#microsporogenesis

[whats-in-a-sentence]

During microsporogenesis, archesporial cells within the locules differentiate into microsporocytes, or pollen mother cells – diploid cells capable of undergoing meiosis to produce the microspores (Figure 21.3A). (...) The tapetum, a layer of secretory cells surrounding the locule, secretes the hydrolytic enzyme callase and other cell wall-degrading enzymes into the locule; this partially digests the cell walls and separates the tetrad into individual microspores (see Figure 21.3A). (...) During microgametogenesis, the haploid microspore develops mitotically into the mature male gametophyte, composed of the vegetative (or tube) cell and two sperm cells (Figure 21.3B).

"Plant Physiology and Development" int'l 6e - Taiz, L., Zeiger, E., Møller, I.M., Murphy, A.

[cytgen]

Abstract Fennel is considered as a very important spice crop with powerful therapeutic potential. An improvement in this valuable crop, selected physical mutagen (Gamma irradiation) on the seeds with five selective doses viz., 50, 100, 150, 200 and 250 Gy for break genetic consistency in narrow genetic base in Fennel crop, remunerative phenomenon of syncytes was seen in some cases, where complete chromatin was transmitted to the recipient PMC, that generates dimorphic pollen grain. Such pollen grain with varying genetic content plays a significant role in the emergence of intraspecific polyploidization of species. A curious biological process which is often observed in microsporogenesis of higher plants like, development of syncytes, cytomixis between plant cells and due to this the creation of big pollen has evolutionary relevance. The cytomictic behaviour of Foeniculum vulgare Mill. has been reported in this experiment.

[artykyn]

During my therapy session I mentioned a project I’ve been doing at work and my therapist was like “what’s a haploid” and that’s the story of the time I basically paid someone $100 to listen to me ramble about plants

[fukuihana]

she waits, seething, blooming

her name is flower,

in the refine of turn into a flower,

it is not instantly simple to make it,

it must first be planted,

in the ground by a seed,

become stems,

forming leaves,

flower induction,

through the day months and years,

through a any process,

megasporogenesis and,

microsporogenesis,

spark,

then the anthesis controls the rhythm,

by needing a lot of sunlight,

and fallen leaves,

she will not,

let the raindrop fall again,

after a massive rainstorm,

she will never let the pluck her petals and,

fall again.

[epecito]

X fin 1 imagen al microscopio q no m dio problemas al ubicar y fotografiar y tenia q ser una anormalidad durante la telofase 1 en Aloe. Al perderse esos genes sueltos durante la meiosis puede generar problemas d fertilidad en la planta resultante #genetica #udo #meiosis #photo #telofase #anormalidad #photography #microsporogenesis #lab #aloe #microscopia #photooftheday #genetic #meiosis1 #laboratorio (en Udo, Sucre Cumaná)

[essay-help-blogs]

-Flowers-Fruits-and-Seeds-9-02-Lab-assignment-help-

Objectives: You will learn about the structure of flowers, fruits and seeds. You should be able to identify the various parts of a typical flower and give their functions. You will learn what represents the male gametophyte and female gametophyte in flowering plants, and what is meant by the term “alternation of generations”. You will learn about the processes of microsporogenesis,…

[aliscience]

लघुबीजाणुजनन तथा परागकण 

लघुबीजाणुजनन तथा परागकण (Microsporogenesis and Pollen Grain)

लघुबीजाणुजनन (Microsporogenesis)

परागमातृ कोशिका (Pollen mother cell) से लघुबीजाणु (Microspore) बनने की प्रक्रिया लघुबीजाणुजनन (Microsporogenesis) कहलाती है।

पुष्प के बनने के समय जब पुंकेसर बन रहा होता है । तो इनकी लघुबीजाणुधानियों में बीजाणुजन उत्तक (sporogenous tissue)पाये जाते है ।  इन बीजाणुजन उत्तक (sporogenous tissue) में परागमातृ…

[howtopronounceenglishcorrectly]

Learn how to pronounce Microsporogenesis in English --- MICROSPOROGENESIS Pronunciation of Microsporogenesis: /ˌmī-krə-ˌspȯr-ə-ˈje-nə-səs/ noun Definition of Microsporogenesis: the formation and maturation of microspores ★ http://Learn2Pronounce.com ★ How to pronounce Microsporogenesis | English pronunciation: https://youtu.be/sFY4MK9Lbpk

[margdarsanme]

NCERT Class 12 Biology Chapter 2 Sexual Reproduction in Flowering Plants

NCERT Class 12 Solutions for Biology Chapter 2 Sexual Reproduction in Flowering Plants

QUESTIONS FROM TEXTBOOK SOLVED

1. Name the parts of anangiosperm flower in which development of male and female gametophytes take place.Ans. Development of male gametophyte (micro- gametogenesis) occurs in pollen sac of anther up to 2 – celled stage. The female gametophyte develops (megagametogenesis) in the nucellus of ovule.

2. Differentiate between microsporogenesis and megasporogenesis. Which type of cell division occurs during these events? Name the structures formed at the end of these two events?Ans.Differences between microsporogenesis and megasporogenesis are as follows –

Each microspore mother cell and megaspore mother cell contain two sets of chromosomes and are therefore diploid. The diploid megaspore mother cell and microspore mother cell enlarges and undergo meiosis to produce, four haploid cells called megaspores and microspores respectively.The chromosome number is reduced by half and therefore megaspores and microspores are haploid.Microsporogenesis and megasporogenesis give rise to pollen grains and embryo sac respectively. Pollen grain is the male gametophyte and embryo sac represents the female gametophyte.

3. Arrange the following terms in- the correct developmental sequence : Pollen grain, sporogenous tissue, microspore tetrad, pollen mother cell, male gametes.Ans. Sporogenous tissue – pollen mother cell – microspore tetrad – pollen grains – male gametes.

4. With a neat, labelled diagram, describe the parts of a typical angiosperm ovule.Ans.A typical angiospermic ovule is a small structure which is formed in the ovary. Ovule first develops as a projection on the placenta and composed of multilayered cellular tissue called the nucellus. The hypodermal cell of die nucellus enlarges and transformed into megaspore mother cell. This cell undergoes meiosis to produce four haploid cells only one of which develops & forms embryo sac (female gametophyte). An ovule may be surrounded by one or two protective layers called integuments, leaving a small opening at one end termed as micropyle which acts as passage for the entry of the pollen tube into the ovule. Thus, a typical ovule consists of a fully developed embryo sac with the nucellus and integuments.

5. What is meant by monosporic development of female gametophyte?Ans. In many flowering plants, only one out of the four megaspores enlarges and develops into female gametophyte or embryo sac. The other three megaspores degenerate. This type of embryo sac formation is called as monosporic type of development.

6. With a neat diagram explain the 7-celled, 8- nucleate nature of the female gametophyte.Ans.Embryo sac (or female gametophyte) is formed by three successive mitotic divisions that take place in the nucleus of megaspore.The nucleus of the functional megaspore divides meiotically to form two nuclei which move to the opposite poles, forming the 2-nucleate embryo sac. Two more sequential mitotic nuclear divisions result in the formation of the 4-nucleate and later the 8-nucleate stages of the embryo sac. After the 8-nucleate stage, cell walls are laid down leading to the organisation of the typical female gametophyte or embryo sac. Six of the eight nuclei are grouped together at micropylar and chalazal end and form the egg apparatus and antipodals respectively. The large central cell left over with two polar nuclei. Thus, a typical female gametophyte consists of 7 cells with 8 nucleus.

7. What are chasmogamous flowers? Can cross-pollination occur in cleistogamous flowers? Give reasons for your answer.Ans. Chasmogamous flowers or open flowers in which anther and stigma are exposed for pollination. Cross-pollination cannot occur in cleistogamous flowers. These flowers remain closed thus causing only self-pollination. In cleistogamous flowers, anthers dehisce inside the closed flowers. So the pollen grains come in contact with stigma. Thus there is no chance of cross¬pollination, e.g., Oxalis, Viola.

8. Mention two strategies evolved to prevent self-pollination in flowers.Ans. Continued self-pollination decreases the vigour and vitality of a particular race. Thus, flowering plants have developed many devices to discourage self-pollination and to encourage cross-pollination.Dichogamy and self-sterility are.two most common devices that ensure cross-pollination. Dichogamy – Maturation of anther and stigma at different times in a bisexual flower prevent self-pollination.Self-sterility (or self-incompatibility) – Due to the presence of self-sterile gene in some flowers, pollen grains do not germinate on the stigma of that flowers. e.g.,- tobacco, potato.

9. What is self-incompatibility? Why does self-pollination not lead to seed formation in self-incompatible species?Ans. When the pollen grains of an anther do not germinate on the stigma of the same flower, then such a flower is called self-sterile or incompatible and such condition is known as self¬incompatibility or self-sterility.The transference of pollen grains shed from the anther to the stigma of the pistil is called pollination. This transference initiate the process of seed formation. Self-pollination is the transfer of pollen grain shed from the anther to stigma of pistil in the same flower. But in some flower self¬pollination does not lead to the formation of seed formation because of the presence of same sterile gene on pistil and pollen grain.

10. What is bagging technique? How is it useful in a plant breeding programme?Ans. It is the covering of emasculated flowers (removal of anthers in bud condition from a bisexual flower by a bag of butter paper or polythene in their bud condition i.e., before anthesis) to prevent contamination of its stigmas with unwanted pollens. When the stigmas of emasculated flowers mature the bags are removed, stigmas are dusted with pollen grains of desired male . plants by means of a presterilized brush and flowers are rebagged till fruit develop. This technique is mainly used in artificial hybridization. Plant breeders often use this technique to prevent the contamination of stigma of the flowers from unwanted pollen grains.

11. What b triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.Ans. Fusion of second male gamete with die two polar nuclei located in the central cell to form the triploid primary endosperm nucleus (PEN) is called triple fusion or vegetative fertilization. This process takes place in the embryo sac. After reaching the ovary, pollen tube enters into the embryo sac from the micropylar end. After penetration, the tip of the pollen tube ruptures releasing the two male gametes. The one male gamete fuses with the egg to form the diploid zygote. This process is called syngamy and the other male gamete fuses with the two polar nuclei to form the triploid primary endosperm & this process is known as triple fusion. These two events of fertilization constitute the process of double fertilization.

12. Why do you think the zygote is dormant for sometime in a fertiUsed ovule?Ans. The zygote after a period of rest develops into embryo. Most zygotes remain dormant till certain amount of endosperm forms. They do so, to provide assured nutrition to the developing embryo.

13. Differentiate between:(a)hy pocotyl and epicotyl;(b)coleoptile and coleorrhiza;(c)integument and testa;(d)perisperm and pericarp.Ans:

14. Why is apple called a false fruit? Which Part(s) of the flower forms the fruit?Ans. Botanically ripened ovary is called a true fruit. The fruits in which thalamus and other floral parts develop along with the ovary are called false fruits. For example – apple, strawberry, cashew etc. In apple the main edible portion of the fruit is the fleshy thalamus. Ovary forms the fruit after fertilization or without fertilization in parthenocarpic fruits.

15. What is meant by emasculation? When and why does a plant breeder employ this technique?Ans. Emasculation is the removal of stamens mainly the anthers from the flower buds before their dehiscence. This is mainly done to avoid self-pollination. Emasculation is one of the measures in the artificial hybridization. Plant breeders employed this technique to prevent the pollination within same flower or to pollinate stigmas with pollens of desired variety.

16. If one can induce parthenocarpy through the application of growth substances, which fruits would you select to induce parthenocarpy and why?Ans. Parthenocarpic fruits are seedless. They develop from ovary without fertilization. Banana, grapes, oranges, Pineapple, Guava, Watermelon, lemon are selected because these seedless of units are of high economic importance. The fruits in which seeds or seed part form edible portion (e.g.,Pomegranate) are not selected to induce parthenocarpy.

17. Explain the role of tapetum in the formation of pollen-grain wall.Ans. Tapetum is the innermost layer of the microsporangium. The tapetal cells are multinucleated and polyploid. They nourish the developing pollen grains. These cells contain ubisch bodies that help in the ornamentation of the microspores or pollen grains walls. The outer layer of the pollen grain is called exine and is made up of the sporopollenin secreted by the ubisch bodies of the tapetal cells. This compound provides spiny appearance to the exine of the pollen grains.

18. What is apomixis and what is its importance?Ans. Apomixis is a mode of asexual reproduction that produces seeds without fertilization, e.g.- some species of Asteraceae and Grasses. This method is important in hybrid seed industry. Hybrids are extensively cultivated for increasing productivity. But the main drawback is that the hybrid seeds are to be produce every year because the seeds of the hybrid plants da not maintain hybrid characters for longer period due to segregation of characters. This can be avoided if apomixis can be introduced in hybrid seeds. For this reason scientists are trying hard to identify genes for apomixis.

from Blogger http://www.margdarsan.com/2020/09/ncert-solutions-for-class-12-biology_17.html

[adashofniallandasprinkleoflunacy]

OK SO ANDY (botany question): my classmate and I were arguing about Microsporogenesis and we had an argument about the ploidy of pollen grains. So, are pollen grains haploid or diploid

A MATURE POLLEN GRAIN IS 2 HAPLOID CELLS

[emmagreen1220-blog]

New Post has been published on Biology Dictionary

New Post has been published on https://biologydictionary.net/pollen/

Pollen

Pollen Definition

Pollen refers to the powdery product synthesized by seed plants responsible for the production of the male gametes of the plant (shown below).

The pollen grains are termed microgameteophytes, and consist of a sporopollenin coating which serves to protect the gameteophytes as they are transported from the stamens (male) or male cone to the pistil (female) or female cone in flowering and coniferous plants, respectively. When the pollen reaches the pistil or female cone, a pollen tube is formed, which transports the sperm to the ovule containing the female gametophyte. The term pollination refers to the transfer of pollen grains from the anther to the stigma of a flower. Cross-pollination involves the transfer of pollen from one flower to the stigma of another flower. In contrast, self-pollination involves the transfer of pollen from one flower to the stigma of the same flower. A diagram illustrating the location of the anther and stigma is shown below.

Pollen Structure

Pollen grains vary in size, shape, and surface characteristics depending on the plant species (shown below). In general, pollen grains have a double wall consisting of a thin inner wall composed of cellulose, termed the endospore, and a thick outer wall comprised of sporopollenin, termed the exospore. The shape and the external features of the exospore are highly variable, and are often used to distinguish pollen grain produced by different species. The purpose of this structure is to protect the male genetic material from the environment (e.g., UV radiation, compression, and water) during the transportation from the anther to the stigma. The surface of the pollen grain also contains various waxes and proteins which help repel moisture and interact with the stigma, respectively. However, such protein structures on the surface of pollen are often recognized by immune cells and are the source of the allergic reactions to pollen observed in humans.

Pollen Formation

In coniferous plants, pollen is formed in the microsporangia of the male cone, whereas it is produced in the anthers of flowering plants (also termed angiosperms). Each microsporocyte is diploid and forms four haploid cells, termed microspores, via meiosis. This process is termed microsporogenesis. The four microspores then form the double wall of the pollen grain within a structure made of callose. During this process, the callose is digested by callase and the pollen grains are able to grow and complete the formation of the endospore and exospore. The diagram below illustrates the release of pollen grains from the callose structures.

Quiz

1. The transfer of pollen from the anther to the stigma of a flower is termed: A. Endoporation B. Germination C. Pollination D. Microsporogenesis

Answer to Question #1

C is correct. The term pollination refers to the transfer of pollen grains from the anther to the stigma of a flower. Cross-pollination involves the transfer of pollen from one flower to the stigma of another flower. In contrast, self-pollination involves the transfer of pollen from one flower to the stigma of the same flower.

2. The primary function of the exospore is: A. Pollination B. Protect the plant’s male genetic material C. Protect the plant’s female genetic material D. Endoporation

Answer to Question #2

B is correct. The exospore is the hard outer wall of the pollen grain, which serves to protect the male genetic material from UV radiation and other potential sources of damage.

References

Clarke A, Gleeson P, Harrison S, and Knox B. (1979). Cell Biology Pollen-stigma interactions: Identification and characterization of surface components with recognition potential. Proc. Nati. Acad. Sci.76(7):3358-3362.

Heberle-Bors E. (1985). In vitro haploid formation from pollen: a critical review. Theoretical and Applied Genetics. 71(3): 361-374.

Gullvag B. (1966). The fine structure of pollen grains and spores: a selective review from the last twenty years of research. Phytomorphology. 16: 211-27.

Ward M, Dick C, Gribel R, and Lowe A. (2005). To self, or not to self… A review of outcrossing and pollen-mediated gene flow in neotropical trees. Heredity.95(4): 246-54.

[eurekamag--com]

The effect of gametocides on microsporogenesis of winter rye

http://dlvr.it/PZzByn

[botanytoo]

Rye B chromosomes and heat tolerance in microsporogenesis Rye supernumerary (B) chromosomes possess an accumulation mechanism involving the subtelomeric domain enriched by B chromosome specific DNA sequence families, D1100 and E3900.

[biologychamps]

Microsporogenesis is the process of formation of microspores from pollen mother cell. Megasporogenesis is the formation of megaspores from megaspore mother cell. Functional megaspore develops into female gametophyte.