Cells and Tissues of the Plant BodyChapter 23

Origin of Primary Tissues

• Primary growth- formation of primary tissues.– Primary plant body.

Growth and Development

• Development- the sum total of events that lead to the formation of the plant body.

• Growth- an irreversible increase in size.– Cell division– Cell enlargement

• Apical Meristems- regions of tissue at the tips of shoots and roots that forms new cells.– Meristematic tissue.

• Much of the plant undergoes unlimited or prolonged growth of the apical meristems= indeterminate.

Morphogenesis and Differentiation

• Morphogenesis- the development of form.

• Differentiation- a process by which a relatively unspecialized cell undergoes a progressive change to form a more specialized cell.

Internal Organization of the Plant Body

• Tissue- a group of similar cells organized into a structural and functional unit.

• Tissue System- a tissue or group of tissues organized into a structural and functional unit; larger units of the plant body.

• There are 3 Tissue Systems– Ground– Vascular – Dermal

Ground Tissue• Parenchyma

– Polyhedral to round in shape.– Occur throughout the plant body.– Photosynthesis, storage, and secretion.

• Collenchyma– Elongate in shape.– Occur beneath the epidermis in young

stems.– Support young growing tissues.

• Sclerenchyma- fibers and sclereids.– Long or stellate in shape.– Occur throughout the plant body.– Support (strengthen) and storage.

Vascular Tissue #1• Xylem- principal water-

conducting tissue in vascular plants; dead at maturity; lignified.

• Tracheary Elements– Tracheid- elongate and tapering;

pits, but no perforations; seedless vascular plants, gymnosperms, and some angiosperms.

– Vessel element- elongate; pits and perforations; angiosperms.

Vascular Tissue #2• Phloem- principal food-conducting

tissue in vascular plants; living at maturity; not lignified.

• Gymnosperm Sieve Elements– Sieve cell- elongate & tapering; with

sieve areas. – Albuminous cell- elongate & tapering;

delivers substances to sieve cells.

• Angiosperm Sieve Elements– Sieve-tube element- elongate &

tapering; with a sieve plate.– Companion cell- variable; delivers

substances to sieve-tube elements.

Dermal Tissue• Epidermis- outermost cell layer of the

primary plant body.– Variable in shape; guard cells and

trichomes.– Outermost layer of plant body.– Protective (cuticle and water loss) and

aeration (stomata).

• Periderm- secondary protective tissues. – Rectangular in shape; cork cells.– Beneath the epidermis.– Protective and aeration (lenticels);

replaces epidermis.