explain secondary growth in dicot root with a diagram.
Secondary growth in dicot root is as follows:
The increase in girth is by activity of two lateral meristems. i.e. vascular and cork cambium.
ORIGIN AND ACTIVITY OF VASCULAR CAMBIUM:
Vascular cambium is absent in the beginning but develops later at the time of secondary growth. The parenchyma cells present just below the primary phloem become meristematic and give rise to 4 separate strips of cambia. The divisions of the cells of the pericycle results in complete cambial ring formation. The strips of cambia cut off cells on their both sides. Xylem towards inside and phloem towards outside. They mature into secondary xylem and secondary phloem respectively.
ORIGIN AND ACTIVITY OF CORK CAMBIUM:
Cells of pericycle become meristematic and form cork cambium. Cork cambium gives rise to periderm. (Protective cell layers). The activity of cork cambium in dicot roots is similar to that found in dicot stem. it forms cork on outer side and secondary cortex on innerside. Cork cells become dead due to deposition of suberin. Due to continuous activity of cork cambium, pressure builds up on remaining layers peripheral to phellogen. Ultimately, these layers die.
The increase in girth is by activity of two lateral meristems. i.e. vascular and cork cambium.
ORIGIN AND ACTIVITY OF VASCULAR CAMBIUM:
Vascular cambium is absent in the beginning but develops later at the time of secondary growth. The parenchyma cells present just below the primary phloem become meristematic and give rise to 4 separate strips of cambia. The divisions of the cells of the pericycle results in complete cambial ring formation. The strips of cambia cut off cells on their both sides. Xylem towards inside and phloem towards outside. They mature into secondary xylem and secondary phloem respectively.
ORIGIN AND ACTIVITY OF CORK CAMBIUM:
Cells of pericycle become meristematic and form cork cambium. Cork cambium gives rise to periderm. (Protective cell layers). The activity of cork cambium in dicot roots is similar to that found in dicot stem. it forms cork on outer side and secondary cortex on innerside. Cork cells become dead due to deposition of suberin. Due to continuous activity of cork cambium, pressure builds up on remaining layers peripheral to phellogen. Ultimately, these layers die.