ANOMALOUS SECONDARY GROWTH ( in Bignonia stem)

A study of Anamolous secondary growth in bignonia stem

1. ANOMALOUS SECONDARY GROWTH

2. ANOMALOUS SECONDARY GROWTH IN DICOTS:
●The normal activities of cambium and phellogen results in the normal secondary
growth in dicots.
●The abnormality in secondary growth is known as anomalous secondary growth.
●It is due to
* unusual position of the cambium
*abnormal functioning of the cambium
*formation of more than one ring in the cambia
*formation of extra stelar cambial ring
*formation of interxylary phloem
*formation of interxylary cork

3. ANOMALOUS SECONDARY THICKENING IN BIGNONIA STEM:
EPIDERMIS:
●Single layered epidermal cells
●Rectangular cells
●Thick cuticle is present
CORTEX:
●It is differentiated into collenchyma and parenchyma
ENDODERMIS:
●It is indistinguishable from the cortical cells
●Lacks casparian strips
PERICYCLE:
●Made up of sclerenchymatous cells
PITH:
●Thin walled and parenchymatous cells

4. VASCULAR SYSTEM:
●Consists of phloem, secondary phloem , xylem and secondary xylem.
●4 longitudinal furrows of secondary phloem are present, which are wedged in
between secondary xylem.
●Secondary phloem is in the form of a ring which remains intruded into the
secondary xylem in 4 places.
●Intruded furrows of the secondary phloem are arranged in the form of a cross.
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●Formation of 4 furrows of secondary phloem in the secondary xylem is due to the
secondary xylem is due to the abnormal functioning of the cambium.
●At 4 or more places of cambium produce less amount of secondary xylem towards
inner side and large amount of secondary phloem towards outer side .
●As a result 4 wedges of secondary phloem are formed.