ANATOMY AND MORPHOLOGY OF PLANT ORGANS

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

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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.

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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.

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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

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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).

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MORPHOLOGY OF APICES

Shoot and Root Apex (Fig. 3.2 from Esau 1960)

Flower Apex (Fig. 2.20 from Wareing and Philips 1981)

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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

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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

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STEM ANATOMY

(Fig. 16.1 from Esau 1960)

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STEM ANATOMY

(Plate 28 from Esau 1965)

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STEM ANATOMY

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

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ROOT ANATOMY

Dicot, Gymnosperm or Monocot - Primary Growth

(Plate 84 & 86 from Esau 1965)

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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)

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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)

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GYMNOSPERM LEAF

(Plate 78 from Esau 1965)

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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)

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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

SECONDARY (woody)

GROWTH

none

none

none

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FLOWER FLOWER - A determinate shoot with leaves highly modified into reproductive parts

FLOWER STRUCTURE

FLOWER TYPES BASED ON PARTS PRESENT complete - contains all floral parts, i.e. sepals, petals, stamens and pistils incomplete - lacks one or more of the floral parts perfect - contains both pistils and stamens (may or may not have sepals or petals) imperfect - lacks either pistils or stamens (may or may not have sepals or petals)

pistillate - contains only pistils (may or may not have sepals or petals) staminate - contains only stamens (may or may not have sepals or petals)

sterile - both stamens and pistils are absent, or are non-functional PLANT TYPES BASED ON FLOWER TYPES PRESENT monoecious - both staminate and pistillate flowers occur on the same plant.

Example corn, cucumber dioecious- staminate and pistillate flowers occur on separate plants.

Example holly, persimmon

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FRUIT - a ripened or matured ovary and its contents plus any accessory tissues. pericarp - the fruit wall, which developed from the ovary wall Composed of 3 layers: 1) exocarp - outer layer of the pericarp 2) mesocarp - middle layer of the pericarp 3) endocarp - inner layer of the pericarp.

FRUIT STRUCTURE

Example of a dry fruit Example of a fleshy fruit

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SEED seed - a ripened or matured ovule consisting of an embryo with associated stored food and

covered by a testa.

STRUCTURE

TESTA STRUCTURE AND FUNCTION

(Fig. 22.3 from Esau 1960, Fig. 10-10 from Leopold and Kriedemann 1964)