Question

Stem of date palm increases in girth due to activity of
a. Intercalary meristem
b. Apical meristem
c. Lateral meristem
d. None of the above

Answer 1

Hint: The increase in girth or the diameter of the stem/root is referred to as secondary growth. In case of dicot stem, lateral (vascular) cambium is responsible for secondary growth and these cambial strips are located in between xylem and phloem, making a vascular bundle that is collateral, conjoint, and open

Complete answer:
It’s important to know, most monocots may undergo no secondary growth or else have anomalous secondary growth of some type. The palm trees increase their diameter of trunk by dividing as well as elongation of parenchyma cells, termed as 'diffuse secondary growth'. In some other monocot stems which go through normal secondary growth, cambium formation is seen but it gives vascular bundles and parenchyma internally and just parenchyma externally. Whereas, some monocot stems increase in diameter by activity of a primary thickening meristem, which is a derivative of apical meristem. Remember, the stem of the date palm is increased in girth due to apical meristem activity and not by intercalary meristem and lateral meristem (involved in normal secondary growth of dicots). Note that, Date palm is monocot and lacks lateral meristem, the meristem which are located along the sides results in the increase in girth of the plant.

It’s a fact, Apical meristem is located at the tips of shoots and roots, and gives rise to primary permanent tissue systems. Keep in mind, the apical meristem results in an increase in height of the date palm from growing tips. The apical meristem is modified to make temporary meristem which perform the function of lateral meristem, as well as divide and produce new cells. Therefore, the enlargement of these peripheral cells results in an increase in the girth of date palm.

The apical meristem, those are separated from apices because of formation of permanent tissues in between, is called an intercalary meristem. It is positioned internodal and carries out localized growth.

Hence, the correct answer is option (B).

Additional information:
You must know, the Monocot Stems cannot increase girth by addition of lateral layers of cells like in case of conifers and woody dicots. On the other hand, they have scattered vascular bundles made of xylem and phloem tissue and each bundle is surrounded by a ring of cells termed as a bundle sheath.

Note: Always remember, in case of stems of Palm trees, parenchyma is abundant tissue located in the ground tissue region. The cells of this parenchyma tissue undergo division and enlargement, which results in increase in girth of the stems. It is termed sometimes as primary gigantism or diffuse secondary growth.