Question

Which of the following statements is not true about secondary growth?

• A. It leads to an increase in the girth of a plant
• B. It occurs in dicotyledonous plants and gymnosperms
• C. Redifferentiation of medullary ray cells form cambium
• D. It adds new conducting tissue to meet the increased demand for food and water

Answer 1

The correct option is C Redifferentiation of medullary ray cells form cambium

Secondary growth is the growth in girth of a plant with the help of lateral meristem such as cambium. It is commonly observed in dicots and gymnosperms. Monocots cannot undergo secondary growth as they lack cambium.

Cambium is of two types: vascular cambium and cork cambium.

Vascular cambium is formed of interfascicular cambium and intrafascicular cambium.
Intrafascicular cambium is formed from the remaining cells of the procambium. Some differentiated (permanent) cells of the medullary rays, which surround the vascular bundles in the dicot stem, dedifferentiate to regain meristematic potential. These meristematic cells form the interfascicular cambium which is formed in between the vascular bundles.
As secondary growth occurs, it adds new tissue of xylem and phloem on either side of the cambium. The newly formed xylem and phloem are called secondary xylem and secondary phloem, respectively.
The new conducting tissue can replace old non-functional tissue or reinforce existing conducting capacity to meet the increased demands of the plant. The increase in demand for food and water post-primary and secondary growth is met by these tissues.