PHA611: Plant Tissues and Arbituary Classification

TISSUE

A group of cells that perform specific function

Meristem

Tissues where the cells are in the mitotic state; actively dividing

Promeristem (primordial meristem)

• Young meristamatic cells of a growing organ

• Occupies a small area at the tip of a stem or a root 

• Divide in order to form primary meristem

Primary meristem

• First derivative of promeristem

• Tip of the stem, root, or appendiges

• Divide repeatedly, develop and mature, to form the primary structure

• Apical meristem

Secondary meristem

• Secondary tissue

• Eg. Lateral and intercalary meristems, vascular cambium

Apical

• Growth region found in root tips and tips of new shoots and leaves

• Differeniate into different cell type

Intercalary

• Growth in length and elongation

• Rapid growth and regrowth

Lateral

Grow in diameter, girth, thickness

Vascular and Core Cambium

Protoderm

Dermatogen

produces the epidermis, a dermal tissue.

Procambium

Plerome

produces the Vascular tissue; xylem and pheolem

Fundamental or Ground

produces Ground tissue hypodermis

PERMANENT

Cells are stable, no longer dividing; matured

SIMPLE PERMANENT TISSUE

• Composed of one type of cell

• Differentiates into dermal or protective and ground or fundamental

Parenchyma Tissue

A mass of parenchyma cells; most common type of tissue constituting all soft parts of a plant

Least specialized permanent tissue composed of living thin-walled cell

Parenchyma Cells

• Most common type of cell

• Has thin primary walls; large vacuole (storage)

• Active matebolically and alive at maturity

• Numerous subtypes are specialized for particular tasks

• Eg. geranium

Chlorenchyma Cells

• Involved in photosynthesis: chloroplast

• The thinnest of the wall allows light and carbon dioxide to pass through to the chloroplasts

• Eg. a leaf of privet

• Elongated cylindrical cells with their long axis at the right angle to th surface of the organ

• Cell contains numerous chloroplast for photosynthesis

Glandular Cells

• Secrete nectar, fragrances, mucilage, resins, and oils

• Contain few chloroplasts but have high amounts of dictyosomes and endoplasmic reticulum

• Eg. A resin canal in pine leaf

Aerenchyma cells

Specialized in gas exchange; large interceullar space

• Irregular cell surrounded with large air space

• Found in stems of aquatic plant

Collenchyma Tissue

A mass of collenchyma cells

Collenhyma cells

• Unevenly thickened primary walls (thin in some areas, thick most often in the corners)

• Typically alive at maturity

• Provide plasticity (the ability to be deformed by pressure or tension and to retain the new shape even if the pressure or tension ceases).

• Present in elongating shoot tips as a layer just under the epidermis or as bands located next to vascular bundles

Usually produced only in shoot tips and young petioles (connects leaf to stem).

• Living cell with thickening in corner leaving the lateral wall thinning

• May be either short and prismatic, elongated and tapering or polygonal in transverse section

plasticity

the ability to be deformed by pressure or tension and to retain the new shape even if the pressure or tension ceases

petioles

connects leaf to stem

Sclereids

under Mechanical (nonconducting)

• Brittle and inflexible

• Form hard, impenetrable surfaces 

• Eg. shells of walnuts and coconuts or the “pits” or “stones” of cherries and peaches

• more or less isodiametric; often dead at maturity

Fibers

under Mechanical (nonconducting)

• flexible; found in areas where strength and elasticity are important (wood of flowering plant, trunk, and branches)

• Resists insects, fungi, pests (bark)

• Elongates as the internode increases in length (node - where leaves grow)

• Long; many types are dead, other types remain alive and are involved in storage

Tracheids

under Conducting (tracheary elements)

• Water-conducting long cells with tapered ends, no perforations

• Only type of water conducting cells in ferns, conifers and most other nonflowering plants

• Dead at maturity (hollow tubular wall)

• Secondary wall has bordered pits (to keep sclereid alive)

• Found in all vascular plants

Vessel Elements

under Conducting (tracheary elements)

• Forms large hole called a perforation  which greatly reduces the friction = water moves much more easily than through pits of tracheids.

• short and wide with rather perpendicular end walls; 

• most contain one or two perforations. 

• Dead at maturity. 

• Found almost exclusively in flowering plants. Among nonflowering plants, only few ferns, horsetails, and gymnosperms have vessels

Sclerenchyma Tissue

• Has both a primary wall and a thick secondary wall that is almost always lignified

• Many dead at maturity

• Provides elasticity ( the ability to be deformed, but snap back to their original size and shape when the pressure or tension is released)

• May or may not be living

• Occurs in cluster or group among parenchymatour cells surrounding vascular tissue

  • Fiber - elongated cells with pointed end walls

  • Sclera’s or Stone Cell - roundish or polygonal cell with walls varying in thickness

Scelerenchyma Cells

Some are involved in water transport

Develop mainly in mature organs that have stopped growing (non-extending parts) and have achieved their proper size and shape)

EPIDERMIS

• Outermost surface of a herbaceous stem, leaf and root

• Uses

  • Protection; regulate exchange of materials

• Encrusted with cutin (cuticle)

• Contains guard cells, trichomes, and root hairs

Cutin

inhibits the entry of Co₂ needed for photosynthesis = plant’s starvation -> pairs of guard cells with a hole (stomatal pore) between them to permit gas entry

• Guard + stomatal pore = stoma/ stomata

• Stomatal pores are open during daytime

Accessory cells

• Serves as reservoir of water and ions

Bulliform cells

Longitudinal rows of vacuolated cells

Epidermal hair

For the elongation of the epidermal cell outward (trichome and root hairs); increase surface area

Trichomes

• aka epidermal outgrowths/hairs

  • Functions:

    • Protection from insects and excessive sunlight

    • Aids in nutrient uptake

    • Spread of seeds

  • Economic Importance

    • Threads -> cloth

Glandular

Glandular or Secretory

Aratiles

Stinging

Glandular or Secretory

Lipa

Branching

Non-glandular/Non-secretory

velvet dock

Bristle

Non-glandular/Non-secretory

(Lipai); thinner

Scale

Non-glandular/Non-secretory

(Lingaro); finer, flower

Stellate

Non-glandular/Non-secretory

(Mallotus); star

Root hair

epidermal outgrowth of root’s epidermis

increase surface area for absorption

Cork or Phellem

• Outer covering of woody stems and roots

• Cell wall is impregnated with suberin

• Produced by the cork cambium (secondary meristem)

• No intercellular spaces (avoid water loss)

COMPLEX PERMANENT TISSUE

Composed of different kinds of cell but perform similar function

Xylem

• Brings water and minerals salts from the roots to the rest of the plants

• tracheids &  vessels - transport water and minerals from roots to all part of the plant

• Principal water conducting tissue composed of lignified dead cells located in the stellar (Vascular) region of stem, root, or leaves

• Various patterned secondary walls called tracheids, vessel, fiber, and parenchyma

Xylem parenchyma

 under xylem

stores water

Xylem Fibers

 under xylem

help in support

Phloem

Moves sugar and other organic nutrients (food) and minerals

• Principal food conducting tissue composed of different type of cells located in the stellar region

• Composed of fibers, parenchyma, sieve cell or tube and companion cells

Sieve tubes and companion cells

transport food from leaves to all parts of the plant

Phloem parenchyma

under phloem

stores food

Phloem fibers

under phloem

help in support

ARBITRARY CLASSIFICATIONS

Easily classify plants; less time consuming; not universal applicable; characteristics (what we observe)

Bryophytes

•  (mosses, hornworts, and liverworts)

  • Lacks vascular tissue but some have water conducting tube

  • Multicelluar embryo remains attached to mother plant nourished and protected

  • Lack leaves, stems, roots (no support)

  • Limited habitats (near water; moisture)

Pteridophytes

• Have vascular tissue

• Seedless but embryo nourished by parent cell (spores)

• Eg. Lycophytes, fern, horsetail, whiskfern, Salvinia Natans

Gymnosperms

• Non-flowering

• Vascular, have seeds which are not enclosed inside an ovary

• Male (smaller) or Female (larger) cones

• Eg. Gingko, Cycas, Gnetae, confider, Giant Sequioa Tree, Sago Palm

• “Naked seeds”

Angiosperms

• Flowering plants (largest family)

• Vascular, seed within ovaries

• Eg. Water lily, Cosmos flower, Sunflower

Tree

• More than 5 heights

• Usually with woody main trunk or stem

• Lives for several years

Shrubs

• Less than 5 meters

• With short main trunk or stem

• Lives for several years

• With numerous lateral branches

Herbs

• Plants with little or no woody tissue; soft stem

• Spices (basil, aragon, celery)

Vine

Plants with climbing or training or trailing stem, maybe herbaceous vine or woody vin

Lianas

• Plants with woody climbing or training stems

• Long flexible; rooted in the grown; Tropical rainforest

• Eg. grapevine

Annual

• Plants that live for only one year or completes the vegetative and reproductive cycle in one growing season

• Seed to flower = one growing season

• Eg. rice

Biennial

• Plants that lives for two year or two growing season

• Vegetative growth is completed during first year and reproductive or flowering takes place in the second year

• First season - vegetative parts; Second season - flower and seeds

Perennial

Plants that live for several years

Mesophytes

Backyard plants

plants that can survive in moderate environments that are neither particularly dry nor particularly wet.

Hydrophytes

• Big amount of water

• Eg. Water lily, aquatic plant

Halophytes

• Watery but salty environment

• Eg. cerop stagal, mangrove

Xerophytes

• Little water, special structure for them to store water to survive droughts

• Eg. cactus

Terrestrial

• land or soil

Aquatic

water

Aerial or Epiphytes

air (eg. orchids

Autotrophic

• Plants that can manufactured their own food

• Usually green due to the presence of chlorophyll

Heterotrophic

• Plants that are non-chlorophyllus

• They get their nourishment from other plants by living as parasite, absorbing nutrient from tissue of their host.