Plant Science NMPS115 Notes

Module Purpose

  • The module aims to equip students with an understanding of plant physiology, focusing on photosynthesis, respiration, transpiration, and nutrient uptake.

  • It also teaches effective science communication.

Module Outcomes

  • Understand the binomial system of nomenclature and hierarchical classification.

  • Understand basic plant taxonomic groups and taxonomic identification.

  • Understand the distinguishing characteristics of common plant families.

  • Learn systematic plant identification using a dichotomous key.

  • Develop meticulous observation and differentiation skills for distinct plant parts.

  • Understand basic plant organography and how its characteristics aid in species identification.

Content Mapping

  • The module outlines which sections cover specific outcomes related to taxonomy, identification, and organography.

Glossary

  • Alluvial material: Material transported by water.

  • Apex: Terminal point of a leaf.

  • Aeolian material: Wind-deposited material.

  • Awn: Bristle-like extension facilitating spikelet dispersal.

  • Axillary bud: Structure forming lateral shoots, located between leaf and stem.

  • Base: Leaf section connecting to the petiole.

  • Berry: Stone-less pulpy fruit with embedded seeds.

  • Bioturbation: Soil mixing by organisms.

  • Blade: Flat, expanded portion of the leaf.

  • Cambium: Tissue layer providing undifferentiated cells for plant growth.

  • Capsule: Fruit from compound ovaries with many openings.

  • Catena: Sequence of soil and vegetation changes down a slope.

  • Colluvial material: Material transported by gravity.

  • Compound leaf: Leaf made of two or more leaflets or pinnae.

  • Culm: Stem or stalk of a grass.

  • Dehiscent: Opening spontaneously when ripe.

  • Dichotomous key: Identification method using a series of choices.

  • Drupe: Fleshy fruit surrounding a shell with a seed inside (stone fruit).

  • Elliptic leaf: Shaped like an ellipse.

  • Fascicle: Vascular tissue supplying nutrients.

  • Floret: Lemma, palea, and flower in a grass plant.

  • Fruit: Structure enclosing seeds, developed from the ovary wall.

  • Gynoecium (Pistil): Female reproductive organs (stigma, style, ovary).

  • Glume: Lowermost bracts protecting a grass spikelet.

  • Herbaceous: Non-woody plants.

  • Indehiscent: Not opening spontaneously when ripe.

  • Inflorescence: Whole flowering portion of a plant.

  • Interfascicular: Occurring between fascicles.

  • Internode: Part of the stem between nodes.

  • Jizz: Overall impression and shape of a tree.

  • Lactifer: Secretory structure producing latex.

  • Lanceolate leaf: Shaped like a lance head.

  • Leaf blade: Flat outgrowth for photosynthesis.

  • Leaf-sheath: Wraps around grass stem.

  • Ligule: Membranous outgrowth at the leaf blade-sheath junction, possibly for protection.

  • Linear leaf: Long, slender leaf.

  • Latex: Liquid exudate.

  • Leaf-like appendages: Stipules at the base of the petiole.

  • Margin: Edge of a leaf.

  • Megaphylls: Leaves with highly branched vascular systems.

  • Microphylls: Small, spine-shaped leaves with a single vascular strand.

  • Midrib: Central structure of a simple leaf.

  • Orbiculate leaf: Circular or nearly circular.

  • Parenchymal cell: Unspecialized cell for metabolism, storage, and differentiation.

  • Pedicel: Stalk of an individual flower.

  • Peduncle: Stalk of an inflorescence.

  • Petal: Part of the corolla, usually brightly colored.

  • Petiole: Leaf stalk.

  • Petiolule: Leaflet stalk.

  • Phloem: Tissue transporting sugar and nutrients.

  • Pinna (Leaflet): Secondary leaf of a compound leaf.

  • Pinnately Compound: Leaflets arranged along a rachis.

  • Pinnule: Single unit of a twice-divided leaf.

  • Pod: Dry, multi-seeded fruit.

  • Poaceae: Grass family.

  • Procambium: Meristem developing into primary vascular tissue.

  • Prickles: Small outgrowths of epidermis or bark.

  • Rachis: Extension of the petiole bearing leaflets.

  • Rachule: Secondary axis of a compound leaf.

  • Receptacle: Base to which flower parts are attached.

  • Rhizome: Underground, horizontal stem.

  • Roots: Absorb water, store nutrients, and provide support.

  • Seed: Fertilized and mature ovule containing an embryonic plant.

  • Sepals: Protective coverings of the bud, collectively called the calyx.

  • Sessile: Attached directly without a stalk.

  • Shrub: Woody, perennial plant smaller than a tree.

  • Simple leaf: Single leaf blade attached to a petiole.

  • Spike: Unbranched inflorescence with sessile spikelets.

  • Spikelet: Flower-bearing parts of a grass plant.

  • Spine: Modified dwarf lateral shoots.

  • Spore: Asexual reproductive cell of primitive plants.

  • Stamen: Male reproductive part (filament and anther).

  • Stipules: Leaf-like appendages at the base of the petiole.

  • Stolon: Horizontal stem forming new plants.

  • Thorn: Modified stipules.

  • Tree: Woody plant exceeding 3 meters.

  • True fruits: Develop from the ovary wall.

  • Vascular tissue: Transports water and nutrients.

  • Xylem: Tissue conducting water and minerals.

Introduction

  • This section introduces the importance of plant physiology and the structure of the course.

  • Section 1 addresses plant taxonomy.

  • Section 2 focuses on Southern African plant families.

  • Section 3 covers plant identification using a dichotomous key.

  • Sections 4-8 describe plant organography.

Section 1: Plant Taxonomy

  • Plant taxonomy is the science of classifying and naming plants.

  • It's crucial for understanding plant biology, ecology, and conservation.

Taxonomic Levels (Largest to Smallest):

  • Kingdom: Highest rank (e.g., plants).

  • Division (Phylum): Below kingdom (e.g., Angiosperms).

  • Class/Order: Below phylum (e.g., Dicots/Monocots, Fabales/Poales).

  • Family: Plants with common characteristics, name ends in "…ceae" (e.g., Poaceae).

  • Genus: First part of the scientific name, italicized and capitalized (e.g., Aristida).

  • Species, subspecies, and variants: Reflect variation within a species, italicized, with genus first and species in lowercase.

Taxonomic Tree Example:

  • Kingdom: Plantae

  • Division: Magnoliophyta

  • Class: Magnoliopsida & Liliopsida

  • Order: Fabales & Poales

  • Family: Fabaceae & Poaceae

  • Genus: Pisum & Zea

  • Species: sativum & mays

  • Common Name: Pea & Corn

Scientific Naming Rules:

  • Binomial convention: Genus name + species name (e.g., Vachellia tortilis).

  • Names are Latinized and italicized, with the genus capitalized.

  • Subspecies have a third Latinized name (e.g., Vachellia tortilis subsp. heteracantha).

  • Abbreviations like subsp. and var. are not italicized.

  • Family names end in "-aceae".

Additional Rules:

  • The second-highest rank is Division (Phylum in Animals).

  • Variety is a lesser rank than subspecies.

  • Descriptive scientific names: Scientific names often come from descriptive terms

  • *pteron; “wing feather”

  • *carpos “fruit”

  • *rotundus “round”

  • *folius; “leaf”

Importance for Conservation:

  • Essential for identifying species and their ecosystems.

  • Helps direct conservation efforts strategically.

  • Feeds into resources like the Red List of South African Plants.

Summary of the Plant Kingdom:

Non-Vascular Plants:

  • Lack specialized vascular structures.

  • Examples: Bryophyta (mosses), Hepatophyta (liverworts).

Vascular Plants:

  • Contain vascular tissue for transporting water and nutrients.

Seedless:

  • Examples: Pterophyta (ferns), Lycophyta (club mosses).

Naked Seeds (Gymnosperms):

  • Examples: Coniferophyta (conifers), Cycadophyta (cycads).

Seeds in a Fruit (Angiosperms):

  • Magnoliophyta (flowering plants), Monocotyledons (grasses), Dicotyledons (most trees).

Section 2: Plant Families

  • The Flora of southern Africa (FSA) region includes South Africa, Namibia, Botswana, Swaziland, and Lesotho

  • The region has a rich floristic diversity of ± 23 000 flowering plants.

Source of Flora's Richness

  • Diverse climate and landscape are responsible for plant life diversity.

  • Cape flora contributes nearly half of this richness.

  • Desert, grassland, and woodland flourish.

  • Clades interconnect.

Flora Overview

Phylum Breakdown:

  • Bryophytes: 97 Families, 903 Species - Mosses, liverworts, hornworts.

  • Ferns: 34 Families, 321 Species - Vascular, seedless plants.

  • Gymnosperms: 6 Families, 68 Species - Cycads, Pines.

  • Angiosperms: 220 Families, 22,800 Species - Flowering plants.

Largest Families

  • Asteraceae (daisies).

  • Mesembryanthemaceae (vygies).

  • Fabaceae (legumes).

  • Iridaceae (irises).

  • Poaceae (grasses).

ASTERACEAE (DAISY)

General Information

  • 1200 genera worldwide with 21,400 species.

  • Annual/perennial herbs and subshrubs/shrubs.

Distribution

  • Found everywhere except Antarctica.

  • Highest concentrations in winter rainfall areas, mountainous & subtropical areas.

Flagship species:

  • Namaqualand daisy (Dimorphotheca sinuata).

Significance

  • Known for food, oil, herbs, ornamentals, insecticide, medicine and herbal remedies.

Identification

  • Flowerhead (capitulum) present.

  • Consisting of one or many florets.

  • Surrounded by a series of protective bracts (involucre).

  • Usually 5 anthers, joined into a collar.

  • Heads can be discoid or radiate

  • Calyx modified into a pappus

MESEMBRYANTHEMACEAE (ICE PLANT / VYGIES)

General Information

  • Annuals, perennials, succulent herbs, shrublets, shrubs.

  • Found in sand dunes to slopes of sub-alpine areas.

Distribution

  • Mostly in southern Africa, but few in Australasia, Mediterranean, Asia, South America & North Africa.

  • Highest diversity is found in the Succulent Karoo Biome.

Flagship species:

  • Carpobrotus edulis, Suurvy or Sour fig.

Significance

  • Ornamental plants in gardens, soil.

  • Various medicinal uses include fungal infections, stimulants and treating sore throats.

Identification

  • Leaves succulent, opposite without stipules

  • Sepals 4-6 united below

  • Flowers regular with brightly colored, free petaloid staminodes
    ol Stamens numerous

  • Many seeded hygrochastic capsular fruit opening with valves, rarely a berry or nut

FABACEAE (LEGUMES)

General information

  • There are 650 genera and 18,000 species worldwide.

  • In South Africa, there are 155 genera and 1516.

Distribution

  • Occurs worldwide, absent from Antarctica.

Flagship Species

  • The Ploegbreker (Erythrina zeyheri).

Significance

  • Farmers plant legumes to increase soil fertility for humans and wood is used in timber industries, and fuel.

  • This family includes species used medicinally, as spices, aromatherapy and as garden ornamentals.

Identification

  • Leaves are pinnately-, bipinnately- or trifoliolata compound

  • Leaf bases are sometimes swollen

  • Fruit pod

IRIDACEAE (IRIS)

General Information

  • South Africa has 33 genera with 1204 species whereas worldwide there are 70 genera with 1800 species.

  • This family consists mostly of deciduous perennial herbs with rhizomes and corms.

Distribution

  • Found in temperate and more tropical areas.

Flagship Species

  • Moraea fugax: Wituintjie. Familiar plant found in sandy coastal areas of Namaqualand.

Significance

  • Important to the cut flower industry.

  • Very important to the cut flower industry.

Identification

  • Perennials with rhizomes, corms or bulbs

  • Leaves sword-shaped in 2 whorls

  • Leaves form a fan and appear with the flowers

  • Inflorescences are generally borne on fleshy stems

  • Almost always with regular flowers; the perianth in 2 whorls with 3 tepals each often united in a tube

  • Three stamens found opposite to outer tepals

  • Fruit a dehiscent loculicidal capsule

POACEAE (GRASSES)

General Information

  • 200 genera and 1016 species found in South Africa.

  • In the world, there are 600 genera and between 9000 and 10 000 species.

Distribution

  • Worldwide occurrence as well as throughout South Africa.

  • The highest densities occur in the Highveld and warmer regions.

Flagship Species

*Themeda triandra: Red grass, rooigras, iNsinde.

Significance

  • Important as a foodstuff for humans and animals.

  • Other uses include horticulture (ornamentals and lawns), construction (building material), and decorations (furniture and flooring).

Identification

  • Herbaceous, culms are usually hollow, cylindrical or compressed
    Obvious nodes and internodes

  • Leaves with blades and leaf sheaths and ligules

  • Inflorescences at the tip of the culms

  • Flowers borne in spikelets

Section 3: Dichotomous Key and Species Identification

  • Dichotomous Key: A tool for identifying items and organisms in the natural world.

  • User is given two choices in each step. If the user makes the correct choice every time, the name of the organism will be revealed at the end

  • Physiological characteristics used in species identification

Identifying Trees

  • Most important identifying characteristics are flowers, fruits and seeds, canopy, trunks and stems, bark, leaves, pods, latex, and presence/absence of thorns and spines

  • Botanists classify and identify trees largely based on their floral structure and fruit

Section 4: Organography of plants: Leaves

  • A leaf is the main organ for photosynthesis in vascular plants, consisting of a broad lamina attached to the stem by a petiole.

  • The leaf grows at a node, with an axillary bud in the axil.

  • Despite their morphological diversity, all leaves are specialized for photosynthesis and are usually green due to abundant chlorophyll.

  • Leaf size and texture depend on environmental factors like light, moisture, and temperature, with shade-grown leaves being larger and thinner than those in direct sunlight.

Internal Leaf Structure

  • Epidermis: Outermost layer with upper (adaxial) and lower (abaxial) surfaces.

  • Cuticle: Waxy layer reducing water loss.
    *Trichomes: Hair-like structures deterring herbivory and reducing transpiration.
    *Facilitating gas exchange of the epidermis, which houses stomata – openings enabling the
    exchange of gases.

Mesophyll:
Beneath the epidermis of dicot leaves lie layers of cells known as the mesophyll, or the middle leaf.
Palisade parenchyma: Column-shaped cells tightly packed together.
Spongy Parenchyma : Loosely arranged cells with an irregular shape
vHypoderm: In forbs, the hypoderm consists of collenchyma cells located directly beneath the epidermis, transitioning gradually into parenchyma tissue

  • Vascular Tissue: Xylem and phloem transport water, nutrients, and sugars, forming veins from the petiole into the lamina.

External Leaf Structure

The outward appearance of leaves is specific for each plant species and is thus of great taxonomic importance.
The leaf base: The lowest portion of the petiole implanted on the stem forms the leaf base.
The petiole (leaf stalk): This is the stalk-like section between the leaf blade and the leaf base. The petiole usually has the same internal structure as the stem
The lamina (leaf blade): This is usually the flattened, thin, green, disc-like part of the euphyll

Leaf Types

  • All leaves have axillary buds in their axils.

  • Cotyledons: First leaves of plants, thick in non-endosperm seeds, thin in endosperm seeds.

  • Euphylls: Ordinary green, vegetative leaves.

  • Cataphylls: Reduced, scale-like leaves protecting the stems' growing points, often in subterranean stems.

  • Hypsophylls: Similar to cataphylls but always associated with flowers and inflorescences.

  • Floral leaves: Modified vegetative leaves like green sepals and petals.

Phyllotaxy (Leaf Arrangements)

  • Spiral Arrangement: One leaf per node in a spiral formation.

  • Alternate Arrangement: One leaf per node alternately.

  • Opposite Arrangement: Two leaves opposite each other at each node.

  • Decussate Arrangement: Two leaves per node, successive pairs at 90-degree angles.

  • Verticillate (Whorled) Arrangement: More than two leaves per node, forming a whorl.

Venation of the Lamina

  • Parallel Venation: Veins run parallel (mostly in Monocotyledons).

  • Pinnate Venation: Midrib in the center with lateral veins (feather-like), commonly in dicots.

  • Palmate Venation: Three or more primary veins from the base, like fingers, found in dicots.

Functions of Normal Leaves

  • Photosynthesis- Harnessing energy from the sun and packing it into sugars with the help of chlorophyll, oxygen is given off.
    *Transpiration- Regulates the evaporation of water entering the plant at the roots.

Metamorphic (Modified) Leaves

  • Leaves with climbing or attaching function

  • Leaves with protective function
    *Leaves with storage function

  • Leaves with water retention function

  • Leaves with root function

  • Leaves with vegetative reproductive function

  • Leaves with sexual reproductive function

  • Petiole with leaf function

Section 5: Organography of Plants: Roots

  • A root is a plant organ typically below the soil, lacking leaves and nodes. The first root is called the radicle.

Origin and Characteristics of Roots

Growing tip protection by calyptra
Roots do not have leaves and axillary buds
Roots are not divided into inodes and internodes.
Internally the vascular tissue is radially arranged

Anatomy of the root

Roots consist of the following tissue
*vascular tissue
*Ground tissue
*Epidermis tissue

Root types

Tap root system- most common of primary system
Adventitious root system-Commonly found in representatives of the Liliidae

Tap root
Adventitious root
Lateral root
Hair root
Root hair
Fibrous roots

Function of roots

  • The three major functions of roots

  • Absorption of water and inorganic nutrients

  • Anchoring of the plants body to the ground

  • Stroage of food and nutrients
    Metamorphic (modified) roots - perform functions over and above the normal function of roots.

Roots are storage organs
Bulb
Stem tube
Corm
Aerial Roots
Velamen Roots
Pnuematophores

Function of roots

Absorption and inorganic nutrients
Anchoring of the plants
Storage of food and nutrients

Types
Taqp root systems
Adventitiouss root system

Metamorphic (modified) roots

These roots are modified to fulfil an exceptional function over and above the normal functions of roots

*Roots as storage organs

  • Stem tube

  • Corm

  • Aerial roots

  • Contractile roots

  • Roots of parasitic plants

Section 6: Organography of Plants: Stems

  • Stem and parts of a tree, facilitation of the transportation of minerals and nutrients
    Acting as the plant axis, the stem supports buds and shoots adorned with leaves, it also gives rise to roots at its base
    Annuals
    Biennials
    Perrenials

Anatomy Stem

Promeristem
Epidermis
Ground tissues
Pith
Vascular tissue

Growth point of stem

Cell Enlargement
Cell differentiation

Types of bud

Can be classified according to the location, status, morphology and function

Branching of stems

Monopodial branching
Sympodial branching
Dichotomous branching

Functions of normal stems

The stem must support the leaf; flower and fruit display/positioning
Xylem & pholem are used to conduct water; minerals and nutrients
The stems store water if need be

Metamorphic (modified) stems

Underground stems as storage organs
Stems as twining and/or climbing organs
Stems with leaf functions
Stems with protective function
Stems with reproductive function
Bulbils
Rizhomes
Stem Cuttings

Section 7: Organography of Plants: Inflorescences and Flowers

  • Flower represents a modified lateral branch and originates from an axillary bud.

  • The biological function of a flower is to mediate the union of male sperm with the female ovum to produce seeds.
    *An Inflorescence is simply a grouping of flowers.

Inflorescences and Flowers Parts

Pedicel- The flower Stalk
Receptable- Is the flattened tip of the peducel
Perianth consists of the sterile leaves of a flower

Stamen of the androecium

Stamen is fertile part of the flower
Is made us of the filament and anther

Based on the position of the micropyle in relation to the funicle and the placenta the following types of ovules can be distinguished:
Orthrotropous avule- the micropyle is situated at the oppositie side of the funicle

  • Based on the position of the micropyle in relation to the funicle and the placenta the following types of ovules can be distinguished:
    *Anatropous avule- as a result of curvature of the funicle the hypocrite lies next to the funicle .

  • Sex of flowers
    *-Most flowers are bisexual

Pollination

Is the process by which pollen is transferred to enable fertilisation and sexual reproduction in plants
*-Cross poilination
*-Self polination

Evolutionary adaptions
*-Anemophily- Flowers pollinated by wind
Entomophily- Insect wind
Zoophily- Animals

Section 8: Organography of plants: Fruits

Fruits can be divided into various groups based onto their origin, the most essential functions are proteting the seeds as well assisting in dispersal

Three general modes of fruit development
Apocorpous Fruits
Synocarpous Fruits
Multiple fruits forms from many flowers

Fruti Types

Fleshy fruit- The whole pericarp and part of the receptable is fleshy
Dry Simple Fruit - The maruitz, their pericarp isn’t fleshy thath means taht ot Is thin and dry
Dehiscent dry fruti- When it’s ripe there is a pod, and it typically splits among two fissures
Indehiscent dry fruits- when there doesn’t pen spontaneously to release the seeds.

Fruit and seed dispersal

Wind-disperserd fruist: This have a low density, and typically possess wing light grouwths or plumess
Water Dipsersed fruitts: thise aare adapted to float I water they mayy contain are in gorves
Animal disperserd fruittys; they usually have a b bright colour or taste very sweet in gerneral, this attract the animal wich then eats the seed, and pass it theu

Plant Science NMPS115: 2025