Study of Angiospermic Families | Botany Optional for UPSC PDF Download

Introduction

The realm of angiosperms, or flowering plants, is a vast and diverse one, boasting a myriad of families that contribute to Earth's rich flora. In this article, readers will be provided with an in-depth exploration of the Families of Angiosperms, shedding light on their classifications, characteristics, and diversity. Moreover, a detailed diagram will accompany the text, enhancing the understanding of these intricate plant families.

I. Dicotyledons

The first major classification of angiosperms, dicotyledons, encompasses plants that typically have two cotyledons (seed leaves). These plants exhibit various characteristics, making them a diverse group within the angiosperms. Below are some key features and subdivisions of dicotyledons:

A. Polypetalae

Within the Polypetalae subclass, there are several orders, each with its own unique characteristics. Here, we explore some of these orders and their representative families:

Series 1. Thalainiflorae

Sepals usually distinct and separate, free from ovary, petals in one, two or many whorls, hypogynous, stamens hypogynous; rarely inserted on a long or short torus or disc; ovary superior.

• Ranunculaceae: These plants are typically herbs with divided leaves and hermaphroditic, actinomorphic flowers. Stamens are usually indefinite, and the gynoecium is superior with one to indefinite ovules. The fruit can be a follicle, capsule, or rarely a berry.
• Nymphaeaceae: Aquatic herbs with large, peltate leaves characterize this family. Flowers are hermaphroditic, and their tepals and stamens are numerous. The fruit can be a spongy berry or an etaerio of achenes or nuts.

This order includes plants with definite or rarely indefinite stamens and united carpels with parietal placentation.
Here are some representative families:

• Papaveraceae: These plants are usually herbs with alternate leaves and latex. Flowers can be actinomorphic or zygomorphic, and the gynoecium is syncarpous with parietal placentation. The fruit is typically a capsule.
• Capparidaceae: This family comprises herbs and shrubs with alternate leaves. Flowers are hermaphroditic, and the gynoecium is syncarpous with indefinite ovules. The fruit can be a capsule, berry, or drupe.
• Brassicaceae (Cruciferae): Herbs with alternate exstipulate leaves characterize this family. Flowers are actinomorphic and hermaphroditic. The fruit is typically a siliqua.

Flowers within this order are typically actinomorphic, and the ovary can be unilocular or imperfectly multi-locular.
Here's a family within this order:

• These plants can be herbs or undershrubs with entire, usually opposite leaves. Flowers often form cymes or panicles and are actinomorphic. The gynoecium is syncarpous with free central placentation, and the fruit can be a capsule or berry.

This order includes plants with regular flowers and various characteristics in terms of stamens, carpels, and placentation.
Two notable families within this order are:

• Malvaceae: These plants can be herbs, shrubs, or trees with simple or lobed stipulate leaves. Flowers are hermaphroditic and solitary, often with epicalyx. The gynoecium is syncarpous, and the fruit can be a capsule or schizocarp.
• Tiliaceae: Usually woody plants with alternate and stipulate leaves characterize this family. Flowers are hermaphroditic and actinomorphic. The gynoecium is usually multi-locular.

Series 2. Disciflorae

This series includes plants with distinct or united sepals and a conspicuous disk. Stamens are usually definite, and the ovary is superior.
Here are some families within this series:

• Rutaceae: These plants are usually woody, with alternate or opposite, simple, or compound leaves. Flowers are actinomorphic, and the gynoecium has two basal ovules per carpel.
• Meliaceae: These woody plants have pinnately compound leaves and actinomorphic flowers in cymose panicles. The gynoecium is syncarpous.

Series 3. Calyciflorae

This series includes plants with united or free sepals and often peri- or epigynous petals. Stamens are perigynous, and the ovary is inferior. Here are some families within this series:

• Fabaceae (Leguminosae): Trees, shrubs, or herbs with alternate stipulate leaves and racemes of regular or zygomorphic flowers characterize this family. The gynoecium usually has one carpel, and the fruit is a pod.
• Rosaceae: Herbs, shrubs, or trees with alternate stipulate leaves are typical of this family. Flowers are regular, and the gynoecium usually has two carpels. The fruit can be a follicle, achene, drupe, or pome.

Order. Myrtales

Flowers within this order are regular or sub-regular, and the gynoecium is usually syncarpous and inferior.
Here is a family within this order:

• Myrtaceae: These woody plants have opposite or alternate, entire leaves. Flowers are actinomorphic, and the gynoecium is usually syncarpous with indefinite ovules.

Order. Passiflorales

Flowers within this order are usually actinomorphic, and the ovary is usually inferior.
Here is a family within this order:

• Cucurbitaceae: Flowers are typically pentamerous and unisexual. The gynoecium is syncarpous, and the fruit is berry-like.

Order. Umbellales

Flowers within this order are actinomorphic and hermaphroditic. The ovary is usually inferior and unilocular.
Here is a family within this order:

• Apiaceae (Umbelliferae): These plants are known for their hollow stems, much-divided leaves, and umbel inflorescences. The fruit is typically schizocarpic.

B. Gamopetalae

In the Gamopetalae subclass, flowers have fused petals forming a gamophyllous corolla. Within this subclass, we find several orders and families with unique characteristics.

Series I. Inferae

In this series, the ovary is inferior, and the stamens are typically as many as the corolla lobes.
Here are some orders within this series:

• Rubiales: Stamens are epipetalous, and the ovary can have multiple locules with one to many ovules in each loculus.
• Asterales: Stamens are epipetalous, and the ovary is typically one-loculed with one ovule. The Asteraceae (Compositae) family, within this order, is known for its unique inflorescence, called a capitulum or head.

Series 2. Bicarpellatae

In this series, the ovary is superior, and the stamens are either as many as or fewer than the corolla lobes. Carpels are typically two.
Here's a representative order:

• Gentianales: Flowers are typically regular and hypogynous, and leaves are generally opposite. The Apocynaceae family, within this order, is known for its latex-containing plants.
• Asclepiadaceae: Flowers in this family have unique corona structures and pollinia. The gynoecium is enclosed in a staminal tube.

Series 3. Calycinae

Flowers within this series typically have sepaloid or absent perianth. The ovary can be free or one-carpelled, with solitary or two ovules per carpel.
Here are some families within this series:

• Amaranthaceae: These plants can be herbs or shrubs with small flowers in cymose inflorescences. Stamens are usually one to five and united below. The ovary is superior.
• Chenopodiaceae: These plants often have cymose inflorescences with hermaphroditic or unisexual flowers. Stamens are usually as many as the perianth lobes.
• Euphorbiaceae: These plants can have latex, compound inflorescences, and male or female flowers. Stamens can vary in number, and the gynoecium is often tricarpellary with two lobed styles.
• Moraceae: Trees and shrubs with latex and unisexual flowers characterize this family. The gynoecium is typically tricarpellary.

II. Monocotyledons

In this second major classification of angiosperms, monocotyledons, plants usually have leaves with parallel venation and flowers with trimerous perianths.
Here's a series within this classification:

Series I. Epigynae

In this series, the perianth is partly petaloid, the ovary is usually inferior, and endosperm is abundant.
Here are some families within this series:

• Musaceae: These are large herbs or trees with compound inflorescences and petaloid bracts. Flowers are often zygomorphic, hermaphroditic, and superior ovary. Fruits can be berries or capsules.
• Amaryllidaceae: Inflorescences can be cymose or on scapes. Flowers are hermaphroditic or zygomorphic, with petaloid perianths. The ovary can be inferior or partially inferior.

Series 2. Coronarieae

In this series, the inner perianth is petaloid, the ovary is typically free, and flowers are typically bisexual.
Here's a family within this series:

• Liliaceae: These plants often have racemose inflorescences with regular, trimerous flowers. The gynoecium is usually superior and multi-locular.

Series 3. Calycinae

In this series, the perianth is often sepaloid and herbaceous. The ovary can be free or one-carpelled, and flowers are usually unisexual.
Here's a family within this series:

• Palmae (Arecaceae): These plants have unisexual flowers arranged in spadices. The gynoecium is typically tricarpellary and apocarpous. The ovary is usually unilocular.

Series 4. Glumaceae

In this series, flowers are often solitary, sessile in the axils of bracts, and arranged in heads or spikelets with bracts. The perianth can be of scales or absent, and the ovary is usually unilocular with one ovule.
Here are some families within this series:

• Cyperaceae: These are often herbs with triangled stems and simple leaves. The gynoecium is monocarpellary and unilocular. The fruit is a caryopsis.

George Bentham and Joseph Hooker, in their monumental work "General Plantarum," have meticulously cataloged 202 families and a staggering 97,205 flowering plant species. This article offers a glimpse into the captivating world of angiosperms, highlighting their incredible diversity and complexity.

Conclusion

Angiosperms, or flowering plants, represent an astonishing array of life forms on Earth. With two major subclasses, dicotyledons and monocotyledons, and numerous orders and families, angiosperms have adapted to a wide range of environments and ecological niches. From the delicate beauty of wildflowers to the towering majesty of trees, the world of angiosperms is a testament to the remarkable diversity of life on our planet.