CDS (II) 2021 General Knowledge · Question 30 of 120

Correct — A, Base of the leaves or internodes. Meristematic tissue is the dividing tissue of a plant, and it is classified by where it sits. Apical meristem is at the growing tips of stems and roots and lengthens them. Lateral meristem, the cambium, sits along the sides and thickens the stem or root. Intercalary meristem is the third kind, so called because it is intercalated — inserted — between mature tissues rather than sitting at a tip, and its position is near the node, that is at the base of the leaves or at the base of the internodes. Grasses are where it matters most. A grass or a cereal grows from these basal zones rather than from the tip, which is why a lawn keeps growing after mowing and why grazing does not kill pasture: the growing region lies below the level at which the blade is cut or bitten off. Bamboo, one of the fastest-growing plants there is, extends by division at exactly these zones above each node.

• (b)Stems or roots — Too vague to identify any one meristem, and as a location it describes the lateral meristem, the cambium, which lies along the sides and increases girth.
• (c)Tips of stems and leaves — The tip of the stem is where the apical meristem lies, and it is apical meristem that increases the length of the stem and the root.
• (d)Base of flower pedicel — Not a standard meristem location. Growth of the flower stalk is not attributed to a named intercalary zone in the syllabus.

Plant growth is confined to particular regions rather than spread over the whole body, and the tissue that does the dividing is the meristem. Its cells are small and active, with dense cytoplasm, thin cellulose walls and prominent nuclei, and they lack vacuoles. Three kinds are recognised by position — apical at the tips, lateral along the sides, and intercalary between mature tissues near the nodes. Cells produced by a meristem later take up a permanent shape, size and function through differentiation, becoming parenchyma, collenchyma, sclerenchyma and the conducting tissues.

The three meristems are best learnt as a set of three positions and three consequences: tips give length, sides give girth, and the intercalary zones give the ability to regrow after the top has been removed. Sorting the options by that scheme leaves only one candidate. The wording differs between textbooks without changing the meaning — some say the intercalary meristem is located near the node, others at the base of the leaves or of the internodes, and a related question in the 2023 CDS paper phrased the same location as the base of leaves in grasses. All three describe the same zone, since the node is exactly where a leaf joins the stem and where the next internode begins. The agricultural point is worth keeping: this tissue is why fodder crops and lawns tolerate repeated cutting, and why grasses have coexisted with grazing animals for millions of years.

• Meristematic tissue is classified by position as apical, lateral and intercalary.
• Apical meristem is present at the growing tips of stems and roots and increases their length; lateral meristem, the cambium, increases girth.
• Intercalary meristem lies between mature tissues, near the node — at the base of the leaves or of the internodes.
• Intercalary meristem is characteristic of grasses and lets them regenerate parts removed by grazing or mowing.
• Meristematic cells have dense cytoplasm, thin cellulose walls and prominent nuclei, and they lack vacuoles.

• Placing the intercalary meristem at the tip; the tip belongs to the apical meristem.
• Reading 'stems or roots' as a location — every meristem is in a stem or a root, so the phrase identifies nothing.
• Assuming grass regrows from the cut end; the growing zone is at the base, below where the blade is cut.

As a locate-the-meristem item, as a match list of meristem types against the kind of growth each produces, or as an application question on why mowed grass and grazed pasture recover.

• practice — not a real PYQ

  The increase in the girth of a dicot stem is due to the activity of

  • (a)apical meristem
  • (b)lateral meristem
  • (c)intercalary meristem
  • (d)permanent tissue

  Answer(b) lateral meristem — the cambium lies along the sides of the stem and thickens it, while apical meristem lengthens it.

• practice — not a real PYQ

  A lawn continues to grow after being mown mainly because grasses possess

  • (a)apical meristem at the leaf tips
  • (b)intercalary meristem near the nodes
  • (c)cork cambium in the leaves
  • (d)sclerenchyma at the leaf base

  Answer(b) intercalary meristem near the nodes — the dividing tissue lies below the level of the cut, so growth resumes from there.