Basic Botany Notes

Basic Botany

Learning Objectives

  • Explain basic plant processes that affect plant growth.
  • Understand the classification system of botanical nomenclature.
  • Distinguish between monocots and true dicots/eudicots.
  • Recognize the basic parts of a plant, their functions, and specialized terms.
  • Understand how plant morphology helps classify and identify plants.

Introduction

What is Botany?

  • The scientific study of plants, including:
    • Classification
    • Evolution
    • Structure
      • Internal structure = anatomy
      • External structure = morphology
    • Physiology
    • Ecology
    • Uses
  • Also known as plant science or plant biology.

What is Horticulture?

  • The art and science of cultivating plants, including ornamentals, fruit, and vegetables.

What is a Science?

  • A study of something.
  • Must distinguish between the different parts.
  • Must try to understand all the parts' functions.
  • Need to understand the roles or influences the parts have on each other.
  • Have the ability to manipulate the parts to change the whole.
  • Horticulturist: a manipulator of nature.

What is a Plant?

  • A photosynthetic, multicellular organism.
    • Containing photosynthetic pigments called chlorophylls.
    • Capable of making its own food (sugar).
    • …and storing it, usually in the form of starch.

Plant Processes

  • Photosynthesis
    • The process of turning light energy into carbohydrates that can be transported and stored by the plant.
    • 6CO2+6H2O+light→C6H12O6 (sugar)+6O2 (oxygen)6 CO2 + 6 H2O + light \rightarrow C6H12O6 \text{ (sugar)} + 6 O2 \text{ (oxygen)}

Plant Processes

  • Respiration
    • The process where carbohydrates are broken down into energy the plant can use.
    • C6H12O6+6O2→6CO2+6H2O+EnergyC6H12O6 + 6 O2 \rightarrow 6 CO2 + 6 H2O + \text{Energy}

Plant Growth – A Balance

  • Photosynthesis
    • Produces food
    • Energy is stored
    • Occurs in cells with chlorophyll
    • Oxygen is released
    • CO2 is used
    • Occurs in light
  • Respiration
    • Uses food for energy
    • Energy is released
    • Occurs in all cells
    • Oxygen is used
    • CO2 is produced
    • Occurs in dark or light

Plant Growth - A Balance

  • P > R (Photosynthesis greater than Respiration)
  • P < R (Photosynthesis less than Respiration)
  • P = R (Photosynthesis equals Respiration)

Plant Processes

  • Transpiration
    • The process by which moisture is carried through plants from roots to small leaf pores (stomates) where it is released as vapor into the atmosphere.
    • Factors that increase transpiration:
      • Warm temperature
      • Bright sunlight
      • Low relative humidity
      • Wind
      • Moist soil
    • Dry wilt versus wet wilt.

Plant Classification

Plant Taxonomy

  • The classification, naming, description, and identification of plants.
  • From Greek: taxis (arrangement) + nomos (laws, rules).

Biological Classification = hierarchical arrangement (from most inclusive to least inclusive)

  • Kingdom
  • Phylum (-phyta)
  • Class (-opsida)
  • Order (-ales)
  • Family (-aceae)
  • Genus (capitalized, italicized)
  • Species (lower case, italicized)

Family, genus, and species are the ranks most relevant to gardeners

  • Kingdom
  • Phylum (-phyta)
  • Class (-opsida)
  • Order (-ales)
  • Family (-aceae)
  • Genus (capitalized, italicized)
  • Species (lower case, italicized)

Botanical Classification - below the species level

  • Subspecies or variety—naturally occurring (designated with subsp. or var. & italicized)
  • Cultivar—bred or selected by man (designated with single quotes or cv. and not italicized)
    • Example: Helianthus debilis subsp. cucumerifolius
    • Example: Camellia japonica ‘Debutante’

Plant Classification (informal)

Plants are classified by:

  • Life cycle (annual, biennial, perennial)
  • Life stages (embryonic, juvenile, transitional, reproduction, dormancy, and senescence)
  • Latitude (arctic, temperate, subtropical, tropical)
  • Usage (fruit, vegetable, ornamental, fiber, dye, medicinal, forage)
  • Growing or flowering season (warm season vs. cool season, wet season vs. dry season)

Plant Classification (informal)

Plants are classified by:

  • Tissue type (herbaceous, softwood, semi-hardwood, and hardwood)
  • Water needs (xerophyte, halophyte)
  • Foliage retention (evergreen, semi-evergreen, and deciduous)
  • Monocot vs. dicot (cotyledons, vascular stem arrangement, leaf venation, and floral part numbers)

Binomial Nomenclature

  • Allows for the unambiguous identification of an organism with just 2 words: Genus + epithet (species).
  • First used consistently by Linnaeus in Species Plantarum (1753).

Gymnosperms: Cycads, Conifers, and Ginkgo

  • Gymnosperm means “naked seed.”
    • Seeds not enclosed within an ovary.
    • Does not produce flowers or fruit.
  • Pollen and ovules produced in separate male and female cones.
  • Reproduce and disperse by means of seeds, which lack an endosperm.

Gymnosperms

  • Gymnosperms are generally woody plants.
  • May have needle-like leaves, scale-like leaves, or broad leaves.
  • Pollen cones and seed cones may be produced on the same plant or on separate plants.
  • In some species, the seed cone may be fleshy and berry-like.

Angiosperms: Flowering plants

  • Angiosperm means “container seed.”
    • Seeds enclosed within an ovary (fruit).
  • Pollen and ovules produced by specialized structures called flowers.
  • Dispersed by means of seeds which have an endosperm.
  • Traditionally divided into monocots and dicots.

Monocots

  • Embryo with one cotyledon (seed leaf)
  • Stems with scattered vascular bundles
  • Leaf veins usually parallel
  • Floral parts in threes
  • No secondary growth (no true wood or bark)

Dicots

  • Embryo with two cotyledons (seed leaves)
  • Stems with vascular bundles in rings
  • Leaf veins usually reticulate (branching)
  • Floral parts in fours or fives
  • Capable of secondary growth (true wood/bark)

But angiosperms are more complicated than that!

  • Includes Basal Angiosperms, Magnoliids, Monocots, and Eudicots.

In the real world…

  • Basal Angiosperms and Magnoliids account for 2% of all angiosperms.
    • Examples: water lilies, star anise, magnolias, nutmeg, peperomias
  • Monocots account for 23% of all angiosperms.
    • Examples: grasses, orchids, bromeliads, palms
  • Eudicots (true dicots) account for 75% of all angiosperms.
    • Examples: oaks, roses, cacti, mints, asters

Plant Morphology

Plant Morphology

  • The study of the physical form and external structures of a plant.
  • Helps understand a plant’s functions and habitat preferences and how best to grow it.
  • Helps to recognize plant families.
    • Plants within a certain plant family typically share a suite of morphological characteristics.

An example: Lamiaceae (mint family):

  • Stems often quadrangular
  • Leaves opposite, simple, often with aromatic glands
  • Flowers perfect, usually tubular and 2-lipped
  • Calyx often enlarged and persistent
  • Fruit a drupe with four stones or a schizocarp with four nutlets

Plant Morphology

First examine the whole plant

  • Habit:
    • Woody (tree, shrub, subshrub)
    • Herbaceous/non-woody (aka, herb or forb)
    • Suffrutescent (mostly herbaceous but developing a woody base over time)
  • In other words, is it a tree, shrub, herb, or vine?
  • Keep in mind that a vine may be herbaceous, woody (aka a liana), or suffrutescent.

First examine the whole plant – continued…

  • Form: upright, sprawling, arching, rosette, trailing, prostrate
  • Branching pattern: unbranched, well-branched, branching near the base, single trunk w/ branched crown
  • Size: height and width
  • Seasonality:
    • Woody: deciduous, evergreen, or briefly deciduous
    • Herbaceous: annual, perennial, or biennial
  • Hardiness: tropical, tender, or hardy

Plant Morphology

…then look at each organ from the ground up:

  • Roots
  • Stems
  • Leaves
  • Flowers
  • Fruits

Roots

Functions:

  1. Absorption of water & minerals
  2. Anchoring plant in place
  3. Conductance (water and minerals move up via xylem, sugars move up and down via phloem)
  4. Storage of water and carbohydrates

Roots: Morphology

  • Primary root = taproot
  • Secondary roots = fibrous roots
  • Adventitious roots = arise from a stem or other plant part (not from a root)
  • Root hairs = tiny outgrowths that absorb water/minerals by osmosis

Stems

Functions:

  1. Conductance via xylem and phloem
  2. Support and elevate the leaves, flowers, and fruit
  3. Storage of water and carbohydrates
  4. In some stems may also play a role in: Photosynthesis (e.g., cacti), Gas exchange (lenticels), Plant defense (thorns)

Stems: Morphology

  • Nodes
    • Points where a leaf or leaves are attached
    • Spaces between nodes are called internodes
  • Buds (growing points)
    • Terminal buds at the apex of stems
    • Lateral buds at the base of leaves
    • Adventitious buds may develop on injured stems

Inside the Stem

  • Phloem
    • Conducts photosynthetic products bi-directionally
  • Xylem
    • Conducts water and minerals uni-directionally from roots to entire plant
  • Both of these tissues are produced by the vascular cambium

Stem Types

  • Crown
  • Simple
  • Branched
  • Climbing
  • Creeping
  • Rhizomes
  • Stolons
  • Acaulescent = no stem!
    • St. Augustinegrass produces stolons (above-ground stems)
    • Bermudagrass produces rhizomes (below-ground stems)

Stem Modifications

For climbing:

  • Twining
  • Tendrils
    • May derive from stems, leaves, leaflets, or inflorescences (position of tendril gives clue to origin)
    • Tendrils may be clawed, twining, or have adhesive discs

Stem Modifications

For storage:

  • Rhizomes (e.g., ginger)
  • Stem tubers (e.g., potatoes)
  • Corms (e.g., taro/cocoyam)

Stem Modifications

For defense:

  • Thorns (modified stems)
  • Spines (modified leaves)
  • Prickles (modified hairs)

Leaves

Functions:

  1. Absorption of sunlight
  2. Photosynthesis (production of sugars from sunlight, carbon dioxide, and water)
  3. Gas exchange (absorb C02, release 02)
  4. Transpiration (loss of water)
  5. Storage of photosynthates
  6. In some plants, leaves may be modified for climbing (tendrils), for plant defense (spines), or for pollination (petal-like bracts attract pollinators).

Leaves: Morphology

  • Blade: flattened, expanded part
  • Petiole: the leaf stalk
  • Stipules: leaf-like appendages at the base of the petiole
  • Base: blade portion closest to stem
  • Tip or Apex: blade portion furthest from the stem
  • Margin: edges of the blade
  • Midrib or Primary Vein: the most prominent central vein
  • Secondary or Lateral Veins: veins that branch from the midvein

Phyllotaxy: Leaf Arrangement

  • Arrangement at a node
    • Alternate: 1 leaf per node
    • Opposite: 2 leaves per node
    • Whorled: 3 or more leaves per node

Phyllotaxy: Leaf Arrangement

  • Arrangement on stem
    • Spiral: leaves at adjacent nodes evenly spaced in a spiral around the stem
    • Distichous: leaves two-ranked (held on a single plane)
    • Decussate: leaves at adjacent nodes rotated 90˚
    • Equitant: two-ranked, flattened leaves overlapping at the base

Simple vs. Compound

A simple leaf has a single blade; a compound leaf has two or more blades (leaflets).

Simple vs Compound

  • Look for an axillary bud to distinguish between a simple leaf and a compound leaf.

Simple vs Compound

Examples of simple, even pinnate, odd pinnate, bipinnate, and palmate leaves

Compound Leaves: Additional Terms

  • Leaflet: the units of a compound leaf
  • Rachis: an extension of the petiole bearing leaflets
  • Petiolule: the stalk of an individual leaflet

Leaf Attachment

  • Petiolate: with a petiole (leaf stalk)
  • Sessile: lacking a petiole (leaf stalk)
  • Clasping: petiole or leaf blade partly or wholly surrounding the stem
  • Peltate: petiole attached to surface of leaf blade instead of to its base or margin

Common Leaf Shapes

Examples: linear, orbicular, oblong, ovate, obovate, deltoid, cordate, lanceolate, elliptic

Leaf Apices (Leaf Tips)

Examples: Acute (< 90°), Obtuse (>90°), Acuminate, Retuse, Emarginate, Mucronate, Rounded, Attenuate, Truncate

Leaf Bases

Examples: Cuneate, Cordate, Inequilateral, Acuminate, Acute, Obtuse, Round, Truncate, Sagittate, Hastate, Auriculate

Leaf Margins

Examples: entire, undulate, finely serrate, coarsely serrate, doubly serrate, crenate, lobed, revolute

Leaf Texture

Examples: Chartaceous (papery), Coriaceous (leathery), Succulent (fleshy, juicy)

Leaf Surfaces

  • Abaxial (lower) surface
  • Adaxial (upper) surface
  • Glabrous (hairless)
  • Glaucous (with a white waxy bloom)
  • Gland dotted
  • Vestiture (hairs/scales)—many variations
    • pubescent (short, soft), tomentose (wooly), sericeous (silky), pilose (long, soft), hispid (coarse, stiff), strigose (sharp, appressed), papillate (bumpy), lepidote (scurfy scales)

Leaf Venation

  • Parallel
  • Pinnate
  • Palmate
    • Trinerved (3)
    • Plinerved (5)
  • Reticulate
  • Impressed, raised, prominent, or obscure

Stipules

  • Leaf appendages (usually paired), located at the base of the petiole and found in select plant families.
  • Stipules function to protect the leaf in bud, but may be modified as spines, tendrils, or be enlarged and leafy.

Modified Leaves: Bracts

  • Bracts attract pollinators and/or protect the developing flowers

Flowers

Functions:

  1. Attract pollinators - petals (and sometimes petaloid sepals or bracts) lure pollinators.
  2. Reproduction - fertilized ovary develops into fruit which contains seeds. Much of the classification of plants is based on floral morphology

Flowers: Morphology

  • Sepals - calyx
  • Petals – corolla
  • Perianth = S and P
  • Stamen
    • filament
    • anther (produces pollen)
  • Pistil
    • stigma
    • style
    • ovary

Flowers: More-phology

  • Complete – has petals, sepals, stamens, and pistils
  • Perfect (bisexual) – has both stamens and pistils
  • Imperfect (unisexual)
    • staminate
    • pistillate
  • Monoecious: both imperfect flowers on one plant
  • Dioecious: either a staminate or pistillate plant

Flowers Exhibit Tremendous Variety!

  • Examples of different flower structures and arrangements.

Pollination Syndromes

  • Flowers are adaptations for pollination.
  • The structure, color, scent, and timing of flowers reflect the pollinating organism or mechanism!

Pollination Syndromes

Basic pollination syndrome character table, comparing characteristics for flowers pollinated by:

  • Bats
  • Birds
  • Bees
  • Beetles
  • Wind
  • Butterflies
  • Flies

Pollination Syndromes: a Famous Example

  • Xanthopan morganii (Morgan's sphinx moth) and Angraecum sesquipedale (Darwin's orchid)

Flowers: Solitary? or Grouped?

  • Solitary
    • A single flower borne at the end of a peduncle
  • Inflorescence
    • A flower cluster borne on a peduncle
    • May be branched or unbranched
    • Individual flowers may be sessile (unstalked) or borne on pedicels (flower stalks)

Inflorescence: Determinate or Indeterminate?

  • Determinate: terminal flower blooms first, halting elongation of the inflorescence axis
  • Indeterminate: lower or outer flower blooms first, allowing for elongation of the inflorescence axis as the flowers develop

Inflorescence: Types

Examples of determinate inflorescences:

  • Simple cyme or dichasium
  • Scorpioid cyme
  • Helicoid cyme
  • Cincinnus
  • Compound dichasium
  • Compound cyme (determinate thyrse)

Examples of indeterminate inflorescences:

  • Spike
  • Raceme
  • Corymb
  • Round umbel
  • Flat umbel
  • Capitulum or head
  • Compound umbel
  • Thyrse
  • Panicle (compound raceme)
  • Compound corymb

Fruits

Functions:

  1. Protect developing seeds (physical barrier between immature seeds and the environment)
  2. Aid in dispersal of mature seeds

Fruits: Morphology

  • Pericarp (fruit wall)
    • Exocarp (skin)
    • Mesocarp (flesh)
    • Endocarp (pit)
  • Placenta (the part of the ovary to which the seeds are attached)
  • Seed (mature ovule, contains embryo, and, in angiosperms, endosperm)

Fruits

  • Ripened, seed-bearing ovaries of flowers
  • Nearly as varied in color, form, size, texture, and number as flowers
  • Can be used as the distinguishing characteristic of a species or cultivar
  • Divided into four large categories
    • Dry or fleshy
    • Dehiscent (splitting open) or indehiscent

Dry Fruits

  • Achene (i)
  • Samara (i)
  • Nut (i)
  • Caryopsis (i)
  • Capsule (d)
  • Silique (d)
  • Legume (d)
  • Follicle (d)

Fleshy Fruits

  • Simple
    • Drupe (i)
    • Berry (i)
    • Hesperidium (i)
    • Pome (i)
    • Pepo (i)
  • Compound
    • Aggregate (from separate carpels of one flower, e.g., blackberry, magnolia, strawberry) (i)
    • Multiple (from pistils of several clustered flowers, e.g., pineapple, mulberry, sycamore) (i)

Seeds

  • Have an outer coat (testa), usually tough
  • Angiosperms have nutritive tissue (endosperm)
  • Contain an embryo, which, upon germination, develops into a new plant
  • Range in size from dust-sized to bigger than your head!

The University of Florida Herbarium

  • Established in 1891, became part of the FLMNH in 1981.
  • Approximately 500,000 specimens--the oldest, largest, and most comprehensive botanical collection in Florida
    • 280,000 vascular plants
    • 160,000 mosses and liverworts
    • 56,500 fungi (housed separately)
    • 15,300 wood samples
    • Library of over 16,000 books, journals, reprints, maps, and illustrations
  • Includes specimens from every continent except Antarctica, but the geographic focus is circum-Caribbean.

UF/IFAS Plant ID & Information Service

  • Established 1927 as a service to Extension personnel.
  • Provides identification of vascular plant samples (ferns, cycads, conifers, flowering plants).
  • Provides information on plants including nativity and current distribution, currently accepted name, invasiveness, regulatory status (prohibited or protected by law), toxicity, ethnobotany, and cultural/zone requirements.
  • Sample submission forms can be found at: http://edis.ifas.ufl.edu/pdffiles/sr/sr02400.pdf