Top 7 Applications of Plant Anatomy | Botany

The following points highlight the top seven applications of plant anatomy. The applications are: 1. Enables to Identify Fragmentary Plant Materials 2. Enables to Detect Adulterants in Crude Drugs 3. Enables to Identify Wood 4. Enables to Identify Archaeological Plant Remains 5. Applied Aspects of Meristem Culture 6. Provides Evidences in Forensic Investigation 7. Provides Characters of Taxonomic Significance.

Application # 1. Enables to Identify Fragmentary Plant Materials:

Since the time of Linnaeus flowers and fruits provided the characters of identification. Sometimes situation arises where these characters are not available.

Example:

Fragments of herbarium specimens, leaf, dried and powdered medicinal plants etc. The prerequisite of any botanical research is the proper identification of the specimen.

Anyone dealing with plants for food, furniture, building materials, medicine etc. the plant breeders, geneticists and cytologists must have proper identifying characters of their source materials. These characters will identify parallel specimens, if required. They will be in a position to verify whether the parallel specimen is from the same species of the source material.

The characters that differentiate a species from other species are considered as of taxonomic significance. Apart from vegetative and reproductive organs plant anatomy provides characters that are of taxonomic significance.

Trichome anatomy, wood and leaf anatomy, leaf epidermis and cuticle etc. provide valuable characters in differentiation between species. As for example the different species of Rhododendron and Ficus can be differentiated by means of trichome characters.

Application # 2. Enables to Detect Adulterants in Crude Drugs:

The medicinal plants provide the crude drug. Drug can be obtained from all parts of a plant (ex. Swertia chirata), leaves (ex. Adhatoda vasica, Andrographis paniculata etc.), roots (Cephaelis ipecacuanha), rhizome (ex. Zingiber officinale, Rauwolfia serpentina etc.), or bark (Alstonia scholaris). The crude drugs are imported in dry form and in some cases in dry powdered form.

In this condition it becomes difficult to identify the materials by macroscopic appearance only. For this reason the microscopical along with morphological characters of drug materials are studied. They are described and published in pharmacopoeia. The pharmacopoeias may be of official publications.

Example:

European Pharmacopoeia, British Pharmacopoeia, British Pharmaceutical Codex, United States Dispensatory, Indian Pharmacopoeia, the Indian Pharmaceutical Codex etc.

A very brief and to the point description of drug material are given in the pharmacopoeias. The characters that will identify the drug specifically are mentioned only. Proper authentication of crude drug material is a prerequisite for importers. They must be sure about the quality, purity and if adulterated, the nature of the adulterants of materials.

Samples to be imported are studied morphologically and anatomically. Their authenticity is established by comparing with the descriptions published in pharmacopoeias. A crude drug may also be identified from its chemistry.

But the identification with the study of microscopical examination is much easier and quicker than that of chemical analysis. Mention may be made of a few drug plants with their uses and adulterants that can be detected microscopically.

Swertia chirata (Family: Gentianaceae), commonly known as chirata is an indigenous drug of India. It is used as stomachic bitter tonic, anthelminthic and in skin diseases. The root is used as a substitute of Centiana lutea, which is used as gastrointestinal tonic, because the root of chirata does not constipate the bowels. The most common adulterant is Swertia angustifolia commonly known as pahari chirata. The distinguishing characters between the two species are given below according to Prasad et al., (1960).

Apart from Swertia angustifolia, Enicostema littorale, roots of Rubia cordifolia and Andrographis paniculata are found to be mixed with Swertia chirata. Andrographis paniculata differs from Swertia chirata in having characteristic cystolith on leaves, diacytic type of stoma and phloem on the dorsal side of xylem only.

Zingiber officinale (Family: Zingiberaceae), commonly known as ginger is rhizome drug. The rhizome is used as carminative medicine. It is used in digestive disorders. It expels gas from stomach and intestine. It dilates the blood vessels causing a warm feeling. It increases the rate of perspiration and thus lowers the body temperature. It is mainly used as condiment.

The rhizome of Zingiber officinale contains abundant starch grains. They remain singly or in groups. Each grain is simple and the shape may be round, oval, oblong and flattened. The hilum is small and terminal. The striations are very faint. The common adulterant is Zingiber mioga. It has compound starch grains and thus can be differentiated.

Starch grains from wheat flower, Curcuma etc. are the other adulterants. The study of starch grains detects them. Adulteration may also occur with ‘spent ginger’ that is exhausted in the preparation of essence. This can be detected by chemical tests only.

Cephaelis ipecacuanha (Family: Rubiaceae) is the root drug and is used in cough mixture. The drug contains abundant starch grains that are mostly compound with 2-4 or five or up to 8 parts. The individual granule is fairly small, not more than 15 µm in diameter. The shape of the granules may be round or oval.

The vessels are moderately thick walled with narrow lumen and numerous bordered pits on walls. Ionidium (Family: Violaceae) and other roots are the adulterant of Cephaelis ipecacuanha. These adulterants have wide vessels and lack the characteristic starch granules. The other adulterant is Cephaelis acuminata that have starch granules up to 22 µm in diameter.

Adhatoda vasica (Family: Acanthaceae) is the leaf drug and is used as an expectorant medicine. It gives relief in bronchitis. The powdered leaf contains fragments of epidermis with diacytic stoma, non-glandular and glandular tichomes. The non-glandular trichomes are elongated, multicellular usually 3-4 celled, conical in shapes with wide bases and the apical cell is pointed.

The glandular trichome is sessile, more or less circular in shape from top view; quadricellular and the partition walls have cross like appearance. Cystoliths are present within the palisade tissues that are double layered. The cystoliths are cylindrical and have warty projections on the surface.

Adhatoda vasica plants grow profusely as a weed and the leaves are collected from natural sources. So they are rarely adulterated. In Kerala Adhatoda beddomei is used as substitute. Adhatoda vasica leaves are used as adulterant of tea (Camellia sinensis).

Digitalis purpurea (Family: Scrophulariaceae) is a leaf drug. It is used as stimulant of heart and as diuretics. The drug makes the heart powerful and causes the complete contraction of heart, and thus the circulatory system is toned up. Digitalis lanata is also used medicinally. D. purpurea can be distinguished from D. lanata. In the former the anticlinal walls of abaxial epidermal cells are more beaded than the latter.

Application # 3. Enables to Identify Wood:

The anatomy of a wood sample reveals many characters that help in the identification of plant from which the wood comes. In each country there are several excellent books on wood anatomy. These books provide not only anatomical description of wood of the plants occurring at the particular part of the world, but also give the salient anatomical features that help in the identification of plants.

In India there are several volumes of book written on wood anatomy. Mention may be made of Indian woods, published by the Manager of Publications, Government of India, Delhi. In these volumes the anatomical description of woods, mostly from Indian origin, are given and the identifying characters are also mentioned.

In India the number of timbers available in large quantities is not more than sixty, among which the following three are most important-Tectona grandis (teak), Shorea robusta (sal) and Cedrus deodara (deodar).

A brief description of the wood of teak, sal and deodar is given below:

i. Tectona grandis Linn. f. (Family: Verbenaceae):

The sapwood and heartwood are sharply demarcated. The colour of sapwood may be white or pale yellow, whereas the heartwood may be of light golden brown or dark brown in colour. The growth rings are conspicuous with ring-porous wood. The vessels of early wood are large in diameter, oval in outline and mostly solitary.

The vessels of latewood are large to small in diameter, oval to round in outline and may occur as single, in radial pairs or radial multiples. The vessels have alternate pittings and simple perforation. The vessels are partly filled with tyloses and sometimes with white powdery deposits. The parenchyma cells are vasicentric and form a thin sheath around the vessel. The rays are moderately broad, 1-3 cells wide, heterocellular and uniformly distributed. The fibres are septate.

ii. Shorea robusta Gaertn. f. (Family: Dipterocarpaceae):

The growth rings are usually absent with diffuse-porous wood. The vessels are moderately large in diameter, moderately few (5-10/mm²) and occasionally numerous (10-20/mm²). The distribution of pores is more or less uniform. The pores are solitary and oval to round in shape and have simple perforation plate. Tyloses are present and they almost completely fill up the pore cavities.

Parenchyma vasicentric forming a narrow sheath round the pores or pore groups. The rays are fine to moderately broad, heterocellular. The gum ducts are present and they are vertical canals. The diameter of gum duct is usually smaller than pore. Each duct remains surrounded by thin-walled epithelial cell. The ducts are very irregularly spaced and occur in one or more rows. The ducts are often filled up with white gummy deposits.

iii. Cedrus deodara D. Don (Family: Pinaceae):

The sapwood and heartwood are sharply demarcated. The sapwood is white to creamy white in colour. The colour of heartwood is yellowish brown turning to purplish-brown on exposure.

The wood is non-porous. Growth rings are distinguishable. The transition from early wood to late wood is either gradual or abrupt. Resin canals are present and they are arranged in long tangential rows. Ray cells are numerous and they are arranged in closely-spaced line.

In the wood of Eucalyptus (Family: Myrtaceae) the vessels are solitary and occur in radial and oblique multiples. The vessels have simple perforation plates. Tyloses are present in lumen of vessels. Parenchyma cells are mostly amphivasal. The rays are wide and heterocellular.

It was previously mentioned that each country has its own publication of name of species from which the wood comes along with their wood anatomy. It is an authoritative work and provides the identifying characters of woods.

Any wood sample in question is studied anatomically and compared with the publications. Thus the identity of wood sample can be established. For correct identification microscopic slides are prepared from wood samples under study and compared with those from reference microscopic slides.

For domestic purposes woods are best used in making furniture and building materials. Craftsman needs the identification of the antique furniture when repairs are necessary. The wood of doors and windows can be checked as declared.

Apart from making furniture and building materials, woods are used for many more specialized purposes. Sometimes normally used species become unavailable. Then search is made for substitute woods. By studying the anatomy of wood that is to be replaced, sometimes it is possible to suggest other species, from which similar properties can be expected.

Mention may be made of the followings from where specialized properties are obtained. The cricket bat is produced from Salix Alba var. caerulea. The wood is light and the cell walls are moderately thick. The walls are resilient and after denting recover their shape better than dense wood. The dense wood of Guaiacum officinale is heavy and the fibres are thick walled.

It is used for making bowls and pulleys. The wood of Ochroma lagopus and O. pyramidale is very light and the wood of former is lighter than cork. The wood consists of large-thin walled parenchyma cells and thin walled fibres. It is used in life boat industries and making insulating materials in aircraft.

The wood of Leguminosae in tangential longitudinal section reveals that the rays and fibres are oriented in regular horizontal rows. This type of figure has decorative value. The wood of Fraxinus and Carya has straight grain, i.e. the elements of wood are oriented parallel to the longitudinal axis of the plant. The wood is resilient and so it is used in making handles of axe and similar tools.

Many woods have the property of resistance against decay, insect and fungus attack. Mention may be made of Tectona, where the heartwood is one of the most durable timbers of the world. The wood contains anthraquinones, which is effective in termites and fungi. The heartwood is used in boat building and it is one of the most important timbers in shipbuilding.

Application # 4. Enables to Identify Archaeological Plant Remains:

The wood-anatomy of present- day-plant provides characters to identify the fragmentary wood. These characters also enable to identify the wood and charcoal preserved in sites from antiquity.

A burnt wood or charcoal sample is collected from the site of excavation. Microscopic slides are prepared and examined thoroughly. The observation shows that the very delicate features like perforation plate and lateral wall pitting are still retained. The wood anatomy of archaeological sample is compared with that of present-day-wood and thus their identity can be detected.

After authentication it can be decided whether it was selected for burning purpose only. It may happen that the plants composed the vegetation of that area at that time. The plants, as they grew locally, were obtainable at ease and so were selected for burning purposes.

A wood is best preserved in those localities where continuous wet or dry conditions prevail. A fluctuating dry and wet atmosphere encourages the growth of pathogenic microorganisms that may attack the wood thus causing the wood to decay. It is not yet definitely known when the first use of wood began. It is assumed that the practice of using wood started in Old Stone Age for digging purposes in search of food.

For the first time, actual evidences of using wood have been recorded from the sites of New Stone Age. But no sites at this age in India produce any evidence of the use of wood. The Indus Valley civilization revealed the uses of wood for many purposes. The different use of wood was also recorded from the archaeological excavation of the proto-historic period in India namely, the Bronze Age civilization of Harappa and the Copper Age civilization of Hastinapura.

It has been reported that the Harappans used the wood of Cedrus deodara (Deodar) and Dalbergia latifolia (Rosewood) for making coffins. These durable and scented woods are still in use after thousands of years for the same purpose. Zizyphus was used as wooden mortar for pounding grains. This wood has the property of shock absorbing and the Harappans were quite aware of the fact.

Dalbergia sissoo (Sissoo) and Holarrhena antidysenterica (Kurchi) —these two timber-yielding plants were found in Hastinapura. These plants provide good fuel woods. It is not known whether these were used as firewood or charcoal. It is assumed that the Copper Age civilization was aware about the woods that have high calorific value.

In Iron Age the species of Quercus were used in making buildings and boats. At the site of exacavation at Brigg at South Humberside a boat made up of Quercus wood was preserved. It was interesting to find that the main logs of the boat were sewn together with twigs of Salix.

The twigs were twisted and passed through the regularly made holes on the timbers. No nails were used to hold the timbers. Corylus were well preserved in waterlogged condition in Somerset at Bronze Age. These were used in building track ways across swampy grounds.

Apart from wood and charcoal other archaeological plant remains are also preserved. As for example a sandal was preserved in ancient Egypt. Anatomical studies reveal that it is composed of Cyperus papyrus and Borassus sp.

Application # 5. Applied Aspects of Meristem Culture:

Meristems may be apical, intercalary and lateral. Each of the meristems is exploited in the improvement of plants.

i. Apical meristem:

Apical meristems occur at the tips of root, leaf and shoot. The shoot apical meristems are particularly used in culture. In culture method the shoot apical meristem is excised out and placed in a glass container, containing nutrient. In a strict botanical sense the cells in the apical dome of shoot apex compose the meristem. In apical meristem culture the sub-millimetre shoot tip with 0.1 to 0.5 mm high apical dome is dissected out and placed in nutrient media.

Different media are used for different plants. The media usually consist of a carbohydrate source, minerals, vitamins, aminoacids, growth regulators and the gelling agent agar. Perfect temperature, humidity, filtered air and controlled light are necessary during the culture. Aseptic condition is the prime importance in all the steps of culture to check the introduction of pathogens.

Sometimes circumstances arise when meristem culture becomes necessary for vegetative propagation. As for example the plant under study is infertile as in the case of triploid Musa sp., certain varieties of apple, tulips, iris, hyacinths etc. In breeding experiments the hybrid of first filial generation (F₁), when heterozygous, never breeds true, i.e. segregation of characters occur in the second filial generation (F₂).

The meristem culture of F₁ plant keeps the progeny alike. In many experiments on plant breeding the hybrid plants fail to produce normal seeds. The seeds are either abortive or nonviable. These hybrids are propagated through meristem culture. The haploid plants produced as a result of anther or pollen culture are always sterile. They become fertile when they are converted to homozygous diploid.

The haploid plants are propagated through apical meristem culture. In apical meristems viruses are either absent or present in a very low concentration because the cells of this region have fast mitotic activity. By apical meristem culture a clone of virus-free plant can be obtained. The clones can be multiplied vegetatively by meristem culture. The problems of plant tumors, especially the crown gall can be eradicated by meristem culture.

It is to note that a virus-free plant is not virus resistant. So aseptic measures are the dominant prerequisite for obtaining virus-free plant that serves as a source for propagation of other virus-free plants. Sometimes plants are imported or exported to other countries.

They are also exchanged in crop improvement programmed. In these cases quarantine laws are applicable. But the quarantine authorities relax the procedure of checking when the plants in question are derived from apical meristem culture.

The apical meristem culture is also useful in micropropagation. Micropropagation is the practice where a stock plant material is multiplied vegetatively into a large number of progeny plants. It is the true-to-type propagation of the selected genotype. Micropropagation gives immediate results in contrast to traditional means of propagation and so it is used to overcome the limitations imposed by long breeding cycle.

The practice of micropropagation is extensively used in horticulture, agriculture, forestry and conservation of endangered plants. It was estimated in 1991 that the world production of micropropagated plants are about 600 million. In horticulture, floriculture especially in cut-flower industry the registered line of stalk plants is maintained by micropropagation.

In cut-flower industry India has bright future. India has more than 35000 hectares of land under flower cultivation and is gradually entering into export market. Traditional methods of plant multiplication are very slow and it takes long time of being commercially available. So micropropagation through apical meristem culture is necessary to meet the high demand of flower, for pathogen-free plants and for hybrid plants etc.

In forestry micropropagation through apical meristem culture is also practiced as it gives immediate result. By traditional means to obtain a homogeneous true seed might take over a hundred years.

The teak wood is obtained from Tectona grandis. This tree grows naturally in India. The other naturally growing species of Tectona occur in Burma, Thailand and the adjoining areas of Laos. Tectona grandis is one of the most important timbers of India. The wood is moderately hard, moderately heavy and strong timber. The heartwood has a reputation of being one of the most durable timbers of the world and is practically immune to fungus and termites.

The essential oil citronella is obtained from the leaves of Eucalyptus citriodora tree. These plants are micropropagated from where about 500 plants of teak and 1000 plants of Eucalyptus citriodora are raised from a single bud (Fig. 32.1) in a year. Apical meristem culture is widely used to raise virus-free plants.

Example:

Manihot esculentus, which is usually infected by Mosaic virus or Streak virus. A single meristem tip of Manihot esculentus provides a number of virus-free plants.

Diagram illustrating the meristem tip culture for rapid propagation of plants.

In the conservation of endangered species micropropagation technique plays an important role. Through this technique endangered plants are propagated and thus conserved. Mention may be made of the orchids Liparis loeselii, Cypripedium calceolus etc., carnivorous plants Nepenthes, Drosera, Dionaea etc. and the woody plant Ramosmania rodriguesii, Hyophorbe lagenicaulis etc.

ii. Intercalary meristem:

A large number of plants have meristem adjacent to and just above most nodes. This meristem is derived from apical meristem. During the course of development of apical meristem of a plant, a portion of meristem becomes separated from apical meristem by more or less mature tissues. This is intercalary meristem. In many plants adventitious roots are formed at nodes from this meristem.

In horticulture this property is used in the propagation of plants by stem cuttings. Adventitious roots are formed in many plants which failed to grow upright and fell to the ground. Ex. Triticum, Dianthus etc. Adventitious roots grew at the nodes and made the plants upright again. The intercalary meristem is capable of producing adventitious roots.

This can be demonstrated by the following experiment. The experimental material is Dianthus. The plant is cut just below a node. The node is split longitudinally up to the intercalary zone. The split was kept apart by means of stick. Proper nutrition and aseptic condition was maintained as usual. It was observed that from the split sides adventitious roots develop (Fig. 32.2).

iii. Lateral meristem:

Lateral meristem occurs on the lateral sides of a plant.

Example:

Phellogen or cork cambium, fascicular cambium that is present between xylem and phloem of a vascular bundle of dicot stem and the inter-fascicular cambium that develops at the time of secondary growth from the tissues present between the two vascular bundles.

The fascicular — and inter-fascicular cambium unites on lateral sides to form a complete cambium ring. The function of cambium ring and phellogen. These cambia, if wounded, normally can regenerate and form callus cells adjacent to them. The cambial continuity is regained and thus the wound is healed. This wound healing property is employed for commercial purposes.

The phellogen donates on the peripheral side phellem cells that are also known as cork. The bottle cork, which is used as stoppers, is obtained from the phellem. Quercus suber provides most of the cork. The bottle corks that are used as stoppers are made sizes by tangential cut to stop leakage from vertically oriented lenticels (Fig. 32.3).

The phellogen of Q. suber persists indefinitely and forms mass of cork tissue externally. After about twenty years of age of the plant the cork tissues are removed by stripping. This cork, also known as virgin cork, consists of phellem cells only and sometimes phellogen and phelloderm may be present. The virgin corks are nearly useless.

After stripping, the underlying phelloderm and cortical cells are exposed and they gradually die. This wound is healed by a cork cambium or phellogen, which originates in the deeper layer of cortex. Phellogen forms new layers of cork, which is harvested after about ten years. This cork is not of good quality but definitely better than the virgin cork.

The better quality of cork is obtained from the third and subsequent stripping. The cork layers are harvested at intervals of nine to ten years until the tree becomes 150 or more years old. Portugal is the centre of cork industry. The recent use of plastic corks is reducing the demand of oak-cork.

The other lateral meristems, fascicular — and inter-fascicular cambium are also employed in plant propagation. This is usually done by cuttings and grafting. Cutting is a method where a shoot is cut away from a desired plant and planted to soil for rooting. Thus a new individual is produced. In horticulture this method is employed to propagate plants thus maintaining similar genotype.

In stem grafting the cut away shoot of a plant, also called scion, is inserted to the stem of another plants, also called stock. In grafting both scion and stock are wounded and the two are joined in such a way that the exposed meristematic cambial cells of them are brought into close contact. The inherent ability of wounds to heal causes the formation of callus tissue.

Through the callus the cambia of stock and scion become continuous and form the secondary vascular tissues as usual. Thus the scion becomes a permanent part of stock. The plants like Mangifera indica, apples, Nephelium litchi etc. are propagated by grafting. This device can regulate the size of the plant and earlier fruiting can be induced.

The gourd root, which is Verticillicum wilt resistant, is used as stock where the watermelon with wilt-prone root is grafted. Thus the wilt disease can be avoided in watermelon. Juniperus glauca has vigorous roots whereas the root of J. virginiana is weak. The latter is the desirable species and so it is grafted to the stock of J. glauca.

In conifers the growth ring are continuous at an early stage below lower branches. At the branch region the continuity of growth ring is interrupted where gap is present. In forestry there is a practice to remove the lower branches of conifers at an early stage. This enables the growth ring to become continuous over the discontinuous growth ring. Thus a sound new wood can be formed.

Application # 6. Provides Evidences in Forensic Investigation:

The application of forensic science is indispensable in investigating a crime. Forensic science has many disciplines and forensic botany is one of them. Forensic botany encompasses many sub- disciplines, which include plant anatomy, plant systematic (taxonomy and species identification), palynology (the study of spores and pollen) etc. They refer the use of plant materials in solving crimes or resolving other legal problems.

Plants remains are present everywhere. In a crime scene they may occur in the form of macroscopic pieces (ex. wood, twigs, leaves, flowers, fruits, seeds etc.) or microscopic forms (ex. pollen, spores, trichomes, cell walls in stomach contents etc.). The morphological and anatomical diversity expressed by plant species provide characters to identify plant parts. Species identification is a prerequisite in analyzing botanical evidences for casework.

Plant anatomy provides characters such as trichomes, stomata, cuticular pattern, leaf venation, wood anatomy, growth rings etc. to aid in species identification and in performing physical matches of evidence. The identified plant materials help the investigators of criminal cases to determine whether a suspect was present in a crime scene, in which season the crime occurred, how long the body has been buried, whether the body has been moved etc.

The following is an example of one of the earliest and famous case in which botanical evidence was used and accepted in court. In 1932, in the evening of March 1^st the infant son of famous American aviation hero Charles Lindbergh was kidnapped from his home in Hopewell, New Jersey, US. For the release of their son, the family paid $50,000. But the kidnapper did not return their son. Two months later the dead body of the son was discovered a few miles away from the family home.

The son was kidnapped from a second-story nursery. The kidnapper used wooden ladders to gain the access there. The ladders were the only evidence left at the scene. They were homemade and crude.

Xylotomist Arthur Koehler of United state Forest Services in Wisconsin examined the wood of the ladder both morphologically and anatomically. Four years later, when the case finally came to trial, Koehler offered the evidences from plant anatomy, which was ever to be heard and accepted in American court.

The ladders had been constructed in three sections. It was presumed that they were made such for ease of transport. Koehler numbered each piece of rungs and side rails. Koehler identified each piece to species. The following four species were used to construct the ladder —namely Yellow pine, Pinus ponderosa, Douglas fir and Betula sp. The basis of identification was the microscopic analysis of grain patterns of the woods.

Next Koehler analyzed the tool marks left on the wood. Koehler was able to differentiate the woods with mill plane marks and hand plane marks. The hand plane marks were distinct by their dull and nicked appearance. The nick was distinct when the wood was placed in oblique light in a dark room. The wood of rail #16 was very distinct from others.

It was from Pinus wood with hand planed marks and had four very prominent marks of square nail holes. Moreover the rail #16 was not weathered suggesting that the wood was removed -from some interior construction like shed. Finally Koehler analyzed the growth ring patterns and knots present on the wood and especially on the rail #16.

The progress of the case was very slow as no suspect was identified. Sometimes in September of 1934 a gas station received some currency notes and it was detected that those were once used to pay the ransom for the release the infant son. Bruno Richard Hauptman, a carpenter from Bronx, New York city paid the notes to the gas station.

Then search was made at Hauptman’s house and $14,600 of the ransom was found in the garage. So Hauptman was arrested. Further search was continued for the recovery of more money of the ransom. During investigation it was noticed that one of the joists of floorboards of Hauptman’s attic was shorter of about eight feet than the others.

This joist had four square nail hole marks and the growth ring patterns and knots were studied. Amazingly it was found that the four square nail hole marks, growth ring patterns and knots matched with rail #16. The hand plane marks of rail #16 matched with the wood of a homemade shelf present in the Hauptman’s garage. A hand plane was recovered from the garage and it made identical nick that was present in rail #16 and wood that constructed the shelf.

Hauptman was convicted and executed on 3rd April 1936.

In the above case the features of plant anatomy provided evidences in solving the kidnapping of infant son of Lindbergh and involvement of Hauptman in the crime.

The anatomical features like silica bodies, starch grains, raphides, sclereids, druse etc. found in edible plants are used to identify the stomach contents and last meal of a victim.

This is necessary to find the victims’ whereabouts and actions prior to death. In the analysis of stomach contents the cell wall provides important identifying characters of many food materials because the cell walls are not easily digested and persist longer time period than other anatomical features. Moreover the characteristic thickening of cell walls is sometimes taxon-specific.

Many dicotyledonous roots show growth rings or annual rings. The number of rings reveals the age of the tree. This property is utilized in forensic anthropology to estimate the time since skeletal remains had been in their present location. In one case living roots were found in the cavity of a skull.

The anatomy and growth ring pattern revealed that the root belongs to Ranunculus ficaria and the plant was approximately one year old. These findings enabled to determine that the skeleton had been there for at least one year. When a grave is dug roots can be damaged but still continue to grow leaving a permanent lesion.

In dicotyledonous roots growth rings are formed as usual and the number of rings formed after the lesion indicates the number of years passed since the damage. So growth rings can indicate the number of years passed since burial. From the number of growth rings or annual rings of root that are in contact with the bones can also indicate minimum time passed since death.

Dendrochronology or tree-ring dating is a method of scientific dating of a tree based on the analysis of annual growth ring patterns. The number of growth ring gives the age of the tree. The growth ring analysts can pinpoint the exact age of a tree and the year when the tree was cut. This enables to detect any art fraud, the provenance of wood arts objects, wood of musical instruments etc.

Many European painters used to paint directly on wood. Dendrochronology techniques enable to date the wood and so the year of painting. These techniques are also used to detect when the wood was used to make art objects or musical instruments etc.

Marijuana is a controlled drug and obtained from Cannabis sativa. In powdered form it is identified microscopically by the presence of characteristic cystolith and hairs. Drug enforcement confirms the drug by chemical tests in combination with microscopic observations. Apart from Cannabis sativa there are large number of plant species, which are used as drugs, substitutes and adulterants.

Most of them are used in a very finely powdered form. Quite a lot of time and effort is needed to authenticate them. There exists enormous genetic diversity among plant populations. Forensic scientists take the advantage of the property of genetic diversity to identify plant species by molecular biology techniques.

The development of DNA typing methods for plant species enables to identify plant species and thus helps in solving criminal and civil cases. Though the traditional microscopic anatomical identification is not always conclusive, it is still in use for preliminary identification. Moreover the anatomical techniques are simple and inexpensive.

Application # 7. Provides Characters of Taxonomic Significance:

It is the prime importance to know exactly to which species a plant specimen belongs. This is necessary for a natural and reliable classification. Most of the plants are classified according to their macro-morphological features. But an accurate classification results when the information from diverse sources are utilized.

The sources may be from anatomical features, palynology, biochemistry, embryology, cytogenetics, phytogeography, physiology etc. It is now realized that alpha taxonomy can form a natural, accurate and reliable classification.

Once morphology and anatomy formed the backbone of taxonomy. Anatomical features provide characters to supplement the macro-morphological characters of plant species.

The following important anatomical features those are often good indicators of the family, genera and sometimes species are discussed below:

i. Trichomes:

Trichomes are the collective term of hairs and papillae. They occur on all organs of a plant. There exists much morphological diversity among them. This property and the simple means of preparation of slides for study enabled the taxonomists to employ the trichome characters for systematic comparisons and individual identification. Metcalfe and Chalk (1950) provided the diverse types of trichome with their structure, nomenclature and distribution. Trichomes are of taxonomic significance especially at generic and specific level.

The families like Restionaceae and Centrolepidaceae can be recognized by the presence of distinctive type(s) of trichomes that are simple and unbranched. The hair of Aphelia cyperoides (Centrolepidaceae) has a boat-hook-shaped end (Fig. 32.4A) that characterizes the species. Leptocarpus (Restionaceae) has flattened multi-cellular stem hairs with short stalk.

There are two major categories of hairs-the glandular and non-glandular. Each of the categories is sub-divided according to their gross structure, cellular constitution, nature of branching etc. There exist much diversities and varied forms in non-glandular hairs than the glandular hair. A few types of hair are illustrated in Fig 32.4.

A particular type of hair is constant in a species. This property is used as an aid to identify the different species of Oleaceae, Ficus and Rhododendron to some extent. Presence of T-shaped hair diagnoses the family Malpighiaceae. Trichomes provide the distinguishing characters within the family Icacinaceae where the genus Ottoschulzia is segregated from Poraqueiba on the basis of trichome characters.

Trichome types with their distribution pattern can be correlated with the sub-generic and specific distinction in Nicotiana. In Sparganiaceae and Typhaceae, the presence of sessile glandular trichomes provides a link between these families. Trichome anatomy is of immense significance in the separation of species and even varieties in the tropical family Combretaceae.

ii. Stomata:

Stoma has been shown to have great value in the taxonomy of several taxa. The distribution, morphology and ontogeny of a stoma are of taxonomic significance. Stoma is absent in roots. In exceptional cases it is reported from Ceratonia siliqua and Pisum arvense seedling roots.

Stomata are also absent from the chlorophyll-less parasitic angiosperm like Monotropa and Neottia. The submerged hydrophytes lack stoma. The floating hydrophytes i.e. Nymphaea, Victoria etc. are epistomatic (= stoma is present on upper surface of a leaf). Hypostomatic (= stoma is present on lower surface of a leaf) leaf occurs on those plants that have xeromorphic habit.

Amphistomatic (= stoma occurs on both upper and lower surfaces of a leaf) leaf is observed in mesophytes. The stomatal frequency and stomatal index have taxonomic importance. The taxonomic groups and the different species of a genus can be differentiated on the basis of stomatal index.

The different morphologic and ontogenetic types of angiosperm stoma. They are of immense taxonomic significance. Metcalfe and Chalk provide a list of angiosperm families where different morphological types of stoma occur. It is shown that paracytic stomata characterize woody Ranales. So it is regarded that such stoma is primitive among dicotyledons.

Sen and De (1992a) recognized 24 types of stoma in ferns among which polocytic stoma is regarded as the basic form from which the other types have ontogenetically been derived. The polocytic stoma is found in Diplazium polypodioides (Fig. 32.5G), Cyathea contaminans etc. This type of stoma has single subsidiary cell. The stoma is attached to the distal side of the subsidiary cell.

Thus the subsidiary cell appears U-shaped or horseshoe shaped. Pant (1965) and Payne provide the different ontogenetic types of stoma. The diameristic and mesoperigenous stoma are thought to be primitive in the Embryophyta. It is to note that monocotyledons are characterized by the above patterns of stoma. In monocots stoma with two or more subsidiaries appears to be more primitive than those with none.

The surface view of guard cells of a stoma can be of taxonomic significance. Rajagopal and Ramayya classified five types of guard cells on the basis of their appearance in surface view under light microscope (Fig. 32.5). The types are (a) dumb-bell type (ex. Cyanodon), (b) rectangular type-A (ex. Eriocaulon), (c) rectangular type-B (ex. Cyperus), (d) elliptic type (ex. Scilla, Mollugo) and (e) right-angle type (ex. Azolla).

The dumb-bell type guard cells characterize the family Gramineae. The monocotyledonous families like Cyperaceae, Restionaceae, Juncaceae, Marantaceae etc. show rectangular type-B guard cells. In dicotyledon rectangular type-B guard cell is reported from Haloxylon articulation (Chenopodiaceae) only. The rectangular type-A guard cells occur in the monocotyledonous families like Xyridaceae, Eriocaulaceae and Palmae.

The elliptic type of stoma is the characteristic of gymnosperms, dicotyledons, most of pteridophytes and some monocotyledonous families like Dioscoriaceae and Liliaceae. Rajagopal and Ramayya regarded that within the monocotyledons the above types of guard cell might have value at higher taxonomic levels. The leaf of Pinus pinea shows circular raised rim above the stoma. The epidermal cells form the rim. It is revealed by the scanning electron micrograph. The raised rim is termed as Florin ring.

iii. Veins:

The veins and their innumerable variations in leaf venation pattern provide various characters of taxonomic importance. The anatomical division of Angiosperm into dicotyledon and monocotyledon is based on venation pattern.

With a few exceptions dicots have reticulate venation and monocots show parallel venation. The veins are the vascular strands or traces that diverse from the vascular cylinder of stem at the nodes. In dicotyledons they may consist of one, three or many traces. These traces and other accessory strands collectively form diverse patterns or types of venation.

In a dicotyledonous leaf the veins may be primary, secondary and tertiary. The primary vein is the widest vein in the leaf. It originates at or just above the petiole. It is usually symbolized as 1° veins. The secondary veins are narrower than the primary. It originates from the primary vein. It is usually symbolized as 2° veins. The tertiary veins are narrower than the secondary.

It may originate from secondary and primaries. It is usually symbolized as 3° veins. (Fig. 32.6). The primary and secondary veins are the structural veins of a leaf. The tertiary veins fill the field of the leaf. The primary and secondary veins gradually taper towards the margin. The tertiary veins connect primary and secondary veins thus forming a more or less regular polygonal field over the leaf area.

A polygonal field is usually designated as vein-islet. Apart from above types most dicotyledonous leaves have higher orders of veins, i.e. after tertiary there are 4°, 5° veins category and they may be up to 7°. In the lamina of many leaves the vein terminates blindly as veinlets in the mesophyll. These veinlets are termed as vein endings. The sieve tube elements are absent from vein endings.

The different categories of vein provide many characters that are very useful in leaf identification. The 1° veins may be single, three or more. The 2° veins form an angle with 1°. The angles are constant in a species. The angles may be uniform, abruptly increasing towards the base, smoothly decreasing towards base etc.

The spacing between 2° veins is also of taxonomic significance. It may be uniform, irregular and increasing or decreasing towards the base. The 3° veins show different angles to 1° (Fig. 32.7A, B, C, & D). The course of 3° veins may be straight, convex and sinuous (Fig. 32.7E, F, and G). The number of vein-islets in a unit area is species-specific.

Usually four square millimetre area of a leaf is considered as a unit in counting the vein-islet numbers. The ultimate free endings of vein-lets have diagnostic value. They may be unbranched, linear or curved 1-branched, 2 or more branched etc. The following features of veins provide taxonomic information.

The veins may or may not be raised above the two epidermises of a leaf. Bundle sheath may be absent or present in vascular bundle, which is the cross-section of veins. When present it surrounds the vascular bundle and may be one or two layered, parenchymatous or sclerenchymatous.

In two-layered bundle sheath both the layers may be parenchymatous or sclerenchymatous, or the inner layer is parenchymatous and the outer layer is composed of sclerenchyma. Chloroplastids may be present or absent from the cells of bundle sheath. Bundle sheath extension may be absent or present and when present it may be composed of parenchyma, collenchyma or sclerenchyma.

It is taxon specific. Hickey (1973, 1974) provides terminologies for the description of leaf form and venation. This enables to identify and classify dispersed leaves. The foliar characters may or may not offer conclusive evidences of affinities, but generally they do allow distinguishing the closely related species.

Moreover the diverse patterns of venation can be utilized in the morphological interpretation of such organs as bracts, sepals and petals. The leaf epidermal characters such as pattern of epidermal cells, cuticular ornamentation, and the patterns of leaf wax structure as revealed by means of electron microscopy have, of late, been demonstrated to be of taxonomic importance of many taxa.

Crystals, especially calcium oxalate crystals, silica bodies on the epidermal cells, foliar sclereids with their types and distribution are taxon specific and hence taxonomically useful.

The measurement called palisade ratio is taxon-specific and hence it is often used to identify a leaf or fragments of leaf. Pharmacognosists frequently use this measurement to authenticate the leaf drug that is mostly obtained in powdered forms. The palisade ratio indicates the number of palisade cells present beneath each epidermal cell.

The cells of epidermis and palisade are observed and counted from surface views. A large number of counts are recorded and an average number is determined from the counts. The average number obtained from a statistically sound count provides a fairly reliable identifying datum of materials.

Example:

The palisade ratio of Swertia angustifolia, S. chirata, S. paniculata and S. dilatata is 2.94, 2.06, 3.27 and 6.5 respectively.

The other taxonomically useful anatomical features are stem, leaf and root anatomy, nodal anatomy, wood anatomy, primary and secondary anomalous structure, ultra-structure of sieve tube, plastids etc.

Examples where anatomical features solved taxonomic problems:

There are numerous examples where the anatomical features were used in solving taxonomic disputes, a few of which are mentioned below.

The ultra-structure of sieve tube plastids was used in circumscribing taxa. Sieve tube plastids are broadly of two types-starch accumulating (S-type) and protein accumulating (P-type). The S-type occurs in Polygonaceae, Plumbaginaceae, Batqceae, Theligoniaceae etc. whereas the P-type is found in Phytolaccaceae, Molluginaceae etc.

There are certain families like Rafflesiaceae, Crassulaceae, and some species of Moraceae etc. where the sieve tube plastids accumulate neither starch nor protein. The ultra-structural details of sieve tube plastids are taxon-specific and hence taxonomically useful. It was best used in elucidating the inter-relationships in the order Caryophyllales.

Mabry (1976) segregated the order into two sub-orders — Chepodiineae and Caryophyllineae, on the basis of pigment biochemistry. Chenopodiineae comprises the betalain containing families and Caryophyllineae includes the anthocyanin containing families —Caryophyllaceae and Molluginaceae.

The nature and character of the ultra-structure of sieve tube plastids suggest that the betalain and anthocyanin families are closely related since all of them possess P-type plastids with a peripheral ring-shaped bundle of proteinaceous filaments. Betalain and anthocyanin families both have characteristic anomalous secondary thickenings and primary anomalous structure.

Moreover anatomical and palynojogical evidences provide no basis for splitting the Caryophyllales into Chenopodiineae and Caryophyllineae. Gisekia has been included under the anthocyanin family Molluginaceae. Unlike other Molluginaceae Gisekia possesses betalain instead of anthocyanin.

So Takhtajan (1980) preferred to shift the genus to the Phytolaccaceae that has several characters common with Gisekia. Gisekia shows globular crystalloid P-type plastids in sieve elements like Molluginaceae and Phytolaccaceae. From the available data from plastid structure, pigmentation and palynology its alignment with Phytolaccaceae is indicated.

The monotypic species Halophytum ameghinoi has often been associated with Chenopodiaceae. Chenopodiaceae and Halophytum both possess P-type plastids with ring shaped bundle of filaments. But Chenopodiaceae lacks the crystalloid in the ring-shaped bundle of filaments. In contrast Halophytum possesses globular crystalloid in the ring-shaped bundle of filaments.

So the structure of sieve element plastids does not favour its association with the Chenopodiaceae. Theligoniaceae had been placed often close to or even into Caryophyllales.

The presence of S-type plastid and anthocyanin argues against its incorporation into the Caryophyllales. On the basis of the plastid data Dysphania can be included in the Chenopodiaceae. It possesses P-type of plastid with ring-shaped bundle of filament; but it lacks the central crystalloid.

Anarthria and Ecdeiocolea were included under the family Restionaceae. Later a survey on anatomical and macro-morphological features of these two genera resulted in the recognition of two families — Anarthriaceae and Ecdeiocoleaceae. The stem anatomy of most Restionaceae shows a continuous parenchymatous cylinder that is absent in the other two families.

Below the epidermis there exists a zone of chlorenchyma in all the three families. The stem anatomy of Ecdeiocoleaceae shows the presence of hypodermal sclerenchyma, which is absent from Restionaceae. In Anarthriaceae there exists the sub-epidermal fibre strands associated with vascular bundles.