Plant Taxonomy

Introduction Taxonomy is the science of classifying and identifying plants. Scientific names are necessary because the same common name is used for different plants in different areas of the world. Latin is the language used for scientific classification.

Classification is the grouping of organisms based on similarities of features. Taxonomy is the science of studying classification. It looks at features and tries to arrange them in a logical order.

Classification is hierarchical! Kingdom Division Class Order Family Genus species Each unit is called a TAXON – there are 7 of them Classification for Rose Kingdom Phylum/Division Class Order Family Genus Species Plantae Angiospermae Dicotyledonae Rosales Rosaceae Rosa indica

Karl von Linne (1707-1778) Swedish botanist Developed binomial classification scheme for plants. Uses two Latin words to indicate the genus and the species. Changed his name to the Latin name of Carolus Linnaeus.

Rules for Binomial nomenclature Name consist of two words-Genus and Species Both words are italicized or underlined First letter of genus is always capital while first letter of species is always lowercase All the names are derived from Latin language Two different organisms cannot have same name

‘Binomial’ = 2 names Allium cepa The first word is the genus and the second word is the species. If there are additional words, they indicate the variety or cultivar. Allium cepa species – all in lower case Italics (or underlined) -to show the words are different to ordinary text. Genus – has a capital letter

Species Species is the basic unit of biological classification and a taxonomic rank. A species is often defined as the largest group of organisms in which two individuals can interbreed to produce fertile offspring.

Genus Plants in the same genus have similar characteristics. Examples: Quercus – Oaks Acer – Maples Pinus – Pines Rosa – Roses Cornus – Dogwoods Allium – Onion/Garlic

Divisions The five divisions of the plant kingdom are…. Vascular Thallophytes (Algae) Bryophytes (Mosses) Pteridophytes (Ferns) Gymnosperms (Bears cones) Angiosperms (flowering plants) Non-vascular Vascular

How are they classified? One way that plants can be classified is by how they carry water. Plants can either be Vascular or Nonvascular. Vascular means “having tubes” Nonvascular means “no tubes”

Vascular Plant Plants that have tubes, roots, stems, and leaves Vascular Plant Plants that have tubes, roots, stems, and leaves. These plants stand up tall.

Why are these trees vascular? They have tubes, roots, stems, and leaves. They also stand up tall.

More Vascular Plants

Nonvascular Plant Plants that do not have tubes, roots, stems, or leaves. These plants soak up water and food from the soil, like sponges. They are also much smaller than vascular plants.

Vascular or Non-Vascular?

Characteristics of Algae Unicellular or multicellular Body is thallus like (not divided into root, stem and leaves) Majorly aquatic, some are terrestrial also Presence of several photosynthetic pigments along with the chlorophyll Volvox Spirogyra

Characteristics of Bryophytes (mosses) .Simplest plants .No true roots, No vascular tissues (no transport) .Simple stems & leaves .Have rhizoids for anchorage .Spores from capsules (wind-dispersal) .Moist terrestrial land

A leaf (finely divided into small parts) Ferns A leaf (finely divided into small parts) underground stem root

Characteristics of Pteridophytes (Ferns) .roots, feathery leaves & underground stems .have vascular tissues (transport & support) .Spore-producing organ on the underside of leaves (reproduction) .Moist & shady places

Gymnosperms Cone Needle shaped leaves

Characteristics of Gymnosperms .tall evergreen trees .roots, woody stems .needle-shaped leaves .vascular tissues (transport) .cones with reproductive structures .naked seeds in female cones .dry places

Angiosperms Monocotyledons Dicotyledons . roots, stems, leaves . vascular tissues (transport) . flowers, fruits (contain seeds)

Characteristics of Monocotyledons . one cotyledon . leaves have parallel veins . herbaceous plants . e.g. grass, maize Parallel veins

Characteristics of Dicotyledons . two cotyledons . leaves have veins in network . e.g. trees, sunflower, rose Veins in network

Plant Characteristics

The Plant Kingdom This kingdom has organisms that are multi-cellular, have cell walls and chlorophyll, produce their own food, and don’t physically move from one place to another.

Plant Parts

Identifying Plants Physical characteristics are used to identify plants which include…. Life Cycle Foliage Retention Plant Parts Use & Location

Life Cycle Annuals Biennials Perennials Plants that complete their life cycle in one year. (ex. Rice, Wheat) Biennials Plants that complete their life cycle in two years. (ex. Onion, Fennel, Spinach) Perennials Plants that live more than two years. (ex. ??)

Foliage Retention Deciduous Evergreen Loses leaves during the dormant season. Evergreen Keeps leaves and remains green year-round.

Leaf The leaf is a green, flattened structure borne on the stem at the nodes and is a lateral appendage of the stem. A typical leaf is also known as the foliage leaf in order to distinguish it from other forms of leaves. Arrangement Shapes Color Vein Pattern Form – Simple or Compound Margin Surface

Leaf Arrangement – Simple – Compound

Leaf Shape

Vein Pattern Pinnate Palmate Parallel Dichotomous Leaf margins

Leaf modifications 1 Succulence: In a dry environment, leaves may either become reduced, like in cacti, or, else, become succulent. Succulent leaves not only retain lots of moisture but also have a lower surface to volume ratio. Stipular Spines: Stipules can become modified into spines for defense. Tendrils: In peas the terminal leaflet of the leaf has become modified into a tendril for climbing. Leaves of certain insectivorous plants such as pitcher plant, venus-fly trap are also modified leaves. 2 3 4

Stem Generally, the stems are aerial and grow above the soil surface. Sometimes, the stem becomes variously modified to perform special functions like perennation, vegetative propagation and food storage. The modified stems may be grouped under three heads viz, underground, subaerial and aerial.

Modification of stem

Modification of stem

Roots Root is the descending portion of the axis of the plant. Originated from the radicle. It is characterized by the absence of nodes and internodes. Can be divided into Tap Roots and Adventitious Roots Tap Roots: The primary root, originated from radical, that persists throughout the life of a plant is known as tap root Adventitious roots: A root that develops from any part except radical is called adventitious root.

Modifications of roots

Flower The angiosperm plants produce characteristic structures called flowers for the purpose of reproduction. A flower is defined as a modified vegetative shoot meant for sexual reproduction. The flower consists of a very short axis on which whorls of different parts arise.

Fruit Cones Nuts (Acorns) Pomes (Apple) Drupes (Peach) After fertilisation the ovary develops into the fruit and the ovules into seed. The ovary wall develops into the fruit wall called the pericarp. In some cultivated varieties of plants like bananas, grapes, apples etc., the ovary may develop into fruit without fertilisation. As a result of this ovules do not develop into seeds. Thus the fruits produced become seedless. Such fruits are called parthenocarpic fruits. Cones Nuts (Acorns) Pomes (Apple) Drupes (Peach) Brambles (Raspberries) Capsules (Willow) Samara (Maple)

Plant Parts – Fruit Cones Acorns Pomes

Plant Parts – Fruit Drupes Samara Capsules Brambles