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I B.Sc Diatoms notes

2. Sexual Reproduction:

The pattern of sexual reproduction differs in both orders — Pennales and Centrales. During this process, auxospore is formed in both the groups. During cell division, those cells become reduced in size, are able to regain their normal size through the formation of auxospore, so it is a “restorative process” rather than multiplication.

Auxospore Formation in Pennales:

It takes place through gametic union, auto­gamy and parthenogenesis.

These are of the following types:

1. Production of one auxospores by two conjugating cells. In this process two uniting cells come very close to each other (Fig. 3.103) and become covered by a mucilaginous sheath. The diploid nucleus of each cell undergoes meiosis.

Out of four nuclei, three degenerate and only one survives. The surviving nucleus behaves as gamete (n). The gametes come out from the parent frustules and unite together, to form a zygote (2n).

After a short period of rest the zygote elongates considerably and functions as an aux­ospore. The auxospore projects out from the par­ent frustules along with mucilage and elongates in a plane parallel to the long axis of the parent diatom.

The auxospore is enclosed in a pectic membrane, the perizonium. The auxospore then develops new frustule inside the perizonium. Thus new diatom cell is formed which regains the normal size. It is found in Cocconis placen­tula, Surirella saxonica etc.

2. Production of Two Auxospores by Two Conjugating Cells:

This is a very common process of auxospore formation. In this process the conju­gating cells come very close to each other and get enclosed by mucilage (Fig. 3.104). The nucleus (2n) of each cell undergoes meiotic division and forms four nuclei.

Out of four nuclei, two degene­rate, the rest two survive. The cytoplasm then divides either equally or unequally and along with one nucleus they behave as gametes. Thus two gametes are formed in each cell.

               

HOLY CROSS COLLEGE(AUTONOMOUS) – TRICHY -2

MAJOR CORE -1 PLANT DIVERSITY - 1

  I.B.Sc botany seminar topics (2019-20 batch)

                                      SEMINAR TOPICS

1.     Abinaya.M     -   Structure and reproduction of  Caulerpa

2.     Aboorva.K  -   Life cycle  pattern of Caulerpa

3.     Almubin.B -  Structure and reproduction of Diatom (Pinnularia virdis)

4.     Amala Oviya. A – Life cycle pattern of Diatam

5.     Deepa.M -  Structure and reproduction of Dictyota

6.     Deepana.E – Life cycle  pattern of  Dictyota

7.     Delsi Mathew – Structure and reproduction of Polysiphonia

8.     Dharshinin.R – Life cycle pattern of Polysiphonia

9.     Divani.A -  Techniques in spirulina cultivation

10.  Divya.D – Economic importance of algae

11. Divya.S. – Outline classification of Fungi.(Ainsworth 1971)

12. Divyadharshini.G – Salient features of  Phycomycetes

13. Femila Anugraga.V – Salient features of Ascomycetes

14. Glory Reshma.S. – Salient features of  Basidiomycetes

15. Gracy Angel.S. – Salient features of  Deuteromycetes

16. Haripriya.B. – Salient features of  Phycomycetes

17. Helan Stanila.A –Morphology and reproduction of Albugo

18. Iswarya.P – Morphology and reproduction of Saccharomyces

19. Janani.K – Morphology and reproduction of Penicillium

20. Janani.P – Life cycle pattern of Caulerpa

21. Jasmine.J- Life cycle pattern of Diatom

22. Jovit suguna.G.- Life cycle patterns ofDictyota

23. Karpagavalli.K – Life cycle pattern of Polysiphonia

24. Kaviya.A. – Structure and reproduction of Diatom.

    Dr.S.Catharin sara

HOLY CROSS COLLEGE(AUTONOMOUS) – TRICHY -2

MAJOR CORE -1 PLANT DIVERSITY - 1

   I.B.Sc botany assignment topics (2019-20 batch)

                                      ASSIGNMENT  TOPICS

1.     Rasika      -   Structure and reproduction of  Caulerpa

2.     Sagaya Rani.L -   Life cycle  pattern of Caulerpa

3.     Sakthi Priya.S -  Structure and reproduction of Diatom (Pinnularia virdis)

4.     Sangeetha Preethi  – Life cycle pattern of Diatam

5.     Santhiya.R.-  Structure and reproduction of Dictyota

6.     Sehanaz.G – Life cycle  pattern of  Dictyota

7.     Selva mathi.M – Structure and reproduction of Polysiphonia

8.     Sherin Silviya.J – Life cycle pattern of Polysiphonia

9.     Sherina Christy.A -  Techniques in spirulina cultivation

10.  Sneha.D – Economic importance of algae

11. Sneha.B. – Outline classification of Fungi.(Ainsworth 1971)

12. Soshina Iswarya.G – Salient features of Phycomycetes

13. Sowndharya.M – Salient features of Ascomycetes

14. Srividhya.K. – Salient features of  Basidiomycetes

15. Subathra.S – Salient features of  Deuteromycetes

16. Suganthi.M. – Salient features of  Phycomycetes

17. Sulochana.M –Morphology and reproduction of Albugo

18. Sweety Reshma.R – Morphology and reproduction of Saccharomyces

19. Subhiksha.T.S. – Morphology and reproduction of Penicillium

20. Udhaya.S – Life cycle pattern of Caulerpa

21. Umarsalma.F- Life cycle pattern of Diatom

22. Vijaya shanthi.P.- Life cycle patterns ofDictyota

23. Vinothini.R – Life cycle pattern of Polysiphonia

24. Yasmeen Banu.S. – Structure and reproduction of Diatom.

1.      Dr.S.Catharin sara

Diatoms photos for I B.Sc students

III B.Sc assignment and seminar topics

HOLY CROSS COLLEGE(AUTONOMOUS) – TRICHY -2

MAJOR ELECTVE  -2    PLANT FOODS

                   III B.Sc botany seminar topics (2019-20 batch)

                                      SEMINAR TOPICS

1.      Ajitha.S                   - 17BO003   – Food safety – Sanitation and Hygiene

2.     Alwin Latrecia.J       - 17BO004   - Food borne diseases

3.     Aswini .R                 - 17BO005 - Food borne diseases by Microorganisms

4.     Bavithra.G                - 17BO007   - Food poisoning

5.     Bhuvaneswari.N      -  17BO008   - Food laws and food standards

6.     Bhuvaneswari.R       –17BO009    - Consumer council and consumer protection

7.     Dhivya Bharathi.G   – 17BO010    - food Allergy

8.     Fiez Rizwana.S         – 17BO012   - Role of FAO

9.     Gayathri.K                -  17BO013   - Role of WHO

10.  Geetha.S.                 –  17BO014   - Role of UNICEF

11. Gowri.S.                  –17BO015        - Role of CFTRI

12. Harini.N                   -17BO016 -     Role of FSSAI

13. Jerlin Preetha.A       - 17BO017    - Physical test for detection of food adulterants

14. Jeya ruthra .B          -17BO018    -  Physical test for detection of food adulterants

15. Jothika.R                -17BO019   -  Physical test for detection of food adulterants

16. Kavithanjali.S.        -17BO021   - Food adulteration

17. Kavya Devi.M        -17BO022  - Flourosis

18.  Keerthana.A                    -17BO023 – Natural food toxicants

Dr.S.Catharin sara

HOLY CROSS COLLEGE(AUTONOMOUS) – TRICHY -2

MAJOR ELECTIVE -2 PLANT FOODS

  III.B.Sc botany seminar topics (2019-20 batch)

                                     ASSIGNMENT  TOPICS

1.     Geetha.S.                 –  17BO014  - Food safety – Sanitation and Hygiene

2.     Gowri.S.                  –17BO015    - Food borne diseases

3.     Harini.N                   -17BO016    - Food borne diseases by Microorganisms

4.     Jerlin Preetha.A       - 17BO017    - Food poisoning

5.     Jeya ruthra .B          -17BO018      - Food laws and food standards

6.     Jothika.R                -17BO019     - Consumer council and consumer protection

7.     Kavithanjali.S.        -17BO021      - Food Allergy

8.     Kavya Devi.M        -17BO022     - Role of FAO

9.      Keerthana.A                    -17BO023     -  Role of WHO

10.  Ketha rani.S           - 17BO024    -Role of UNICEF

11. Lalithambigai.S       -17BO025     - Role of CFTRI

12. Monisha.R.             - 17BO026      - Role of FSSAI

13. Naseema Banu.M   - 17BO027   - Physical test for detection of food adulterants

14. Noorul Huda.M      -17BO028    - Physical test for detection of food adulterants

15. Praveena.B             - 17BO029    - Physical test for detection of food adulterants

16. Preethi.R.               -17BO030     - Food adulteration

17. Priya dharshini.C.   -17BO031   - Flourosis

18. Punitha.R.              - 17BO032    - Natural food toxicants

Dr.S.Catharin Sara

Diatoms notes

Occurrence of Diatoms:

Diatoms are found in all possible habitats. Commonly they are found in fresh water (Denticula tenuis, Navicula pupula, Meridion circulare, Cymbella ventricosa, Melosira variens, Amorpha ovalis etc.), sea water (Corethron, Biddulphia, Sceletonema, Fragilaria, Tropido- nensis etc.) and soil (Pinnularia, Navicula, Frustulia etc.).

The terrestrial species (Amorpha, Navicula, Pinnularia etc.) are able to withstand desiccation for a long period. Some diatoms (Gomphonima, Cymbella etc.) can grow as epi­phyte on other algae (Enteromorpha, Cladophora etc.) and higher plant. Licmophora, a member of diatom, grows endozoically.

Plant Body of Diatoms:

Plant body is unicellular, generally moves singly. The cells are of different shapes viz. round, oval, elongated, rod-shaped, triangular, disc-shaped etc. Sometimes they become aggre­gated and get embedded in a gelatinous matrix, but they do not behave like multicellular orga­nisms.

In colonial form the cells may be present as uniseriate row (e.g., Melosira), like a branched body (e.g., Licmophora flabellate) or other forms also.

Cell Structure of Diatoms:

The cell consists of cell wall and protoplast (Fig. 3.101 A, B, C). The cells are covered by a siliceous wall, the frustule. It consists of two overlapping halves, the theca. The upper one is epitheca and lower one is hypotheca.

Both the theca consist of two portions:

(a) Valve — the upper flattened top and (b) Con­necting band or cingulum (pl. cingula) — the incurved region.

The common region of the con­necting bands, where both the theca remain fitted together, is the girdle. [When the diatoms are observed from the valve side i.e., valve side is uppermost, called the valve view, but when viewed from the connecting band, it is the girdle view]. Depending on symmetry, the cells are divided into two orders: Pennales (bilaterally symmetry) and Centrales (radially symmetry).

In some pinnate diatoms (Cybella cistula, Pinnularia viridis etc.) an elongated slit is present on their valves, called raphe. The raphe is interrupted at its midpoint by thickening of the wall called central nodule. Similar thickening is also present at the ends called polar nodules. Some members like Tabellaria fenestrate etc. of the order Pennales, do not have raphe, called pseudoraphe.

Besides raphe or pseudoraphe, the cell walls have other types of openings, called pores and locules.

The cell wall is mainly made up of pectic substances, impregnated with silica. The content of silica varies from 1% (Phaeodactylum tricornutum) to about 50% on the basis of dry weight of the cell.

Protoplast:

The entire content present inside the cell wall is the protoplast. The cell membrane encloses a large central vacuole surrounded by cytoplasm. The cytoplasm contains single nucle­us, mitochondria, golgi bodies and chloroplasts. The chloroplasts may be of different shapes like stellate, H-shaped, discoid etc. In some species the chloroplasts contain pyrenoids.

The photosynthetic pigments are chlorophyll a, c₁ and c₂, β-carotene, fucoxanthin, diatoxanthin and diadinoxanthin. The latter two are pre­sent in small quantity. (The golden-brown colour of diatom cells is due to the presence of xanthophylls like fucoxanthin, diatoxanthin and diadinox­anthin.

The term diatomin is used for the mixture of chlorophyll and carotenoids, particularly carotene and several brown xanthophylls pigments.) The reserve food of diatoms is chrysolami- narin and oil droplets (they do not store in the form of starch).

Locomotion:

All diatoms with raphe are motile. Most of the members of the order Pennales contain raphe and perform gliding movement. The gliding movement is caused by the circulation of cytoplasm within the raphe by the release of mucilage. The rate of movement varies from 02-25 µm/sec. The locomotion is affected by temperature, light etc.

Reproduction of Diatoms: 

Diatom reproduces by vegetative and sexual means.

1. Vegetative Reproduction:

Vegetative reproduction performs with the help of cell division (Fig. 3.102). It takes place usually at midnight or in the early morning.

During cell division the protoplast of the cell enlarges slightly, thus the cell increases in volume and slightly separates both the theca (epitheca and hypotheca). Then the protoplast undergoes mitotic division and gets separated along the longitudinal axis through the median line.

Thus one half of protoplast remains in epitheca and the other one in hypotheca. One side of the protoplast thus remains naked. Now both the theca i.e., epitheca and hypotheca of mother cell behave as epitheca of the daughter cells.

Thus new silicious valves are deposited towards the naked sides of the protoplast and always behave as hypotheca of the daughter cells. Connecting bands are developed between the theca. Later on, the daughter cells get sepa­rated.

During cell division, both the theca i.e., epitheca and hypotheca of the mother cell behave as epitheca of the daughter cells. So at the side where the hypotheca behaves as epithe­ca, the cell becomes reduced in size. Thus with continuous cell division some cells gradually become reduced in size.

Economic Importance of Diatoms: 

The diatoms are used in various purposes either directly or indirectly.

The different uses of diatoms are:

1. Diatomite:

After the death of diatom cells the outer coverings i.e., the silicified walls become accumulated at the bottom of water. The accumulation may be thicker during favourable conditions. These deposits are called diatomaceous earth, diatomite or keiselghur.

It is very suitable for use in different industries:

a. As Filter

It is used as filter in different industries like sugar (to filter microorga­nism), oil and chemical industry. Diato­mite is also used as filter for battery boxes.

b. As Insulator:

It is used as insulator in boilers and blast furnaces for its heat- resistant ability.

c. As Absorbent:

It is used as absorbent of liquid nitroglycerine.

d. Other Uses:

Diatomite is used as abra­sive (i.e., capable of rubbing or grinding down) substance for the manufacture of metal paints, polish, varnish, toothpaste etc. It is also used with bake-lite for elec­trical fuse and switch boxes.

2. Petroleum:

Much of the petroleum is con­sidered to be of diatom origin as they are found in association with large oil deposits.

3. Food:

Due to their great abundance in the different seas and their use as food by marine animals, they are called the ‘grasses of the sea’. Those animals may be con­sumed as food by man and maintain the food chain.

4. Testing of Microscopic Lenses:

Due to the fine markings on shell, the diatom cells are used to test microscopic lenses.

 

http://www.biologydiscussion.com/algae/diatoms-characteristics-occurrence-and-reproduction/46940