Plants shows secondary anomalous behaviour in secondary growth region.

1. TOPIC:-
ANOMALOUS SECONDARY GROWTH
Under the supervision of:- Presented BY:-
Dr. NIMISHA AMIST
FACULTY OF BOTANY
UNIVERSITY OF ALLAHABAD
SALMAN KHAN
M.Sc-2nd SEM
DEPARTMENT OF BOTANY
UNIVERSITY OF ALLAHABAD

2. Anomalous Secondary Growth
Anomalous secondary growth is the result of deviation in the
cambial activity from the normal type found in most of the
dicot.
 Haberlandt classified anomalous secondary growth into-
adaptive and non-adaptive anomaly.
Adaptive anomaly includes lianas which are woody climbers
of tropics.
Non adaptive anomaly includes anomaly of Rumex,
Boerhaavia, Bougainviella, Mirabilis, Chenopodium etc.

3. Types of Anomalous Secondary Growth
1-Abnormal behaviour of normal cambium:-
(A) The cambium forms vascular tissues only in the region of vascular
bundle.
(B) The cambium forms usually large proportion vascular tissues only
in the region of vascular bundle.
(C) The cambium forms irregular patches of parenchyma in xylem
2-Abnormal behaviour of abnormal cambium:-
(A)Formation of rings of vascular bundles embedded in
parenchymatous tissue.
(B)Formation of rings of vascular bundles embedded in conjunctive
tissues.

4. 1:- Abnormal Behaviour of Normal Cambium:-
In many woody climbers or lianas the cambium is normal in position but its
activity is abnormal and with the result anomalous structure are formed.
Examples:-
 The stem of Cucurbita ten vascular bundles arranged in two rings of five each.
 Each vascular bundle is conjoint, open and bicollateral having an outer and
inner cambium.
 The outer cambium of both inner and outer bundles becomes active along
with the parenchymatous cells of the ground tissue and the combine to form a
more or less wavy ring of cambium.
 This normal cambium behaves abnormally as it cuts off secondary xylem and
phloem in vascular bundle region only, resulting in the increased size of the
bundle.
Cucurbita stem:-
(A) The cambium forms vascular tissues only in
the region of vascular bundle.

5. TS in Cucurbita stem

7. (B) The cambium forms usually large proportion
vascular tissues only in the region of vascular
bundle.
Bignonia stem:-
 The young stem shows a wavy outline with prominent ridges and furrows.
 At the start of secondary growth, the fascicular and interfascicular cambium
become active and join to form a cambium ring.
 This cambium ring behaves "normally in the beginning, giving more secondary
xylem towards inner side and less secondary phloem on outer side.
 However, after sometime the cambium ring develops unidirectional areas of
cambium at four diagonal points.
 Hence at these four points lesser amounts of xylem are cut off internally,
whereas massive amounts of secondary phloem are cut off externally.
 These phloem masses intrude inwards forming four deep wedges of irregular
width and supported by transverse bands of sclerotic cells.

8. TS in Bignonia stem

9. TS in Bignonia
stem
fibers

10. TS in Bignonia stem

11. 3. The cambium forms irregular patches of
parenchyma in xylem:-
Urtica dioica stem :
 The young stem of U. dioica shows a typical dicotyledonous structure
having a ring of conjoint, open and collateral vascular bundles.
 At an early stage, a normal cambial ring is formed which behaves
Normally cutting off secondary xylem towards inner side and secondary
phloem towards outer side.
 However, after sometime the cambium begins to behave abnormally at
certain places only, cutting off parenchymatous cells on the inner side,
instead of secondary xylem.
 After cutting off a group of parenchymatous cells, the cambium again
begins to behave normally and resumes its normal activity, forming
secondary xylem above the parenchymatous group.
 The process sis repeated again and again, resulting in the formation Of
islands of parenchyma which are embedded in the secondary xylem or
wood.

12. TS in Urtica stem showing
alternative bands of 2ry xylem
and parenchymatous bands
(Parenchyma islands
Parenchyma band
(Parenchyma islands)
2ry xylem band

13. 2:- Abnormal cambium showing abnormal
activity
A new cambium ring or accessory cambium arises from the cortex or pericycle.
The cambial ring being placed abnormally functions in an abnormal manner.
 The stem has a typical dicotyledonous structure.
 Extra-stelar cambium originates from the cells of the inner cortex or
the pericycle.
 It forms secondary xylem and secondary phloem. A ring of conjoint,
collateral vascular bundles is thus formed, separated by
parenchymatous cells.
 The first cambium ceases its function after forming the ring of vascular
bundles.
Mirabilis stem:-
(A) Formation of rings of vascular bundles
embedded in parenchymatous tissue.

14.  The last cambial ring cuts off sclerenchyma alternating with secondary
xylem on the inner side and secondary phloem and parenchyma on the
outer side.
 Hence the last ring of vascular bundles are embedded in lignified tissue
and provide mechanical strength to the stem.
TS in Mirabilis stem
 Successive rings of accessory cambia are formed, from the secondary
parenchyma, behave in a manner similar to the first one

15. Sclerenchyma at the
outermost ring of VB

16. (B) Formation of rings of vascular bundles
embedded in conjunctive tissues.
 The cambial ring originates in the conjunctive tissue and gives off
secondary xylem tissue on the inner side and secondary phloem tissue
outside.
 The vascular bundles appear to be embedded in a mass of conjunctive
tissue, e.g. Bougainvillea, Boerhaavia etc.
 The first cambial ring is extra-stelar in origin and arise from the
pericycle, followed by successive rings of cambia.
 The cambial ring cuts off secondary xylem alternating with secondary
parenchyma on the inner side and secondary phloem above secondary
xylem.
 The cells of the secondary parenchyma are fusiform, more or less
radially arranged and usually develop lignified, thickened walls.
 These are referred to as conjunctive tissue or ground tissue.
Bougainvillea stem:-

17.  In some species of Bougainvillea, the conjunctive tissue consists
entirely of sclerenchyma and cannot be demarcated from the xylem
of the embedded vascular bundles, hence the secondary phloem
appears in the form of islands or isolated groups apparently
surrounded by conjunctive tissue.
 They should not be mistaken as included phloem.
 Successive rings of cambia are which behave in a manner similar to the
first ring, as a result, concentric layers armed of vascular bundles are
formed embedded in conjunctive tissue.
 Successive rings of cambia are formed which behave in a manner
similar to the first ring, as a result, concentric layers of vascular
bundles are formed embedded in conjunctive tissue.

18. TS in Bougainvillea stem

19. TS in Bougainvillea stem

20. This micrograph shows the
beginning of secondary growth
within the Bougainvillea stem.
Note the cambial zone (CZ)
immediately beneath the starch
sheath (SS), and the central
part of the stem which is
occupied by primary bundles,
within which secondary growth
is occurring. The internal
vascular bundles are associated
with conjunctive tissue. The
primary bundle (encircled) has
been formed by the vascular
cambium.

21. Detail, showing several included vascular
bundles. The vascular cambia produce vessels,
axial parenchyma and sometimes fibres to the
inside and indefinite amounts of secondary
phloem to the outside in these included
bundles
Details of the anomalous growth
which occurs in Bougainvillea Note
the included vascular bundles
(white ovoids), embedded

22.  The vascular bundles are arranged in three rings (anomalous structure,
two large centrally placed in medulla, middle ring of 6-14 loosely
arranged bundles and an outer ring of small 15-20 bundles.
 The three rings of bundles originate from the procambial strands.
 Secondary growth in the two medullary bundles and in the bundles of
the middle ring is limited, resulting in slight increase in size only
 The intra- fascicular cambium of these bundles function normally,
forming secondary xylem on the inner side and secondary phloem on
the outer side, and as secondary growth progresses, the primary
phloem gets . crushed, forming a cap like structure of dead cells over
the newly formed phloem.
Boerhaavia:-
 However, most of the secondary growth of the stem takes place from the
cambial activity of the outer ring of bundles.
 The intra-fascicular and interfascicular cambium join to form a cambium
ring.

23.  Maheswari (1930) observed that the ring forms secondary xylem in the
intrafascicular region and lignified, conjunctive tissue in the
interfascicular region on the inner side, and secondary phloem above.
 The secondary xylem and parenchyma opposite to conjunctive tissue, on
the . outer side.
 After the formation of secondary tissue, the cambium. ceases its activity
and a new cambium ring arises by the joining of secondary parenchyma
cells, opposite to the conjunctive tissue, and the pericycle

24. TS in Boerhaavia stem

25. Cross section of Boerhaavia stem, showing
successive rings of xylem and phloem

26. TS in Boerhaavia stem