REVISION SUMMARY: Anatomy of Flowering Plants (NCERT Class 11)
1. Chapter at a glance
- Anatomy is the study of internal structure and organisation of plants into tissues and organs.
- Three tissue systems exist based on structure and location: epidermal tissue system, ground (fundamental) tissue system and vascular (conducting) tissue system.
- Epidermal tissue system forms the outermost covering and includes epidermis, stomata and trichomes/hairs.
- Ground tissue system comprises all tissues except epidermis and vascular bundles; it includes parenchyma, collenchyma and sclerenchyma.
- Vascular tissue system consists of xylem and phloem forming vascular bundles that may be open/closed or radial/conjoint.
- Dicot and monocot roots, stems and leaves differ in arrangement, number and type of vascular bundles, presence/absence of cambium, pith size and mesophyll differentiation.
- Vascular bundles are open (with cambium) in dicot stems and closed (without cambium) in monocot stems; roots show radial arrangement while stems and leaves show conjoint arrangement.
- Secondary growth occurs in dicot roots and stems via cambium; monocot roots lack secondary growth.
2. Definitions and laws
- Anatomy: Study of internal structure of plants.
- Epidermal tissue system: Forms the outer-most covering of the whole plant body and comprises epidermal cells, stomata and the epidermal appendages – the trichomes and hairs.
- Stomatal apparatus: The stomatal aperture, guard cells and the surrounding subsidiary cells are together called stomatal apparatus.
- Ground tissue system: All tissues except epidermis and vascular bundles constitute the ground tissue.
- Vascular tissue system: Consists of complex tissues, the phloem and the xylem; xylem and phloem together constitute vascular bundles.
- Open vascular bundles: Vascular bundles that possess cambium between phloem and xylem and have the ability to form secondary xylem and phloem tissues (dicot stems).
- Closed vascular bundles: Vascular bundles that lack cambium and therefore do not form secondary tissues (monocot stems).
- Radial vascular bundles: Xylem and phloem arranged in an alternate manner along the different radii (roots).
- Conjoint vascular bundles: Xylem and phloem jointly situated along the same radius (stems and leaves).
- Stele: All tissues on the inner side of the endodermis such as pericycle, vascular bundles and pith constitute the stele.
3. Important diagrams and activities
- Figure 6.1: Diagrammatic representation of stomata with bean-shaped guard cells (dicot) and dumb-bell shaped guard cells (grass) – demonstrates structure of stomatal apparatus and guard cell wall thickening.
- Figure 6.2: Various types of vascular bundles (radial, conjoint closed, conjoint open) – shows arrangement of xylem and phloem and presence/absence of cambium.
- Figure 6.3: T.S. of dicot root (sunflower) and monocot root – demonstrates differences in number of xylem bundles, pith size and absence of secondary growth in monocot root.
- Figure 6.4: T.S. of dicot stem and monocot stem – demonstrates ring vs scattered vascular bundles, open vs closed bundles, hypodermis type and pith.
- Figure 6.5: T.S. of dorsiventral (dicot) leaf and isobilateral (monocot) leaf – demonstrates mesophyll differentiation, stomatal distribution and bundle sheath.
4. Common misconceptions and exam pitfalls
- Confusing open vascular bundles (dicot stems, cambium present) with closed (monocot stems, cambium absent) or radial (roots) with conjoint (stems/leaves).
- Assuming all roots have few xylem bundles; monocot roots are polyarch (more than six).
- Mixing up presence of phloem parenchyma (present in dicot stem, absent in monocot stem) and water cavities (monocot stem only).
- Forgetting that endodermis has Casparian strips in roots but forms starch sheath in dicot stems.
- Overlooking that bulliform cells are specific to monocot (grass) leaves and cause inward curling under water stress.
- Drawing vascular bundles without showing endarch protoxylem in stems or correct position of xylem in leaf bundles.
5. Formula sheet
None present in the chapter.