Morphology of Flowering Plants Flashcards
Root
The Root System in Flowering Plants**
- Definition: The root is the underground part of the plant responsible for anchorage, absorption, storage, and synthesis of plant growth regulators.
- Types of Root Systems:
- Tap Root System: Found in dicotyledonous plants (e.g., mustard), where the primary root elongates and gives rise to lateral roots.
- Fibrous Root System: Found in monocotyledonous plants (e.g., wheat), where the primary root is short-lived and is replaced by many roots arising from the base of the stem.
- Adventitious Roots: Roots that arise from parts of the plant other than the radicle (e.g., grass, Monstera, banyan tree).
- Functions:
- Absorption of water and minerals
- Providing anchorage
- Storage of reserve food
- Synthesis of plant growth regulators
Regions of the Root**
- Root Cap: A thimble-like structure that protects the tender root tip as it moves through the soil.
- Region of Meristematic Activity:
- Just above the root cap, consists of small, thin-walled cells with dense protoplasm.
- Cells divide repeatedly.
- Region of Elongation:
- Above the meristematic region, responsible for growth in root length.
- Region of Maturation:
- Cells differentiate and mature.
- Epidermal cells give rise to root hairs that absorb water and minerals.
stem
- Definition: The stem is the ascending part of the plant that develops from the plumule of the embryo and bears branches, leaves, flowers, and fruits.
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Characteristics:
- Has nodes (regions where leaves arise) and internodes (regions between two nodes).
- Bears terminal and axillary buds.
- Young stems are green, and older stems become woody and dark brown.
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Functions:
- Spreads out branches with leaves, flowers, and fruits.
- Conducts water, minerals, and food.
- May function in storage, support, protection, and vegetative propagation.
modifications of root and stem
Modifications of Roots**
Roots undergo modifications to perform functions other than absorption and anchorage. The major types of root modifications include:
1. Storage Roots (For Food Storage)
- Examples:
- Taproots: Carrot, turnip, radish, beetroot
- Adventitious roots: Sweet potato
2. Prop Roots (For Support)
- Definition: Large, pillar-like adventitious roots that provide mechanical support to heavy branches.
- Example: Banyan tree
3. Stilt Roots (For Additional Support)
- Definition: Thick, supporting roots that grow obliquely from the lower nodes of the stem.
- Examples: Maize, sugarcane, screwpine
4. Pneumatophores (For Respiration)
- Definition: Aerial roots that grow vertically upward from soil or waterlogged areas to facilitate gaseous exchange.
- Example: Rhizophora (mangrove trees)
5. Haustorial Roots (Parasitic Roots)
- Definition: Roots that penetrate the host plant and absorb nutrients.
- Examples: Cuscuta (dodder), Orobanche
6. Nodulated Roots (For Nitrogen Fixation)
- Definition: Roots that have nodules containing nitrogen-fixing bacteria (Rhizobium).
- Examples: Pea, beans, groundnut
modifications of stem
Modifications of Stems**
Stems may be modified to perform additional functions such as storage, vegetative propagation, protection, and climbing.
1. Underground Stem Modifications (For Perennation & Storage)
- Rhizome: Ginger, turmeric
- Tuber: Potato
- Bulb: Onion, garlic
- Corm: Colocasia, saffron (Crocus)
2. Subaerial Stem Modifications (For Vegetative Propagation)
- Runner: Strawberry, grass
- Stolon: Mint, jasmine
- Sucker: Chrysanthemum, banana, pineapple
- Offset: Water hyacinth, Pistia (water lettuce)
3. Aerial Stem Modifications (For Protection, Climbing & Photosynthesis)
- Thorns: Bougainvillea, citrus (For protection)
- Tendrils: Cucumber, watermelon, grapevine, passionflower (Passiflora) (For climbing)
- Phylloclade: Opuntia, Euphorbia (For photosynthesis in xerophytic plants)
- Cladode: Asparagus, Ruscus
leaf
• The leaf is a lateral, generally flattened structure borne on the stem.
• Develops at the node and bears a bud in its axil, which may develop into a branch.
• Leaves originate from shoot apical meristems and are arranged in acropetal order.
• Most important vegetative organ for photosynthesis.
• A typical leaf consists of three main parts:
1. Leaf base – attaches the leaf to the stem and may bear stipules.
2. Petiole – holds the blade to light; long, flexible petioles allow fluttering, aiding cooling and gas exchange.
3. Lamina (leaf blade) – green, expanded part with veins and veinlets; the midrib is the prominent central vein.
• Functions of veins:
o Provide rigidity to the leaf blade.
o Act as channels for transport of water, minerals, and food materials.
• The shape, margin, apex, surface, and incision of the lamina vary among different leaves.
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Venation
• Venation: Arrangement of veins and veinlets in the leaf lamina.
• Types of venation:
1. Reticulate Venation:
Veinlets form a network.
Found in dicotyledonous plants.
Example: Peepal (Ficus religiosa).
2. Parallel Venation:
Veins run parallel to each other.
Found in monocotyledonous plants.
Example: Grass, Banana, Maize.
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Types of Leaves
• Simple Leaf: Lamina is entire or incised, but the incisions do not touch the midrib.
• Compound Leaf: Lamina is divided into leaflets, with incisions reaching the midrib.
o Types of Compound Leaves:
1. Pinnately Compound Leaf:
Leaflets arranged on a common axis (rachis, representing the midrib).
Example: Neem (Azadirachta indica).
2. Palmately Compound Leaf:
Leaflets attached at a common point (tip of petiole).
Example: Silk cotton (Bombax ceiba).
• Axillary Buds are present in both simple and compound leaves but not in leaflets of a compound leaf.
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Phyllotaxy (Leaf Arrangement)
• Phyllotaxy: The pattern of arrangement of leaves on the stem or branch.
• Types of Phyllotaxy:
1. Alternate Phyllotaxy:
A single leaf arises at each node in an alternate manner.
Examples: China rose (Hibiscus rosa-sinensis), Mustard (Brassica), Sunflower (Helianthus annuus).
2. Opposite Phyllotaxy:
A pair of leaves arises at each node, opposite to each other.
Examples: Calotropis, Guava (Psidium guajava).
3. Whorled Phyllotaxy:
More than two leaves arise at a node and form a whorl.
Example: Alstonia.
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Key Features
Pulvinus: Swollen leaf base in leguminous plants.
• Sheathing Leaf Base: Present in monocots, partially or wholly covering the stem.
• Functions of Leaves:
o Photosynthesis.
o Transpiration.
o Gaseous exchange.
o Vegetative propagation
inflorescence
• Inflorescence is the arrangement of flowers on the floral axis.
• A flower is a modified shoot where the shoot apical meristem changes to floral meristem.
Types of Inflorescence
1. Racemose:
o Main axis continues to grow.
o Flowers are arranged in acropetal succession (younger flowers at the tip, older at the base).
2. Cymose:
o The main axis ends in a flower, growth is limited.
o Flowers develop in basipetal order (older flowers at the tip, younger at the base).
The Flower – Structure and Symmetry
• The flower is the reproductive unit in angiosperms.
• It consists of four whorls on the thalamus/receptacle:
1. Calyx (Sepals) – Protection
2. Corolla (Petals) – Attraction
3. Androecium (Stamens) – Male reproductive part
4. Gynoecium (Carpels) – Female reproductive part
Symmetry of Flowers
• Actinomorphic (Radial Symmetry): Can be divided into equal halves in any plane (Mustard, Datura, Chilli).
• Zygomorphic (Bilateral Symmetry): Can be divided into two equal halves only in one plane (Pea, Bean, Gulmohur, Cassia).
• Asymmetric (Irregular): Cannot be divided into equal halves (Canna).
Floral Classification
• Bracteate: Flowers with bracts (leaf-like structures at the base of pedicel).
• Ebracteate: Flowers without bracts.
• Trimerous, Tetramerous, Pentamerous: Floral appendages in multiples of 3, 4, or 5, respectively.
: Flower Position Based on Ovary
- Hypogynous (Superior Ovary): Gynoecium at the highest position (Mustard, China Rose, Brinjal).
- Perigynous (Half- inferior Ovary): Gynoecium in the center, floral parts at the same level (Plum, Rose, Peach).
- Epigynous (Inferior Ovary): Ovary is enclosed by the thalamus, floral parts above it (Guava, Cucumber, Sunflower ray florets).
calyx and corolla
Calyx (Sepals)
• Outer whorl for protection.
• Gamosepalous: Sepals united.
• Polysepalous: Sepals free.
Corolla (Petals)
• Brightly colored for pollination.
• Gamopetalous: Petals united.
• Polypetalous: Petals free.
Aestivation (Arrangement of Sepals/Petals in a Bud)
1. Valvate: Margins touch but do not overlap (Calotropis).
2. Twisted: One margin overlaps the next (China Rose, Lady’s Finger, Cotton).
3. Imbricate: Margins overlap but not in any particular order (Cassia, Gulmohur).
4. Vexillary: Largest petal (Standard) overlaps the two lateral petals (Wings), which overlap two smallest petals (Keel) (Pea, Bean).
androecium
- Consists of stamens (filament + anther).
- Anther: Bilobed with two pollen sacs producing pollen grains.
- Staminode: A sterile stamen.
- Stamens may be attached:
o Epipetalous (to petals) – Brinjal.
o Epiphyllous (to perianth) – Lily. - Stamens can be free (polyandrous) or united:
o Monoadelphous: One bundle (China Rose).
o Diadelphous: Two bundles (Pea).
o Polyadelphous: More than two bundles (Citrus).
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Variation in the length of filaments-Salvia and Mustard
Gynoecium – Female Reproductive Part and Placentation
- Composed of carpels (stigma + style + ovary).
- Apocarpous: Free carpels (Lotus, Rose).
- Syncarpous: Fused carpels (Mustard, Tomato).
- Ovary matures into fruit, ovules into seeds.
Placentation (Ovule Arrangement in Ovary)
1. Marginal – Along one ridge (Pea).
2. Axile – In a multilocular ovary (China Rose, Tomato, Lemon).
3. Parietal – ovules On inner ovary wall;a false septum called replum develops in the ovary (Mustard, Argemone).
4. Free Central – On a central axis (Dianthus, Primrose).
5. Basal – At the base of ovary, single ovule (Sunflower, Marigold).
Fruit
• Definition: A mature or ripened ovary that develops after fertilization.
• Parthenocarpic Fruit: Formed without fertilization (e.g., banana).
• Structure:
o Pericarp: Can be dry or fleshy.
o If fleshy, it is divided into:
Epicarp (outermost layer)
Mesocarp (middle layer, fleshy in some fruits)
Endocarp (innermost layer, can be hard or soft).
• Drupe: A type of fruit from a monocarpellary superior ovary, with one seed.
o Mango: Epicarp is thin, mesocarp is fleshy, endocarp is stony.
o Coconut: Mesocarp is fibrous, endocarp hard.
Ovule
- Definition: A fertilized ovule that develops into a seed, consisting of a seed coat and embryo.
- Embryo Parts:
o Radicle: Develops into root.
o Embryonal axis.
o Cotyledons: One in monocots (e.g., maize), two in dicots (e.g., pea).
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: Structure of a Dicotyledonous Seed - Seed Coat:
o Testa (outer layer).
o Tegmen (inner layer). - Hilum: A scar where the seed was attached to the fruit.
- Micropyle: A small pore above the hilum.
- Embryo:
o Cotyledons: Fleshy, store food.
o Radicle: Develops into root.
o Plumule: Develops into shoot. - Types:
o Endospermic (Albuminous) Seeds: Retain endosperm (e.g., castor).
o Non-Endospermic (Exalbuminous) Seeds: Endosperm is used up during development (e.g., bean, gram, pea).
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Structure of a Monocotyledonous Seed - Mostly endospermic, except in orchids.
- Seed Coat: Thin, often fused with the fruit wall (e.g., maize).
- Endosperm:
o Bulky, stores food.
o Separated from embryo by a protein-rich aleurone layer. - Embryo:
o Scutellum: A large, shield-shaped cotyledon.
o Plumule: Develops into shoot, enclosed in coleoptile.
o Radicle: Develops into root, enclosed in coleorhiza.
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key features
Key Features
• Fruit: Ripened ovary; drupe (mango, coconut).
• Seed: Consists of seed coat & embryo.
• Dicot Seed:
o Two cotyledons.
o May be endospermic (castor) or non-endospermic (pea, gram).
• Monocot Seed:
o One cotyledon (scutellum).
o Mostly endospermic (except orchids).
o Aleurone layer separates endosperm and embryo.
o Coleoptile (protects plumule), coleorhiza (protects radicle).
summary
: General Features of Flowering Plants
• Variation: Enormous diversity in shape, size, structure, nutrition, lifespan, habit, and habitat.
• Organ Systems: Well-developed root and shoot systems.
• Root System:
o Tap root: Present in dicots.
o Fibrous root: Present in monocots.
o Modifications: Storage (e.g., carrot), support (e.g., banyan), respiration (e.g., mangrove roots).
• Shoot System:
o Differentiated into stem, leaves, flowers, and fruits.
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Features of Stem and Leaf
• Stem:
o Differentiated by nodes and internodes.
o Multicellular hair and positively phototropic (grows towards light).
• Leaf:
o Lateral outgrowth of stem.
o Develops exogenously at nodes.
o Green due to chlorophyll → Photosynthesis.
o Shows variation in shape, size, margin, apex, and lamina incisions.
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Flowers and Reproduction
• Flower:
o A modified shoot for sexual reproduction.
o Arranged in different inflorescences.
o Variation in structure, symmetry, ovary position, arrangement of petals, sepals, and ovules.
• Fertilization:
o Ovary → Fruit.
o Ovules → Seeds.
o Seeds can be monocotyledonous or dicotyledonous.
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Classification and Floral Representation
• Floral Characteristics: Basis for classification and identification of flowering plants.
• Scientific Description:
o Defined sequence using scientific terms.
• Floral Representation:
o Floral Diagram: Graphical representation.
o Floral Formula: Symbolic representation.
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Key Features
• Roots: Tap in dicots, fibrous in monocots, modified for support, storage, or respiration.
• Stems: Identified by nodes, internodes, phototropism, and multicellular hairs.
• Leaves: Outgrowth of stem, performs photosynthesis, shows variation in shape and size.
• Flowers: Sexual reproductive structure, different types of inflorescences.
• Seeds: Monocot or dicot, varying in shape, size, viability.
• Classification: Based on floral features, represented by floral diagrams and formulas.
