NCERT Solutions for Class 11 Biology Chapter 6 Anatomy of Flowering Plants

Short Note:

• Meristematic Tissues: Actively dividing cells responsible for plant growth.

  - Apical Meristem: Present at tips of roots and shoots; responsible for primary growth (length).

  - Intercalary Meristem: Occurs between mature tissues (e.g., grasses); aids in regeneration after grazing.

  - Lateral Meristem: Occurs in mature regions of roots and shoots; responsible for secondary growth (girth), e.g., Fascicular cambium, Cork cambium.

• Permanent Tissues: Cells that have lost the capacity to divide and have attained specialized structures.

  - Simple Permanent Tissues: Parenchyma (thin-walled, storage/photosynthesis), Collenchyma (thickened at corners with pectin, flexibility/mechanical support), Sclerenchyma (dead, lignified walls, structural support, e.g., sclereids and fibers).

  - Complex Permanent Tissues: Xylem (transports water/minerals; made of tracheids, vessels, xylem fibers, xylem parenchyma) and Phloem (transports food; made of sieve tube elements, companion cells, phloem parenchyma, phloem fibers).

Short Note:

• Epidermal Tissue System: Outermost protective layer consisting of epidermis, stomata, and epidermal appendages (trichomes on stems, root hairs on roots).

• Ground Tissue System: Forms the main bulk of plant body between epidermis and vascular bundles. Includes cortex, pericycle, pith, and mesophyll in leaves.

• Vascular Tissue System: Comprises xylem and phloem bundled together.

  - Radial Vascular Bundles: Xylem and phloem arranged in alternate radii (e.g., Roots).

  - Conjoint Vascular Bundles: Xylem and phloem jointly situated along the same radius (e.g., Stems and Leaves).

  - Open vs Closed: Open bundles possess cambium between xylem and phloem (Dicots); Closed bundles lack cambium (Monocots).

Short Note:

• Dicot Root vs Monocot Root:

  - Dicot Root: Diarch to hexarch vascular bundles (2–6 xylem patches), small or inconspicuous pith, secondary growth present.

  - Monocot Root: Polyarch vascular bundles (>6 xylem patches), large and well-developed pith, secondary growth absent.

• Dicot Stem vs Monocot Stem:

  - Dicot Stem: Epidermis with trichomes, hypodermis made of collenchyma, vascular bundles arranged in a distinct ring, open conjoint bundles with cambium.

  - Monocot Stem: Hypodermis made of sclerenchyma, vascular bundles scattered in ground tissue, closed conjoint bundles wrapped in sclerenchymatous bundle sheath, water-containing cavities present.

Short Note:

• Dorsiventral Leaf (Dicot Leaf):

  - Stomata generally more abundant on the lower epidermis (abaxial surface).

  - Mesophyll differentiated into Palisade parenchyma (upper, elongated cells with abundant chloroplasts) and Spongy parenchyma (lower, loosely arranged cells with air cavities).

• Isobilateral Leaf (Monocot Leaf):

  - Stomata distributed equally on both surfaces (amphistomatic).

  - Mesophyll is not differentiated into palisade and spongy parenchyma.

  - Contains specialized large, empty Bulliform cells in upper epidermis that cause leaf rolling during water stress to minimize transpiration.

Short Note:

• Increase in girth/girth expansion of dicot stems and roots due to activity of secondary lateral meristems.

• Vascular Cambium: Forms a continuous ring (intrafascicular + interfascicular cambium). Cuts off secondary xylem toward inside and secondary phloem toward outside.

• Spring Wood vs Autumn Wood: Spring wood has larger vessels with wider cavities formed during active spring season; Autumn wood has narrower vessels formed in autumn. Together they form an Annual Ring (used for dendrochronology).

• Heartwood vs Sapwood: Heartwood is dark, hard, central dead wood containing tannins/resins (provides structural strength); Sapwood is peripheral, lighter, and actively conducts water.

• Cork Cambium (Phellogen): Forms phellem (cork) outside and phelloderm (secondary cortex) inside. Together, phellogen, phellem, and phelloderm constitute the Periderm.