Anomalous secondary growth in Plants with special reference to Bignonia, Boerhavia, Aristolochia & Dracaena

This PPT intends to explore the most exception of nature-anomalous secondary growth in plants.

1. WELCOME TO
ANOMALOUS SECONDARY GROWTH w.s.r to
Bignonia, Boerhavia, Aristolochia & Dracaena
BY N.SANNIGRAHI, ASSOCIATE PROFESSOR,
DEPARTMENT OF BOTANY,
NISTARINI COLLEGE, PURULIA(W.B) INDIA

2. BRIEF IDEA ABOUT ANOMALOUS SECONADRY GROWTH
•Majority of the plants possess stelar structure of normal type but several of them
are unusual structure that reflects ther common statement-Exceptions are the law
of nature.This unusual structure differs from the usual types and therefore defined
as anomalous.As a consequence, combinations of unusual structure, certain
anomalous and extremely complex structure are formed termed as anomalies and
this is very common in angiosperms.
•These anomalies may be different reasons as follows:
•1.ANOMALOUS SECONDARY GROWTH IN DICOTYLEDONS
•a. Anomalous position of cambium,
•b. Abnormal beheaviour of normal cambium
•c. Accessory cambium formation and its activity
•d.Extrastelar Cambium
•e,Interxylary phloem

3. SECONDARY GROWTH

4. ANOMALOUS SECONDARY GROWTH

5. CASUES OF ANOMILIES
•2. Absence of vessels in xylem,
•3. Scattered Vascular bundles in dicot,
•4. Presence of exclusive phloem and xylem bundles,
•5. Presence of medullary bundles,
•6. Presence of cortical bundles,
•7. Intraxylary Phloem,
•8. Vascular bundles arranged in ring in Monocots,
•9. Secondary growth in monocotyledons.
•Those are the some of the important reasons deserve mentioning in order to
address the anomalous beheaviour of the dicot stem in course of the secondary
growth of the plant after the completion of the usual primary growth by the
primary meristematic tissues of the plant body.
•Examples: Bignonia, Securidaca, Bauhinia, Sarjania, Thinouia, Aristolochia,
Bignonia, Bougainvillaea,Mirabilis, Boerhaavia, Tecoma, Amaranthus,
Achyranthus,Chenopodium,CombretumStrychnos, Salvadora, PaperomiaCuscuta

6. Bignonia sp . Plant image

7. ANOMALOUS GROWTH IN Bignonia

8. How does anomaly develop in Bignonia ?
•The anomalous growth in the secondary structure in Bignonia of Bignoniaceae is
a typical example where Cambium normal in structure but functionis abnormal.
•Here, the cambium function mostly in two ways-
•1. Certain segments of cambia cease to produce secondary xylem; instead of that,
these segments of cambia donate secondary phloem only towards exterior.
•2. The other segments of cambia produce secondary phloem and secondary
xylem by usual means-the secondary xylem more towards the centre and
secondary phloem towards the periphery.
•As a result, the woody cylinder appears to have ridges and furrows in
longitudinally in stele.The ridges are wider than the grooves.The camium breaks
up into a number of strips.The wider ones remain on the top of the ridges while
narrower ones remain at their bases of the grooves.In the secodary phloem
formed in the groove parallel strips of bast fibres are formed.

9. Development Pattern
•This is a kind of adaptive anomaly having the arrangement of tissues from
periphery to the centre in the following sequences: Cuticle-Epidermis-
Hypodermis(Parenchyma-Starch sheath-Sclerenchyma)-Primary phloem-
Cambia-Bast fibres interpolated-Phloem wedge-Secondarey xylem-Primary
xylem-Pith
•Bignonia is a woody climber-liane and the stem is twining and thus is
inextensible as it hangs freely and has to bear its own weight.
•The stem is also flexible as it has to withstand high velocity of wind and again
subject to radial compression due to unequal growth in thickness for twining
purposes.
•For those reasons, the woody climber in the form of solid mass, instead of split
into separate portions by the interpolations of the softer tissues into the woody
mass to acheive inextensibility and flexibility. In Bignonia, softer phloem tissues
is interpolated into the woody cylinder by the formation of grooves.

10. DIAGRAMATIC VIEW OF THE ANOMALOUS GROWTH

11. ANOMALOUS GROWTH IN Boerhaavia
•In Boerhaavia, it is anomalous growth derived from the accessory cambium along
with Bougainvillaea and Mirabilis.Several cambia arise successiuvely in centrifugal
direction.Each cambia produces xylem and conjunctive tissuesto the inside and
phloem & conjunctive tissue to the outside.The resulting tissue gives the concentric
appearence of concentric rings of vascular bundles embeded in the conjunctive
tissues.
•According to P. Maheswari(1930) , the development of Boerhaavia dissusa is as
follows:
•The t.s of the vstem shows two medullary bundles-a middle ring oif 6-14 bundles and
another ring of 15-20 or more bundles.
•The bundles of middle ring increases in thickness to a limited extent by a fascicular
cambium.
•The bundles of outer ring are initially separate, quite small and each provided with its
own fascicular cambium.

12. Boerhaavia sp plant

13. IMAGE OF SECONDARY GROWTH -ANOMALY

14. COMPARATIVE GROWTH PATTERN

15. MODE OF DEVELOPMENT
•The fascicular cambia of the bundles become interconnected by interfascicular
cambium of the bundles become interconnected by interfascicular cambial areas
producing a cylindrical meristematic zone which gives rise to interfascicular
parenchymatous or slightly prosenchymatous ground tissues between the bundles.
•Thereafter, the cambium ceases to function and new meristem arises in the secondary
parenchymatous or prosenchymatous tissue to which the first has given on the
outside and the process repeats at interval.
•Frequently, the successive cambia are ontogenetically interrelated , in the sister cells
of one cambium layer become cambial cells of another layer.

16. Aristolochia sp. Plant

17. ANOMALOUS GROWTH IN Aristolochia

18. WHAT HAPPENS IN Aristolochia
•Aristolochia, a dutchman's pipe is a climber belongs to Aristolochiaceae enjoys the
anomalous secondary growth due to its climbing actvity.Here, the cambium is normal
in structure but abnormal in function.The sequence of the growth pattern is as
follows.
•i. The cambial ring forms by the union of the interfascicular & fascicular bundles to
form vascular cambial ring.
•ii.The function of the vascular cambium ring becomes anomalous where the
intrafascicular cut off xylem & phloem as usual external and internal side.
•iii. but the interfascicular zone insted of giving xylem and phloem, it cuts off
parenchymatous cells both on the inner and outer sides, thus they form like
parenchyma.
•The new cambial segments constantly form the rays of parenchyma, thus increasing
the diameter.

19. STEPS FOLLOWED-------------
•As the vascular cylinder, broken by wide rays, increases in circumference the
cylinder of sclerenchyma that encircles the bundles bercome ruptured and the
adjacent parenchyma grows intrusively into the gaps.
•Eventually, a very fluted vascular cylinder is formed.
•The species of aristolochia are woody climbers or lianes, which have diverse
taxonomic affinities and often show anomalous structural features.
•Among other characteriustics, the vessels are often unusually wide diameter.
•Pith and medullary rays are crushed due to growth of secondary xylem.
•After sometime, the pericycle breaks and the adjacent parenchyma cells invade to
the breaks by the intrusive growth.
•Thus, cambium normal in position but abnormal in function that reflects by its
anomaly.

20. ANOMALOUS GROWTH IN Dracena sp.

21. About Dracena Plant & Growth Beheaviour
•Some monocotyledons belonging to family, Liliaceae have arborescent habit with
woody stems like Dracaena, Yucca, Cordyline, Agave, Aloe etc experiences another
special type of secondary growth although the normal secondary growth is absent in
monocot stems due to close vascular bundles.They exhibit an anomalous secondary
growth in thickness producing a cambium-abnormal both in position and function.
•Dracaena is a genus having 120 species belong to Agavaceae family under APGIV
system of classification. The plant have special thickening called dracaenoid
thickening due to abnormal beheaviour.Two type of species are found-wood tree like
with cluster of leaves (D.fragrans) & rhizomatous (D.agolensis).
•The anomalous secondary growth in this plant is an attraction of the anatomists due
to following peculiar beheaviour which is reflected during its later stages of the
growyth when the primary growth is over.

22. SECONDARY THICKENING
•The following steps are followed in course of anomalous secondary thickenings:
•i.Secondary growth is initiated by the special meristematic zone in the inner cortical
region of the stem or very often from pericyle.
•ii.A multilayered cambial cells formed from the inner cortical cells lying outside the
vascular bundles.
•iii. The cambium is formed in the region of the stem where the growth has been
ceased.
•iv. A large number of cambial cells in the inner side and small number on the outer
sides.
•v.The cells produced to the external side of the cambia are parenchymatous.
•vi.The cells produced to the internal side are partially parenchymatous and partially
vascular in nature remain separated from each other by lignified tissues and
sometimes the tissue remains unlignified and thin walled.
•vii.The parenchymatous cells produced internally to the cambia devloped into
lignified conjunctive tissues

23. MICROSCOPIC IMAGE OF T.S UNDER MICROSCOPE

24. STEPS FOLLOED IN COURSE OF ANOMALY
•viii.The vascular tissues produced internal to the cambium are vascular in nature and
the vascular bundles are become concentric amphivasal type.This is formed due to
the anticlinal divisions followed by periclinal division and even haphazardly to form
xylem and phloem of the sercoindary bundles.
•The small amount of phloem consist of short sieve tubes, companion cells and
phloem parenchyma and the xylem is made of only tracheids, usually with
sclariform thickening and small amount of xylem parenchyma with lignified walls.
•The cambium add small amount of parenchyma cells outside and the primary
vascular bundles appear larger.
•The secondary bundles are smaller in size but more numerous in number.
•It is to be remembered that in Dracaena, anomalous secondary thickening is brought
about by a special cambium-secondary thickening meristem.Due to its actvity,
conjunctive tissues and secondary vascular bundles originate.Contiuous formation of
secondary tissues results in the increase in diameter even the girth of 45 feet
(D.draco) with height of 70 feet of about 1000 years old.

25. ANATOMY OF Dracaena sp.

26. CONCLUSION
•In Dracaena, no typical periderm formation by the activity of phellogen is found but
storied cork cells are formed by the continuous periclinal division of the outermost
cortical cells followed by the suberisation of the walls.Thus, storied cork cells form
special mtype of protective layer outside the stem.
•Thus, from the above discussion it is quite clear that anomalous forms of secondary
growth into two categories-adaptive and non-adaptive.In contrast to the non-adaptive,
anomaly is not an adaptation to definite external condition but it represents
variations in design.The exception is the law of the nature- it has been reflected in
terms of the anomalous secoindary growth as found in the different type of plants as
you have gone through the anatomy of Bignonia, Boerhaavia, Aristolochia and last
but not least in Dracaena.

27. EXCEPTIONS-THE RULE OF NATURE

28. THANKS A LOT FOR YOUR MEANINGFUL PARTICIPATION