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Is their any difference b/w Double Fertilization and Triple Fusion.

Please explain me meaning of both the words

Double fertilization and triple fusion are the two phenomena related to the fertilization in plants. Triple fusion is one of the fusion other than syngamy that takes place during double fertilisation.

Double Fertilization:

During fertilization in plants, two pollen nuclei (male gametes) enter inside the ovule. In the ovule one male nucleus  fuses with the egg cell to form zygote called syngamy and other male gamete fuses with the two polar nuclei or secondary nuclei to form the triploid endosperm. As this involves fusion of three haploid nuclei (two polar nuclei and one male gamete), it is termed as triple fusion.  As the two types of the fusions, syngamy and triple fusion take place in an embryo sac, the phenomenon is  termed as double fertilization. 

 

 

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the fusion of one of the male gametewith secondary nucleus is termad as triple fusion it involves the fosiun of 3 nuclei

one male gamete fuses with the egg cell and other with fused nuclei of polar bodies is termed as double fertilization. it involves the fusion of 2 nucei

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Double fertilisation is type of fertilization in which male gamete fuses with female gamete resulting to zygote formation. After this another male gamete fuses the secondary nucleus resulting to endosperm nucleus formation, this is called Triple Fusion.

•Homosporous plants are those plants which produce spores of same size and type while Heterosporous plants are those plants which produce spores of two size. Larger spores function as female while smaller as male

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 triple fusion- the fusion of one of the male gamates with secondary nucleus is termed as triple fusion, as it involves the fusion of three nuclei.

double fertilization- in flowering plants, each pollen grain produces two male gamates. one male gamate fuses with the female gamate and the other fuses with secondary nucleus. since there are two fertilizations, it is called double fertilisation.

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Fertilisation in Plants

 

The pollen grains which reach the sticky stigma, absorb these secretions, swells up and ruptures at one of the germ pores. The thin intine emerges out in the form of a pollen tube which continues to grow and penetrates deep into the style.

 

stages in the germination of pollen grain

 

(A - E), A, a microspore of an angiosperm;B E, stages in the germination of pollen grain anddevelopment of male gametophytes

The contents of the pollen grain move into the pollen tube. The tube nucleus moves first and comes to lie at the tip of the pollen tube. This is followed by the migration of the generative cell or the two male gametes if they have already formed.

Longitudinal section of a flower

Longitudinal section of a flower showing germination of pollen grains and the phenomenon of fertilization. One pollen tube has grown through the style and has entered the embryo sac through the micropyle

The pollen tube enters into the ovule, through the micropyle. Inside the embryo sac, the tip of the pollen tube ruptures and the 2 male gametes are set free near the egg apparatus. Inside the embryo sac, one of the 2 male gametes fuses with the egg nucleus and forms a diploid zygote. This process is called syngamy or true fertilisation. The other male gamete pushes further into the embryo sac and fuses with the secondary nucleus and gives rise to a triploid nucleus called the primary endosperm nucleus. This process of nuclear fusion is called triple fusion.

This entire phenomenon of fertilisation involving the fusion of the egg and one of the male gametes, together with the union of the second male gamete with the secondary nucleus or the polar nuclei is called as double fertilisation.

ovule showing different stages of fertilisation

Longitudinal section of an ovule showing different stages of fertilisation

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3: Plant Kingdom

In the previous chapter, we looked at the broad classification of living organisms under the system proposed by Whittaker (1969) wherein he suggested the Five Kingdom classification viz. Monera, Protista, Fungi, Animalia and Plantae. In this chapter, we will deal in detail with further classification within Kingdom Plantae popularly known as the ‘plant kingdom’.

We must stress here that our understanding of the plant kingdom has changed over time. Fungi, and members of the Monera and Protista having cell walls have now been excluded from Plantae though earlier classifications put them in the same kingdom. So, the cyanobacteria that are also referred to as blue green algae are not ‘algae’ any more. In this chapter, we will describe Plantae under Algae, Bryophytes, Pteridophytes, Gymnosperms and Angiosperms.

Let us also look at classification within angiosperms to understand some of the concerns that influenced the classification systems. The earliest systems of classification used only gross superficial morphological characters such as habit, colour, number and shape of leaves, etc. They were based mainly on vegetative characters or on the androecium structure (system given by Linnaeus). Such systems were artificial; they separated the closely related species since they were based on a few characteristics. Also, the artificial systems gave equal weightage to vegetative and sexual characteristics; this is not acceptable since we know that often the vegetative characters are more easily affected by environment. As against this, natural classification systems developed, which were based on natural affinities among the organisms and consider, not only the external features, but also internal features, like ultra- structure, anatomy, embryology and phytochemistry. Such a classification for flowering plants was given by George Bentham and Joseph Dalton Hooker.

At present phylogenetic classification systems based on evolutionary relationships between the various organisms are acceptable. This assumes that organisms belonging to the same taxa have a common ancestor. We now use information from many other sources too to help resolve difficulties in classification. These become more important when there is no supporting fossil evidence. Numerical Taxonomy which is now easily carried out using computers is based on all observable characteristics. Number and codes are assigned to all the characters and the data are then processed. In this way each character is given equal importance and at the same time hundreds of characters can be considered. Cytotaxonomy that is based on cytological information like chromosome number, structure, behaviour and chemotaxonomy that uses the chemical constituents of the plant to resolve confusions, are also used by taxonomists these days.

 
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 double fertilisation is the process , in which two fusions, syngamy and triple fusion take place.

the fusion of the one male gamete with the egg which is contained in the embryo sac of the ovule is called syngamy and its product is the zygote.

the other male gamete fuses with the two polar nuclei and this process is called triple fusion, where three nuclei are involved in the fusion process, one male gamete and two polar nuclei.

 

hope it helps......

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 DOUBLE FERTILISATION

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Sample Paper – 2008

Class – X

Subject – Science


 

  1. Mention the advantages of sexual reproduction over a asexual.

  2. What is the difference between unisexual and bisexual (hermaphrodite)?

  3. What are various methods of vegetative propagation? Discuss any one method with example.

  4. What are the advantages of vegetative propagation?

  5. Explain the term fission, regeneration, budding, layering as used in relation to reproduction.

  6. Which method would you apply to cultivate Rose and Jasmine plant? Explain.

  7. What is tissue culture? Explain.

  8. How does Bryophyllum reproduce vegetatively?

  9. Explain how grafting is done in certain plants during vegetative propagation in plants.

  10. How are stock and scion interrelated?

  11. Name the reptile in each case where higher temperature results in a) Male progeny, b) Female progeny.

  12. Fusion of male and female gamete is called_____. What is the product of this process?

  13. Draw a labeled diagram of flower. What happens to the pollen of a mango flower if it falls on stigma of some other flower?

  14. In flowering plants, there occurs ‘double fertilization and triple fusion’. Briefly explain the events and justify the above phrase.

  15. Draw the labeled longitudinal region diagram of the Pistil.

  16. What is Pollination?

  17. Differentiate between self and cross pollination.

  18. Explain fertilization in plants with diagram (With the help of diagram explain double fertilization in plants).

  19. Describe the terms in relation to the human reproduction:
    1. Fertilisation 2. Implantation 3. Placenta 4. Gestation 5. Parturition

  20. What do you mean by Menarche and Menopause?

  21. Where do you find follicles and what is its function?

  22. Define ovulation.

  23. Explain male and female reproductive organ in detail? Draw diagram also?

  24. With a labeled diagram describe the female reproductive system.

  25. What are IUCD’s? Give two examples.

  26. Write full form of HIV and AIDS.

  27. Name any two sexually transmitted diseases.

  28. What are the male and female organs in human beings? What are the enzymes secreted by them and their functions?

  1. Why copper T is made up of copper?

  2. What is syngamy?

  3. What is puberty?

  4. Differentiate between binary fusion and multiple fusion?

  5. Draw a labeled diagram of budding in hydra?

  6. How does oral contravites work? What is their role?

  7. Where is testis located in human male body? Give the reasons?

  8. Where is ovary located in human female body? Give the reasons?

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