INTRO TO BOTANY AND TISSUE SYSTEMS

  1. Botany - Plant Biology

  • Origin

  • Diversity

  • Structure

  • Internal Processes

  • Relationships with other living and non living physical environment

  1. Characteristics of Plants

  • Highly organized

  • Take in and use energy

    • Energy related activities: Photosynthesis and cellular respiration

  • Respond to stimuli - changes in the environment to which organisms respond and react

    • Tropism: responses by a part of a plant towards or against a stimuli

  • Grow and develop

    • Alteration of generation: life cycle made up of two stages

      • Sporophyte: Plants make spores that are genetically identical to parent plants

      • Gametophyte: female gametophytes produce egg, male gametophyte produce sperm

  • Reproduce

  • DNA transmits information from one generation to the next

  • Multicellular eukaryotes

  • Rigid cell wall (which are dead aka nonliving)

  • Large central vacuole - stores water, helps keep plant upright, the bigger the vacuole is the older it is

  • Have plastids

    • Etioplasts: crystalline prolamellar bodies, precursor of chlorophyll

    • Chloroplasts: photo and lipid synthesis

    • Chromoplasts: Pigment

    • Proteinoplasts: site of enzyme activity

    • Leucoplasts: synthesizes fatty acids and amino acids

    • Amyloplasts: store starch and sugars

  1. Plants

    1. Vascular (Tracheophytes)

      1. Angiosperms (Flowering)

      2. Gymnosperms (Cone bearing)

      3. Pleridophytes (spores)

    2. Non vascular (Atracheophytes)

      1. Bryophytes

      2. Thallophytes

  1. Dermal - Outer covering, protects soft tissues of the plants, control interactions with the plant’s surroundings, arises from protoderm

  • Like “skin” of animals

  • Forms outer bark of trees

  • Stems and leaves: secretes cuticle - waxy layer that prevents water loss

  • Some have trichromes, hairs

  • Roots epidermis: Root hairs for water and nutrient absorption

  1. Epiderm - complex tissue, functions include protection and gas exchange, outermost layer of cells, usually one cell thick, covers the primary plant body, first line of defense, for herbaceous plants only epidermis consist the dermal tissue system 

  • Stems: thick layer of epidermal cells, are thick-walled and are meant for protection, hairs are meant for secretion of some compounds

  • Leaves: thick layer of epidermal cells, thick-walled and are meant for protection, two layers one for each surface of the leaf, hairs are meant for secretion of some compounds

  • Roots: thin layer of epidermal cells, unicellular, for water and mineral salt absorption, root hairs penetrate soil to absorb them

  • Composed primarily of unspecialized living cells consisting of:

  1. Epidermal cells

  • Cell walls thicker towards outside the plant to provide protection

  • Generally have no chloroplasts and are transparent to allow light to pass through to interior tissues of stems and leaves

  • Photosynthetic tissues lie beneath it (in both stems and leaves)

  • Secretes Cuticle: waxy layer to reduce water loss in epidermis

    • Formed mainly of Cutin: aggregates of modified fatty acids partly combined with alcohols

    • Varies in thickness

    • Prevents carbon dioxide required for photosynthesis from diffusing from the atmosphere to the stem and leaves

  1. Stomata - opening in the epidermis of leaves and stems

  • Occurs in both surfaces or only in lower surfaces, in water plants the occur on upper surfaces

  • Open during the day when photosynthesis is occurring, closed during night

  • Closed in the day during drought 

  • Loss of water happens during the day when it’s open providing evaporative cooling for leaves

  • Parts: 

    • Guard Cells: found in the epidermis, arranged in pairs, form and surround the stomata, regulates its opening and closing, with chloroplasts

    • Subsidiary Cells: surround guard cells, provide support, assist, reinforce, or protect guard cells, no chloroplasts, differ in size, shape, arrangement, and sometimes in content with neighbouring cells

  • Functions:

    • Gas Exchange: opening and closing help in gaseous exchange between the plant and surroundings

    • Helps in transpiration and the removal of excess water in the form of water vapor

    • Closure during night helps prevent water escaping

    • Maintains moisture balance according to weather by opening and closing

    • Facilitate carbon dioxide uptake and release of oxygen during photosynthesis

  • Types:

    • Anomocytic (Irregular-celled or Ranunculaceous): no subsidiary cells, surrounded by epidermal cells, stomata appears embedded in epidermis, no definite number and arrangement of cells surrounding stomata (eg. Ranunculaceae, Malvaceae, Papaveraceae, Neen, Artimisia, Fennel, Clove, Eucalyptus)

    • Anisocytic (Unequal-celled or Cruciferous): 3 subsidiary cells having unequal cells, one is smaller than the other two cells. (eg. Cruciferacea, Solanum, Nicotiana, etc. Tobacco, Belladona)

    • Diacytic (Cross-celled or Caryophyllaceous): pair of subsidiary cells perpendicular to the guard cells (eg. Acanthacea, Caryophyllaceae Peppermint, Spearmint)

    • Paracytic (Parallel-celled or Rubiaceous): pair of subsidiary cells parallel to the guard cells (eg. more than a hundred dicot families such as Rubiaceae, Convolvulaceae and Fabaceae, Coca, Senna)

    • Gramineous: two dumbbell-shaped guard cells (narrow in the middle and wider at the ends) surrounded parallel to two lens-shaped subsidiary cells

    • Actinocytic (Radiate-celled or Star-celled): at least 5 subsidiary cells forming a star-like circle

    • Tetracytic (Four-celled): four subsidiary cells, one for each guard cell and ends of stomata pore (eg. many monocot families, but also can be found in some dicots, such as Tilia and several Asclepiadaceae)

  • Monocot: dumbbell-shaped, stomata arranged regularly, occurs in both upper and lower epidermis

  • Dicot: bean-shaped, stomata arranged irregularly, occurs mostly in lower epidermis

  1.  Trichromes

  • Special outgrowths or hairs of the shoot epidermis

  • Occur in many shapes and forms

  • If short and conical then it is called papillae and the epidermis is described as papillosed

  • Play a key role in the development of plants and occur in a wide variety of species

  • Foot: embedded in the epidermis, Body: free part

  • Root hairs:  Simple unbranched trichomes that  increase water uptake by increasing the surface area of the cell., tube extensions from epidermal cells

  • Unicellular or multicellular appendages, extension of the above-ground, classified into:

    • Glandular: trichomes with glandular head and secrete secondary metabolites, participate in production, storage and liberation of biologically active chemical compounds, prevent herbivory by storing substances that are harmful to insects.

      • Unicellular

        • Unicellular head e.g. Mentha.

        •  Bicellular head e.g. Digitalis.

        • Multicellular head e.g. Labiaceous hair in Mentha and clavate hair in Belladonna.

      • Multicellular

        • Uniseriate stalk e.g. Belladonna

        • Biseriate stalk and biseriate head or compositae type e.g. Chamomile.

        • Pluriseriate stalk and a head with numerous mostly eight radiating cells e.g Cannabis.

        • Branched stalk: the branch ending in head as in Hyoscyamus muticus.

    • Non-glandular 

      • Unicellular

        • Unbranched

        • Branched

      • Multicellular

        • Unbranched

          • Uniseriate: formed of one row

          • Biseriate: formed of two rows, each row of one (twin cell) as in Arnica flower, or more cells as in Calendula.

        • Branched

          • Simple branched: with uniseriate body ending in two branches e.g. Tobacco.

          • Stellate: radiating unicellular hairs e.g. Karkadeh.

          • Peltate: with a very short axis surmounted by a plate-like structure of closely joined cells e.g. Olea.

          • Candelabra: having uniseriate axis from which arise numerous unicellular branches of hairs e.g. Verbascum.

  • Functions:

  • Remove excess salt that has accumulated in halophytes

  • Increase the reflection of light off the desert plants which keep the internal tissues cooler and decreasing water loss.

  • Protective function

  • Waxes protect plants from extreme heat and sunlight.

  • Oils from such plants as Cymbopogon act as insect repellent

  1. Periderm - replace epidermis in older regions of stems and roots, as woody plants begins to increase in girth, epidermis sloughs off and gets replaced by this, complex tissue composed mainly of cork cells and cork parenchyma cells.

  • Periderm formation is a common phenomenon in stems and roots of dicotyledons and gymnosperms, which increase in thickness by secondary growth, as well as in lenticels, abscission zone, and upon wounding.

  • The bark is everything outside the vascular cambium.

  • Periderms form the outer bark.

  • Plays key role in in various fruits and vegetables

    • Constitutes the skin of potato tubers, sweet potato storage roots, and carrot and forms the reticulated structures decorating different species of melon and cucumber, as well as the cork of tree barks.

    • has negative outcomes, such as skin russeting in potato, apple, pear, and tomato.

  1. Phellem (Cork) - Forms a series of cell layers at the outermost level of the periderm and is derived from the underlying meristematic phellogen layer (cork cambium). Produced by the phellogen towards the outside.

  • As phellem cells develop, they become suberized and then die, creating an external protective layer by reducing water loss

  • Phellem replaces the epidermis as the tree increases in girth.

  • Main function is to provide protection.

  • Cells are highly suberized.

  • Cells are impermeable to water

  • Plenty of tannin occurs in the cells.

  • Dead cells, closely packed

  • Photosynthesis can take place in some trees both through the phellem and in fissures.

  1. Phellogen (Cork cambium) -region of cell division that forms the periderm tissues. Phellogen development influences bark appearance.

  • layer of meristematic tissue which produces the phellem and the phelloderm together known as the bark.

  • the source of the periderm, a protective tissue that replaces the epidermis when the secondary growth displaces, and ultimately destroys, the epidermis of the primary plant body.

  • The cork cambium gives rise to the secondary plant body’s protective covering, or periderm

  • Periderm consists of the cork cambium plus the layers of cork cells it produces

  • Bark consists of all the tissues external to the vascular cambium, including secondary phloem and periderm

  • Lenticels in the periderm allow for gas exchange between living stem or root cells and the outside air

  • Periclinal divisions of sub-epidermal cells leads to the development of phellogen

  • In Quercus alba, the phellogen originates in sub-epidermal cells

  • In Solanum (nightshade), the phellogen arises from the epidermis

  • Phellogen in Clematis originates deep in stem tissue from phloem parenchyma cells below the fiber caps

  • In grape vines, the phellogen also originates in the primary phloem

  1. Phelloderm (Secondary cortex)

  • The parenchyma-like phelloderm forms the innermost layers of the periderm and is similarly derived from the phellogen layer.

  • It is a living tissue having a cellulosic cell wall, active parenchyma tissue. Loosely packed

  • It can contain chlorophyll and function in defense and even cell division

  • Function primarily for storage of materials and ergastic substances

  • Not suberized, permeable to water, no tannin deposition, pores or lenticels are absent

  1. Inner Bark

  • Phloem tissue makes up the inner bark.

  • However, it is vascular tissue formed from the vascular cambium.

  • Sieve tube elements actively transport photosynthates down the stem.

  • Conifers have sieve cells instead.

Polyderm – special type of protective

tissue that occur in roots and

underground stem


Boundary layer – impervious layer that

seals the newly exposed surface

Humans and secondary plant Growth

  • Bamboo products

  • Bark products

  • Salix alba (White willow) - salicin to aspirin

  • Cinchona species – Quinine

  • Cinnamon

  • Quercus suber

  • Taxus brevifolia (Pacific Yew) - Taxol

  • Woody plants as art

  • Dendrochronology

Bristlecone pines- Oldest organism – 4767 yrs. Old

Baobab (Adonsonia digitata) grow up to 45 ft. in diameter

Black River Swamp (Pender

and Bladen Counties)

The Black River, a blackwater

tributary to the Cape Fear River,

provides wonderful opportunities

to explore old-growth forests on

a half-day canoe trip. Surrounded

by classic blackwater river

swamp, the Black River is home

to the oldest living trees east of

the Rocky Mountains according

to research conducted by

dendrochronologists from the

University of Arkansas.

Individual trees with swollen

buttresses, often exceeding 15

feet in diameter, may be

1,700-2,000 years old.





  1. Vascular - “Vessels” throughout the plant, transport materials, arises from/derivative of procambium

  • Occur in the form of strands known as fascicles or vascular bundles that extend from one end of the plant body to another, in the leaf these are known as veins

  • Runs continuously throughout the plant

  • Transports materials between roots and shoots

  • Vascular bundles may contain only xylem, phloem, or both

  • Cambium: Piece of meristematic tissue sometimes enclosed in vascular bundles, brings about secondary growth in bundles

    •  Present Cambium = Open Bundle

    • Absent Cambium = Closed Bundle

  1. Xylem - complex tissue,  transports water and ions upward

    1. Tracheids

    2. Vessels

    3. Parenchyma cells

    4. Sclerenchyma tissues (sclereids or fibers)

  2. Phloem - complex tissue, functions as sugar, amino acid, and hormone transport, transport food from the leaves to the roots and non-photosynthetic parts of the shoot system

    1. Parenchyma cells (sieve tube members, companion cells)

    2. Sclerenchyma cells (sclereids or fibers)

  1. Ground - “Body” of the plant; metabolism (photosynthesis and respiration);  mainly involved in storage; support, arises from/derivative of  ground meristem

  • Represented by the different regions in the plant body

  • In cylindrical parts of the plant body (roots, stems) they are differentiated into various regions, in a typical condition, the regions can be recognized as

    • Cortex: Between the epidermis and vascular tissues

    • Pith: Surrounded by vascular bundles

  1. Parenchyma - simple tissue, composed of parenchyma cells, functions as synthesis and storage

  • Thin-walled, can perform photosynthesis if there’s chloroplast

  1. Sclerenchyma - simple tissue, composed of sclereids or fibers, functions as support, provides strength 

  • Thick-walled, composed of hollow, nonliving support cells with secondary walls

  1. Collenchyma - simple tissue, composed of collenchyma cells, functions as support, provides strength

  • Thicker, uneven cell walls, provides flexible support (eg. Celery) 

  1. Organs: tissues that act together to serve a specific function (all have dermal, vascular, and ground tissues

    1. Roots

    2. Stems

    3. Leaves

      1. Structure

  • Cuticle

  • Palisade mesophyll

  • Spongy mesophyll

  • Vein

  • Air Spaces

  • Stomata