Biology: Class 11 — Chapter 5: Morphology of Flowering Plants

• Tap Root System: Consists of the primary root and its lateral branches (secondary, tertiary roots). Seen in dicotyledonous plants like the mustard plant.
• Fibrous Root System: The primary root is short-lived and replaced by a large number of roots originating from the base of the stem. Seen in monocotyledonous plants like wheat.
• Adventitious Roots: Roots that arise from parts of the plant other than the radicle. Examples include grass, Monstera, and the banyan tree.

1. Root Cap: A thimble-like structure covering the apex of the root, protecting its tender tip as it makes its way through the soil.
2. Region of Meristematic Activity: Located a few millimeters above the root cap. Cells are small, thin-walled, with dense protoplasm, and divide repeatedly.
3. Region of Elongation: Cells undergo rapid elongation and enlargement, responsible for the growth of the root in length.
4. Region of Maturation: Cells gradually differentiate and mature. Epidermal cells in this region form very fine, delicate, thread-like structures called root hairs, which absorb water and minerals from the soil.

• Leaf Base: Attaches the leaf to the stem. May bear two lateral small leaf-like structures called stipules. In leguminous plants, the leaf base may become swollen, called the pulvinus.
• Petiole: Helps hold the leaf blade to light and allows it to flutter in the wind, cooling the leaf.
• Lamina (Leaf Blade): The green expanded part with veins and veinlets. The middle prominent vein is the midrib.

The arrangement of veins and veinlets in the lamina of a leaf is called venation.

• Reticulate Venation: Veinlets form a network; characteristic of most dicotyledonous plants.
• Parallel Venation: Veins run parallel to each other; characteristic of most monocotyledonous plants.

• Simple Leaf: Lamina is entire or, when incised, incisions do not touch the midrib.
• Compound Leaf: Incisions of the lamina reach the midrib, breaking it into leaflets. A bud is present in the axil of the petiole but not in the axil of leaflets.
• Pinnately Compound Leaf: Leaflets are present on a common axis, the rachis (e.g., neem).
• Palmately Compound Leaf: Leaflets are attached at a common point at the tip of the petiole (e.g., silk cotton).

The pattern of arrangement of leaves on the stem or branch:

• Alternate: A single leaf arises at each node in an alternate manner (e.g., china rose, mustard, sunflower).
• Opposite: A pair of leaves arise at each node and lie opposite to each other (e.g., Calotropis, guava).
• Whorled: More than two leaves arise at a node and form a whorl (e.g., Alstonia).

• Actinomorphic (Radial Symmetry): Can be divided into two equal radial halves in any radial plane passing through the center (e.g., mustard, datura, chilli).
• Zygomorphic (Bilateral Symmetry): Can be divided into two similar halves only in one particular vertical plane (e.g., pea, gulmohur, bean, Cassia).
• Asymmetric (Irregular): Cannot be divided into two similar halves by any vertical plane passing through the center (e.g., canna).

A typical flower has four whorls arranged on the swollen end of the stalk (thalamus or receptacle):

1. Calyx: Outermost whorl composed of sepals. Can be gamosepalous (sepals united) or polysepalous (sepals free).
2. Corolla: Composed of petals. Can be gamopetalous (petals united) or polypetalous (petals free).
3. Androecium: Composed of stamens (male reproductive organ). Each stamen consists of a filament and a bilobed anther containing pollen-sacs.
4. Gynoecium: Female reproductive part composed of one or more carpels (stigma, style, and ovary).

The mode of arrangement of sepals or petals in a floral bud with respect to other members of the same whorl:

• Valvate: Sepals or petals just touch one another at the margin without overlapping (e.g., Calotropis).
• Twisted: One margin of the appendage overlaps that of the next one (e.g., china rose, lady's finger, cotton).
• Imbricate: Margins overlap but not in any particular direction (e.g., Cassia, gulmohur).
• Vexillary (Papilionaceous): Five petals: largest (standard) overlaps two lateral petals (wings), which overlap the two smallest anterior petals (keel) (e.g., pea, bean).

The arrangement of ovules within the ovary is known as placentation:

• Marginal: Placenta forms a ridge along the ventral suture of the ovary (e.g., pea).
• Axile: Placenta is axial and ovules are attached to it in a multilocular ovary (e.g., china rose, tomato, lemon).
• Parietal: Ovules develop on the inner wall of the ovary (e.g., mustard, Argemone).
• Free Central: Ovules are borne on the central axis and septa are absent (e.g., Dianthus, Primrose).
• Basal: Placenta develops at the base of the ovary and a single ovule is attached to it (e.g., sunflower, marigold).

• Seed Coat: Outer testa and inner tegmen.
• Hilum: A scar on the seed coat where the seed was attached to the fruit.
• Micropyle: A small pore above the hilum.
• Embryo: Consists of an embryonal axis and two cotyledons. The ends of the axis are the radicle and the plumule.
• Endospermic Seeds: Castor (food storing tissue present).
• Non-endospermic Seeds: Bean, gram, pea (endosperm absent in mature seeds).

• Generally endospermic, but some (like orchids) are non-endospermic.
• Aleurone Layer: A proteinous layer separating the embryo from the endosperm.
• Scutellum: The single large, shield-shaped cotyledon.
• The plumule and radicle are enclosed in protective sheaths called coleoptile and coleorhiza, respectively.

• Vegetative Characters: Mostly herbs, shrubs, and rarely small trees. Leaves are alternate, simple, exstipulate with reticulate venation. Underground stem in potato (Solanum tuberosum).
• Floral Characters:
  • Inflorescence: Solitary, axillary, or cymose.
  • Flower: Bisexual, actinomorphic.
  • Calyx: Sepals 5, united, persistent, valvate.
  • Corolla: Petals 5, united, valvate.
  • Androecium: Stamens 5, epipetalous.
  • Gynoecium: Bicarpellary, syncarpous, ovary superior, bilocular, placenta swollen with many ovules, axile placentation.
  • Fruits: Berry or capsule.
  • Seeds: Many, endospermous.
• Floral Formula: $$\oplus \ \Phi \ K_{(5)} \ \overbrace{C_{(5)} \ A_5} \ \underline{G}_{(2)}$$
• Economic Importance: Source of food (tomato, brinjal, potato), spice (chilli), medicine (belladonna, ashwagandha), fumigatory (tobacco), and ornamentals (petunia).