Describe the internal structure of a dicot stem with a labelled diagram.

1. 1 · Open in one line. The T.S. of a dicot stem (sunflower) shows an epidermis, a cortex, and a stele with a ring of vascular bundles around a large pith.
2. 2 · Draw and label. [T.S. of sunflower stem: cuticle, epidermis, multicellular hair, hypodermis, cortex, endodermis, pericycle, phloem, cambium, xylem, medullary ray, pith]
3. 3 · Epidermis and cortex.
   • Epidermis: one layer, cuticle, multicellular hairs.
   • Hypodermis: collenchyma; then chlorenchyma and parenchyma; endodermis: starch sheath.
4. 4 · Stele.
   • Pericycle: sclerenchyma patches alternating with parenchyma.
   • Vascular bundles in a ring: conjoint, collateral, open, endarch.
   • Pith: large, of parenchyma; medullary rays between the bundles.
5. 5 · Real life. Cambium lets dicot trees such as neem and mango grow thicker every year; monocots such as coconut do not.
6. 6 · Close in one line. So the dicot stem is strong, flexible and able to grow in thickness.

Scoring tip: A neat ring of 6 to 8 bundles with the cambium clearly marked scores better than a crowded drawing.