CELLTYPES

VEGETATIVE CELL TYPES IN SEED PLANTS

Examine the Differentiation Potential of all cell types.

CELL TYPE	SUBCATEGORIES	LOCATION	ORIGINATES FROM	FUNCTION	EXAMPLES
MERISTEMATIC = SELF PERPETUATING
1. Apical meristem A. Single cell B. Multiple cells	1. Shoot A. Terminal B. Lateral C. Adventitous 2. Root A. Terminal B. Lateral C. Adventitous	1. Tip (apex) of vegetative stems, developing inflorescences, and flowers 2. Beneath inner edge of root cap at tip (apex) of roots	A. Initial terminal population are lineal descendents of cells of embryo B. Subsequent lateral ones arise from existing shoot meristems or from pericycle of roots C. Adventitious meristem cells arise from vascular cambium, pericycle, and cortex parenchyma	Self perpetuating Formation of primary meristmatic tissue	Coleus shoot apex Allium root apex
2. Vascular cambial cell	1. Fusiform Initials 2. Ray Initials	Between secondary xylem and secondary phloem	A. Procambium of fascicular regions and from parenchyma of interfascicular regions in stems. B. Procambium between xylem and phloem and periclycle outside xylem in roots.	Self perpetuating in tangential direction Formation of secondary xylem in interior radial direction Formation of secondary phloem in exterior radial direction	Three year old twigs of Tilia Pinus
3. Cork cambial cell (Phellogen)		Between cork (phellem) and either phelloderm, cortex, or phloem tissue Beneath surfaces exposed by abscission of leaves and stems and wounds	In stems, from either the epidermis, cortex, or phloem parenchyma cells In roots, from the pericycle	Self perpetuating in tangential direction in some species; not in most Formation of cork (phellem) in exterior radial direction Formation of phelloderm in interior radial direction in some species	Three year old twigs of Pinus Tilia Potato tuber
CELL TYPE	SUBCATEGORIES	LOCATION	ORIGINATES FROM	FUNCTION	EXAMPLES
DERIVED EXCULSIVELY FROM PRIMARY MERISTEMS
4. Epidermal	1. Ground 2. Trichomes	Outermost cell layer of foliar and floral organs; primary stems and roots	Protoderm	Restriction of gaseous exchange Protection against disease vectors Storage of water and elaborated reserves Absorption of water in roots and certain foliar structures	Leaves of Zea Bryophyllum Pinus
5. Guard Cells	Classified on basis of Geometric or Ontogenetic relationships with Subsidiary Cells	Outermost cell layer of foliar and floral organs; primary stems	Guard Cell Mother Cells of the protoderm which may also form some or all of the associated Subsidiary Cells	Regulation of gaseous exchange	Leaves of Zea Bryophyllum Pinus
6. Collenchyma	Classified on basis of where the thicker regions of primary cell wall are located within the cells	Subepidermal layers or strands of stems, petioles, larger veins of some leaves, and cortex of some roots.	Ground meristem	Mechanical support of primary plant body Photosynthesis Carbohydrate storage	Stems of Solanum Helianthus Rheum petiole
CELL TYPE	SUBCATEGORIES	LOCATION	ORIGINATES FROM	FUNCTION	EXAMPLES
DERIVED FROM BOTH PRIMARY AND SECONDARY MERISTEMS
7. Parenchyma	Classified on basis of function or position in the plant body	Most all plant organs	Ground meristem, procambium, vascular cambium, and cork cambium	Dedifferentiation to form interfascicular cambium and adventitious shoots and roots Hydrostatic support of primary plant body Photosynthesis Storage of water and elaborated reserves Secretion and excretion of various substances Formation of callus in response to wounding	Three year old twigs of Tilia Pinus Potato tuber Leaves of Zea Bryophyllum Pinus
8. Sclereid	Classified on basis of cell geometry	Outer layer of seeds and some fruits; diffusely distributed in pith, cortex, phloem, outer bark, and leaf mesophyll	Protoderm, ground meristem, procambium, vascular cambium, and phellogen. Also from sclerosis of parenchyma cells.	Protection of embryos and seeds Mechanical support	Pyrus fruit Phaseolus seed Camellia petiole Leaves of Nymphaea Osmanthus Olea
9. Cork (Phellem)	Lenticels	Peripheral regions of stems, roots, certain fruits, some bud scales, and petioles; often produced in response to wounds	Cork cambium (Phellogen)	Restriction of gaseous exchange Protection against disease vectors and fire	Three year old twigs of Tilia Pinus Potato tuber
10. Fiber	1. Bast (Phloem) 2. Libriform (Xylem) 3. Fiber-tracheid	Cortex, vascular tissues of stems and roots, as strands or sheaths of leaf veins, epidermis of some leaves	Protoderm, ground meristem, procambium, and vascular cambium	Mechanical support	Leaves of Zea Helianthus Twigs of Tilia Fraxinus
11. Tracheid	1. Vascular 2. Vasicentric	Xylem, transfusion tissue of gymnosperm leaves	Procambium, vascular cambium	Transport of water, elements, and some phytohormones Mechanical support	Twigs of Quercus Pinus
12. Vessel member or element		Xylem	Procambium, vascular cambium	Transport of water, elements, and some phytohormones Mechanical support	Twigs of Quercus Magnolia
13. Transfer cell	Classified on basis of location of wall ingrowths in vascular tissue	Primary xylem and phloem, pericycle of root nodules, stigmata of some flowers, secretory structures	Procambium, protoderm	Transport of water, elements, and organic molecules over short distances where normal transport connections are not found	Legume root nodule Anthocerus sporophyte/gametophyte
14. Sieve cell		Gymnosperm Phloem	Procambium, vascular cambium	Transport of photosynthate	Twigs of Pinus Thuja
15. Sieve-tube member or element		Angiosperm Phloem	Procambium, vascular cambium	Transport of photosynthate	Cucurbita stem Liriodendron twig
16. Laticifer	Classified on basis of presence or absence of A. Anastomoses B. Articulations	Pith, xylem rays, phloem, cortex, leaf mesophyll	Ground meristem, procambium, and vascular cambium	Secretion and storage of latex	Leaves of Allium Lactuca Asclepias Ficus Stems of Ficus Cannabis