Cut a transverse section of young stem of a plant from your school garden and observe it under the microscope. How would you ascertain whether it is a monocot stem or a dicot stem? Give reasons.

Cut a thin transverse section (T.S.) of a young stem using a sharp blade or scalpel.

Place the section in water to prevent it from drying, then transfer it to a slide.

Add a drop of safranin or any suitable stain to highlight cell structures.

Gently place a coverslip and observe the section under a compound microscope at low and then high magnification.

To ascertain whether the stem is from a monocot or dicot plant, analyze the following anatomical features:

Vascular bundle arrangement

Monocot: Vascular bundles are numerous, scattered throughout the ground tissue without a definite arrangement.

Dicot: Vascular bundles are fewer in number, arranged in a circular ring.

Vascular bundle structure

Monocot: Bundles are closed (no cambium present), thus no secondary growth.

Dicot: Bundles are open (cambium present between xylem and phloem), allowing secondary growth.

Presence of cortex and pith

Monocot: Ground tissue is not clearly differentiated into cortex, endodermis, pericycle, and pith.

Dicot: Ground tissue is distinctly differentiated into cortex, endodermis, pericycle, and central pith.

Bundle sheath

Monocot: Vascular bundles are usually surrounded by a sclerenchymatous bundle sheath.

Dicot: Bundle sheath is either absent or not well-developed.

Secondary growth

Monocot: Absent due to lack of vascular cambium.

Dicot: Possible due to presence of vascular cambium.

Hypodermis

Monocot: Usually sclerenchymatous (for mechanical strength).

Dicot: Usually collenchymatous (for support and flexibility).

By carefully comparing these features under the microscope, the stem’s classification as monocot or dicot can be determined accurately.