.png)
%20of%20New%20Picture.png)
Anatomy of dicotyledonous and monocotyledonous seeds:- The structure of monocot and dicot seeds can be described based on the following parts:
1. Seed Coat:-
> The seed coat is the outermost covering of the seed which in some cases might remain fused with the fruit wall.
> The seed coat is formed from two integuments or layers of cells present on the outside of the ovule. The tissue is derived from the mother plant where the inner layer forms the tegmen and the outer forms the testa.
> In some monocots, the layers of the seed coat are not distinct and might even remain fused with the fruit wall. The outer layer, when distinct, consists of patterns or some patches of hair.
> The number of layers of the seed coat depends on the characteristic of the ovules. In the case of bitegmic ovules, the inner layer either remains as a single layer or divides to form two or three layers and accumulate food materials.
> The outer layer, in turn, contains cells with tannin deposits, resulting in a dark-colored appearance.
> As the cells of the seed coat begin to enlarge, the outer layer continues to deposit different substances that cause their walls to thicken.
> The seed coat contains an oval depression called hilum which represents the point where the ovules were attached to the wall of the ovary.
> The seed coat of some seeds might have hair or wings which help in the dispersal of the seed by the wind. Similarly, some seed coats are composed of waterproof materials to protect it from drying or decaying during dispersal by water.
2. Endosperm:-
> The endosperm is a mass of tissues formed within the seed during the process of fertilization.
> The cells of endosperm are unique in that they are triploid with three sets of chromosomes per nucleus.
> The primary purpose of endosperm is to surround the embryo and provide nutrition to the embryo.
> The formation of endospore requires one of the sperm cells to fertilize with the diploid central cell of the female gametophyte. This results in the formation of primary endosperm cell with triple fusion nucleus.
> Most of the flowering plants are polyploidy, but others might have a triploid or diploid set of chromosomes.
> The size of the endosperm is quite big in monocots as endosperm is the primary source of nutrition for the embryo. In dicots, however, the nutrient is provided by the two cotyledons.
> The endosperm consists of three different types of cells; the starchy endosperm cells, the basal transfer layer, and the aleurone layer.
> Most of the endosperm is occupied by the starchy endosperm. The endosperm is composed of dead cells filled with starch granules and protein bodies.
> The cells of the basal layer are characterized by the presence of cell wall ingrowths with cell membrane that is up to 22-fold more than normal plant cell.
> The aleurone layer is a single-cell layer, but in some monocots, the layer can be three-layered thick. The layer surrounds the starchy endosperm and the embryo.
3. Embryo:-
> Embryos are the simple multicellular structure of undifferentiated cells formed as a result of fertilization of haploid egg cell by a sperm cell.
> The embryo is composed of DNA obtained from the ovule as well as pollen forming a zygote.
> The embryo is the part of a seed and is protected within the seed by various structures like endosperm and seed coat.
> The zygote resulting from fertilization undergoes first cell division which is asymmetrical. The asymmetrical division results in the formation of an embryo with a small cell and a large cell.
> The small apical cells eventually develop to form parts like stem, leaves, and roots, whereas the larger cell gives rise to the connective. The connective connects the embryo to the endospore.
> As the embryo continues to grow, it separates into distinct regions in which cell division occurs and areas where non-reproductive activities like metabolism, respiration, and storage take place.
> The embryo has the highest concentration of lipid and lipid-soluble vitamins among all the other parts of the seed.
> In monocots, the embryo is present in a groove at one end of the endosperm with one larger shield-shaped cotyledon called scutellum.
> The embryo axis contains other structures like plumule, radicle, hypocotyl, and epicotyl that eventually lead to the formation of a new plant by embryogenesis.
4. Plumule:-
> The plumule is a part of the seed embryo that eventually develops into the shoot with vegetative parts like leaves and stems.
> It appears as a bud at one of the axis of the embryo and is often termed as the embryonic shoot.
> Plumule is negatively geotropic unlike radical and might or might not contain leaf structure when present within the seed.
> In some plants like sunflower, the plumule has no leaf structure, and the growth also doesn’t occur until the cotyledons are present above the ground.
> In others, however, a leafy structure is present which develops through the soil with cotyledons still present below the surface.
> In monocots, the plumule is surrounded by a coleoptile which is absent in the plumules of dicot seeds.
5. Epicotyl:-
> Epicotyl is the region of the embryo that is present above the stalks of the seed leaves, which is essential for the beginning stages of plant germination.
> Epicotyl grows rapidly than other parts of the embryo and exhibits hypogeal germination. Hypogeal germination is defined by the growth of plumule above the soil while the cotyledons are still below the surface.
> The growth of the epicotyl region is responsible for the extension of the stem above the soil surface.
> The growth of the cells of the epicotyl region forms the point of attachment between the shoot apex and the first true leaves of the embryo.
> The concept of epicotyl is different in monocots and dicots. In monocots, the shoot that emerges from the soil or the seed is considered the epicotyl whereas, in dicots, the epicotyl represents the region of the shoot above the cotyledons.
6. Hypocotyl:-
> Hypocotyls is the region of the seed present below the seed leaves (or cotyledons) and bove the radicle.
> Hypocotyl eventually becomes part of the stem, but one of its essential functions is to push the cotyledons outer of the soil surface during germination.
> Even though hypocotyl doesn’t grow as rapidly as the epicotyl, it is the first structure of the plant that emerges out of the soil.
> The hypocotyl, along with the radical, makes way for the epicotyl as the cells of the epicotyl are delicate and might suffer damage during growth.
7. Radicle:-
> Radicle is the region of the embryo, which is the first to emerge from the seed during germination that eventually leads to the formation of roots.
> Radicle is often called the embryonic root as it is positively geotropic and grows downwards into the soil. The radicle comes out of the seed through the micropyle.
> Radicels are of two types depending on their orientation; antitropous radicles point away from the hilum on the seed coat whereas syntropous radicles point towards the hilum.
> The radicle in monocots is surrounded by a thin sheath called coleorhiza, whereas that in dicots, is not. The radicle does, however, have a root cap that protects it during the early growth stages.
8. Cotyledon:-
> Cotyledon is the embryonic leaf in the seed which occupies most of the space in the seed and provides nutrients and protection to the embryo.
> The number of cotyledons present within a seed is one of the characteristics used to differentiate flowering plants into different groups.
> Seeds with two cotyledons are termed dicotyledonous whereas seeds with a single cotyledon are termed monocotyledonous.
> In dicot plants, the cotyledons are photosynthetic and functionally similar to plant leaves.
> In monocot plants, the cotyledon is modified to form a scutellum which is non-photosynthetic and functions to absorb stored food from the adjacent endosperm.
> The number of cotyledons can be higher than two as well, like in pines and cypress that have about 24 cotyledons.
> The life of a cotyledon differs in different species as in some it lasts for a few days whereas in others it lasts for up to a year.
%20of%20New%20Picture.png)
Stamen Origin and evolution:- The stamen is the male reproductive organ in angiosperms. It is also known as androecium or microphylls. The stamen composed of slender stalk with a supporting knob. Each anther consists of two lobes connected by a connective. Each anther has two pollen sacs placed longitudinally. The pollen chamber represents a microsporangium that contains many microspores. Each stamen consists of two parts- filament and anther. Some morphologists believed that the stamen consists of three parts-filament, anther and connective. Filament is the midrib, while anther is formed by the union of the margins of the foliage leaves. Various interpretations have been advanced from time to time regarding the morphology of the stamen.
Classical view:- Goethe proposed that flowers are like abbreviated vegetative leaves. De Candolle
further elaborated the theory and stated that the stamens and carpels are all similar to leaves. Thus,
the individual stamen is a leaf which has been modified to form a reproductive organ. The anther
represents the lamina and the filament is the midrib and the whole structure may be a set of
modification of lamina. Arber and many other reported the homology of stamen parts with the foliage
organs.
Telome theory:- Wilson stated that Goethe’s hypothesis is lacking palaeobotanical evidences.
According to him no theory of the origin and morphology can be established based on assumption
without fossil evidences. Various studies led to the view that the body of early land plant was the
branched axis. The proximal portion becomes differentiated into an absorbing organ and the distal
organs evolves a fertile and sterile branched system. These systems probably grow dichotomously,
and sporangia are formed terminally. Based upon the fact, the foliar organs and other parts of the
angiosperms derived from the sterile branched system and the essential parts the flower from the
fertile system. Accordingly, the modern system came into being as a result of extensive reduction and
specialization of fertile dichotomous branched system. The four celled anther of the angiosperm
stamen is explained by he reduction of ultimate and penultimate branch and then by fusion give rise
to paired sporangia. Wilson though believed that the stamen has evolved from dichotomous system,
yet the final evidence is lacking. However, he forwarded his opinion as the Goethe’s hypothesis is
rational.
Revolutionary view:- Thomson put forwarded another views on the ontogeny of the flowers.
According to him the flower is essentially a heterogenous fertile axis bearing floral parts in the torso.
The base is sterile and produces bracteole, bracts and sepals. Rest of the superficial axis is potentially
sporogenous which give rise to petals, staminode, stamens and carpels. Work of Thomson is opened
for memoir of interpretation. According to Hunt, the stamen is not homologous to entire leaf but a part of leaf and the term sporophyll may not be applied to modern stamen.
Note:- Reviewing all the theories proposed so far, the classical theory looks more convincing, as it stated that flower is a modified shoot and the stamen is a part of it.
%20of%20New%20Picture.png)
Carpel evolution:- i. Conduplicate theory:- According to the most widely accepted hypothesis, the carpel constitutes a modified, conduplicate megasporophyll bearing two, adaxial rows of ovules (Figure 6.9D). Recall that a “megasporophyll” is a modified leaf that bears megasporangia, which in the seed plants are components of the ovules and seeds;
ii. Appendicular theory:- This theory was put forwarded by De Candolle, Van Teighem and others and
supported by Eames (1961). According to this theory the inferior ovary has developed as a result of
the fusion of the bases of sepals, petals and stamens and as such appended to the axis of the flower
which has nothing to do with the formation of the ovary wall. Eames stated that due to evolution,
inferior ovary was developed from the superior one by the process of gradual fusion of the bases of
sepals, petals and stamens and adnation of the same to the gynoecium wall which indicate the
superiority of inferior vary over inferior ovary.
iii. Receptacular theory:- According to Schleiden and others, the receptacle of the flower has become
the instrumental in the formation of the inferior condition of the ovary. This has achieved through the
gradual sinking of the ovary to the deep cup shaped receptacle with the process of invagination of the
tip of the thalamus. After sinking down of the ovary the bases of sepals, petals and stamens have been
fused much in the same manner as in case of the appendicular theory.
.png)
%20of%20New%20Picture.png)
Embryo sac types:- Depending on how many megaspore nuclei are involved in embryosac formation, the embryosac may be:
1. Monosporic embryo sac:- The chief characteristic of a monosporic embryo sac is that it is derived from only one of the four megaspores. All the nuclei in such an embryo sac are genetically identical because they are derived through mitosis of a single nucleus. There are two types of monosporic embryo sacs:
i. Polygonum Type:- It is the most common type (81% families). It was first time described in Polygonum divaricatum by Strasburger (1879). The embryo sac is formed by the chalazal megaspore of the tetrad and is eight nucleate. The mature embryo sac comprises a 3- celled egg apparatus, three antipodal cells, and a binucleate central cell.
ii. Oneothera Type:- This type of embryo sac is derived from the micropylar megaspore of the tetrad and is four nucleate. The organization of the mature embryo sac is_ an egg apparatus and a uninucleate central cell. It does not have antipodals. This type of embryo sac is characteristic of the family Onagraceae. Schisandra chinensis, however, is the only example outside this family where such a type of embryo sac occurs.
2. Bisporic embryo sac:- In plants bearing bisporic embryo sacs the first meiotic division is accomplished by wall formation, so that a dyad is formed. Only one of the dyad cells undergoes the second meiotic division whereas the other one degenerates. In the functional dyad cell wall formation does not occur after the second division, and both the megaspore nuclei contribute to the formation of the embryo sac. Each megaspore nucleus undergoes two mitotic divisions forming eight nuclei.
On the basis of the position of functional dyad bisporic embryo sacs are of two types:
i. Allium Type:- The embryo sac is derived from the chalazal dyad cell.
ii. Endymion Type:- The embryo sac is formed by the micropylar dyad cell.
3. Tetrasporic embryo sac:- In this type of embryo sac, meiotic division of the megaspore mother cell is not accompanied by cytokinesis and hence all the four haploid nuclei lie in a single cell called Coenomegaspore. All four nuclei of coenomegaspore participate in the formation of embryo sac. Genetically, it is more heterogeneous than bisporic type of embryo sac because the four products of meiosis involved in its formation are genetically different. The tetrasporic embryo sacs are further divided into many types:
i. Adoxa Type:- It has 8 nuclei which are formed by the mitotic division of the four haploid nuclei of the coenomegaspore. The arrangement of the 8 nuclei in the embryo sac is the same as in Polygonum type. Example –Adoxa, Sambucus, Ulmus, Tulipa, Erythronium etc.
ii. Plumbago Type:- This type of embryo sac is characterized by the absence of synergids and antipodals. Out of four haploid coenomegaspore one migrates to the micropylar end, one at chalazal end and two at the lateral sides. Each nuclei divides again and formed four groups of two nuclei. One of the nucleus from each group moves to the center of the cell and form four polar nuclei. The remaining nucleus at the micropylar is cut off by a membrane and form the egg. There are no synergids. The other three nuclei usually disappear but occasionally they too may be cut off by membranes and appear as accessory egg cells. Example –Plumbaginaceae family.
.bmp)
iii. Penaea Type:- The four haploid nuclei of the coenomegaspore undergo two successive mitotic divisions forming 16 nuclei. These nuclei arrange themselves in four groups of four each, one at the micropylar end, one at chalazal end and one each on the two lateral sides. Now one nucleus from each groups migrates to the centre, and these four nuclei in the centre form polar nuclei. The three nuclei at the micropylar end are cut off by membranes and form the egg apparatus. The remaining three groups of nuclei (one chalazal and two lateral) degenerate at maturity. Example –Family Penaeaceae, Malpighiaceae and Euphorbiaceae.
.bmp)
iv. Peperomia Type:- The egg apparatus of Peperomia type is characterized by a single synergid. The four haploid nuclei of coenomegaspore undergo two successive mitotic divisions forming 16 nuclei. Two nuclei at the micropylar end form egg and a synergid, eight fuse in the centre of the cell to form a polar nucleus and the remaining six at the chalazal end formed antipodals. Example-Peperomia and Gunnera.
v. Drusa Type:- 16 nucleate embryosac. This type of embryo sac is characterized by large number of antipodals. In the mature embryo sac three nuclei form egg apparatus. Two act as polar nuclei and the remaining 11 nuclei are cut off by membrane and form antipodal cells. The number and organization of nuclei may vary due to irregularity in the divisions. Example– Drusa, Rubia, Chrysanthemum,Ulmus etc.
%20of%20New%20Picture.png)
Self Incompatibility (स्वअनिषेच्यता):-
· जब एक पुष्प के परागकण उसी पुष्प या उसी पौधे के अन्य पुष्प को निषेचित करने में असमर्थ होते हैं तथा अन्य पौधे के पुष्प को निषेचित करने में समर्थ होते हैं तो इसे स्वअनिषेच्यता कहते हैं। लगभग 3000 से भी अधिक पौधों में यह पायी जाती है।
(When pollens of a flower are unable to fertilize the same flower or other flower of the same plant and are able to fertilize the flower of the other plant, it is called self-incompatibility. It is found in more than 3000 plants.)
· जब एक अनिषेच्य परागकण वर्तिकाग्र को परागित करता है तो यह निम्न 4 अवस्थाओं में से किसी एक पर वृद्धि को रोक लेता है जिससे स्व निषेचन असफल हो जाता है:-
(When an incompatible pollen pollinates the stigma, it stops growth at any one of the following 4 stages, causing failure of self-fertilization:-)
i. वर्तिकाग्र पर परागकण अंकुरित नहीं होता है।
(Pollen does not germinate on stigma.)
ii. वर्तिकाग्र पर परागकण अंकुरित होता है परन्तु परागनाल वर्तिकाग्र को भेद नहीं पाती है।
(Pollen germinates on the stigma, but the pollen tube does not penetrate the stigma.)
iii. परागनाल वर्तिकाग्र को भेदने के पश्चात बहुत धीमी गति से वृद्धि करती है।
(The pollen tube grows very slowly after penetrating the stigma.)
iv. निषेचन होने पर भ्रूण अत्यन्त तरुण अवस्था में ही नष्ट हो जाता है।
(Upon fertilization, the embryo is destroyed in a very young state.)
Interspecific incompatibility (अंतरजातीय असंगति):- Interspecific incompatibility refers to the failure of pollen from one species to germinate and/or grow on the stigma of another species. Intraspecific incompatibility is incompatibility that occurs within a species.
[अंतरजातीय असंगति से तात्पर्य एक प्रजाति के परागकणों के दूसरी प्रजाति के वर्तिकाग्र पर अंकुरित होने और/या उगने में विफलता से है। अंतरजातीय असंगति वह असंगति है जो किसी प्रजाति के भीतर होती है।]
%20of%20New%20Picture.png)
In-vitro pollination:-
Introduction:-
> ‘vitro’ means glass or glassy substances. So, ‘in vitro’ means in glass or glass tube. Cultivation of plant tissue or other organs on artificial media in a test tube or conical flask is called in vitro technique.
> The process of seed formation following stigmatic pollination of cultured pistil has been referred to as in vitro pollination and the development of seed through in vitro fertilization.
History:-
> German Botanist Harberlandt (1902) develops the concept of in vitro culture.
> This in vitro pollination technique was developed at university of Delhi to produce hybrid among species of pavaceraceae and solanece. Barriers during pollination and fertilization of in vitro technique
> Pollination and fertilization under in vitro condition offer an opportunity for producing hybrid embryos among plants that can’t be crossed by conventional method of plant breeding.
> In hybridization programs, transferring viable pollen from one parent to another does not always lead to seed setting.
Types of in vitro pollination:-
i. Ovular pollination:- Application of pollen to excised ovule.
ii. Ovarion pollination:- Application of pollen to excised ovary.
iii. Placental pollination:- Application of pollen to ovules attached to the placenta.
iv. Stigmatic pollination:- Application of pollen to stigma.
.png)
Tapetum:-
> A tapetum is the deepest layer of the anther, which encompasses the sporogenous tissue. The sporogenous tissue produces microspores that supply enzymes and nutrition for pollen development. Tapetum is mostly multinucleated due to mitotic cell division. Abnormal cell division can also lead to tapetum polyploidy.
> The tapetum is a huge structure, and thus can absorb food and provide nutrition to the development of the pollen grains. They also aid the regulatory molecules that help in the formation of the pollen grains. The cells of tapetum have dense cytoplasm.
Structure of Tapetum:-
Tapetum is a thick single-celled nutritive layer found behind the epidermis and endodermis. Their cells are initially diploid in nature but can become polyploid due to abnormal cell division. Their primary role is to absorb nutrition from the middle layer, and provide it to the microsporocytes. Also, the tapetum cells can secrete enzymes and hormones. The tapetum layer is almost lost in the mature anther.
Types of Tapetum:-
i. Secretory or Glandular Tapetum:- They surround the anther locule. This type of secretory tapetum is more common in angiosperms.
ii. Amoeboid or Plasmodial Tapetum:- After the disintegration of the tapetal cell wall, a multinucleate structure, along with the cell protoplast called the plasmodium tapetum, is formed.
Role of Tapetum in Pollen Development:-
i. Tapetum provides nutrition for the developing pollen grains.
ii. They also act as a precursor source for the pollen wall or pollen coat.
iii. It transports supplements to the anthers.
iv. Pollenkitt is also formed by the tapetal cells around the microsporocytes. This pollenkitt is responsible for nutrition and pollen development.
v. The tapetal cells act as a precursor to sporopollenin. The outer wall of pollen grains contains a chemical called sporopollenin that protects the pollen from harsh external factors.
vi. Tapetum expels Ubisch bodies, which helps thicken the pollen grain membrane. These ubisch bodies or orbicules are a part of the sporopollenin.
vii. Also, it secretes the callase enzyme that breaks the callose compounds used to unite four pollens (pollen tetrad). Thus, they allow pollens from a tetrad to be separated.
.png)
परागकोष संवर्धन (Anther Culture):-
1. परिचय (Introduction):-
· परिभाषा (Definition):- यह एक कृत्रिम तकनीक है जिसके द्वारा परिवर्धित हो रहे परागकोषों को एक बन्द पुष्प कालिका से एक ठीक व नाजुक अवस्था पर निकाला जाता है और पोषक माध्यम पर संवर्धित किया जाता है। जहाँ परागकोष के अंदर उपस्थित लघुबीजाणु कैलस ऊतक या भ्रूण समान संरचना में विकसित हो जाते हैं जो अंग निर्माण या भ्रूण निर्माण के माध्यम से अगुणित पौधों का निर्माण करते हैं।
(It is an artificial technique by which the developing anthers are collected from a closed floral bud at a fine and delicate stage and cultured on a nutrient medium. Where the microspores develop into callus tissue or embryo like structure, that develop haploid plants through organ formation or embryo formation.)
· अभी तक लगभग 250 पादप जातियों में परागकोष संवर्धन किया गया है। तीन कुलों में अधिक सामान्य है –
(So far anthers have been cultured in about 250 plant species. The three families are more common -)
i. Solanaceae
ii. Criciferae
iii. Poaceae
2. इतिहास (History):-
· W. Tulecke (1953):- इसने सबसे पहले देखा कि अनावृतबीजी पौधे Ginkgo biloba के परिपक्व परागकणों को संवर्धन में अगुणित कैलस निर्माण के लिए प्रेरित किया जा सकता है।
(He first observed that mature pollens of the gymnosperm plant Ginkgo biloba can be induced to form haploid callus in culture.)
· S. Guha and P. Maheshwari (1964):- इन्होने सबसे पहले देखा कि Datura innoxia के निकाले गए परागकोषों के संवर्धन से लघुबीजाणुओं से भ्रूणो का प्रत्यक्ष विकास होता है।
(They first observed that the embryos are developed from the microspores directly in anther culture of Datura innoxia.)
· J. P. Bourgin and J. P. Nitsch (1967):- इन्होने तंबाकू (Nicotiana tabacum) के परागकोष संवर्धन द्वारा पूर्ण रूप से अगुणित पौधे प्राप्त किए।
[They obtained fully haploid plants by the anther culture of tobacco (Nicotiana tabacum).]
· Niizeki and Oono (1968):- ये जापान के वैज्ञानिक थे। इन्होने धान में परागकोष संवर्धन करके पादप प्रजनन के लिए अगुणित पौधे विकसित किए।
(He was a Japanese scientist. He developed haploid plants for plant breeding by anther culture in paddy.)
3. सिद्धान्त (Principle):-
· लघुबीजाणु की पूर्णशक्तता के उपयोग से अगुणित पौधे का निर्माण किया जाता है।
(The haploid plant is produced using the totipotency of the microspore.)
· लघुबीजाणु में गुणसूत्रों का केवल एक समुचय उपस्थित होता है।
(Only one set of chromosomes is present in the microspore.)
· अगुणित पादप निर्माण की प्रक्रिया में लघुबीजाणु का नर युग्मक निर्माण का सामान्य विकास व कार्य रुक जाता है। कायिक कोशिका विभाजन के लिए इसे बलपूर्वक नए उपापचय पथ की ओर मोड़ दिया जाता है।
(In the process of haploid plant development, the normal growth and functioning of the microspore of developing male gametes is halted. It is forced into a new metabolic pathway for somatic cell division.)
· परागकोष संवर्धन में परागकोष के अंदर उपस्थित लघुबीजाणु के प्राकृतिक आवास व वातावरण को परिवर्तित नहीं किया जाता है। संवर्धन परिस्थितियों में माध्यम पर परागकोष का द्विगुणित ऊतक बिना विभाजन किए जीवित रहता है और पोषण प्रदान करके लघुबीजाणु के कायिक विभाजन को प्रेरित करता है।
(Anther culture does not alter the natural habitat and environment of the microspores present inside the anther. In culturing conditions, the diploid tissue of the anther survives on the medium without cell division and induces somatic cell division of the microspore by providing nutrition.)
4. विधि (Procedure):-
· पुष्पन पर तंबाकू की बन्द पुष्पीय कलिकाओं को एकत्रित करते हैं। 17 – 22 mm लंबाई की पुष्पीय कालिका का चयन करते हैं जब बाह्यदलों की लंबाई दलों की लंबाई के बराबर होती है। खुल रही सभी पुष्पीय कलिकाओं को त्याग देते हैं।
(Collect the closed floral buds of tobacco upon flowering. A floral bud of length 17 - 22 mm is selected when the length of the sepals is equal to the length of the petals. Discards all floral buds are to be opened.)
· चयनित पुष्पीय कलिकाओं को LAF कैबिनेट के अन्दर ले जाते हैं। प्रत्येक पुष्पीय कलिका में 5 परागकोष होते हैं और बन्द कलिकाओं के अन्दर इनकी सतह स्वत: निर्जमित होती है। पुष्पीय कलिकाओं के सतही निर्जमीकरण के लिए इन्हें पहले 10 सेकंड के लिए 70% ऐथेनोल में डुबोकर रखते हैं और फिर 10 मिनट के लिए 20% सोडियम हाइपोक्लोराइट विलयन में डुबोकर रखते हैं। अतिरिक्त रसायन को सतह से हटाने के लिए पुष्पीय कलिकाओं को निर्जमित आसुत जल से 3 बार धोते हैं। अंत में इन पुष्प कलिकाओं को निर्जमित पेट्रीडिश में स्थानांतरित कर देते हैं।
(Selected floral buds are carried inside the LAF cabinet. Each floral bud has 5 anther and its surface is sterilized automatically inside the closed buds. For surface sterilization of the floral buds, first of all dip them in 70% ethanol for 10 seconds and then in 20% sodium hypochlorite solution for 10 minutes. To remove excess chemicals from the surface, the floral buds are washed 3 times with sterilized distilled water. Finally these floral buds are transferred to the sterilized patridish.)
· अब एक तीखे चाकू के द्वारा कालिका के एक तरफ कट लगाते हैं और चिमटी की सहायता से दलों व बाह्यदलों को हटा देते हैं। अब एक अन्य चिमटी की सहायता से 5 पुंकेसरों को पुतन्तु सहित उखाड़कर एक अन्य निर्जमित पेट्रीडिश में स्थानांतरित करते हैं। अब 5 पुंकेसरों के पुतन्तुओं को चाकू या ब्लेड से काटकर अलग कर देते हैं जिससे केवल परागकोष रह जाते हैं। क्षतिग्रस्त परागकोषों को भी त्याग देते हैं।
(Now with a sharp knife, cut one side of the floral bud and remove the petals and sepals with the help of forceps. Now with the help of another forceps, collect 5 stamens along with their filaments and transfer them to another sterilized patridish. Now cut the filaments of 5 stamens with a knife or blade, leaving only the anthers. Damaged anthers are also discarded.)
· अब इन स्वस्थ व साबुत परागकोषों को ठोस अगार माध्यम पर स्थापित करते हैं। परागकोष संवर्धन के लिए निम्न में से कोई एक माध्यम उपयोग किया जाता है-
(Now these healthy and intact anthers are placed on solid agar medium. One of the following mediums is used for anther culture -)
i. MS माध्यम (MS medium)
ii. White माध्यम (White's medium)
iii. Nitsch & Nitsch माध्यम (Nitsch and Nitsch medium)
· प्रारम्भ में संवर्धन को अंधेरे में रखा जाता है। 3 – 4 सप्ताहों में परागकोष के अंदर उपस्थित लघुबीजाणु भ्रूणजनन करते हैं और संवर्धित परागकोषों से अगुणित भ्रूण बन जाते हैं। कुछ पौधों में परागकोष के प्रवर्धन द्वारा कैलस ऊतक का निर्माण हो सकता है जिन्हें अगुणित प्लांटलेट्स बनाने के लिए प्रेरित किया जा सकता है।
(Initially the culture is kept in the dark. In 3–4 weeks, the microspores present inside the anther show embryogenesis and haploid embryos are developed from cultured anther. In some plants anther culture can lead to the formation of callus tissue that can be induced to form haploid plantlets.)
· अब इन अगुणित भ्रूणो को नये ताजा अगार माध्यम पर संवर्धन ट्यूब में स्थापित करते हैं। इस अवस्था पर संवर्धनों का 24 – 28°C ताप पर ऊष्मायन किया जाता है। 14 घंटे का प्रकाश व 10 घंटे का अंधकार दिया जाता है। प्रकाश की तीव्रता 2000 लक्स रखी जाती है।
(Now these haploid embryos are established on a new fresh agar medium in culture tube. At this stage the cultures are incubated at 24 - 28 ° C temperature. 14 hours of light and 10 hours of darkness are given. Light intensity is maintained at 2000 lux.)
· जब अगुणित प्लांटलेट्स की लंबाई 50 mm हो जाती है तो अगार माध्यम से स्वतंत्र करने के लिए नल के बहते हुए पानी में धोया जाता है। अब तुरन्त इन्हें औटोक्लेवित कम्पोस्ट युक्त छोटे गमलों में रोपित कर दिया जाता है। शुष्कन को रोकने के लिए प्रत्येक पौधे को काँच के बीकर से ढक देते हैं और आगे के परिवर्धन के लिए नम ग्रीन हाउस में रख देते हैं। कुछ सप्ताहों पश्चात काँच के बीकरों को हटा देते हैं और पौधों को मृदा युक्त बड़े गमलों में रोपित कर देते हैं जहाँ ये पौधे परिपक्व होकर अंत में पुष्पन करते हैं।
(When the length of haploid plantlets becomes 50 mm, they are washed in running tap water to free them from the agar medium. Now they are immediately planted in small pots containing autoclaved compost. To prevent drying, cover each plant with a glass beaker and place it in a moist greenhouse for further growth. After a few weeks, the glass beakers are removed and the plants are planted in large pots containing soil where these plants mature and eventually flowering.)
.png)
Polyembryony:- Presence of more than one embryo inside the seed is known as polyembryony. It was first reported by A.V. Leuwenhoek (1719) in Citrusi Fam-Rutaceae).This phenomenon is very common in gymnosperm than angiosperm. Besides normal embryoe (develops from Zygote), other embryos are formed inside seed maybe as haploid (n) or Diploid (2n).
Types of Polyembryony:-
i. Induced Polyembryony:- When polyembryony is induced in plants and animals for experiments, it is referred to as induced polyembryony.
ii. Spontaneous Polyembryony:- When polyembryony occurs naturally in plants and animals, it is called natural or spontaneous polyembryony.
iii. True polyembryony:- Many embryos are developed inside single embryo sac.
iv. False polyembryony:- If the ovule carries more then one embryo sac & embryos develop in each embryo sac.
v. Cleavage polyembryony:- In cleavage polyembryony, a single fertilised egg can give rise to multiple embryos. When an embryo divides into several identical parts, each part can develop into a mature embryo. A common example of cleavage polyembryony is seen in Pinus.
vi. Simple polyembryony:- This type of polyembryony occurs when several archegonia are fertilised. When more than one egg is fertilised, it is called simple polyembryony. Adventive polyembryony is the formation of additional embryos through sporophytic budding. It is common in Cycas, lemon, groundnut, mango, Pinus, onion, and orange.
vii. Rosette polyembryony:- In rosette polyembryony, multiple additional embryos are produced from cells known as rosette cells.
Cause of polyembryony in angiosperm:- Polyembryony takes place due to:
i. Cleavage of proembryo:- It is simplest method of polyembryony where zygote divides into many units & each unit develops an embryo.
ii. Development of many embryo from synergid, antipodal cells, endosperm except egg.
iii. Development of many embryo due to presence of more than one embryo sac.
iv. Development of polyembryo from nucellus, integument (outside the embryo sac). According to Haberiandt (1921)” Stimulus for polyembryony is provided by degenerating cells nucelleus Necrohormone theory).
Importance of Polyembryony:-
i. Plant breeding and horticulture:- The embryos in fruit trees, such as citrus and mango, are often free from genetic variation, making them valuable for maintaining desirable traits in new generations of plants.
ii. Nucellar disease:- Polyembryony plays a role in the propagation of fruit trees, as the embryos produced are genetically uniform, helping to ensure consistent quality and characteristics in seedlings.
iii. Propagation:- Polyembryony offers a method for developing homozygous diploid plants, which can be advantageous in breeding programmes aimed at fixing desirable traits.
iv. Artificial production:- Polyembryony can be artificially induced to produce genetically uniform plant material from eggs or synergids, ensuring the quality and productivity of fruit tree crops.
.png)
असंग जनन (Apomixis):- जब जनक पौधे से भ्रूण व बीज का निर्माण बिना निषेचन के होता है तो इसे असंग जनन कहते हैं। बीजांड की कोई भी कायिक कोशिका ज़ाइगोट के समान कार्य करने लगती है। इसके फलस्वरूप बने संतति पौधे अपने जनकों के क्लोन होते हैं। यह तीन प्रकार का होता है -
(When embryo and seed are produced from the parent plant without fertilization, it is called asexual reproduction. Any vegetative cell of the ovule acts as a zygote. The resulting seedlings are clones of their parents. It is of three types -)
a. अपस्थानिक भ्रूणता (Adventive Embryony)
b. अपबीजाणुकता (Apospory)
c. द्विबीजाणुकता (Diplospory)
a. अपस्थानिक भ्रूणता (Adventive Embryony):- जब भ्रूण का विकास बीजाण्ड की किसी कायिक कोशिका (अध्यावरण या बीजाण्डकाय या निभाग) से बिना भ्रूणकोष बने होता है तो इसे अपस्थानिक भ्रूणता कहते हैं। जैसा कि नीचे diagram में प्रदर्शित किया गया है। उदाहरण:- नींबू, आम आदि।
(When the embryo develops from a vegetative cell of ovule (integument or nucellus or challaza) without the formation of embryo sac, it is called adventive embryony. As shown in the diagram below. Examples: Lemon, mango etc.)
b. अपबीजाणुकता (Apospory):- जब भ्रूणकोष का विकास बीजाण्ड की किसी कायिक कोशिका (अध्यावरण या बीजाण्डकाय या निभाग) से बिना अर्धसूत्री विभाजन हुए होता है तो इसे अपबीजाणुकता कहते हैं। अर्थात यहाँ गुरुबीजाणु का निर्माण नहीं होता है। भ्रूणकोष की प्रत्येक कोशिका द्विगुणित होती है। भ्रूणकोष की किसी भी एक कोशिका से भ्रूण बन जाता है। जैसा कि नीचे diagram में प्रदर्शित किया गया है। उदाहरण:- Crepis
(When the development of the embryo sac occurs without meiosis from any vegetative cell of ovule (integument or nucellus or challaza), it is called as apospory. It means megaspore is not produced here. Each cell of the embryo sac is diploid. An embryo is developed from any one cell of the embryo sac. As shown in the diagram below. Example: - Crepis)
c. द्विबीजाणुकता (Diplospory):- जब भ्रूणकोष का विकास द्विगुणित गुरुबीजाणु से होता है तो इसे द्विबीजाणुकता कहते हैं। गुरुबीजाणु का निर्माण बिना अर्धसूत्री विभाजन के होने के कारण यह द्विगुणित होता है। अत: भ्रूणकोष की प्रत्येक कोशिका भी द्विगुणित होती है। जैसा कि नीचे diagram में प्रदर्शित किया गया है।
(When the embryo sac develops from a diploid megaspore, it is called as diplospory. Megaspore is diploid because it is formed by mitosis instead of meiosis. Therefore, each cell in the embryo sac is also diploid. As shown in the diagram below.)
भ्रूण का विकास निषेचन के बिना होता है। भ्रूण का विकास भ्रूणकोष की कौनसी कोशिका से होता है, इस आधार पर द्विबीजाणुकता 2 प्रकार की होती है-
(Embryo development occurs without fertilization. Depending upon the embryo develops from which cell of the embryo sac, there are 2 types of diplospory -)
i. अनिषेकजनन (Parthenogenesis)
ii. अपयुग्मन (Apogamy)
i. अनिषेकजनन (Parthenogenesis):- जब भ्रूण का विकास अण्ड कोशिका से होता है तो इसे अनिषेकजनन कहते है। जैसा कि नीचे diagram में प्रदर्शित किया गया है। उदाहरण:- Taraxacum (घास)
[When the embryo develops from the egg cell, it is called parthenogenesis. As shown in the diagram below. Example: - Taraxacum (grass)]
ii. अपयुग्मन (Apogamy):- जब भ्रूण का विकास प्रतिमुखी कोशिका या सहायक कोशिका से होता है तो इसे अपयुग्मन कहते हैं। जैसा कि नीचे diagram में प्रदर्शित किया गया है। उदाहरण:- प्याज
(When the embryo develops from the antipodal cell or the synergid, it is called apogamy. As shown in the diagram below. Example: - Onion)
Importance of apomixis:-
i. Development of Purelines:- Apomixis is an effective means of rapid production of pure lines. Haploid parthenogenesis and haploid apogamy give rise to haploid plants which after colchicine treatment will produce diploid purelines. Such purelines can be used in breeding programmes for developing high yielding cultivars and hybrids.
ii. Maintenance of Purity:- The obligate apomixis breeds true for the characteristics of mother plant. Thus it is useful in maintaining the genetic purity from generation to generation. It can maintain a genotype for unlimited number of generations. In other words, apomictic lines always breed true irrespective of homozygosity and heterozygosity.
iii. Conservation of Heterosis:- The obligate recurrent apomixis is useful in conserving heterosis or hybrid vigour for unlimited generations. Apomixis does not permit segregation. Hence heterosis can be easily conserved.
iv. Easy Hybrid Seed Production:- Apomixis provides an easy way of hybrid seed production. The hybrid seed is automatically produced by apomictic means. There is no need of crossing. In other words, in apomictic genotypes crossing is not required for hybrid seed production. Once the hybrid is developed using apomictic line as one of the parents, the hybrid seed production will occur automatically. Thus it permits commercial seed production of hybrids.
v. Cheaper Hybrid Seed:- Use of apomixis is the cheaper way of hybrid seed production. It does not require crossing. Hence it helps in saving lot of money which is required for engaging labourers for crossing purpose in conventional hybrids for production of hybrid seed.
vi. Easy for Handling:- The handling of apomictic genotypes is easy. When the hybrid is developed using apomixes, we have to handle one genotype only. When the hybrid is developed using cytoplasmic genie male sterility, the breeder has to handle three type of material i.e. A, B and R lines. The purity of apomictic lines/genotypes is maintained automatically, whereas A, B and R lines require lot of labour and care for maintenance of their genetic purity. In other words, when obligate apomixis is available, there is no need for using male sterility for hybrid development.
vii. No Need of Isolation:- In case of apomixis, there is no need of isolation distance, where as in case of hybrid seed production by conventional method by using male sterility system, the proper isolation distance is required for maintaining the genetic purity of parental lines.
viii. No Outcrossing:- The apomixis is genetically controlled. It is governed by one or few dominant or recessive genes. Hence no seed setting occurs with cross pollination. Thus it does not permit outcrossing. In other words, contamination of apomictic genotypes through outcrossing is not possible.
ix. No Segregation:- Apomictic lines always breed true (as stated above) to the characteristics of mother plant. The hybrid seed is produced automatically. There is no need of making crosses every year to produce hybrid seed. This is the cheaper method of hybrid seed production. The apomictically propagated hybrid can be used as a variety, because it does not permit segregation.
x. Useful to Farmers:- Apomictically propagated cultivars and hybrids are useful to the farmers, because farmers can produce their own seed. Thus farmers need not to purchase fresh seed every year from seed companies.
Endosperm Haustoria:-
> Characteristic feature of cellular endosperm.
> One or more cells becomes specialized to function as haustoria.
> The haustoria are formed at micropylar or chalazal or at both the ends and penetratethe nucellar tissue to absorb nutrition.
> Some secondary haustoria are also formed in addition to micropylar and chalazal haustoria. Example- Alectra.
> Multinucleated chalazal endosperm haustorium occurs in Magnolia obovata.
.png)
Role of Embryology in Plant Breeding:-
> Embryology helps in understanding the processes of fertilization, embryo formation, and seed development, which are essential for crop improvement.
> It assists plant breeders in identifying the causes of hybrid incompatibility and fertilization failure between different species or varieties.
> Embryo rescue techniques enable the recovery of hybrid embryos that would otherwise abort, allowing the production of wide hybrids.
> It facilitates interspecific and intergeneric hybridization by overcoming post-fertilization barriers.
> Knowledge of embryo sac development helps in understanding mechanisms of self-incompatibility and cross-compatibility.
> Embryological studies aid in the development and maintenance of male sterile lines used in hybrid seed production.
> It helps in identifying the type and inheritance of male sterility (genic or cytoplasmic-genic), which is important for hybrid breeding.
> Embryology contributes to the production of haploid and doubled haploid plants through anther, microspore, and ovule culture, leading to rapid development of homozygous lines.
> It supports the development of apomictic plants, enabling the fixation and maintenance of hybrid vigor (heterosis) across generations.
> Studies of endosperm development help overcome endosperm failure in distant crosses, improving hybrid seed viability.
> Embryological knowledge is useful in detecting abnormalities during embryo and seed development, helping select viable hybrids.
> It plays an important role in polyembryony studies, which are useful in the propagation and breeding of certain horticultural crops.
> Embryological techniques support in vitro culture methods, such as ovule and ovary culture, for successful breeding of difficult crosses.
> It provides valuable information on reproductive biology, flowering behavior, and fertilization patterns, improving breeding efficiency.
> Embryology serves as a foundation for modern biotechnological approaches, including genetic transformation, somatic embryogenesis, and synthetic seed technology, thereby accelerating crop improvement programs.
भ्रूणविज्ञान का पादप प्रजनन में योगदान:-
> भ्रूणविज्ञान (Embryology) निषेचन, भ्रूण निर्माण तथा बीज विकास की प्रक्रियाओं को समझने में सहायता करता है, जो फसल सुधार का आधार हैं।
> यह विभिन्न जातियों एवं प्रजातियों के बीच संकरण (Hybridization) में होने वाली असंगति तथा निषेचन विफलता के कारणों की पहचान करने में सहायक होता है।
> भ्रूण बचाव (Embryo Rescue) तकनीक द्वारा ऐसे संकर भ्रूणों को विकसित किया जा सकता है जो सामान्य परिस्थितियों में नष्ट हो जाते हैं।
> यह अंतर-प्रजातीय (Interspecific) एवं अंतर-वंशीय (Intergeneric) संकरण में निषेचनोत्तर (Post-fertilization) बाधाओं को दूर करने में सहायक है।
> भ्रूणकोष (Embryo Sac) के विकास का अध्ययन स्व-असंगति (Self-incompatibility) एवं पर-अनुकूलता (Cross-compatibility) की क्रियाविधि को समझने में मदद करता है।
> भ्रूणविज्ञान संकर बीज उत्पादन में प्रयुक्त नर बंध्यता (Male Sterility) रेखाओं के विकास एवं अनुरक्षण (Maintenance) में महत्वपूर्ण भूमिका निभाता है।
> यह नर बंध्यता के प्रकार (जीनीय, साइटोप्लाज्मिक अथवा साइटोप्लाज्मिक-जीनीय) एवं उसकी वंशागति को समझने में सहायता करता है, जिससे संकर प्रजनन अधिक प्रभावी बनता है।
> एन्थर, सूक्ष्मबीजाणु (Microspore) तथा बीजांड (Ovule) संवर्धन द्वारा हैप्लॉइड एवं डबल्ड हैप्लॉइड पौधों के उत्पादन में सहायता करता है, जिससे शीघ्र शुद्ध (Homozygous) रेखाएँ विकसित की जा सकती हैं।
> एपोमिक्सिस (Apomixis) के अध्ययन द्वारा संकर बल (Heterosis) को पीढ़ी-दर-पीढ़ी स्थिर बनाए रखने में सहायता मिलती है।
> एण्डोस्पर्म (Endosperm) के विकास का अध्ययन दूरस्थ संकरणों में एण्डोस्पर्म विफलता की समस्या को दूर कर संकर बीजों की जीवितता बढ़ाने में सहायक है।
> भ्रूण एवं बीज विकास के दौरान उत्पन्न असामान्यताओं की पहचान कर स्वस्थ एवं जीवक्षम संकरों के चयन में सहायता करता है।
> बहुभ्रूणता (Polyembryony) के अध्ययन से विशेषकर बागवानी फसलों के प्रजनन एवं प्रवर्धन में लाभ मिलता है।
> बीजांड संवर्धन (Ovule Culture) तथा अंडाशय संवर्धन (Ovary Culture) जैसी इन विट्रो (In vitro) तकनीकों को सफल बनाने में भ्रूणविज्ञान महत्वपूर्ण आधार प्रदान करता है।
> यह पौधों की प्रजनन जीवविज्ञान (Reproductive Biology), पुष्पन व्यवहार तथा निषेचन की प्रक्रियाओं को समझने में सहायता करता है, जिससे प्रजनन कार्यक्रम अधिक सफल बनते हैं।
> भ्रूणविज्ञान आधुनिक जैव-प्रौद्योगिकी तकनीकों, जैसे सोमैटिक भ्रूणजनन (Somatic Embryogenesis), आनुवंशिक रूपांतरण (Genetic Transformation) तथा कृत्रिम बीज (Synthetic Seed) तकनीक, के विकास एवं उपयोग का आधार है, जिससे फसल सुधार की गति तेज होती है।
.png)
%20of%20New%20Picture.png)
.bmp)
%20of%20New%20Picture.png)
%20of%20New%20Picture.png)
.png)
%20of%20New%20Picture.png)
.bmp)
.bmp)
.bmp)
.bmp)
.bmp)
.bmp)
.bmp)
.bmp)
.png)
.png)
%20of%20New%20Picture.png)
%20of%20New%20Picture.png){kind=small}
.bmp)
.png)
.png)
.png)
.png)
.png){kind=small}
.png)
.png)
.png)
.png)
.png)