plant systematics

What is plant systematics?

The study of biodiversity in an evolutionary context

field botany

skills used to recognize and identify plants in the field

plant taxonomy

the study and practice of identifying plants

nomenclature

the rules and practices of giving scientific names

classification

producing a coherent and useful system for organizing plant diversity

phylogenetics

constructing testable hypotheses about evolutionary relationships

the basic conceptual sequence of plant taxonomy is

phylogeny → classification → Nomenclature

Phylogenies are?

hypothesized evolutionary relationships

phylogeny asks?

How are organisms evolutionarily related?

Classification asks?

How should we organize organisms into groups based on these relationships?

Nomenclature asks?

What names should these groups have and what rules should govern these names?

What are the plant taxonomic ranks and give example?

Order → family → genus → species

Asterales → Asteraceae → Solidago → Solidago canadensis

what is a monophyletic group?

All of the descendants of a shared common ancestor, also called a clade?

What are the three parts of a scientific name?

Genus + specific epithet + Authority

Rules for writing a genus

Capitalized, can be abbreviated after first use

rules for writing specific epithet

acts as an adjective, lowercase, its ending may change depending on grammatical gender of the genus.

what is the authority?

Standardized form of the name of the person who formally described the taxon

Together the genus and the specific epithet form the ___?

binomial

who invented binomial nomenclature?

Linnaeus

what is the principle of priority?

the correct name for a taxon is the name published according to the rules of nomenclature

morphology

the study of the form of things

synapomorphy

a shared derived trait, helps set monophyletic groups apart.

stem

the main aboveground structural axis, functions include

• supporting leaves

• supporting reproductive structures

• containing vascular tissue

what are the two basic stem units?

Node - the point where a leaf attaches, usually contains an axillary bud

Internode - the point of stem between leaves and nodes

leaves

a leaf is usually the main photosynthetic unit of a plant

what are the leaf positions

alternate - one leaf per node

opposite - two leaves per node

whorled - more than two leaves per node

basal - leaves appear to arise from the base of the plant

what are the leaf divisions

simple leaves - the lamina is undivided

lobed leaves - the lamina is divided but not to the midrib, also called a pinnatifid

divided/compound leaves - the leaf is divided to the midrib at least once

what are the two major patterns of compound leaves

palmate - leaflets radiate from a common point (think fingers from a hand)

pinnate - leaflets occur along an axis

how do you tell if something is a leaf or a leaflet

look for the axillary bud?

what are some common terms for leaf shape?

ovate

obovate

elliptic

narrowly elliptic

linear

lanceolate

indument

the plant surface

• scales = more than one cell wide

• hairs = one cell wide

stipules

small appendage underneath leaf that look like little leaves

tendrils

used for climbing, may be modified

• stems

• leaves

• leaflets

• stipules

what is the difference between a thorn, spine, and prickle?

thorn - modified branch

spine - modified leaf or stipule

prickle - outgrowth of the epidermis

rhizome

horizontal stem, usually underground

bulb

compact underground stem with very short internodes

tuber

a thickened stem or root used for storage

what makes an angiosperm an angiosperm?

enclosed ovules - angiosperms “wrap up their seeds”

carpels - the female reproductive unit of a flower, an enclosed structure bearing ovules, a synapomorphy for angiosperms

flower, name 4 parts

the entire reproductive unit of a flowering plant

has four major whorls

• sepals

• petals

• stamens

• pistil

all four are modified leaves

sepals

• the first whorl

• usually green, leaf life

• collectively are known as the calyx

petals

• second whorl

• often brightly colored to attract pollinators

• collectively are known as the corolla

the calyx and the corolla make the ____?

perianth

stamens

• third whorl of a flower

• produce pollen

• each stamen has the filament and the anther which are collectively the Androecium

pistil

female reproductive structure

collectively the gynoecium

carpels make up pistils, one pistil may be one carpel, several separate carpels, or several fused carpels.

the three parts of a carpel

stigma - apical portion

style - middle portion

ovary - enlarged basal proportion

ovary contains one or more ovules, ovules are attached to placentas and eventually become seeds, the ovary contains one or more compartments called locules

carpels vs pistils

if carpels are not fused:

• carpel = pistil

if carpels are fused:

• multiple carpels = one pistil

all pistils in a flower collectively form the gynoecium

flowers can vary in _____

number of parts

Prescence/absence of parts

fusion

symmetry

ovary position

variation in number of floral parts is widespread, common numbers include ____

2

3

5

multiples of these numbers

perfect/bisexual flower

has stamens and a pistil

imperfect/unisexual flower

either has stamens or pistils

monoecious vs dioecious

monoecious - one plant has both pistillate and staminate flowers

dioecious - a plant has flowers of only one sex

types of floral fusion

connate - fusion between parts of the same whorl (ex. petal + petal, sepal + sepal)

Adnate - fusion between parts of different whorls (stamen + petal, pistil + stamen)

hypanthium

a special case of adnation

it involves fusion of sepals, pistils, stamens

it produces a cup like structure

the two types of floral symmetry

actinomorphic - radially symmetrical

zygomorphic - bilaterally symmetrical

the three types of ovary position

superior - ovary is above the other whorls

half inferior - ovary is apprx in the middle

inferior - ovary is below the other whorls

inflorescence

an arrangement of flowers

determinate vs indeterminate inflorescences

indeterminate - the inflorescence continues developing

determinate - the central flower develops first

what are some major indeterminate inflorescences

• raceme

• spike

• panicle

• corymb

• umbel

• capitulum

bracts

modified leaves associated with an inflorescence

fruit

a fruit is a seed surrounded by ovary-derived tissue

the ovary derived tissue is collectively the pericarp

the three layers of the pericarp

exocarp - the outer layer or skin

the mesocarp - the middle layer or flesh

endocarp - the inner layer or pit/core

simple fruit

derived from one pistil (grape)

aggregate fruit

derived from more than one pistil but from a single flower (raspberry)

multiple fruit

derived from many flowers (pineapple)

accessory fruit

an aggregate or multiple fruit in which substantial tissue other than ovary-derived tissue contributes to the fruit (an apple)

Dry fruits can be dehiscent or indehiscent

dehiscent - fruit splits open along a seam to release seeds

indehiscent - fruit does not split open

dehiscent dry fruits

follicle - derived from one pistil, has one locule, splits along one seam

legume - variation of a follicle, derived from one pistil, splits along two seams

capsule - derived from a compound pistil, multiple locules, opens along joined seams

schizocarp - variation of a capsule, one seed per locule, splits apart into one-seeded units called mericarps

indehiscent dry fruits

achenes - single seeded, does not split open, seed is held loosely within a hardened pericarp (think a samara)

nuts - single seeded, indehiscent, seed fused to hardened pericarp, usually associated with an involucre (hat of an acorn)

fleshy fruits

mostly indehiscent

berries - have one or more seeds, usually many, fleshy pericarp, has skin or a rind

drupes - like a berry but one seed, seed is surrounded by a pit

placentation

describes where ovules attach inside the ovary

types of placentation

marginal - seeds attach along a single line

parietal - seeds attached along several lines

axile - seeds attach to a central column

free central - seeds attached to a central column but no walls between locules

basal - seed attached at the base of the ovary