is a complex and heterogeneous tissue composed of four types of elements
namely (a) tracheids ,(b) vessels ,(c) fibers ,and (d) xylem parenchyma .
• The first three elements are dead and lignified. Hence, xylem is described as a dead
tissue.
7. Phloem
• It is a living, complex and heterogenous food-conducting tissue.
• It is composed of (a) sieve tubes, (b)companion cells, (c) phloem fibers and (d)
parenchyma .
• In plants, vascular tissues are organized into strands called vascular bundles.
• These are spread over all parts of the plant and form the vascular tissue system.
• In gymnosperms and dicotyledons, cambium is also present in the vascular bundles.
8. Steles:
• The vascular tissues are organized into steles. The vascular bundles, with or without other
non- vascular tissues, when surrounded by the pericycle and the endodermis are referred
to as steles.
• Main types of steles and their evolution
• Protostele This is the simplest and most primitive type of stele in which xylem forms the
central cylinder and is surrounded by phloem cells.
• Pith is totally absent.
• Common in pteridophytes like Psilotum, Lycopodium, etc.
9. vascularization
• Vascularization refers to the process of the formation of
the vascular tissues of the xylem and the phloem. The
meristem that gives rise to the vascular tissues is called
the cambium.
• During the primary growth of the plants, the procambium
develops first which then forms the xylem followed by
the phloem.
• During the secondary growth, this task is performed by
the vascular or secondary cambium. Hence, the correct
answer is 'Differentiation of procambium followed by the
development of xylem and phloem.'
10. What happen during vascularization:
• Development of vascular bundles from procambium is called as vascularization.
• Thin walled elongated procambium strands are produced during the early growth
and differentiation, which in turn immediately differentiate into primary xylem and
primary phloem simultaneously.
• Development of procambium is followed by formation of primary vascular
tissues. Secondary xylem is developed from vascular cambium during secondary
growth, not from procambium.
11. • It is widely held that the vascular systems in flowers are conservative, that is, they may
remain relatively unchanged even when the general shape of the flower has altered by
evolution.
• This may lead to the formation of odd-looking loops or curves in some of the
• vascular strands to accommodate changes in the relative positions of the floral parts..
Vascularization gives the origin of
flowering plants
12. In some flowers, small branches of the vascular system end blindly.
This could be taken to mean that in one or more of the ancestors of the plant
similar strands served some organs or appendages that are lacking in the
present-day representative.
For example, a modern, unisexual female flower might have remnants of a
vascular system that would have served stamens in a bisexual ancestor.
13. Fusion in vascularization
• Stamen fused with a petal
• It often follows that the vascular supplies of the two
become fused into one strand. Bundle fusions can make
it more difficult to interpret the vascular systems of
flowers in comparative studies..
14. Traces in floral description
• The number of traces to each floral organ can vary. Often petals have
only one trace, but petals in certain families regularly have three petal
traces.
• The number of traces to each sepal is often the same as that to the
foliage leaves of the same plant.
• Stamens may have one or three traces, but one is by far the most
common number.
• Carpels may possess one, three, five or more traces. Dorsal and
marginal or ventral traces are distinguished in descriptions, when
three or more are present.
15. Theories of vascularized angiosperm
• Several theories concerning the origin of the angiosperm flower have their basis in
comparative studies of floral and vegetative vascular pat-terns of both living and fossil
plants. Despite the amount of work done by numerous people, there is no common
consensus.
• Doubtless, new theories will be proposed.
• Some think that we have all the evidence we need, if only we will interpret it properly.
• Others consider that there are such large gaps in the fossil record that no one will ever be
able to prove their theories! Modern molecular studies have led to the development of
much less subjective phylogenies, and it has become profitable to study flower
morphology in the light of the new information these contain
16. First condition
In one of them the
to floral parts on the same
radius arises from a common
bundle in the ovary wall as
in Gaylussacia frondosa and
bundles as seen in cross-
section have the xylem
internal to the phloem.
Thus, they are found, for
example, in the Rosaceae and
Ericaceae as well as in other
families
Second condition
In the other organization, the
bundles that supply the carpel
arise from a recurved bundle in
the ovary wall as
in Nestroniaumbellulata , where
the recurved bundles in the fruit
wall are in-verted, so that the
phloem is interior to the xylem.
they are found, for example, in the
Cactaceae and Santalaceae as well
as in other families
Basic pattern of vasculature to floral part:
18. SUMMARY- VASCULARIZATION
Conducting tissues in sporophyte plant body of vascular
plants were evolved in response to terrestrial habitat.
Xylem conducts water and minerals, while phloem
conducts organic solutes.
The strands of xylem and phloem form vascular bundles,
which may or may not have cambium.
The vascular bundles are organized into various types of
stele.
The simplest type is the protostele, while the eustele of
dicots and the atactostele of monocots are supposed to be
the most evolutionary advanced type.
