Question

The vascular cambium normally give rise to
(a) Periderm
(b) Phelloderm
(c) Primary phloem
(d) Secondary xylem

Answer 1

Hint: These are formed during secondary growth from the vascular cambium. Its main function is water transport from roots to the other parts of the plant. It also provides mechanical support to the plant body.

Complete step by step answer:
The vascular cambium is the main growth tissue present in the stems and roots of many plants. During secondary growth, it produces secondary xylem inwards, towards the pith, and secondary phloem outwards, towards the bark. It is a layer of meristematic tissue which is present between the primary xylem and primary phloem of a young stem or root. During secondary growth, the parenchymatous cells become meristematic and begin to produce secondary xylem or wood toward the inside of the cambium and secondary phloem toward the outside of the cambium. That means vascular cambium divides to form secondary xylem and phloem and helps in secondary growth and wood formation.
So, the correct answer is, ‘(d) Secondary xylem’.

Additional Information:
- The cambium present between the primary xylem and primary phloem is called the intrafascicular cambium within vascular bundles.
- During secondary growth, cells of medullary rays, in a line between neighboring vascular bundles, become meristematic and form new interfascicular cambium between vascular bundles. - The intrafascicular and interfascicular cambia thus join up to form a ring in three dimensions, a tube that separates the primary xylem and primary phloem, is called the cambium ring.
- The vascular cambium produces secondary xylem on the inside of the ring, and secondary phloem on the outside of the ring, in this way the cambium ring is pushing the primary xylem and phloem apart.
- Periderm is a group of secondary tissues forming a protective layer by replacing epidermis and composed of cork cambium, phelloderm, and cork.
- Phelloderm are structurally similar to the cortex cell generated by phellogen and contain chlorophyll and function in defense.
- Primary phloem from the procambium during the primary growth and it enables the growth in the length of the plant.

Note:
- Vascular cambium is found specifically in dicot plants such as buttercups and oak trees, gymnosperm plants such as pine trees, and also in certain vascular plants.
- During secondary growth the secondary xylem or wood is produced toward the inside of the cambium and secondary phloem toward the outside of the cambium.
- The vascular cambium produces secondary xylem on the inside of the cambium ring and secondary phloem on the outside of the cambium ring.