Secondary growth in dicot roots is essential to provide strength to the growing aerial parts of the plants. It is similar to that of the secondary growth in dicot stem. However, there is marked difference in the manner of the formation of vascular cambium.
The vascular cambium is completely secondary in origin. It originates from a combination of conjunctive tissue located just below the phloem bundles, and as a portion of pericycle tissue present above the protoxylem to form a complete and continuous wavy ring. This wavy ring later becomes circular and produces secondary xylem and secondary phloem similar to the secondary growth in stems.
Differences Between Secondary Growth in Dicot Stem and Root
| Secondary growth in dicot stem | Secondary growth in dicot root |
|---|---|
| The cambial ring formed is circular in cross section from the beginning. | The cambial ring formed is wavy in the beginning and later becomes circular. |
| The cambial ring is partially primary (fascicular cambium)and partially secondary (Interfascicular cambium) in origin. | The cambial ring is completely secondary in origin. |
| Generally, periderm originates from the cortical cells (extrastelar in origin). | Generally, periderm originates from the pericyle. (intrastealar in origin) |
| More amount of cork is produced as stem is aboveground | Generally, less amount of cork is produced as root is underground. |
| Lenticels of periderm are prominent. | Lenticels of periderm are not very prominent. |