In many vascular plants, secondary growth is the result of the activity of the two lateral meristems, the cork cambium and vascular cambium. Arising from lateral meristems, secondary growth increases the girth of the plant root or stem, rather than its length. Secondary tissues comprise the greatest volume of the root mass of woody perennial plants. Primary tissues continue to form in the feeder roots, but the support. The roots increase in thickness by the formation of secondary vascular tissues. Secondary growth is common in gymnosperms and dicotyledonous roots.
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More amount of cork is produced for protection. Lenticels on periderm are very prominent.
Difference Between the Secondary Growth in Dicot Stem and Dicot Root - MD
The cambial ring formed is wavy in the beginning and later becomes circular. Lateral meristems[ edit ] Diagram of secondary growth in a tree showing idealised vertical and horizontal sections.
New wood is added in each growth season by the lateral meristems, the cork cambium and vascular cambium. In many vascular plantssecondary growth is the result of the activity of the two lateral meristems, the cork cambium and vascular cambium.
Arising from lateral meristems, secondary growth increases the secondary growth in dicot root of the plant root or stem, rather than its length. Certain dicotyledonous roots do not show secondary growth. The secondary vascular tissues originate as a result of the cambial activity.
Secondary Growth in Dicotyledonous Roots |Botany
The phellogen gives rise to the periderm. Formation of Cambium and Development of Secondary Tissues: The dicotyledonous roots posses a limited number of radial vascular bundles with exarch xylem. Normally the pith is very little or altogether absent.
On the initiation of secondary growth, a few parenchyma cells beneath each group of phloem become meristematic and thus as many cambial strips are formed as the number of phloem groups. The cambial cells divide tangentially again and again and produce secondary tissues.
Thereafter some of the cells of single layered pericycle become meristematic lying against the protoxylem groups, which divide and form a few layers of cells. Secondary growth in dicot root cells of the uniseriate pericycle against the protoxylem group now divide and form a few layers.
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- Secondary Growth in Dicotyledonous Root (With Diagram)
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- Difference Between the Secondary Growth in Dicot Stem and Dicot Root
The first- formed cambium now extends both ways and reaches the innermost derivatives of the xylem groups. As a rule the cambial cells produce much more xylem than phloem; and because the first-formed cambium started producing secondary xylem much earlier secondary growth in dicot root produces secondary xylem much more rapidly, the wavy cambium cylinder is ultimately rendered circular.
As already stated, the secondary vascular tissues are fundamentally similar to those of the stem. They form a continuous cylinder and the primary xylem gets completely embedded in it.