Scope and significance of plant anatomyy

Scope and significance of plant anatomy

1. Scope and Significance in Plant Anatomy and Role of Anatomy in Phylogeny Aleena Stanley 1st Msc Botany St.Teresa’s College Ernakulam ‹#›

2. Plant Anatomy.. The study of Internal Gross Structure of by the technique of sectioning and cutting is called as Plant Anatomy . Originally it included plant morphology, the description of the physical form and external structure of plants, but since mid-20th century plant anatomy has considered a separate field referring only to internal plant structure . It is now frequently Investigated at the cellular level, and often involves sectioning of tissues and microscopy. ‹#›

3. Scope And Significance of Plant Anatomy. ROLE IN TAXONOMY Anatomy provides evidence concerning the inter relationships of large groups such as families or in helping establishing the real affinities of genera of uncertain taxonomic status.Anatomy form the backbone of taxonomy. Study of anatomical features of flowering details has a long history of its own. The discovery of various modern techniques and vast improvement in tools, especially the invention of microscope have certainly add a lot to the finer detail of plant tissue. Anatomy sometimes proves very helpful for individual identification. The anatomical methods are great value in identifying the herbarium specimens which do not bear flowers or fruits. The Anatomical methods are also used in identification of commercial sample of medicinal plants, timber, fibers etc.. ‹#›

4. Significance of Anatomical Features in Relation To Taxonomy According to Metcalfe (1968) identified several herbarium specimens using vegetative Anatomy. According to Radford (1986) some of basic evidentiary characters of well established taxonomic values were:- type, size,shape,type of vascular bundles, rays, ground tissue parenchyma, epidermal and mesophyll tissue, stomatal nodes etc.. ‹#›

5. EPIDERMIS OR EPIDERMAL CELLS Shape, size, outline, wall thickness and inclusions of epidermal cells are some of the characters of taxonomic importance in different families and genera. Characters such as partly or wholly crystalliferous epidermis on the cells with specific chemical contents are of importance because of their restricted occurrence. Epidermal cells with horizontal and vertical partition are of specific or almost generic value. Presence and distribution of silica bodies in cyperaceae. Sclerification on the wall of epidermal cells in some genera of compositae and presence of narrow epidermal cells in stylidiaceae are some characters of useful economic importance. ‹#›

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7. 2. STOMATA Stomata are minute pores which occur in the epidermis of the plant cell. Each stoma is surrounded by two kidney shaped epidermal cells the guard cells.It occurs on any part except at the root. There are four types of stomata in Dicotyledons . RANUCULACEOUS TYPE ( Anomocytic) Stoma is surrounded by a limited number of cells that are indistinguishable in size, shape or form from those of the remainder of the epidermis. ‹#›

8. 2. CRUCIFEROUS TYPE (Anisocytic type) Stoma surrounded by three cells of which one is distinctly smaller that other two . 3. CARYOPHYLLACEOUS TYPE (Diacytic type) Stoma enclosed by a pair of subsidiary cells whose common wall is right angle to the guard cells. 4. RUBIACEOUS TYPE (Paracytic type) Stoma surrounded by either side by one or more subsidiary cells parallel to the long axis of the pore and guard cells. ‹#›

9. STOMATA - MONOCOTYLEDONS The graminaceous type of stoma is believed to be confined to the monocotyledons where it is specially characteristics of Gramineae and Cyperaceae. The “Gramineous” stoma posses guard cells of which the middle portions are much narrower than the ends so that the cells appear, dumbbell shaped in surface view. The subsidiary cells are found lying parallel to the long axis of the pore. ‹#›

10. 3 . STEM ANATOMY A natomy of vegetative structures has been importance in separating higher categories, such as gymnosperms from angiosperms and monocots from dicots. CORK The position in which the cork originates in a young stem is diagnostic value within limits.In an individual species, the first cork to be formed is often more superficial than that which arises later.In some families the origin of cork is seems to be constant. ENDODERMIS In most Dicot stems the endodermis is inconspicuous. In some the endodermis consists of a distinct layer of cells which are differentiated from the neighbouring cells in containing starch .In another group endodermis consists of cells with well marked casparian thickening In few species it is wholly suberized. ‹#›

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12. 3. Sclerenchyma of Pericycle The presence and absence of nature of sclerenchyma has a diagnostic value. The most common type seen in T.S of the stem are 1)Stone cells are present, no fibers present 2)An interrupted ring of fibres 3) continuous ring of fibres 4) Interrupted ring of mixed fibres and stone cells 5) Continuous ring of mixed fibre and stone cells - COMPOSITAE Percycle sclerenchyma is not found in the members of PITTOSPORACEAE . Ring of sclerenchyma is found in all the members of GERANIACEAE. ‹#›

13. 4. Bicollateral Bundle The occurrence of bicollateral bundle in the axis of Cucurbitaceae is of much taxonomic value. In certain families e.g Solanaceae, Asclepiadaceae the presence of internal phloem make a good taxonomic value. ‹#›

14. 4. Nodal Anatomy According to Dickison (1975) correlations of nodal anatomy with some other features might help significantly in tracing phylogeny in angiosperms. Nodal Anatomy is an aid to taxonomy. Unilacunar Nodes(Single gap and single trace to a leaf) are found in Lurales, Caryophyllales, Ericales, Ebenales, Primulales. Multilacunar Nodes (several gaps and trace associated with single leaf) found in Magnoliales , Piperales, Umbellales, Asterales etc.. ‹#›

15. 5. Leaf Anatomy It provides various characters of taxonomic importance .Leaf Anatomical studies associated with C 4 -Photosynthetic pathway have resulted in a revised classification of several genera of grass family. Leaf Anatomy characters include nature and thickness of epidermis, mesophyll types, pattern of sclerenchyma, venation patterns, crystals etc.. Leaf Anatomy has been widely used in several taxonomic groups such as Euphorbiaceae, Gramineae, Cyperaceae and conifers of Gymnosperms ‹#›

16. 6.Floral Anatomy The research in Floral Anatomy in the fifteen years (1963-77) has been active at Meerut and Bombay. V.Singh (1966) in a series of papers has described the vascular anatomy of members of the flower of Alismaceae,Butomaceae, Hydrocharitaceae. On the basis of Kala and Pai(1979) have supported the removal of genus Trichopus from family Dioscoreaceae and creation of a new family Trichopodiaceae. Saxena N.P(1964) has worked out the floral anatomy of 37 species like Moringaceae , Papaveraceae etc.The placentation of these families is parietal, but the placental strands occur on the secondary marginal bundles possessing normal orientation. ‹#›

17. On the basis of floral anatomical studies, Roy(1949) proposed the removal Trapa from Onagraceae and placed in another separate family Tapaceaea. N.P Saxena (1977) described the floral anatomy of 7 species of sub family Hydrangeaceae and Saxifragaceae. The Contribution of Floral Anatomy in Resolving Taxonomic Positions of some Families Floral Anatomy of Annonaceae, Calycanthaceae confirms that all these originated from Ranunculaceae. Uniformity in vasculature of Solanaceae and Scrophulariaceae suggest that both should be included in one single order, Scrophulariales. Separation of Paeonia from Ranunculaceae and placed in a separate family was supported by anatomical studies. ‹#›

18. 2. Significance of Wood Anatomy Secondary xylem is a complex tissue, known as Wood. The study of wood by Preparing for microscopic observations is defined as Xylotomy. Secondary Xylem is derived from vascular cambium. It develops in Stems and roots of gymnosperms and angiosperms-dicotyledonous plants. Woods are divided into two-POROUS AND NON-POROUS ( based on the presence and absence of vessels ) Non-porous wood predominate in gymnosperms (tracheids with a small amount of Parenchyma) Porous wood or Angiosperm wood is referred as hardwood. ‹#›

19. Vessels Features like distribution, pattern, diameter, thickening and presence of tyloses have been found useful in many Anatomical studies. Vessels found Solitary are considered as primitive than those aggregated in groups, such as pore multiples, pore clusters etc.. Similarly , Non- porous wood is more primitive without vessels(gymnosperms),than porous wood, and diffuse porous wood is more primitive than ring porous. ‹#›

20. Key to Identification of some common woods Wood non-porous or without vessels Resin canal absent - Fir ( Abies pindrow) white wood, less odour Resin canal Present 1. Resin canals in long tangential band- Deodar (yellow wood, light with strong pungent smell) 2.Resin canals scattered - Spruce and Chir (Pinus varieties ) Wood ring porous to semi ring porous Rays distinct into very broad and fine types, pores arranged in long radial forms - Indian Oak Rays one type, not prominent and pores not arranged in long radial forms - Teak Wood Diffuse porous Gum ducts vertical - Sal ( Shorea robusta) Vertical gum ducts absent- Sisso and Ebony ‹#›

21. RAY PARENCHYMA Ray Parenchyma cells are of various shapes and the two most common forms are where the longest axis of the cell is either vertical or radial.The former one, where the longest axis is oriented vertically is called erect ray cells.Where the latter one longest axis is oriented radially. In RLS the parenchyma cells appear as fine as horizontal lines. And it occurs variously 1) Uniseriate:the ray cells are entirely one cell in width e.g Pinus 2)Biseriate: any portion is more than two cells in width e.g Quercus The uniseriate and multiseriate rays both may be either homocellular or heterocellular.In dicots homocellular rays consists of single type of cells only .In heterocellular composed of both type of cells. ‹#›

22. Axial Parenchyma The distribution of axial parenchyma is very characteristic in dicotyledons wood. Parenchyma may independent of vessels or they are distinctly associated with them.These two forms are known as APOTRACHEAL AND PARATRACHEAL forms. APOTRACHEAL TYPE:- Parenchyma cells are not in contact with the vessels. Diffuse Apotracheal type :- Parenchyma cells occur singly among the fibres and tracheids . Terminal Apotracheal type :-The bands of parenchyma are confined to the end of the growth rings. Banded Apotracheal type :- Parenchyma cells occurs in bands ‹#›

23. PARATRACHEAL TYPE :- Parenchyma cells which are in contact with the vessels. Vasicentric Parenchyma : Forms complete sheaths or borders around the vessels.It is also known as Aliform Confluent Parenchyma. Aliform Parenchyma : Tangential “wing like” arrangements appearing in cross section as diamond shape areas. Confluent Parenchyma : Tangential Projections of parenchyma masses join to form irregular bands. ‹#›

24. 3 . Role of Anatomy in Forensic science and Pharmacognosy Anatomical Characters are potentially useful to identify small fragments or commercially important herbal products as well as toxic plants that may be relevance in forensic investigations. An Increased number of indigenous medicinal plants are used in both formal and informal economy. Unfortunately very few among this has been studied anatomically. Plants often causes fatalities due to inappropriate use of herbal medicines or the use of misidentified plants. Anatomical characters of these plants are useful as the evidence for forensic work which help to identify the plant when medical diagnosis/ chemical forensic studies turn out to be inconclusive. Anatomical characters of potential diagnosis value will be presented for a selection of herbal medicines and highly toxic plants. Herbal Medicines - Nerium oleander, Catha edulis, Agathosma betulina , Aloe ferox ‹#›

25. 4. Role of Anatomy in Paleobotany Anatomical Features can aid in the identification of archaeological materials, they can be employed in identification of fossils and place them among extant plant families and genera. Anatomical features however allows us to determine if the plant part is a root or stem or leaf simply by the presence and absence of exarch or endarch protoxylem. Some fossils may be sectioned , others may be ground down to thin sections suitable for microscopic examinations and still others are fossilized in the form of charcoal. ‹#›

26. 5. Anatomy of Floral Parts A typical flower is composed of sepals, petals, stamens and carpels. SEPALS The anatomical features of sepal resemble leaf.Each sepal consists of epidermis, ground parenchyma and branched vascular system. The green sepals has chlorophyllous cells but usually there is no differentiation into palisade and spongy parenchyma. Lactifiers and tannin cells are present in it. The hairs are present on stomata and epidermis . Vascular traces found is similar in origin and number. ‹#›

27. PETALS The anatomical features shows resemblance with those of leaves. Each petal consists of epidermis, ground parenchyma and more tiers of branched vascular system. Crystal containing cell, lactifiers, tannin cells are present. Sometimes, epidermal cells contain volatile oils which emit the characteristic fragrance to the flower. Stomata and epidermal trichomes may also be present. Cells of ground tissue contain abundant chromoplast rich in water soluble anthocyanin. ‹#›

28. STAMENS Stamen consists of Filament, connective and an anther. Commonly anther is dithecous or two lobed. Anatomical features of Filament is relatively simple. The epidermis is cutinised and bears trichomes and stomata. It has a single vascular bundle that runs throughout the filament and end blindly in connective. The vascular bundle is amphicibral which remains surrounded by parenchyma. ‹#›

29. ANTHER The Anatomy of Anther is little complex. Its outermost wall is single layered epidermis which is followed by single layered endothecium. Cells of endothecium are hygroscopic, fibrous bands arising from lower transverse wall and almost touching upper transverse wall. Endothecium helps in dehiscence of pollen grains. Next to endothecium and towards inner side are 4-3 layers cells of wall layers. The innermost layers is the Tapetum. It is the nutritive layer. Tapetal cells undergo various types of divisions. Anther has a procambial strand in centre which later forms the vascular bundle. Atypical two lobed anther has 4 microsporangia, (two in each lobe). In each microsporangium several pollen grain are formed. On maturation of pollen, the tapetum and wall layers usually disintegrate leaving pollen sac surrounded by endothecium and epidermis. At the time dehiscence of anthers, pollen are released through stomium. ‹#›

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31. GYNOECIUM It represent the female sex organs of the flower. It is constituted by one or more units known as carpels. Of these, ovary is the important structure within which ovules are present attached on placenta. In general , ovary and style composed of epidermis, parenchymatous ground tissue and vascular bundle. Epidermis is cuticularised and may possess stomata. Number of vascular bundle are usually 3-5 in each carpel. ‹#›

32. 6. NODAL ANATOMY In Angiosperms and especially dicots, the primary vascular cylinder is interrupted at each node by the exit of one or more bundles that enter the leaves. The stelar bundle, which are the continuation of the bundles in the leaf base, are called leaf trace. At each node, portions of the vascular system are deflected into the leaf, which is attached at this node. The parenchymatous regions in the vascular system of the stem located adaxially from the diverging leaf trace are called leaf gaps or lacunae. ‹#›

33. There are three common types of nodes in Dicots. UNILACUNAR NODE The node with a single gap and a single trace to a leaf is known as unilacunar. Eg. Ocimum, Eucalyptus. TRILACUNAR NODE The node with three gaps and three traces to a leaf (one median and two lateral) is known as trilacunar.Eg. Brassica, Annona. MULTILACUNAR NODE The node with several to many gaps and traces to a leaf is known as Multilacunar. Eg: Rumex,Aralium. ‹#›

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35. PHYLOGENETIC CONSIDERATIONS : 1 .Sinnotts View Sinnot recognised 3 fundamental types of Nodal Anatomy in dicots unilacunar, trilacunar and multilacunar. He put forward view concerning the phylogeny of angiosperms on the basis of nodal organisation. He believed trilacunar is primitive form. 2. Marsden and Baileys View Marsden and Bailey (1955) discovered a Trilacunar and multilacunar types originated by the addition of lateral traces arising from new gaps in vascular cylinder. 3 . Takhtajan’s View The most accepted concept is that the trilacunar condition is primitive in dicots and unilacunar and multilacunar have been derived from it. Several monocots plants with sheathing leaf bases and nodes with a large number of leaf traces separately inserted around the stem. ‹#›

36. 6. Role of Anatomy in Phylogeny Phylogeny is the study of relationships among different groups of organisms and their evolutionary development. Phylogeny attempts to trace the evolutionary history of all life on the planet. It is based on the phylogenetic hypothesis that all living organisms share a common ancestry. The relationships among organisms are depicted in what is known as a phylogenetic tree. Relationships are determined by shared characteristics, as indicated through the comparison of genetic and anatomical similarities. Anatomical features have played an increasingly important role in elucidation of phylogenetic relationships. ‹#›

37. Anatomical characteristics are investigated with the help of a light microscope whereas ultrastructure and micromorphology are brought out using an electron microscope. Anatomical characters of vegetative and floral parts of flowering plants have been successfully employed to solve taxonomic problems and for the elucidation of phylogenetic relationships.. It was Bureau, who for the first time used anatomical characters in plant classification for the delimitation of taxa of various levels, within the family Bignoniaceae. ‹#›

38. Anatomical evidence can be useful in systematics in several ways: ( i ) It can well be exploited taxonomically in the identification of fragmentary material, say a piece of wood. (ii) When morphological characters prove to be of no help in the preliminary identification of herbarium material, anatomical study may prove helpful. (iii) Anatomical data has proved to be very useful in discerning evolutionary trends and interrelationships of taxa at and above the species level and at higher taxonomic categories. They are most useful in determining relationship between different genera, families, orders and other taxonomic categories. (iv) The internal structures of the plants have added a lot in understanding the relationships between the taxa. The organization of the vascular system in stem and leaf, petiole and nodal anatomy, leaf vasculature and architecture and epidermal studies are considered important characters in phylogeny and taxonomy. ‹#›

39. Reference :- Daniel, L. Molecular Biology And Evolution, Volume 17, Issue 12, December 2000, Pg 18885-1895 Fahn, A. (1977). Plant Anatomy. Oxford:Pergamon Press Metcalfe, C. R. Comparative anatomy as a modern discipline . Adv. Bot. Res 1, 101-147, 1968 Murty, Y. S. and V. Puri, 1980, Fl oral anatomy in relation to taxonomy Pandey, B. (1996). Plant Anatomy and Embryology . New Delhi: S Chand & Comp. P.M. Tilney, B-E. Van Wyk Department of Botany and Plant Biotechnology, University of Johannesburg, PO Box 524, Auckland Park 2006, South Africa. Record, S. J Role of wood Anatomy in taxonomy. Trop Woods 37, 1-9 ‹#›

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