Taxonomic Evidence- Vegetative Characteristics

Character and Character States

Character states that can be quantified or measured against a standard are quantitative characters

Other characters that cannot be measured as a numerical value such as ovary position, fruit type, or presence of

secondary compound are qualitative characters.

Taxonomists employ many different kinds of characters in their studies of plant variation.

Discontinous vs. Continuous Characters

Vegetative terminology

Plants often vary continuously, and the structures that you observe on a given plant will probably not

match the illustrations or definitions precisely.

You may encounter a feature that is an intermediate between two terms.

Microscopic features

Macroscopic features

An aspect of a plant, such as leaf shape or petal color is a character.

Each character can have a character state, such as red or white petals.

Measurements of quantitative characters yield continuous data (value ranges) (Ex: plant height),

or discontinous data for discrete, integer,or number values ( Ex: numbers of leaves).

In this situation, terms are often used in combination such as leaves linear-lanceolate.

Traditionally, the flowering plants were divided into :

Recent molecular studies do not support the simple division of monocots and dicots.

Several distinct lineages of flowering plants:

Major monocot groups are the lilies, palms, grasses,

sedges and bromeliads

Monocot Dicot

Eudicots

Monocots

Life span

Plant habit

Shrub-

Tree-

Succulent-A plant with thick, watery leaves and/or stems.

Vine-A woody or herbaceous plant that trails on the ground or climbs.

A large woody plant with one to several relatively massive trunks and elevated crown.

Growing condition may determine whether a particular woody plant matures as a tree or a shrub.

Plant organs

-Roots

-Stems

-Leaves

The roots have multiple functions, including

Annual- A plant that completes its life cycle in one growing season.

Biennial-A plant that completes its life cycle in two growing seasons.

Perennial- Any plant that lives for more than 2 growing seasons. All trees and shrubs are perennials.

Herb- A plant with little or no above-ground perennial tissue. Annual (underground parts die back), biennial, or

perennial.

A woody perennial plant of comparatively low stature with 1 to many relatively slender trunks from near its

base.

1) absorption of water and nutrients

2) anchorage of the plant in the soil

There are two major types of root system:

1) Fibrous root system.

Fibrous root systems are highly branched, with several

main roots.

Annual grasses generally have fibrous root systems.

2) Tap root system.

Tap root systems have a single main root with only short

lateral branches.

Development of the root system

Fibrous roots often have different modes of development.

In many grasses, multiple roots originate from embryonic roots above the

radicle. These are called seminal roots.

Adventitious roots develop from the shoot system.

Plant organs

Stems are part of the shoot system and have several functions.

Provide support for the leaves and flowers.

Conduct water and nutrients

Produce new shoot cells and tissues in apical meristems.

The primary stem of dicots differs from the stem of monocots.

Nodes – the region of the stem from which 1 or more leaves or

branches emerge

Internode – the stem regions between the nodes

Plant organs

-Stem types

Stem modifications for special functions

Rhizomes:

They have all the structures of stems and can branch

underground or produce new upright stems and complete

new plants with adventitious roots.

Tubers:

Tubers have large quantities of stored starch and function

in vegetative reproduction.

Corms are also modified stems used for storage and

vegetative reproduction.

Leaves

The basic function of most leaves is photosynthesis, the process that transforms light

energy into chemical energy and produces sugars.

Monocot leaves are different from those of dicots.

Leaves are shaped to capture light.

The monocot leaf also has parallel venation.

Dicot leaves have netted venation and are connected to the stem by a petiole.

The expanded region of the leaf is called the blade.

The petiole is the stalk of the leaf, sometimes absent.

They are sometimes attached to the petiole, sometimes to the stem, or fused to the stem.

Stipules

Leaf Complexity

Leaves with a single blade are called simple leaves.

Simple leaves can have smooth or toothed margins.

The leaves may also be lobed or divided.

Leaf Complexity

A palmately compound leaf has the leaflets diverging from a single point, like digits from the palm of a hand.

A pinnately compound leaf has the leaflets arranged along an axis, like the pinnae of a fern.

The petiole of dicot leaves is a fairly simple extension attachment of the leaf blade to the stem.

The sheath of monocot leaves is more complex.

In grasses, the sheath wraps completely around the

stem, often extending most of the length of the

internode.

Leaves that are so deeply divided that the blade forms

several separate units are called compound leaves.

Leaf Attachment

Leaf Arrangement (Phyllotaxy)

Leaf Venation

Leaf Blade Shape

Leaf Apices

Leaf Bases

Leaf Margins- as view from the top/as viewed from the side

Special Features

Surface Features

tendril- leaf or portion of the stem modified into a thin, coiled structure.

spines – modified leaf

thorn – modified stem that arises from the axil of a leaf

prickles - sharp outgrowth from the epidermis or cortex of the stem.

Study outline- Taxonomic Evidence- Vegetative Characteristics

-Understand the following terms and examples: character, character state, quantitative vs qualitative characters,

continuous vs. discontinuous characters, macroscopic vs. microscopic

-Know general characteristics of eudicots and monocots

-Know different life spans- annual, biennial and perennial

-Know different plant habits- herb, shrub, tree, succulent, woody vine, epiphyte (lab), parasite (lab0

-Know general characters of plant organs-roots, leaves and stems

-Know general functions of roots

-Know difference between fibrous and tap roots

-Know different modified roots- seminal roots, prop roots, adventitious roots

-Know general functions of stems

-Differentiate between monocot and dicot stems

-General characteristics-node, internode

-Know different modified stems-rhizomes, corms, tubers

-Know general functions of leaves

-Differentiate between monocot and dicot leaves

-Know general leaf terminology- blade, petiole, stipule, adaxial vs abaxial, basal vs apical

-Know leaf complexity- simple vs. compound, pinnately compound, palmately compouond, bipinnately compound,

unifoliate (lab), bifoliate (lab) and trifoliate (lab)

-Know leaf attachment-petiolate, sessile, perfoliate, clasping, sheathed

-Know leaf arrangement (phyllotaxy)-basal, opposite, alternate, whorled

-Know leaf venation- palmate (netted), pinnate (netted), parallel, and rotate

-Know other leaf characteristics-leaf blade shape, leaf apices, leaf bases, leaf margins, special features (tendril, spine,

thorn and prickle), surface features