Morphology of Flowering Plants – CBSE NCERT Study Resources

Roots in flowering plants undergo structural modifications to perform specialized functions beyond anchorage and absorption. Our textbook shows three main types: storage, support, and respiratory roots.

• Storage roots: Swollen taproots in carrot (Daucus carota) store food
• Prop roots: Banyan (Ficus benghalensis) develops hanging roots for support
• Pneumatophores: Rhizophora in mangroves grows upward for oxygen uptake

These adaptations demonstrate evolutionary responses to environmental challenges. Storage roots help perennial survival, while pneumatophores solve hypoxia in waterlogged soils.

Inflorescence refers to flower arrangement patterns. Racemose shows indefinite growth with acropetal succession, while cymose has definite growth with basipetal order.

• Racemose: Mustard (Brassica) has simple raceme
• Cymose: Hibiscus shows solitary cyme

Racemose maximizes pollination exposure, while cymose conserves energy. These patterns reflect evolutionary optimization for reproductive success.

Placentation refers to ovule arrangement in the ovary. Our textbook classifies five main types based on placenta position.

• Axile: Tomato (Lycopersicon) with central placenta
• Parietal: Mustard with ovules on ovary wall
• Free central: Primrose (Primula) with single column

Placentation determines seed packing efficiency. Axile allows maximum ovules, while free central benefits lightweight seeds for wind dispersal.

Aestivation describes petal/sepals arrangement in bud condition. Four main patterns exist: valvate, twisted, imbricate, and vexillary.

• Twisted: Cotton (Gossypium) shows overlapping petals
• Vexillary: Pea (Pisum) has large standard petal

These patterns protect reproductive parts during development. Vexillary aids pollinator targeting, while valvate provides compact protection.

Phyllotaxy refers to leaf arrangement on stems. Three primary patterns exist: alternate, opposite, and whorled, each with distinct advantages.

• Alternate: Sunflower (Helianthus) shows spiral arrangement
• Opposite: Calotropis has paired leaves at nodes

Alternate phyllotaxy minimizes shadowing, maximizing light absorption. Opposite arrangement provides structural stability, showing adaptation to environmental needs.

Roots in flowering plants undergo structural modifications to perform specialized functions beyond anchorage and absorption. We studied three primary types: storage, support, and respiratory roots.

• Storage roots: Swollen taproots in carrot (Daucus carota) store food
• Prop roots: Banyan (Ficus benghalensis) develops hanging roots for support
• Pneumatophores: Rhizophora in mangroves grows upward for oxygen uptake

These adaptations demonstrate evolutionary responses to environmental pressures. Our textbook shows how pneumatophores combat hypoxia in waterlogged soils.

Understanding root modifications aids in crop improvement and ecological conservation, especially for mangrove ecosystems.

Inflorescence refers to the arrangement of flowers on the floral axis. We studied two fundamental patterns: indefinite growth (racemose) and definite growth (cymose).

Racemose allows continuous pollination opportunities, while cymose ensures concentrated energy for fruit development. Our textbook shows how cymose is evolutionarily advanced.

This knowledge helps in plant breeding programs to manipulate flowering patterns for higher yields.

Placentation refers to ovule arrangement in the ovary. We studied five types: marginal, axile, parietal, free-central, and basal.

• Marginal: Pea (single placenta along one margin)
• Axile: Tomato (multiple placentae in partitioned ovary)
• [Diagram: Cross-sections showing placentation types]

Placentation determines seed packing density. Our textbook shows how axile placentation in citrus allows maximum seed production.

Understanding this helps predict fruit development patterns and improve seed yield in crops.

Entomophilous flowers develop specific adaptations to attract pollinators. We studied how structure, color, and reward systems co-evolve with pollinators.

• Salvia: Lever mechanism ensures pollen deposition on bee's back
• Orchids: Mimic female insects to trigger pseudocopulation

These adaptations demonstrate precise pollinator specificity. Our textbook shows how Salvia's staminal lever increases cross-pollination efficiency by 80%.

Such knowledge is crucial for conservation biology as pollinator decline threatens these specialized relationships.

Dicot seeds like bean (Phaseolus) have distinct structural components that differ fundamentally from monocots like maize.

• Dicot features: Two cotyledons, plumule-radicle axis, hilum
• Monocot contrast: Single scutellum, coleoptile/coleorhiza
• [Diagram: Comparative seed structure]

Our textbook shows dicot cotyledons store nutrients (proteins in pea) while monocots use endosperm (starch in wheat).

This understanding aids in seed technology applications like hybrid seed production and storage optimization.

Roots in flowering plants undergo various modifications to perform specialized functions beyond absorption and anchorage. These adaptations help plants survive in diverse environments. Here are the key modifications:

• Storage roots: These become fleshy to store food. Taproots of carrots and radishes swell to store nutrients, while adventitious roots of sweet potatoes form tuberous roots.
  Adaptation: Helps plants survive unfavorable conditions by utilizing stored food.
• Prop roots: Found in plants like banyan, these roots grow from branches downward into the soil for additional support.
  Adaptation: Provides stability to tall or heavy plants.
• Pneumatophores: Seen in mangroves like Rhizophora, these roots grow upwards out of the waterlogged soil to facilitate oxygen absorption.
  Adaptation: Enables respiration in oxygen-deficient environments.
• Parasitic roots: In plants like Cuscuta, roots penetrate the host plant's vascular tissue to absorb nutrients.
  Adaptation: Allows survival without photosynthesis.

These modifications showcase the evolutionary flexibility of roots to meet ecological challenges.

Placentation refers to the arrangement of ovules within the ovary. It is crucial for seed development and varies among flowering plants. The main types are:

• Marginal: Ovules are arranged along the fused margin of a single carpel (e.g., pea).
  Diagram shows single line of ovules along the ovary's edge.
• Axile: Ovules are attached to the central axis of a multi-chambered ovary (e.g., tomato).
  Diagram shows radial arrangement in a partitioned ovary.
• Parietal: Ovules develop on the inner ovary wall in a single chamber (e.g., cucumber).
  Diagram shows ovules lining the periphery.
• Free central: Ovules attach to a central column in a single-chambered ovary (e.g., primrose).
  Diagram shows stalk-like placenta with ovules.
• Basal: Single ovule attaches at the ovary base (e.g., sunflower).
  Diagram shows solitary ovule at bottom.

These patterns influence fruit development and seed dispersal mechanisms.

The three families exhibit distinct floral characteristics:

• Fabaceae:
  Floral formula: % K₍₅₎ C_1+2+(2) A₍₉₎₊₁ G₁
  Description: Zygomorphic flowers with papilionaceous corolla (1 standard, 2 wings, 2 keel petals). Stamens are diadelphous (9 fused +1 free). Superior ovary with single carpel.
• Solanaceae:
  Floral formula: ⊕ K₍₅₎ C₍₅₎ A₅ G₍₂₎
  Description: Actinomorphic flowers with fused sepals and petals forming a tube. Stamens epipetalous. Bicarpellary syncarpous superior ovary with axile placentation.
• Liliaceae:
  Floral formula: ⊕ P₃₊₃ A₃₊₃ G₍₃₎
  Description: Trimerous flowers with undifferentiated perianth (tepals). Six stamens in two whorls. Tricarpellary syncarpous superior ovary.

These differences reflect evolutionary adaptations to specific pollination strategies.

A dicot leaf's transverse section reveals specialized tissues arranged in layers:

• Upper epidermis: Single layer of tightly packed cells with thick cuticle.
  Significance: Prevents water loss and protects against pathogens.
• Palisade parenchyma: Elongated chlorophyll-rich cells below epidermis.
  Significance: Main site for photosynthesis due to maximum light exposure.
• Spongy parenchyma: Loosely arranged cells with air spaces.
  Significance: Facilitates gas exchange and contains some chloroplasts.
• Vascular bundles: Located in midrib and veins, with xylem (top) and phloem (bottom).
  Significance: Xylem transports water/minerals; phloem carries photosynthetic products.
• Lower epidermis: Contains stomata guarded by kidney-shaped cells.
  Significance: Regulates transpiration and gas exchange.

This organization optimizes photosynthesis while minimizing water loss, demonstrating perfect adaptation for terrestrial life.

In flowering plants, roots are primarily classified into two types: tap roots and adventitious roots. Each type has specific modifications to perform specialized functions.

1. Tap Root System: This develops from the radicle of the embryo and forms the primary root with lateral branches.

• Modifications:
  - Storage roots: Swollen for food storage (e.g., carrot and radish).
  - Respiratory roots (Pneumatophores): Found in mangroves (e.g., Rhizophora) for gaseous exchange.

2. Adventitious Root System: These arise from parts other than the radicle, such as stems or leaves.

• Modifications:
  - Prop roots: Provide mechanical support (e.g., banyan tree).
  - Stilt roots: Offer additional anchorage (e.g., maize and sugarcane).
  - Climbing roots: Help plants cling to surfaces (e.g., money plant).

These modifications ensure survival in diverse environments by aiding in nutrient absorption, support, and adaptation.

Inflorescence refers to the arrangement of flowers on the floral axis. It enhances pollination efficiency and seed dispersal.

Structure: It consists of a peduncle (main axis), pedicel (flower stalk), and floral buds.

Types:

• Racemose Inflorescence:
  - The main axis grows indefinitely, producing flowers laterally.
  - Younger flowers are at the apex, older ones at the base.
  - Example: mustard and radish.
• Cymose Inflorescence:
  - The main axis terminates in a flower, limiting growth.
  - Older flowers are at the apex, younger ones at the base.
  - Example: Hibiscus and Bougainvillea.

Significance: Inflorescence attracts pollinators, ensures genetic diversity, and optimizes reproductive success.

Roots in flowering plants undergo various modifications to perform specialized functions beyond anchorage and absorption. These adaptations help plants survive in diverse environments.

• Storage roots: Swollen roots store food, e.g., taproots in carrot (Daucus carota) and radish (Raphanus sativus). These help plants survive unfavorable conditions.
• Prop roots: Aerial roots from branches (e.g., banyan Ficus benghalensis) provide additional support to heavy trunks.
• Stilt roots: Adventitious roots from lower nodes (e.g., maize Zea mays) offer mechanical support in shallow soils.
• Respiratory roots (pneumatophores): Found in mangroves (e.g., Rhizophora), these roots grow vertically upward to facilitate oxygen exchange in waterlogged soils.
• Parasitic roots (haustoria): In Cuscuta, roots penetrate host plants to absorb nutrients.

These modifications showcase how plants evolve structurally to thrive in specific habitats, ensuring survival and reproduction.

A flower is the reproductive unit of angiosperms, consisting of four whorls arranged on the thalamus:

• Calyx: Outermost whorl of sepals; protects the bud and may be green or colored.
• Corolla: Composed of petals, often brightly colored to attract pollinators.
• Androecium: Male reproductive part with stamens (filament + anther). Anthers produce pollen grains.
• Gynoecium: Female reproductive part with carpels (ovary, style, stigma). Ovary contains ovules for seed formation.

Diagram: (Draw a labeled flower with all four whorls clearly marked.)

Significance:
1. Enables sexual reproduction through pollination and fertilization.
2. Facilitates genetic diversity via cross-pollination.
3. Fruits formed from ovaries aid in seed dispersal.
4. Flowers attract pollinators, ensuring ecological balance.

Thus, flowers are vital for species propagation and ecosystem sustainability.

Flowering plants exhibit two primary types of root systems: taproot system and fibrous root system.

Taproot System: Found in dicotyledonous plants, this system consists of a primary root (taproot) that grows vertically downward, with smaller lateral roots branching from it.
Significance:

• Provides strong anchorage to the plant.
• Penetrates deeper into the soil to access water and minerals.
• Stores food in some plants (e.g., carrot, radish).

Fibrous Root System: Common in monocotyledonous plants, it comprises numerous thin roots of similar size originating from the base of the stem.
Significance:

• Forms a dense network near the soil surface, preventing soil erosion.
• Efficiently absorbs surface-level nutrients and water.
• Adapts well to shallow soils.

Additionally, some plants develop adventitious roots (e.g., prop roots in banyan, stilt roots in maize) for specialized functions like support or respiration.

Leaves in flowering plants undergo various modifications to perform specialized functions beyond photosynthesis. These adaptations enhance survival in diverse environments.

1. Tendrils: Example: Pea plant.
Adaptive Significance: Thin, coiled structures help the plant climb and support weak stems for sunlight exposure.

2. Spines: Example: Cactus.
Adaptive Significance: Reduce water loss by minimizing surface area and deter herbivores.

3. Storage Leaves: Example: Onion.
Adaptive Significance: Fleshy leaves store water and nutrients, aiding survival in arid conditions.

4. Insectivorous Leaves: Example: Venus flytrap.
Adaptive Significance: Modified to trap and digest insects to supplement nitrogen in nutrient-poor soils.

5. Phyllodes: Example: Australian acacia.
Adaptive Significance: Flattened petioles mimic leaves to reduce water loss in hot climates.

These modifications showcase the remarkable adaptability of plants to ecological challenges.