Anatomy of Flowering Plants Notes: Class 11 Biology Chapter 6
Class 11 Biology Chapter 6 Anatomy of Flowering Plants covers the internal structure and organisation of tissues in roots, stems, and leaves, along with primary and secondary growth.
Overview of Topics & Subtopics (Click to Jump)
1. Plant Tissues
Short Note:
• Meristematic tissue (apical, lateral, intercalary) consists of actively dividing cells responsible for growth; permanent tissue (simple — parenchyma, collenchyma, sclerenchyma; complex — xylem, phloem) is made of differentiated cells performing specific functions.
• Xylem conducts water and minerals (composed of tracheids, vessels, xylem fibres, xylem parenchyma); Phloem conducts food (composed of sieve tubes, companion cells, phloem fibres, phloem parenchyma).
2. Anatomy of Dicot and Monocot Root/Stem
Short Note:
• In dicot roots, xylem and phloem are typically arranged alternately in a limited number (2-6) of radial bundles, and a cambium develops later for secondary growth. Monocot roots have a larger number of xylem/phloem bundles (polyarch) and lack cambium (no secondary growth).
• In dicot stems, vascular bundles are conjoint, collateral, and open (with cambium), arranged in a ring; monocot stems have scattered vascular bundles that are closed (no cambium).
3. Secondary Growth
Short Note:
• Secondary growth (increase in girth) occurs in dicot stems and roots due to the activity of vascular cambium (produces secondary xylem and phloem) and cork cambium/phellogen (produces the periderm, replacing the epidermis).
NCERT Textbook Exercise Questions
What is the effect on stem and root anatomy if a plant is not able to form secondary xylem and phloem?
Answer: Without secondary xylem and phloem formation, the plant would be unable to undergo secondary growth (increase in girth); it would remain thin and could not develop the strength needed to grow tall or support extensive branching, as seen typically in monocots which lack this feature.
Draw illustrations to bring out the anatomical differences between a monocot root and a dicot root.
Answer: A dicot root shows a limited number of xylem bundles (2 to 6, exarch), pith is generally small or absent, and a cambium ring develops between xylem and phloem for secondary growth. A monocot root shows many xylem bundles (polyarch), a well-developed central pith, and no cambium (hence no secondary growth).
Explain the process of secondary growth in the stems of woody angiosperms with the help of schematic diagrams.
Answer: Secondary growth begins with the formation of a continuous ring of vascular cambium between xylem and phloem. This cambium divides to produce secondary xylem towards the inside and secondary phloem towards the outside, increasing the girth of the stem. Simultaneously, cork cambium (phellogen) develops in the outer cortex region, producing cork (phellem) outward and secondary cortex (phelloderm) inward, together forming the periderm which replaces the epidermis.
How is the study of plant anatomy useful to us?
Answer: The study of plant anatomy helps us understand the internal structure and functioning of different plant parts, distinguish between monocots and dicots, understand mechanisms like water/food conduction and mechanical support, and has practical applications in areas like wood/timber industries, plant identification, and agriculture.
