Practical Experiment
Practical Experiment
ALGAE
Experiment – 1
Object: To study the external features of thallus of Oedogonium. Procedure:
(i) Collect a few filaments from pools or ponds.
(ii) Place it on a slide.
(iii) Prepare a safranin stained slide of a few filaments.
(iv) Wash it properly with water.
(v) Mount in glycerine.
(vi) Observe it under the microscope.
Comments:
(i) Thallus is multicellular, filamentous and unbranched.
(ii) A filament is differentiated into three types of cells according to their position: (i) basal, (ii) intercalary and (iii) apical
(iii) The basal cell of filament functions as a holdfust. The flower part of the holdfast is either disc-like or finger-shaped. The upper part is mostly broad and rounded. The basal part of cell generally lacks green pigment and therefore, is non-green unlike other cells of the filament.
(iv) A cell at the tip of the filament is known as apical cell. It is rounded at its free surface.
(v) The cells present between basal and the apical cells are intercalary cells. These show typical cell structure.
(vi) The typical cell is cylindrical.
(vii) Cell wall is thick and three layered.
(viii) Internal to cell wall is a reticulate chloroplast that runs parallel to the long axis of the cell. Many pyrenoids are present in the chloroplast.
(ix) The cell is uninucleate. The nucleus is situated near the cell wall and is held hy thin and delicate cytoplasmic-strands.
Identification
(a) Chlorophyll present.
(h) Chloroplasts grass-green.
(c) Filaments unbranched.
(d) Holdfast well developed.
Experiment – 2
Object: To study the external features of thallus of Nostoc. Procedure:
(i) Place a part of colony on the slide.
(ii) Press it little by another slide so that it spreads flat.
(iii) Stain in safranin.
(iv) Mount in glycerine.
(v) Now study the external features.
Comments:
(i) Thallus is colonial. Young colonies are microscopic, spherical and solid.
(ii) Mature colonies become irregular and hollow.
(iii) Colonial envelope encloses many filaments.
(iv) A filament has diffluent gelatinous sheath.
(v) The trichomes are unbranced.
Identification:
(i) Thallus simple.
(ii) Presence of chlorophyll.
(iii) Cell wall of cellulose.
(iv) Chromatophore not organised.
(v) Thallus with trichomes, unbranched or branching false.
(vi) Trichomes simple, unbranched, uniseriate and approximately of the same diameter throughout.
(vii) Trichomes much twisted into a mass of definite form with a firm colonial envelope.
(viii) Heterocysts intercalary and single.
FUNGI
Experiment -3
Object : To study the thallus of Synchytrium. Procedure:
(i) Collect a few specimen of diseased plants including the potato tuber.
(ii) Cut a transverse section of the diseased plant part of cucurbits, Peristrophe, etc.
(iii) Stain in cotton blue.
(iv) Now, mount in lactophenol.
(v) Study the cells.
Comments:
(i) The thallus is unicellular and non-filamentous.
(ii) It is endobiotic (lying wholly within the host cell or cells) and holocarpic (whole of the vegetative thallus forms the reproductive unit).
(iii) The globose, one-celled thallus may either be surrounded by a thick or a thin wall.
(iv) The plant body is composed of a single uninucleate cell with a definite cell wall.
(v) The organism absorbs its food material from the cell contents of the host.
(vi) It is incapable of extending to other cells.
Identification:
(i) Chlorophyll absent.
(ii) Cell wall of-fungal cellulose.
(iii) A definite cell wall present.
(iv) Presence of motile spores.
(v) Zoospores uniflagellate.
(vi) Asexual reproduction by posteriorly uniflagellate zoospores.
(vii) Thallus divided into a number of reproductive units and forms a sorus.
(viii) Galls are produced on host.
Experiment – 4
Object : To study the internal structure (Anatomy) of thallus of Pellia. Procedure:
(i) Cut V.T.s of thallus.
(ii) Stain in safranin.
(iii) Mount in glycerine and study.
Comments:
(i) The section of the thallus shows homogeneous internal structure. Only the surface layers are little different while cells forming the rest of the tissues are all similar.
(ii) The section shows ventrally projected midrib and wings. The midrib is 8-14 cells in thickness passing gradually on either sides into one celled wings.
(iii) The epidermal cells are smaller and contain more chloroplasts, than the other cells which have distinct starch grains and oil bodies.
(iv) In P. epiphylla and P. neesiana there are some thick-walled cells in the midrib portion which travel longitudinally from posterior to anterior end.
(v) Rhizoids arise from the lower epidermis in the midrib region.
(vi) Vegetative reproduction takes place by adventitious shoots arising either from the midrib or from margins of the dorsal side.
Identification :
(i) The true roots are absent.
(ii) They lack typical vascular tissues.
(iii) Dorsiventrally differentiated thallus.
(iv) Chloroplasts without pyrenoids.
(v) Rhizoids aseptate.
(vi) Capsule without columella.
(vii) Rhizoids smooth walled and scales absent.
(viii) Globose or sub-globose antheridium found on stalk.
(ix) Neck of archegonium is composed of five vertical rows of cells.
(x) The apical cell is not consumed in the formation of archegonium.
(xi) Jacket of the capsule is 2 to 5 layer thick.
(xii) Sex organs are scattered on the dorsal surface of thallus.
(xiii) Archegonia are present just behind the apical cell in groups of 4 to 12. (xiv) Capsule dehisces by 4 valves.
Experiment – 5
Object: To study the external features of the plant Rhynia Procedure:
(i) Study the reconstruction of plant.
(ii) Observe the differentiation of plant body into rhizoids, rhizome and leaf-less aerial branches.
Comments:
(i) Rhynia is a fossil member (not found living in the present age), discovered from Rhinichert Beds in Aberdeenshire of scotland by Kidston and Lang in 1917.
(ii) The two species R. major, about 40-50 height and R. gwynne- vaughani, about 20 cms in height, found at this station, were well preserved, hence their form and structure are well known.
(iii) The plant grew in swampy marshes. It was differentiated into horizontally creeping rhizome and an upright branched shoot without leaves.
(iv) There were no roots. Unicellular rhizoids were borne in patches, on the underside of the rhizome.
(v) The upright branches were dichotomously branched and gradually tapering. The sporangia terminated these branches.
Identification :
(i) True vascular strand present.
(ii) True roots absent.
(iii) Shoot differentiated into subterranean rhizome and apical portion.
(iv) Sporangia generally borne singly.
(v) Rhizoids unicellular.
(vi) Aerial portion leafless.
(vii) Subterranean portion not corm-like.
(viii) No columella in sporangia.
PLANT PATHOLOGY
Experiment 6
Object : To study the symptoms and causal organism of Tobacco Mosaic. Procedure:
Study the specimen provided.
Symptoms:
(i) Symptoms exhibited are, leaf mottling of light and dark green patches, distortion of leaves, unnatural and irregular leaf shape, stunting of the whole plant, variegation, mosaic patterns, necrosis, etc.
(ii) The first symptoms to appear are clearing of veins, forming mosaic patterns, characteristic mottling and ultimately distortion.
(iii) The virus is sap transmissible and enters the host through wounds. Causal organism: Nicotiana Virus I
Experiment – 7
Object: To study the symptoms and causal organism of Late Blight of Potato.
Procedure:
Study the potato tuber showing disease.
Symptoms:
(i) The first symptoms are the brown spots or necrotic areas on the leaves.
(ii) These areas later become larger brownish black lesions.
(iii) The lesions first appear at the tips of margins of the leaves. These later spread downward and inward and increase in size.
(iv) Generally the lower leaves are attacked first.
(v) The underside of the leaves show whitish or greyish fungal growththe downward hanging of sporangiophores with sporangia.
(vi) Tubers get infected while they are still attached to the plant.
(vii) The first symptoms of the tuber are brown purple discolouration of the tuber skin followed by brownish dry rot.
Causal organism: Phytophythora infestans.
Experiment – 8
Object : To study the symptoms and causal organism of Leaf Curl of Potato.
Procedure:
Study the diseased leaf.
Symptoms:
(i) Leaves curl from the margins towards the mid-rib.
(ii) In case of severe infection, leaves become almost tubular.
(iii) The texture of the leaves also changes.
(iv) Colour of the foliage changes from dark-green to yellowish
(v) The size of the tubers reduce.
Causal organism: Virus I or Solanum.
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