Weed Biology and Identification-205

Target students: M.Sc. Students in Weed Science

Lecture:

Dr. Majid AghaAlikhani (Ph.D.)

Academic position :

Associate Prof. of Tarbiat Modares Universitymaghaalikhani@modares.ac.ir

1

Plant Taxonomy

By: Johnny M. JessupAgriculture Teacher/FFA

Advisor

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.

Taxonomy: D.I.N.C.

Description

Identification

Nomenclature

Classification

DescriptionAssignment/listing of features or attributes to a taxon

character= a featuree.g., “flower color”

character states= two or more forms of a charactere.g., “white,” “red,” “yellow”

Identification

Associating an unknown taxon with a known one

How?taxonomic keycompare to a

photograph/illustrationcompare to a specimenask an expert

NomenclatureFormal means of naming life.

E.g., binomial nomenclature for species names:

For Adenostoma fasciculatum Hook. & Arn.

Adenostoma = genus namefasciculatum = specific epithetAdenostoma fasciculatum =

species nameHooker & Arnott = authors of

species name

Classification

= placing objects, e.g., life, into some type of order.

Taxon = a taxonomic group (plural = taxa).

Why classify??

How to classify life

Phenetic classification

Based on overall similarity

Those organisms most similar to one another are classified more “closely” together.

Problem with phenetic class.:

Can be arbitrary, e.g., classify these:

Definitions

Taxonomy -- the naming of groups (taxa, singular taxon)

Systematics -- a method (or system) for classifying organisms into groups

Why classify??

Goals of Classification

• Simplify

• Communicate

• Predict

How to classify plants?

Functional classifications Based on function or overall similarity No assumption of evolutionary relationship

History - Functional classification systems All cultures classify plants in ways meaningful to them

Examples of early plant classifications

2000 BC - Indian (Ayurvedic) texts described medicinal plants

1000-1700 AD - “Age of Herbals” in Europe

Botanical tradition

Carolus Linneaus (Systemae naturae, 1732)

- defined groups based on sexual characters

- developed binomial system of plant nomenclature

Engler, Bessey, Cronquist etc. (1800 - 1980s)

- sought to define evolutionary groups of plants

- published many regional floras (still in use)

History - Evolutionary classification systems

Evolutionary classification(includes both traditional systematics and modern phylogenetics)

1. Living species are related to one another by descent from common ancestors

2. Shared character states are clues to relatedness

Reasoning

What about convergent evolution??

Modern solution: Phylogenetic systematics Reconstructs relationships using lots of characters Now, primarily uses DNA sequence data

From Nickrent et al.

Land plants (Embryophytes)

Vascular plants

~450 millionyears ago

Present

Bryophytes(mosses, liverworts)

Lycopods(club mosses)

Seed plantsMonophilites

(ferns, horsetails)

woodiness

seeds

tracheids(vascular cells for water transport)

“true” leaves

multiple adaptations to life on land

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.

Scientific Names

• The first word is the genus and the second word is the species.

• If there are additional words, they indicate the variety or cultivar.

Genus

• Plants in the same genus have similar characteristics.

• Examples:• Quercus – Oaks• Acer – Maples• Pinus – Pines• Ilex – Hollies• Cornus – Dogwoods• Ficus – Figs

Species

• Plants in the same species consistently produce plants of the same types.

Species

• A distinct types of organism capable of breeding with other members of its own kind - but not with other species….

• Basic category in biological nomenclature

Varieties (subspecies)

• Sargent

• Quercus alba L. var. alba• Quercus alba L. var. latiloba Sarg.

• If Q. latiloba was a new species?• Quercus latiloba Sarg.

hybridization

• Q. velutina X Q. rubra X Q. palustris

• Echinacea pallida

• Echinacea paradoxa

• Echinacea pallida X paradoxa

Relationship between Genus and Species

• Genus - a group of related species

• Quercus (oaks) Carya (hickories)• rubra - ovata• velutina - cordiformes• alba

Related• 1. Have similar characteristics

(may hybridize)• 2. Have a common ancestor back

in evolutionary time• velutina rubra alba

Related• 1. Have similar characteristics

(may hybridize)• 2. Have a common ancestor back

in evolutionary time• ovata cordiformes

Scientific Classification

• The broadest category of scientific classification is the Kingdom.• Either Plant or Animal

• The broadest category of the plant kingdom is Division or Phylum.

Scientific Classification

Natural System

• Our present system attempts to group organisms in accordance with natural (evolutionary) relationships.

• Homology• internal structures, embryology, DNA,

proteins• Analogy

• based on superficial characteristics• outward form and function

Kingdoms

Plants Aristotle Gr 4thC BC

Animals Aristotle Gr

Protista E. Haeckel Ger 19thC

Fungi R H Whitaker USA 20thC

Archebacteria (Archaea) C. Woese USA 20th C

Eubacteria (Bacteria) C. Woese USA 20th C

Domains

Rank Classification

Hierarchical - each higher rank is inclusive of lower ranks Rank Example EndingPhylum Magnoliophyta -phyta

Class Liliopsida -opsidaOrder Liliales -ales

Family Liliaceae -aceaeGenus Lilium

Species Lilium parryi

Divisions

• The four most important divisions of the plant kingdom are….• Thallophites• Bryophytes• Pteriophytes• Spermatophytes

Spermatophytes

• Includes flowering or seed-bearing plants.

• The two subdivisions are….• Gymnosperms• Angiosperms

Kingdom Viridiplantae (green plants)Phylum/Division

Embryophyta (land plants)Subphylum

Tracheophytina (vascular plants)Class

Angiospermopsida (angiosperms)Subclass

CaryophyllidaeOrder

Caryophyllales Family

Portulacaceae (Purslane family) Genus

LewisiaSpecies

Lewisia rediviva

Lewisia rediviva (Bitterroot)

Plant nomenclature in practice

Plant nomenclature in practiceHigher ranks

- Each rank has a characteristic ending (ex. -idae for subclasses, -ales for orders)

- Ideally, all taxa are monophyletic, but ranks are arbitrary

- In this class, we’ll focus on lower taxonomic levels

--> subclass (ex. Rosidae vs. Asteridae)

--> family (ex. Salicaceae vs. Betulaceae)

--> genus (ex. Populus vs. Salix)

--> species (ex. P. tremuloides vs. P. deltoides)

Plant nomenclature in practice

ICBN (International Code of Botanical Nomenclature)

Goal: Standardization of scientific names for plants

- First adopted in 1903; includes fungi, lichens and algae

Basic rules

- Every taxon must have a type specimen

- Names of higher ranks must be based on names of lower ones

- Priority of publication determines “correct” name

- Only 1 name is allowed per taxon, 1 taxon per name

Standard Endings (ICBN)

• Division: phyta• Class: opsida• Order: ales• family: aceae• Genus:• species:

Plant nomenclature in practice

Families- All end in -aceae (easiest to pronounce a-cee-ee)

- Older alternate names also allowed for 8 familiesexamples: Crucifereae = Brassicaceae (mustard family) Umbellifereae = Apiaceae (carrot family) Compositae = Asteraceae (sunflower family)

- Always capitalize family names

Plant nomenclature in practice

Species names (“scientific names”) are Latin binomials

Lewisia rediviva Pursh.

• Genus (pl. genera)• Always capitalized• Abbreviated on 2nd use

(L. rediviva)

• Authority• Specific epithet• Not capitalized• Often a descriptive adjective

Always underline or italicize species names (genus + specific epithet)

Plant nomenclature in practice

Why do names change?• New evolutionary data

• Rediscovery of older names• Lumpers vs. splitters

Agropyron spicatumElymus spicatusPsuedoroegneria spicataBluebunch wheatgrass

Plant Characteristics

Identifying Plants

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

Life Cycle

• Annuals• Plants that complete their life cycle in

one year.• Biennials

• Plants that complete their life cycle in two years.

• Perennials• Plants that live more than two years.

Growth Habits

• Trees• Shrubs• Vines

Growth Forms

• Columnar• Spreading• Weeping

• Round• Oval• Pyramidal

Growth Forms

Spreading

Columnar

Weeping

Growth Forms

Round Oval Pyramidal

Foliage Retention

• Deciduous• Loses leaves during the dormant

season.• Evergreen

• Keeps leaves and remains green year-round.

Plant Parts – Leaf

• Arrangement• Shapes• Color• Vein Pattern• Form – Simple or Compound• Margin• Surface

Leaf Arrangement – Simple

Leaf Arrangement – Compound

Leaf Shape

Vein Pattern

• Pinnate• Palmate• Parallel• Dichotomous

Leaf Margin

Leaf Surface

• Glabrous• Pubescent• Villous• Tomentose

• Scabrous• Glaucous• Rugose• Glandular

• There are 8 common leaf surfaces.

Leaf Surface – Glabrous

• The surface is smooth, not hairy.

Leaf Surface – Pubescent

• Short, soft hairs cover the surface.

Leaf Surface – Villous

• Long, straight hairs cover the surface.

Leaf Surface – Tomentose

• Covered with wool-like hair.

Leaf Surface – Scabrous

• Covered with short, prickly hairs.

Leaf Surface – Glaucous

• Covered with a bluish-white waxy substance.

Leaf Surface – Rugose

• Surface is wrinkly.

Leaf Surface – Glandular

• Glands filled with oil or resin cover the surface.

Plant Parts – Flowers

• Color• Shape• Size

Plant Parts – Bud & Stem

• Shape & Color• Stem Modifications

• Thorns• Spines• Prickles

Plant Parts – Modified Stems

Thorn

Prickle Spine

Plant Parts – Roots

• Tap• Fibrous• Bulb

Plant Parts – Roots

Tap Root

Tuberous Root

Fibrous Root

Plant Parts – Fruit

• Cones• Nuts (Acorns)• Pomes (Apple)• Drupes (Peach)

• Brambles (Raspberries)• Capsules (Willow)• Samara (Maple)

Plant Parts – Fruit

Cones

Acorns

Pomes

Plant Parts – Fruit

Drupes

Brambles

Capsules

Samara

Use & Location

• Not absolute, but helpful.• Indoor or outdoor.• Altitude• Wet or dry• Hardiness Zone• Sun, partial shade, or shade.• Landscape purpose – specimen, border,

etc.

Collecting, Preparing and Preserving Plants

Collecting, Preparing and Preserving Plants

Collecting, Preparing and Preserving Plants

Designed By:

• Johnny M. Jessup, FFA Advisor• Hobbton High School