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Dr. (Miss) Kalpana R. DatarAssistant Professor
DEPARTMENT OF BOTANYWillingdon College, Sangli
Anomalous secondary growth in Bignonia.
B.Sc.-II
1. Secondary growth in plants is due to the cambial activity.
2. Cambium is the lateral meristem normally present in
vascular region.
3. In dicotyledonous stems union of fascicular and inter
fascicular cambium results into the formation of
cambium ring.
4.Cambium ring produces more xylem towards inner side
and less amount of phloem towards outer side.
5. Any deviation or change in the normal secondarygrowth is referred as ‘Anomalous or Abnormalsecondary growth’.
Abnormal or Anomalous secondary growth is due to –
1.Abnormal position of cambium.
2.Abnormal activity (behaviour ) of cambium.
3.Abnormal position as well as abnormal behaviour
of cambium.
Anomalous or abnormal secondary growth in
Bignonia.
1. If anomalous secondary growth has relation with
the habit or physiological function, such anomalous
secondary growth is called
Adaptive anomalous secondary growth.
2. If anomalous secondary growth has no relation
with the habit or physiological function, such
anomalous secondary growth is called
Non Adaptive anomalous secondary growth.
Anomalous or abnormal secondary growth in
Bignonia.
Anomalous or abnormal secondary growth in
Bignonia.
Anomalous or Abnormal secondary growth in Bignonia.
1.Bignonia is a dicot woody climber belongs to familyBignoniaceae.
2.Anomalous secondary growth in this stem is due toabnormal behaviour of the cambium during laterstages.
3.The origin, position and function of cambium ring isnormal in the initial stages of growth.
4.In initial stages, cambium produces large amount ofSecondary xylem towards inner side and small amountof Secondary phloem towards outer side.
Normal cambium with abnormal activity
1. After producing some secondary tissues in normal
manner, at four regions in crosswise places, cambium
produces more amount of secondary phloem towards
outer side and less amount of secondary xylem towards
inner side.
2. These phloem patches later on get embedded or
intruded deeply into the secondary xylem.
3. This results in the formation of four deep wedges of
secondary phloem.
Anomalous or Abnormal secondary growth in Bignonia.
4. At these four places less amount of secondary
xylem and more amount of phloem is produced.
This is abnormal behaviour of cambium.
5.This anomalous activity is restricted only at
four diagonal places.
6. The phloem patch is traversed by sclerenchyma
bars. Sclerenchyma gives mechanical support to thin
walled phloem tissues.
Anomalous or Abnormal secondary growth in Bignonia.
7. It results in four wedge shaped phloem patches
and four fan shaped xylem patches.
8. After addition of secondary xylem and phloem the
development of periderm takes place in the
epidermal region(extra stelar region).
Anomalous or Abnormal secondary growth in Bignonia.
Bignonia is a climber.
1.When the stem grows around the support, its
inner side gets compressed and outer side
gets stretched.
2.If only hard tissue like secondary xylem
remains in the central part of the stem, during
compression and stretching, the stem would
break or crack.
Anomalous or Abnormal secondary growth in Bignonia.
3.To avoid the breaking or cracking of the
stem, it requires some soft tissue in the central
region.
4.Central hard tissue is traversed by four
phloem patches(soft tissue) at four diagonal
places.This is due to abnormal behaviour of cambium.
Anomalous or Abnormal secondary growth in Bignonia.
There is a direct relation between
anomalous secondary growth and
climbing habit of the plant.
Hence this anomalous secondary
growth in Bignonia stem is described as
Adaptive anomalous secondary
growth
Anomalous or Abnormal secondary growth in Bignonia.
1.Cambium is normal in origin as well as
activity is normal in initial stages of growth.
2.Four regions of cambium developed more
secondary phloem towards outer side than
secondary xylem at inner side.
Important features of the anomalous secondary growth in Bignonia
3.Four secondary phloem furrows with
sclerenchyma bars.
4.Secondary xylem is fan shaped.
Thus, Bignonia stem shows abnormal
behaviour of normal cambium. Also it is adaptive,
anomalous secondary growth to avoid breaking of
stem. It helps the climbing habit of plants.
