Anatomy of Flowering PlantsNEET Botany · Class 11 · NCERT Chapter 5

You can expect 2 to 3 questions from this chapter in NEET 2027. It is a medium-weightage chapter with consistent PYQ frequency. The most tested topics are differences between dicot and monocot root/stem, xylem and phloem elements, types of simple tissues (especially sclerenchyma), and secondary growth (annual rings, heartwood vs sapwood).

All three are simple permanent tissues. Parenchyma: thin cellulose walls, living, loosely packed, stores food and water, chlorenchyma (with chloroplasts) does photosynthesis, aerenchyma (with air spaces) provides buoyancy in aquatic plants. Collenchyma: unevenly thickened walls (pectin + cellulose at corners), living, provides flexible mechanical support; found in hypodermis of dicot stems and petioles. Sclerenchyma: heavily lignified walls, dead at maturity; two types: fibres (long, in jute/hemp/flax) and sclereids (short/stone cells, in pear grit cells and coconut shell).

Xylem conducts water and minerals upward (soil to leaves). It has four elements: tracheids (dead, main conductor in gymnosperms), vessels (dead, main conductor in angiosperms), xylem parenchyma (living, only living xylem element), and xylem fibres (dead). Phloem conducts food both ways (bidirectional). It also has four elements: sieve tube elements (dead-like, no nucleus at maturity, large sieve pores), companion cells (living, controls sieve tube, present only in angiosperms), phloem parenchyma (living), and phloem fibres (dead).

Look at two things: (1) Number of xylem poles: dicot root has 2 to 6 xylem poles; monocot root has many (polyarch, more than 6). (2) Pith: dicot root has a small or absent pith; monocot root has a large, well-developed pith. Both have exarch protoxylem. Dicot root can undergo secondary growth; monocot root cannot.

Three key differences: (1) Vascular bundle arrangement: dicot stem has vascular bundles arranged in a ring; monocot stem has vascular bundles scattered throughout the ground tissue. (2) Vascular bundle type: dicot stem has open bundles (with cambium); monocot stem has closed bundles (no cambium). (3) Hypodermis: dicot stem has collenchymatous hypodermis; monocot stem has sclerenchymatous hypodermis. Monocot stem also has no distinct cortex-pith boundary (called ground tissue).

Secondary growth increases girth and happens in two stages. Stage 1: Vascular cambium (ring formed from intrafascicular + interfascicular cambium) produces secondary xylem (wood) toward the inside and secondary phloem toward the outside. Annual rings form because spring wood (large vessels) and autumn wood (dense, small vessels) alternate each year. Stage 2: Cork cambium (phellogen) forms in cortex, produces cork (phellem, dead, suberised) outside and phelloderm inside. Together they form the periderm. Lenticels in cork allow gas exchange.