Organography and Plant Histology of Azadirachta indica (Meliaceae)

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This contribution, deals with the aspects related to the organographic and histological structures that exhibit the plants of agronomic interest, in this opportunity I will describe the species Azadirachta indica (MELIACEAE), this with the firm purpose of being able to contribute in the spreading of the biological-technical elements and agro-ecological potentiality of this important vegetable resource.


Introduction


The plant species, against the attack of insects interpose certain biological mechanisms as a defensive response, within these, the most effective are listed the physical and biochemical, the first admit certain morphological adaptations, for example; The lignification of the cholenchymal and sclerenchymal tissue, a biological action developed with the purpose of avoiding the access of the oral structures of herbivorous insects to the organographic structures of succulent condition (foliar laminae, young stems among others).

Now, in relation to the defensive responses of action biochemical, the vegetal species by means of biosynthesis, generate complex molecules whose structure and toxic content, cause damage to a great number of insects particularly against lepidoptera, such is the case of the species Azadirachta indica (Meliaceae) whose vegetative and reproductive organs are used in organic farming because of the adverse effect produced by the bio-molecule azadirachtin on these types of insects.

Consequently, and starting from the effect of the azadirachtin essential component of the plant species Azadirachta indica (MELIACEAE), the objective of this post is to socialize its potential bio-insecticide and to describe the organographic and histological characteristics of this important biological resource.

Biological classification


Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Orde: Sapindales
Family: Meliaceae
Gender: Azadirachta
Species: indica

Common names

Azadirachta indica, is widely known in South America as Nim or Neem, however, in countries of the Asian continent from where it is believed to be originated, it is usually identified as Nimbo, it is also called Paradise of India or Margosa in Spain.


Bio-insecticide property of Neem


The toxic bio-molecules of certain vegetables, represent a very attractive agro-ecological alternative from the economic point of view, from there that the elaboration of extracts based on organographic structures generates an added value in the agricultural production, in the case of the bio-insecticides elaborated based on Azadirachta indica, either, of foliar tissue or mature seeds, besides being an economic option, the effectiveness to cause the damage and to diminish populations of insects is the element of greater significance.

According to biochemical records, the bio-molecules or secondary metabolites of toxic effect present in the organographic structures of Azadirachta indica and that cause mortality on a wide range of insects are azadirachtin, salanine, meliantriol and some triterpenoids. However, the effect associated with the agroecological management of extracts of Nim A. indica, is the repellent and alimentary result that causes azadirachtin on insects of the order lepidoptera.

These adverse effects, generated by the bio-molecule azadiractine on this group of insects, have comparative advantages over synthetic insecticides because, in addition to having a certain specificity, they have the ability to biodegrade, biological aspects of great importance in organic farming, first because this bio-insecticide action does not cause pollution on ecosystems and allows to maintain the cultivated areas with densities of herbivorous insects at low levels, without affecting the balance of beneficial insects.


Origin and distribution


Although there is no precision, the origin of Azadirachta indica has been related to its ease of natural growth in southern regions of the Asian continent, specifically in the mountainous areas of India and Burma, in relation to its distribution is predominantly tropical, reaching adaptive diversity in dry ecosystems [1].


Botanical description


Way of life

Azadirachta indica, has a biotype of tree and perennial condition, its specimens can exhibit size variability, however, it is common to observe a medium to large growth behavior [4].

Root

The root system in Azadirachta indica, is of normal origin and pivotal morphology, of rapid growth and development equivalent to the stem.

Stem

The stem is of a woody consistency, moderately thick, corky and visibly cracked bark characterized by toxic, viscous and colorless sap.

Fig. 2 Stem fromAzadirachta indica. Author: @lupafilotaxia.

Fig. 3 Visibly cracked bark from the stem of Azadirachta indica. Author: @lupafilotaxia.

Leaf

The foliar laminae of Azadirachta indica, are of peciolated insertion, composed of imparipinnate type, of oblanceolated morphology of light green color, serrated edge, obtuse apex, cuneiform base, pinnatinervia and alternate phyllotaxy.

Fig. 4 Leaflets composed of imparipinnate type of Azadirachta indica. Author: @lupafilotaxia.

Inflorescence

The Nim exhibits inflorescence in the form of cluster, of axillary condition and with multiple lateral divisions from where each flower arises.

Fig. 5 Inflorescence of Azadirachta indica. Author: @lupafilotaxia.

Flower

The flowers of Azadirachta indica, are bisexual or male and actinomorphic in nature, with white or yellow petals.

Fruit

Azadirachta indica, has fruits of ellipsoidal morphology type drupe, with exocarp in immature state of green or yellow color and purple in the mature phase, while the endocarp is of cartilaginous consistency.

Fig. 6 The fruit of Azadirachta indica. Author: @lupafilotaxia.

Seeds

It has seeds of ovoid morphology, wrapped in a protective structure of dark brown.


Reproduction


Sexual reproduction

The Nim Azadirachta indica, exhibits a system of sexual reproduction mediated by its seeds, however, some self-incompatibility has been reported, on the other hand, it is important to emphasize that this means of propagation in A. indica the dispersion of the seeds, generally occurs by endozoocoria particularly by migratory birds [4].

Asexual reproduction

Even when Azadirachta indica, presents sexual reproduction its organographic structures can regenerate in a vegetative way, this artificial or asexual reproduction, is used in nurseries and seedbeds in desert bio-regions that use the trees of Nim to generate shade [1].


Growth


After the germination of the seeds, the newly formed seedlings of Azadirachta indica, begin a moderate foliar growth, opposite action occurs in the root system that is considerably accelerated, in relation to the size of the stem, this can reach 2 meters approximately in the first year of phenological age, and according to the rate of annual growth, the plants in long-lived state generally reach 12 meters of height [3].


Ecology


Although the specimens of Azadirachta indica, present ecological amplitude and usually develop in dry climates, the periods of prolonged droughts affect considerably the foliage, tending to lose in front of these conditions a high percentage of its foliar laminae, its maximum vegetative and reproductive potentiality is expressed in predominantly tropical climates and in bio-regions that are located between 0 and 1,500 msnm, with average temperatures of 32 °C and slightly acidic to neutral soils.


Histology and organography


Microscopic study

In order to extend the existing information, it was developed a histological study about the vegetative structures of Azadirachta indica, using the optical microscope for the morphological characterization at tissue level, it was executed in the Botanical Laboratory of UNESUR.

Collection

The vegetative material of Azadirachta indica, was collected from the ornamental spaces of the University Canteen of UNESUR, institution located in Santa Bárbara de Zulia, biogeographic zone of the South of the Lake of Maracaibo - Venezuela.

Histological identification

The vegetative structures of Azadirachta indica, were placed in containers with water to guarantee the turgidity of the tissues, later they were transferred to the laboratory facilities of Botany of UNESUR.

Materials and reagents used

  • Vegetative structures of Azadirachta indica
  • Carrier sheets and coverslips
  • Botanical dissection team
  • Petri dishes
  • Optical microscope
  • Distilled water
  • Lugol
  • Safranin
  • Floroglucin

Tissue observation

The histological structures of Azadirachta indica, were observed using OPTIKA brand microscopes, for the identification of epidermal tissue, photosynthetic mesophilic, transverse, longitudinal and tangential cuts were made to the leaves (both sides), first proceeded to focus at 4x to locate tissues and then changed to 10x, for morphological characterization.

For the observation of xylem conduction and phloem tissues, cross sections to petioles of Azadirachta indica were made.


Histological results


Epidermal characterization

According to the microscopic observations, carried out to the foliar laminae of Azadirachta indica, it was possible to appreciate an external segment at the level of the beam (cuticle) of thin aspect, adaxial epidermal cells appreciably elongated in tangential sense.

Stomatic characterization

Hypoestomatic disposition was found in the foliar segments of Azadirachta indica, this indicates that stomas are located only in the abaxial face (back side or lower face) of the foliar laminae, in relation to the morphology of the stoma was observed of anomocytic type.

Fig. 7 On the right side, tangential cut of the leaf underside of Azadirachta indica, on the left side are shown anomocytic stomas. Author: @lupafilotaxia.

Parenchymal characterization

The mesophilic leaf of Azadirachta indica, presents two segments of opposite morphology (dorsiventral), as for the structure and composition parenchymal cells were observed palisades in discontinuous disposition and of polygonal aspect.

Xylematic and phloematic characterization

As for the histological observations made to the leaf petioles of Azadirachta indica, epidermal tissue could be appreciated, followed by mechanical cells of cholenchimatic type with angular morphology, polyhedral parenchyma appreciably abundant around the central nerve and vascular beams in the shape of half moon.

Fig. 8 On the right side, the cross section of the petiole of Azadirachta indica, is detailed. On the left side, histological description is indicated. Author: @lupafilotaxia.


SCIENTIFIC CONTRIBUTIONS OF THIS PUBLICATION


  • The morphological characters determined by observation in situ and developed in the post, emphasize the histological and organographic characterization that shows the species Bio-insecticide Azadirachta indica, among which the following stand out; corky-looking bark visibly cracked and characterized by containing toxic, viscous and colorless sap, seeds wrapped in a protective structure of cartilage consistency, sexual reproduction system with some self-incompatibility, root growth opposite to leaf growth, in addition to key histological attributes that the species has, such as hypostomatic disposition, dorsiventral mesophilic leaf type, polyhedral parenchyma around the central nerve in the leaf petioles and vascular bundles in the shape of a half moon.


BIBLIOGRAPHICAL REFERENCES CONSULTED AND CITED:


[1] Ahmed S., and Grainge M. Potential of the neem tree (Azadirachta indica) for pest control and rural development. Economic Botany. 1986; 40; 2: 201-209. Article: Online access

[2] Alcalá M., Vargas N., y Pire A. Efecto de extractos vegetales y fungicidas sintéticos sobre el crecimiento micelial in vitro de Sclerotium rolfsii y Thielaviopsis basicola. Revista de la Facultad de Agronomía. 2005; 22 ;4: 315-323. Article: Online access

[3] Girish K., and Shankara S. Neem – A Green Treasure. Electronic Journal of Biology. 2008; 4; 3: 102-111. Article: Online access

[4] Gruber A. Biología y ecología del árbol de Nim. Ceiba. 1992; 33; 1:2 49-256. Article: Online access

[5] Lemmens R., Soerianegara I., and Wong W. Plant resources of south-east Asia. Timber trees: minor commercial timbers, Backhuys Publishers, Leiden. 1995; 5: 2. Article: Online access

[6] Stace C. The significance of the leaf epidermis in the taxonomy of the Combretaceae. Journal of the Linnean Society of London. 1965; 59: 229-252. Article: Online access


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The plant grows well around here and popularly known for its antimalarial properties.

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(Edited)

Greetings friend @gentleshaid I hope you find healthy above all, I have seen that you have stopped publishing.

The widespread use of Neem in South America is mainly due to its bioinsecticity action, I have read about its effective antimalarial capacity. In these countries, society uses little or nothing of Neem phytomedicinal properties. Thank you for leaving your comment, I appreciate it very much, it even encourages me to write something later about the phytopharmacological potential of Neem.

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(Edited)

I've been a bit busy offline. We are currently protesting against police brutality in my country and that has taken my attention away from publishing. I will be back soon.

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Friend @gentleshaid, paradoxically here you do not hear anything about problems in Nigeria, for your message, I'm reading some news about the situation of tension in your country, I hope things can improve, and everything returns to normal.

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