HORT 604

ANATOMY AND MORPHOLOGY OF PLANT ORGANS

· Anatomy of roots, stems, leaves, flowers and fruit

REFERENCES USED IN ANATOMY AND MORPHOLOGY SECTION

Anzai, T. 1975. Two phases in adventitious root formation in Phaseolus mungo hypocotyl cuttings. J. Exp. Bot. 26:580-588.

Argles, G.K. 1959. Root formation and root development in stem cuttings: A re-examination of certain fundamental aspects. Ann. Appl. Bot. 47:626-628.

Cameron, R.J. and G.V. Thomson. 1969. The vegetative propagation of Pinus radiata: Root initials in cuttings. Bot. Gaz. 130:242-251.

Clowes, F.A. 1961. Apical Meristems. Bot. Monogr. Vol. 2, Oxford, Blackwell.

Davies, F.T., J.E. Lazarte and J.N. Joiner. 1982. Initiation and development of roots in juvenile and mature Ficus leaf bud cuttings. Amer. J. Bot. 69:804-811.

Dermen, H. 1960. Nature of Plant Sports. Amer. Hort. Mag. 39(3):123-173

Dore, J. 1965. Physiology of regeneration in cormophytes. Encycl. Plant Physiol 15:1-91.

Esau, K. 1960. Anatomy of Seed Plants, John Wiley & Sons, Inc., NY

Esau, K. 1965. Plant Anatomy, John Wiley & Sons, Inc., NY

Ginzburg, C. 1967. Organization of the adventitious root apex in Tamarix aphylla. Amer. J. Bot. 54:4-8.

Girouard, R. M. 1967. Initiation and development of adventitious roots in stem cuttings of Hedera helix. Can. J. Bot. 45:1877-1884.

Hartman, H.T., D.E. Kester and F.T. Davies, Jr. 1990. Plant Propagation - Principles and Practices. Prentice Hall, Inc., Englewood Cliffs, NJ.

Leopold, A.C. and P.E. Kriedemann. 1964. Plant Growth and Development. McGraw-Hill, Inc., NY.

Naylor, E.E. and B. Johnson. 1937. A histological study of vegetative reproduction in Saintpaulia ionantha. Amer. J. Bot. 24:673-678.

Romberger, J.A. 1963. Meristems, Growth and Development in Woody Plants, USDA Technical Bulletin No. 1293.

Sachs, 1965, Annual Rev. Plant Physiol. 16:73-96.

Siegler, E.A. and J.J. Bowman. 1939. Anatomical studies of root and shoot primordia in 1-year apple adventitious roots. J. Agr. Res. 58:795-803.

Smith, D.R. and T.A. Thorpe. 1975. Root initiation in cuttings of Pinus radiata seedlings. I. Developmental sequence. J. Exp. Bot 26:184-192.

Stewart, R.N. and H. Dermen. 1979. Ontogeny in monocotyledons as revealed by studies of the developmental anatomy of periclinal chloroplast chimeras. Amer. J. Bot. 66(1):47-58.

Strangler, B.B. 1955. Origin and development of roots in stem cuttings of chrysanthemum, carnation and rose. N.Y. Ag. Exp. Sta., Mem 342, pp.3-24.

Tilney-Bassett, R.A.E. 1986. Plant Chimeras. Edward Arnold Ltd., Baltimore, MD.

Walker, R.I. 1940. Regeneration in the scale leaf of Lilium candidum and L. longiflorum Amer. J. Bot. 27:114-117.

Wardlow, C.W. 1957. On the organization and reactivity of the shoot apex in vascular plants. Amer. J. Bot. 44:176-185.

Wareing, P.F. and I.D.J. Philips. 1981. Growth and Differentiation in Plants, Pergamon Press, NY

Wilkenson, R.E. 1966. Adventitious shoots on salt cedar roots. Bot. Gaz. 127:103-104.

Yarborough, J.A. 1936. Regeneration in the foliage leaf of Sedum. Amer. J. Bot. 23:303-307.

ORGANS AND TISSUE SYSTEMS

Plants are composed of 3 vegetative and 1 reproductive organ.

Three tissue systems comprise each organ and are contiguous between each of the three organs.

PLANT ORGANS, TISSUE SYSTEMS, TISSUES AND CELL TYPES

3 TISSUE SYSTEMS OCCUR IN PLANTS

1) Dermal Tissue System

Function: Protection from the environment and water loss.

Tissues:

a) epidermis - single layer of cells on primary (herbaceous ) plant parts.

b) periderm or bark - a corky tissue that replaces epidermis on secondary (woody) plant parts.

2) Vascular Tissue System

Function: Conduction of water, nutrients, sugars and hormones throughout the plant.

Tissues:

a) xylem - conducts water and nutrients up roots, stems and leaves.

b) phloem - conducts water, sugar, hormones, etc. primarily down roots, stems and leaves, but also can move up at times.

3) Ground or Fundamental Tissue System

Function: Storage, support, filler tissue and site of photosynthesis.

Tissues:

a) cortex - outer region of stems and roots.

b) pith - center of stems.

c) mesophyll - middle of leaves and flower petals

CELL TYPES

1) parenchyma

-thin, non-lignified primary cell walls

-filler, storage, protection, photosynthesis

-examples: flesh of potato, lettuce

isodiametric

2) collenchyma

-unevenly thickened, non-lignified primary cell walls

-support in growing tissues

-example: strings in celery

longer than wide

3) sclerenchyma

2 Types

a) fiber

b) sclereid or
stone cell

-evenly thickened, lignified (tough) secondary cell walls

-support in mature tissue

-examples:
fiber -bamboo cane
sclereid - seed coat
stone cell -pear fruit

fiber

sclereid stone cell

MERISTEMS AND GROWTH

Primary Growth - growth in length that gives rise to primary (herbaceous) tissues called the primary plant body.

2 -Types

apical meristem or apex - the growing points located at the tips of stems and roots

intercalary meristem - the growth region at the base of grass leaves that causes
leaves to elongate.

Secondary Growth - growth in width or diameter that gives rise to secondary (woody
or corky) tissues called the secondary plant body.

lateral meristem - meristematic regions along the sides of stems and roots.

2 Types

vascular cambium or cambium - gives rise to secondary xylem (wood) on the
inside and phloem on the outside.

cork cambium or phellogen - gives rise to the periderm (bark).

MORPHOLOGY OF APICES

Shoot and Root Apex

(Fig. 3.2 from Esau 1960)

Flower Apex

(Fig. 2.20 from Wareing and Philips 1981)

ORGANIZATION OF APICAL MERISTEMS

Geometrical Organization or Tunica-Corpus Concept - Shoot (Esau 1965, Romberger 1963) 1) tunica (mantle) – outer covering of apex – only anticlinal divisions 2) corpus (core) - inner region of apex - anticlinal and periclinal divisions
Morphological Organization - Shoot Wardlaw (AJB 44:176 1957) 1) distal - outer covering (like tunica) 2) sub-distal - region of physiological inception of growth centers 3) organogenic - region of 1st visual appearance of growth centers 4) subapical - region of growth of organs 5) region of maturation Sachs (ARPP 16:73 1965) 1, 2 & 3) - apical region, where differentiation/organogenisis occurs 4 & 5) - sub-apical region - where elongation occurs
Cytological and Histological Organization - Shoot Buvat (see Esau 1965, Romberger 1963) 1) distal zone - waiting or promeristem 2) peripheral zone - initiating ring or eumeristem 3) inner zone - medullary or rib meristem
Quiescent Center Concept - Root Clowes (Bot.Mono., vol. 2, 1961) 1) initials for root cap 2) initials for epidermis 3) initials for cortex 4) quiescent center - no cell division 5) initials for vascular cylinder
	Monocots, Dicots and Gymnosperms
		DISTINGUISHING CHARACTERISTIC
	DIVISION	Spermatophytes (Spermatophyta-seed bearing plants)
	SUBDIVISION	Angiosperms (Angiospermae) (flowering plants with seeds enclosed)		Gymnosperms (Gymnospermae) (naked seeds)
	CLASS	Monocots (Monocotyledoneae) (1 cotyledon)	Dicots (Dicotyledoneae) (2 cotyledons)
	Seeds	1 cotyledon; endosperm often present	2 cotyledons; endosperm often lacking	1 to many cotyledons; no endosperm; female gametophyte tissue present
	Flowers	Flower parts in multiples of 3	Flower parts in multiples of 4 or 5	No true flowers
	Leaves	Linear; leaf base or petiole (if present) sheathing; parallel venation	Broad; petiole present; net venation	Needle-like or scale-like
	Vascular System of Stem	Scattered vascular bundles; no cambium or secondary growth	Ring of vascular bundles in primary growth; cambium present in secondary growth	Ring of vascular bundles in primary growth; cambium present in secondary growth
	Growth Habit	Herbaceous to wood-like (ex. palm), but no true wood (secondary xylem)	Herbaceous or woody	Herbaceous or woody
	Morphology

STEM ANATOMY

(Fig. 16.1 from Esau 1960)

STEM ANATOMY

(Plate 28 from Esau 1965)
STEM ANATOMY

(Plate 58 from Esau 1965, Fig. 17.8 from Esau 1960)
ROOT ANATOMY

Dicot, Gymnosperm or Monocot - Primary Growth

(Plate 84 & 86 from Esau 1965)
ROOT ANATOMY

DICOT/GYMNOSPERM - SECONDARY GROWTH

A woody dicot or gymnosperm root in secondary growth looks very similar to a stem in secondary growth.

(Fig.15.4 from Esau 1960)

LEAF ANATOMY

(Plate 73 from Esau 1965)

MONOCOT

(Similar to dicot, except no palisade, mesophyll is all spongy parenchyma)

(Fig. 19.6 from Esau 1960)

GYMNOSPERM LEAF

(Plate 78 from Esau 1965)

LEAF PARTS - FUNCTION

STOMATE

An open aperture surrounded by 2 guard cells.

a) open when guard cells are turgid

b) closed when guard cells are flaccid

Diurnal Cycle
a) open in day
b) closed at night
c) except CAM plants, just opposite (open night, closed day)

Designed for gas exchange

a) CO₂ in and 0₂ out for photosynthesis

b) CO₂ out and 0₂ in for respiration

c) H₂0 out during transpiration
Usually more frequent on epidermis of lower leaf surface

MESOPHYLL

Palisade parenchyma

- contains 70-80% of the chloroplasts in the leaf

- specialized for photosynthesis because it contains a large number of chloroplasts and it occurs towards the adaxial side of leaf

- thinner on a sun grown leaf

Spongy mesophyll

- contains large air spaces

- specialized for gas exchange -because of the large air space and more stomata occur on the epidermis of abaxial leaf surface

- thicker on a shade grown leaf

ABSCISSION ZONE

Leaves of deciduous plants form an abscission zone in a discrete region at the base of the petiole. The surface is sealed and suberized over before the leaf falls off.

(Fig. 18.10 from Esau 1960)

SUMMARY OF ANATOMY

		MONOCOT	DICOT	GYMNOSPERM
STEM	PRIMARY (herbaceous) GROWTH
	SECONDARY (woody) GROWTH	none
ROOT	PRIMARY (herbaceous) GROWTH
	SECONDARY (woody) GROWTH	none
LEAF	PRIMARY (herbaceous) GROWTH