PHA611 LEC: Plant Tissues

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 organOccupies a small area at the tip of a stem or a root Divide in order to form primary meristem

Primary meristem

First derivative of promeristemTip of the stem, root, or appendigesDivide repeatedly, develop and mature, to form the primary structureApical meristem

Secondary meristem

Secondary tissueEg. Lateral and intercalary meristems, vascular cambium

Apical

Growth region found in root tips and tips of new shoots and leavesDiffereniate into different cell type

Intercalary

Growth in length and elongationRapid growth and regrowth

Lateral

Grow in diameter, girth, thicknessVascular and Core Cambium

Protoderm

Dermatogenproduces the epidermis, a dermal tissue.

Procambium

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 cellDifferentiates 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 plantLeast specialized permanent tissue composed of living thin-walled cell

Parenchyma Cells

Most common type of cellHas thin primary walls; large vacuole (storage)Active matebolically and alive at maturityNumerous subtypes are specialized for particular tasksEg. geranium

Chlorenchyma Cells

Involved in photosynthesis: chloroplastThe thinnest of the wall allows light and carbon dioxide to pass through to the chloroplastsEg. a leaf of privetElongated cylindrical cells with their long axis at the right angle to th surface of the organCell contains numerous chloroplast for photosynthesis

Glandular Cells

Secrete nectar, fragrances, mucilage, resins, and oilsContain few chloroplasts but have high amounts of dictyosomes and endoplasmic reticulumEg. A resin canal in pine leaf

Aerenchyma cells

Specialized in gas exchange; large interceullar spaceIrregular cell surrounded with large air spaceFound in stems of aquatic plant

Collenchyma Tissue

A mass of collenchyma cells

Collenchyma 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 inflexibleForm hard, impenetrable surfaces Eg. shells of walnuts and coconuts or the “pits” or “stones” of cherries and peachesmore 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 perforationsOnly type of water conducting cells in ferns, conifers and most other nonflowering plantsDead 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

Has both a primary wall and a thick secondary wall that is almost always lignifiedMany dead at maturityProvides 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 livingOccurs in cluster or group among parenchymatour cells surrounding vascular tissueFiber - elongated cells with pointed end wallsSclera’s or Stone Cell - roundish or polygonal cell with walls varying in thickness

sclerenchyma

Some are involved in water transportDevelop 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 rootUsesProtection; regulate exchange of materialsEncrusted 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 entryGuard + stomatal pore = stoma/ stomataStomatal 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/hairsFunctions:Protection from insects and excessive sunlightAids in nutrient uptakeSpread of seedsEconomic ImportanceThreads -> cloth

Glandular

Glandular or Secretory Aratiles

Stinging

Glandular or Secretory Lipa

The ___ trichomes of the leaves and stems have bulbous tips that break off when brushed against, revealing needlelike tubes that pierce the skin

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 rootsCell wall is impregnated with suberinProduced 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 plantstracheids &  vessels - transport water and minerals from roots to all part of the plantPrincipal water conducting tissue composed of lignified dead cells located in the stellar (Vascular) region of stem, root, or leavesVarious patterned secondary walls called tracheids, vessel, fiber, and parenchyma

Xylem parenchyma

under xylemstores water

Xylem Fibers

under xylemhelp in support

Phloem

Moves sugar and other organic nutrients (food) and mineralsPrincipal food conducting tissue composed of different type of cells located in the stellar regionComposed 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 phloemstores food

Phloem fibers

under phloemhelp in support