Q.3:- Explain the process of secondary growth in the stems of woody angiosperms with the help of schematic diagrams. What is its significance?
The cambial ring becomes active and starts cutting off new cells; both on the inner and the outer sides. The cells which are cut off towards the pith mature into secondary xylem. The cells which are cut off towards the periphery mature into secondary phloem. The cambium is usually more active on the inner side than on the outer side. Hence, a large number of secondary xylem is produced compared to the secondary phloem. The secondary xylem; thus produced soon forms a compact mass.
While the cambial ring forms the major portion during secondary growth in woody stem, the broken epidermal layer is replaced by the activity of cork cambium.
Secondary growth is necessary for growth in girth of the stem. Moreover, secondary growth also provides additional mechanical strength to the stem.