Continuation of survey of algae

                A.            Last times                                1.             Kingdom Monera: Class Cyanobacteriae (Class Cyanobacteria (cyano))                                2.             Kingdom Protista: Phylum Euglenophytya (euglena), Phylum Chromophyta (Class Chrysophyceae and Class Bacillariophyceae (silica)), and Phylum Dinophyta (pirate boat)                B.            This period                                1.             Kingdom Protista: Phylum Rhodophyta (red), Phylum Chlorophyta (chlorophyll), Phylum Chromophyta (Class Phaeophyceae (fart))                C.            Phylum Rhodophyta (red algae - red): mostly marine - use agar for food                                1.             Eucaryotic, cellulosic walls, puzzling animatronics cycles                                2.             Found at massive depths                                3.             Used in agar, in baked goods to prevent ventilation out and giving out of icing, as an ice cream thickener, and in toothpaste                D.            Phylum Chlorophyta (green algae - chlorophyll): photosynthetic pigments same to that of nature                                1.             Green algae found predominantly in spacious water                                2.             Contain chlorophyll a and b, cellulosic walls, and stored starch                                3.             Ancestors of in addition to natural world?                                4.             Diverse morphology - unicellular, filamentous, colonial, sheetlike                E.            Phylum Chromophyta (Class Phaeophyceae) (brown algae - fart): largest algae, used as food                                1.             Brown algae that contain cellulose in cell wall                                2.             Largest algae, conducting stuff from above (near sun) to knocked out                                3.             Most obscure algae                                4.             Dominant generation, in some cases, is diploid.

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Cell Structure of Plants

I.              The cell

                A.            Cells are fundamental organizational units of all living things

                B.            Types of cells

                                1.             Prokaryotic

                                2.             Eukaryotic

                                                a)             Plant

                                                b)             Animal

II.            Protoplast

                A.            Protoplasm within membrane / cell contents without the cell wall

III.           Organelles

                A.            Cell wall

                                1.             Plants

                                2.             Support, structure, & protection

                B.            Nucleus

                                1.             Genetic information - DNA

                                2.             Cell regulation - "the brains"

                C.            Chloroplasts

                                1.             Plants

                                2.             Photosynthesis

                                                a)             Thylakoids - light capture

                                                b)             Stroma - conversion to sugar

                                3.             Contain some DNA

                D.            Mitochondria

                                1.             Energy from sugars

                                2.             Contain some DNA

                E.             Cytomembrane system

                                1.             Packaging & transport

                                                a)             Golgi apparatus (dictyosomes)

                                                b)             Endoplasmic reticulum

                                                c)             Ribosomes

                F.             Microbodies

                                1.             Peroxisomes - photorespiration

                                2.             Glyoxisomes - conversion of fats into sugars

                G.            Microtubules - movement & wall synthesis

                H.            Ergastic materials

                                1.             Starch grains - storage

                I.              Vacuoles

                                1.             Storage

                                2.             Waste

                                3.             Water regulation

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Nutrient Mobility

Nutrient Mobility

WITHIN PLANT

An important characteristic of some nutrients is the ability to move within the plant tissue. In general, when certain nutrients are deficient in the plant tissue, that nutrient is able translocate from older leaves to younger leaves where that nutrient is needed for growth. Nutrients with this ability are said to be mobile nutrients, and include nitrogen, phosphorus, potassium, magnesium, and molybdenum. In contrast, immobile nutrients do not have the ability to translocate from old to new growth. Immobile nutrients include calcium, sulfur, boron, copper, iron, manganese, and zinc.
Nutrient mobility, or immobility, provides us with special clues when diagnosing deficiency symptoms. If the deficiency symptom appears first in the old growth, we know that the deficient nutrient is mobile. On the other hand, if the symptom appears in new growth, the deficient nutrient is immobile.

WITHIN THE SOIL

Mobility of a nutrient within the soil is closely related to the chemical properties of the soil, such as CEC and AEC, as well as the soil conditions, such as moisture. When there is sufficient moisture in the soil for leaching to occur, the percolating water can carry dissolved nutrients which will be subsequently lost from the soil profile. The nutrients which are easily leached are usually those nutrients that are less strongly held by soil particles. For instance, in a soil with a high CEC and low AEC, nitrate (an anion) will leach much more readily than calcium (a cation). Additionally, in such a soil, potassium (a monovalent cation) will leach more readily than calcium (divalent cation) since calcium is more strongly held to the soil particles than potassium.

Silica from minerals also dissolves and leaches from the soil profile during the processes of weathering. It is this dissolution and leaching that transforms primary minerals to the more weathered, secondary minerals that make up the finely-textured soils of Maui.

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Effect on Carbon Dioxide Fertilization in Plants

The increasing abundance of greenhouse gases in the atmosphere has the following three main effects:

(i) CO2 fertilisation effect on plants

(ii) Global warming and

(iii) Depletion of ozone (O3) layer in the stratosphere.

Carbon dioxide (CO2) Fertilisation Effect on Plants:

The data produced in USA have shown that atmospheric carbon-dioxide concentration has been rapidly rising since 1959 as shown in the graph. If such rising trend continues, by the end of twenty first century the atmospheric concentration of CO2 shall increase to a level between 540 and 970 ppm.

When the CO2, concentration of the atmosphere is more or less doubled, the growth of many plants i.e., C3, plants in particular, under favourable conditions of water, nutrients, light and temperature, could increase by about thirty per cent on average, in the short term of few years or so.

The response of plants to elevated concentrations of CO2, is called carbon dioxide fertilisation effect.

Due to increased carbon-dioxide concentration, the rate of photosynthesis also increases, and the stomatal conductance decreases due to partial closure of stomata. Hence, the transpiration rate reduces, and water-use efficiency increases.

Such effect allows many species to grow successfully in regions of water scarcity.

Under higher atmospheric carbon dioxide concentrations, plants allocate, a greater proportion of photosynthate to roots. However, greater root production increases development of mycorrhiza and fixation of nitrogen in root nodules, thus, makes possible the plants to grow in soils which are poor in nutrition.

However, in natural conditions the beneficial effects of increased carbon dioxide may not be there because of negative effects of global warming.

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Morphology of Cycus

1. A small palm-like tree.

2. Plant body differentiated into root, stem and leaves; the roots are of two types- normal and coralloid.

3. In the beginning the stem is tuberous, later on becomes columnar, un-branched and covered with persistent leaf bases.

4. Leaves large and compound with circinate vernation; leaf crown on the top of the plant.

5. Xylem consists of tracheids; companion cells absent from phloem; secondary xylem tracheids do not possess spiral thickenings.

6. No resin canals; mucilage canals present in the mesophyll tissue.

7. Root stele diarch to tetrarch.

8. Girdle traces present in the cortex of stem.

9. During secondary growth several successive rings of cambium are formed; the primary cambium is short lived; secondary cambium rings form concentric zones of xylem; no annual rings.

10. Mesophyll tissue differentiated into palisade and spongy tissue; no peg-like infolding’s; xylem mesarch in the midrib.

11. Transfusion tissue well developed in the leaves.

12. Vegetative reproduction by buds or bulbils.

13. Plants usually dioecious; cones simple and unisexual.

14. Sporophylls differ from foliage leaves, arranged in cones, i.e., male and female cones..

15. Microsporophyll triangular, woody, not peltate bearing numerous microsporangia.

16. Male cone terminal, large bearing numerous microsporophylls.

17. Microspores (pollen) not winged.

18. Female cone has a whorl of loosely arranged megasporophylls.

19. Each megasporophyll quite large in size, bearing 1-5 pairs of big ovules.

20. Ovule bears 1-2 integuments.

21. One megaspore (embryosac) in each megasporangium (ovule).

22. A sharp nucellar beak and a pollen chamber.

23. Nucellus free in the upper part or through out and not fused with the integument.

24. At the time of fertilization the embryo sac consists of a gametophyte having many food laden cells and 2-3 archegonia.

25. 3-celled pollen are shed from the pollen sacs and pollinated by wind. Pollen grains are caught in the mucilage drop oozing out from the micropyle. As the drop dries the pollen are taken back into the pollen chambers.

26. Pollen deposited directly on the nucellus during pollination; further development of pollen is completed in pollen chamber.

27. Microspore germinates in situ (within microsporangium) while the germination is completed on the nucellus after pollination.

28. The microspore cuts off only one prothallus cell, which is persistent (male gametophyte).

29. Generative cell produces two male gametes while large vegetative cell gives rise to tube cell and stalk cell.

30. The male gametes are large and multiflagellate.

31. The motile sperms move in the pollen tube and reach the neck of the archegonium; here the pollen tube acts as haustorium.

32. The female gametophyte is formed by the free nuclear di\i- on of the nuclear embryo sac cell; wall formation starts when numerous (1000) nuclei nave been formed within the megaspore

33. The megaspore germinates inside the megasporangium (ovule).

34 Female gametophyte bears 3-6 archegonia per ovule; neck present; no ventral canal cell: ventral nucleus present.

35. Female gametophyte parasitic on nucellus.

Morphology of Pinus tree

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Morphology of Pinus tree

Pinus:

1. A tall, branched tree.

2. Plant body differentiated into root, stem and leaves; tap roots and mycorrhizic roots.

3. Stem cylindrical, branched; the branches are of two types, i. e, branches of limited growth (dwarf shots) and branches of unlimited growth (long shoots).

4. Leaves needle-like and grow on dwarf shoots; no circinate vernation.

6. Resin canals present; no mucilage canals.

7. Root stele diarch to hexarch.

8. Girdle traces absent.

9. Secondary growth; the cambium ring is persistent and produces a continuous cylinder of secondary xylem; annual rings are formed.

10. Mesophyll not differentiated into palisade and spongy tissue; mesophyll cells have peg-like infoldings; two vascular bundles with endarch xylem.

11. Transfusion tissue less developed.

12. No vegetative reproduction.

13. Plants usually monoecious; cones simple and unisexual.

14. Sporophylls arranged in male and female cones.

15. Microsporophyll scaly, not peltate, bearing two microsporangia.

16. Male cones small, grouped in clusters replace the dwarf shoot and not ma

17. Microspores (pollen) winged exine inflated to form balloon-like expans

18. Female cone compact and corresponds to an inflorescence; ovuliferous scale represents female flower.

19. Each megasporophyll or carpel is quite simple; each ovuliferous scale bears two ovules on its upper surface near the central axis.

20. Ovule bears single integument.

22. Pollen chamber and nucellar beak absent.

24. At the time of fertilization the embryosac consists of a gametophyte having many food laden cells bearing 2-3 archegonia.

25. Wind pollination; pollen grains enter the open ovuliferous scale and get entangled in the oozing mucilage drop from micropyle.

28. The microspore cuts off two prothallial cells towards the pointed end (male gametophyte).

30. Male gametes small non-motile.

31. The non-motile sperms are carried to the mouth of archegonia through pollen tube; pollen tube acts as sperms carrier and haustorium.

34. Female gametophyte bears one or two archegonia; no neck canal cell.

36. Usually a time interval of one year in between pollination and fertilization; fertilization occurs in the end of April; pollen tube reaches the neck of archegonium; the neck breaks and receives the contents from pollen tube; male nucleus fuses with the egg nucleus forming oospore.

38. Wall formation starts when eight-nucleate stage is attained.

39. Proembryo has four distinct tiers.

40. Four potential embryos, but only one matures; common occurrence of-cleavage polyembryony.

41. Perisperm present; numerous cotyledons in each seed; no aril; testa dry; endospermic.

42. Seeds winged.

43. Epigeal germination of seed. 

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Definition of the ecosystem.

Meaning of Ecosystem:

The populations of organisms interact with each other in biological communities, and no biotic community can live in isolation. It lives in an environment which supplies its material and energy requirements and provides other living conditions. A biological community interacting with the non-living environment is called an ecosystem. An ecosystem can be natural or artificial, temporary or permanent.

A pond, a lake, a tract of forest, a coral reef, a large grassland, a village, an aquarium, a field of sugarcane, a manned spaceship, or a laboratory culture can all be regarded as ecosystems. Thus, an ecosystem may be defined as a dynamic system which includes both organisms (biotic component) and abiotic environment influencing the properties of each other and both necessary for the maintenance of life.

The concept of ecosystem was first put forth by Sir Arthur Tansley in 1935. Ecosystems can be recognised as self-regulating and self-sustaining units of landscape. Ecosystem is the major ecological unit.

In nature, two major categories of ecosystems may be distinguished:

(i) Terrestrial, and

(ii) Aquatic.

Forests, grasslands and deserts are main examples of terrestrial ecosystems, while ponds, lakes, streams or salt water (marine estuaries) represent aquatic ecosystems.

Ecosystem has both structure and function. The structure is related to species diversity. The more complex is the structure the greater is the diversity of the species in the ecosystem. The function of ecosystem is related to flow of energy and cycling of materials through structural components of the ecosystem.

According to E.P. Odum, the ecosystem is the basic fundamental unit of organisms and their environmental interacting with each other and with their own components. All the ecosystems of the earth are connected to one another, e.g., river ecosystem is connected with the ecosystem of oceans, and a small ecosystem of dead logs is a part of large ecosystem of a forest.

However, human activities may modify natural ecosystems into man -made or anthropogenic ecosystems. For example, natural forests have been cut and the land converted to tree plantations or agricultural systems. Sometimes dam construction involves submergence of forests and conversion to water reservoirs.

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Culture of Ovaries of Plants

Culture of Ovaries:

Rau (1956) attempted to culture pollinated ovaries of Phlox drummondii and studied the influence of extraneous chemicals on the pattern of development of the endosperm and embryo.

The addition of colchicine to the medium caused aberrant divisions, fusion and aggregation of endosperm nuclei and finally a degeneration of the endosperm. In 12 to 14-days old cultures the embryo also aborted and the seeds were malformed.

Nirmala Maheshwari and Lal (1961) excised the flowers of Iberis amara one day after pollination and planted them on agar nutrient media. Fruits of normal size were obtained in two weeks on a medium containing Knop’s mineral salts + Nitsch’s trace elements + sucrose + B vitamins.

The seeds formed in vitro contained viable embryos. Removal of the sepals slowed down the growth of the ovaries showing that the calyx is by no means an unessential structure but has an important role in the physiology of the fruit.

Pollinated ovaries of a few other plants have also been reared into fruits, but when unpollinated ovaries are taken, the fruits are either not formed or are seedless.

Johri and Sehgal (1963) cultured the ovaries of Anethum graveolens at the zygote stage on White’s basal medium containing yeast extract and /or casein hydrolysate thirteen to twenty weeks later, a polyembryonate mass developed by the proliferation of the zygotic proembryo and ruptured the pericarp.

Further growth resulted in the production of multiple shoots some of which flowered in the test tube after about seven months. Thus this was possible to obtain several seedlings from a single fertilized ovule.

However, it is easier to maintain ovules in sterile culture when they are left in situ within the ovary. The physiological requirements of fertilized ovules do not appear to be species specific, since young ovules of widely different species have grown to mature seeds following transplantation on to the placenta of Capsicum fruits.

Culture of Ovules and Parts of Ovules:

White (1932) was the pioneer to culture the ovules. White and La Rue cultured ovules of Erythronium and Antirrhinum on White basic medium containing indole acetic acid lAA.

Nirmala Maheshwari and Lal (1961) cultured the ovules of Papaver somniferum excised six days after pollination when they contained only a 2-celled proembryo and a free nuclear endosperm. These grew to maturity in twenty days and even germinated and produced seedlings in the culture tubes.

Several genera, such as Citrus, Eugenia and Mangifera show the occurrence of nucellar embryos. Since they have the same genetical composition as the maternal parent, they are of much importance for the clonal propagation of desirable varieties.

Rangaswamy (1961) reported that if the nucellar tissue of Citrus microcarpa is grown on a suitable nutrient medium containing casein hydrolysate, it proliferates profusely and on subculturing produces embryo-like regenerants termed “pseudobulbils”, which can develop into seedlings so that an indefinite number of new plants can be obtained from a single nucellus.

A. N. Rao (1963) successfully germinated seeds of an interspecific hybrid of Vanda on a simple agar nutrient medium. Some of the fertilized ovules directly produced seedlings; others gave rise to a callus from which new plants arose subsequently.

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Somatic Hybridization of Plants

Somatic Hybridization:

Fusion between protoplasts of the selected parents is induced by a solution of polyethylene glycol (PEG), or by very brief high voltage electric current. Somatic hybridisation allows the production of hybrids between lines and species that cannot be produced normally by means of sexual hybridisation.

Fusion of cytoplasm of two protoplasts results in coalescence of cytoplasm. The nuclei of two protoplasts may or may not fuse together even after fusion of cytoplasms. The binueleate cells are known as heterokaryon.

When nuclei are fused the cells are known as hybrid, and when only cytoplasms fuse and genetic information from one of the two nuclei is lost is known as cybride i.e, cytoplasmic fuse and genetic information from one of the two nuclei is lost is know as cybrid i.e, cytoplasmic hybrid.

However, production of cybrids which contain the mixture of cytoplasms but only one nuclear genome can help in transfer of cytoplasmic genetic information from one plant to another. Thus, information of cybrid can be applicable in plant breeding experiments.

For example, in China, cybrid technology in rice is a great success. Such plants are very useful in producing hybrid seeds without emasculation. Today, cybrid technology has successfully been applied to carrot, mustard, citnis, tobacco and sugar beet.

Somatic hybrids may also be used for gene transfer, transfer of cytoplasm and production of useful allopolypoloids.

Tissue and protoplast cultures have been used in genetic engineering for the transfer of DNA and extrachromosomal bodies — plasmids, mitochondria, chloroplasts, nif (nitrogen fixing) genes from the nitrogen fixing bacterium Klebsiella pneumoniae to a strain of the colon bacterium Escherichia coli. Isolated protoplasts have great advantage in all the afore mentioned uses.

For transformation purposes cultured apical meristems are also usable because these can easily be regenerated into whole plants and also because intact DNA taken up by plants appears to be rapidly transported to meristematic regions, where growth and differentiation are centred.

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Culture of Plant Materials in Plant Tissue Culture

Culture of Plant Materials in Plant Tissue Culture:

Explant Culture:

There are a variety of forms of seed plants, such as trees, herbs grass, which exhibit the basic morphological units, i.e., root, stem and leaves, versatile of all types of tissues. They are capable of division and growth.

Development of a tissue is characterized:

(i) Cell division,

(ii) Cell elongation, and

(iii) Cell differentiation.

For this reason, the explants from healthy and young part of the plant are used. Presence of parenchyma is first consideration in a particular species, parenchyma from stems, rhizomes, tubers; root is easily accessible and will generally respond quickly to culture conditions in vitro.

Callus Formation and its Culture:

In nature, callus develops by infection of microorganisms from wounds due to stimulation by endogenous growth hormones, the auxins and cytokinins. However, it has been artificially developed by adopting tissue culture techniques.

A callus is an amorphous mass of loosely arranged thin walled parenchyma cells developing from proliferating cells of the parent tissue. The unique feature of callus is that the abnormal growth has logical potential to develop normal root, shoots and embryoids ultimately forming a plant.

In callus culture, cell division in the explant forms a callus, an un-organised mass of cells. It is maintained on a medium gelled usually with agar. The medium ordinarily contains the auxin 2, 4 – D (2, 4 – dichlorophenoxyacetic acid), and often a cytokinin BAP (benzylaminopurine).

When an explants is placed on such a medium, many of the cells become meristematic and begin to divide. In about 2 to 3 weeks, a callus mass is obtained.

Cell (Suspension) Culture:

A suspension culture consists of single cells and small groups of cells suspended in liquid medium. Cell suspension is prepared by transferring a fragment of callus (about 500 mg.) to the liquid medium (500 ml.) and agitating them aseptically to make the cells free in medium. The medium ordinarily contains the auxin 2, 4 – D. Suspension cultures must be constantly agitated at 100 – 250 rpm (revolutions per minute).

Agitation serves three important purposes.

They are as follows:

(i) Aeration of culture;

(ii) Constant mixing of the medium and

(iii) Breakage of cell aggregates into smaller cell groups. Suspension cultures grow much faster than callus cultures.

It is difficult to have suspension of single cell. However, the suspension includes single cell, cell aggregates (varied number of cells), residual inoculum and dead cells. King (1980) has described that a good suspension consists of a high proportion of single cells than small cluster of cells.

Cell suspension cultures have many advantages over the callus cultures.

They are as follows:

(i) The suspension can be pipetted.

(ii) They are less heterogeneous and cell differentiation is less pronounced.

(iii) They can be cultured in volumes up-to 1500 litres.

(iv) They can be subjected to more stringent environmental controls.

(v) They can be manipulated for production of natural products by feeding precursors.

Sub-Culturing:

After some time, the under-mentioned three things happen in all types of plant tissue cultures:

(i) Cell/tissue dry matter known as biomass increases,

(ii) The level of nutrients in the medium decreases, and

(iii) The medium volume declines due to evaporation.

Hence, if tissue cultures were kept in the same culture vessel, they will die in due course of time. Due to this reason, cells/tissues are regularly transferred into new culture vessels containing fresh media. This process is called sub-culturing.

Precaution is taken that during sub-culture, only a part of the culture from a vessel is transferred into the new culture vessel.

Difference between callus and suspension cultures:

Callus Culture:

a. Her cell division in the explant forms a callus, which is an unorganised mass of cells.

b. It is maintained on a medium gelled usually with agar.

c. The medium ordinarily contain the auxin 2, 4-D, and often a cytokinin like BAP.

d. There is no need of agitation.

e. In about 2-3 weeks, a callus mass is obtained.

Suspension Culture:

a. Suspension culture consists of single cells and small groups of cells.

b. Here, cells are suspended in liquid medium.

c. Usually the medium contains the auxin 2, 4-D.

d. They must be constantly agitated at 100-250 rpm (revolutions per minute).

e. suspension culture grow much faster than callus cultures.

 Uses of Callus and Suspension Cultures:

The callus and suspension cultures can be used to achieve cell biomass production which may be used for biochemical isolation.

Also used for regeneration of plantlets, i.e., newly regenerated plants through tissue culture.

Production of transgenic plants and isolation of protoplasts

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