Q.25. Dstinguish between any two of following. (2013)
(a) Isogamous and Oogamous
(b) Aplanospore and Zoospore
(c) Cleistothecium and Apothecium
Ans. (a) Isogamous and Oogamous: -
Isogamous: - Isogamous kind of sexual reproduction is of common occurrence among unicellular algae. In such forms both (male and female) gametes are morphologically similar but they differ physiologically. This type of sexual reproduction is of primitive nature.
Oogamous: - Being an advanced type of sexual reproduction, it is quite common among the higher algae. The male gametes are motile and are formed in large number whereas female gametes are non-motile and bigger in size, and produced few in number. Male gametes (the antherozoids) are produced in the antheridium (male reproductive bodies) whereas the female gamete, an egg or ovum is produce in oogonium (female reproductive body). Somce complex type of reproductive bodies found in Rhodophyceae are called spermatium and carpogonium, the male female reproductive organs, respectively.
Fig. Sexual reproduction. A- isogamous type, B - anisogamous type and C- oogamous type. (A and B - Chlamydomonas spp. and C - Oedogoniumsp.).
(b) Aplanospore and Zoospore: -
Aplanospores: - Aplanospores are non-motile and are produced in aplanosporangia one or more in number. They are of common occurence in Chlorella and Draparnaldia. In Ulothrix aplonospores are formed in large numbers.
Zoospores: - Zoospores are motile and naked spores produced within the zoosporangium. These frequently move with the help of flagella which may be two or more. In Chlamydomonas, the zoospores are exactly similar to the parent cells and are formed in variable numbers (4, 8 or 16) by the division of the cell content and liberated by the rupture of parent cell wall. In filamentous forms, the number of zoospores produced within a single cell exhibits a marked variation. In Ulothrix, a cell produces upto 8 or 16 biflagellate or 4 quadriflagellate zoospores while in Oedogonium, a single multiflagellate zoospore is formed from each cell. In Hydrodictyon, the number may reach as man as 256 within a single cell.
(c) Cleistothecium and Apothecium:-
Cleistothecium: - It is a more or less globose ascocarp which has no natural opening. The cleistothecial wall, the peridium may or may not be covered without growths called the appendages. Asci in a cleistothecium may be arranged in a hymenial layer or they may be scattered throughout the interior. Asci and ascospores are liberated by the disintegration of the wall of cleistothecium.
(ii) Apothecium: - An apothecium is a cup- or saucer shaped ascocarp, the upper surface of which is exposed and forms hymenium. The hymenium consists of asci and parahyces.
Q.26. Differentiate between the following- (2008)
(a) Ascocarp and Basidiocarp
(b) Sporangium and Conidium (2012)
(c) Loose Smut and Covered Smut (2016)
(d) Oosphere and Ospore
(e) Homothallic and Heterothallic (2011)
(f) Simple Septum and Dolipore Septum.
Related Questions -
Q. Write short note on Dolipore Septum. (2012)
Q. Write short note on Sporangium. (2013)
Ans. (a) Ascocarp and Basidiocarp: -
An ascocarp, or ascoma (plural: ascomata), is the fruiting body (sporocarp) of an ascomycete fungus. It consists of very tightly interwoven hyphae and may contain millions of asci, each of which contains typically eight ascospores. Ascocarps are most commonly bowl-shaped, but may take on a number of other designs.
Basidiocarp, basidiome or basidioma (plural: basidiomata), is the sporocarp of a basidiomycete, the multi-cellular structure on which the spore-producing hymenium is borne. Basidiocarps are characteristic of the hymenomycetes; rusts and smuts do not produce such structures. As with other sporocarps, epigeous (above-ground) basidiocarps that are visible to the naked eye (especially those with a more or less agaricoid morphology) are commonly referred to as mushrooms, while hypogeous (underground) basidiocarps are usually called false truffles.
(b) Sporangium and Conidium: -
Sporangium (pl., sporangia) is a plant, fungal, or algal structure producing and containing spores.Sporangia occur in angiosperms, gymnosperms, ferns, fern allies, bryophytes, algae, and fungi. Their spores are sometimes called sporangiospores.
Types: -
Microsporangia are the structures on the stamens of flowers called anthers, and the pollen-producing structures on the microsporophylls of male conifer cones or cycad cones.
Megasporangia are the comparable “female” structures on these plants, associated with the flower carpel and the megasporangial cone.
In ferns, the mature plant is a sporophyte that develops sporangia, tiny, stalked sacs which contain spores. The sporangia may cover the entire underside of the leaf, or occur in lines or clusters called sori. The sporangia are always borne on what is anatomically the underside of the leaf, (the abaxial surface), even if this surface is turned upward. The lycophytes, in contrast, always bear their sporangia on the upper, adaxial surface. A fern may bear sporangia on all leaves or on specialized leaves called sporophylls. Most ferns produce haploid spores.
In mosses, the little case that rises above the vegetative growth on a thin stalk is a sporangium often called a capsule that, as in ferns, produces meiospores. This sporophytic (diploid) growth arises out of the gametophytic (haploid) archegonium after the ovum is fertilized. The sporophyte initially has some chlorophyll, but later turns brown and becomes dependent upon the gametophyte for nutrition, which is absorbed through the foot (base of the stalk), embedded in the archegonial tissues
Conidia, sometimes termed conidiospores, re asexual, non-motile spores of a fungus; they are also called mitospores due to the way they are generated through the cellular process of mitosis. They are haploid cells genetically identical to the haploid parent, can develop into a new organism if conditions are favorable, and serve in biological dispersal.
Asexual reproduction in Ascomycetes (the Phylum Ascomycota) is by the formation of conidia, which are borne on specialized stalks called conidiophores. The morphology of these specialized conidiophores is often distinctive of a specific species and can therefore be used in identification of the species.
The terms “microconidia” and “macroconidia” are sometimes used.
(c) Loose Smut and Covered Smut: -
Loose smut of barley is caused by Ustilago nuda. It is a disease that can destroy a large proportion of a barley crop.
Symptoms: -
Loose smut first becomes visible at heading time. Masses of smut spores replace the entire head of plants, except for the rachis. Smutted heads often emerge before healthy heads. Spores are dislodged and scattered by wind soon after emergence. The fungus infects open flowers and becomes established in the embryo of the developing seed. The spore masses look like those of false loose smut, but are lighter in color.
Covered smut of barley is caused by the fungus Ustilago hordei. The disease is found worldwide and it is more extensively distributed than either loose smut or false loose smut
Symptoms: -
Infected plants do not demonstrate symptoms until heading. Kernels of infected plants are replaced by masses of dark brown smut spores. Smutted heads are hard and compact. Infected plants may be stunted. Occasionally smut sori may also develop in leaf blades, where they appear as long streaks.
(d) Oosphere and Oospore: -
Oosphere is a large non motile female gamete or egg cell formed in an oogonium and ready for fertilization. Whereas An oospore is a thick-walled sexual spore that develops from a fertilized oosphere ( union of oogonium and antheridium) in some algae and fungi.
(e) Homothallic and Heterothallic: -
Heterothallism may be defined as the requirement of two thalli of opposite sex potentialities for fertilization. As in number of species of Zygomycetes, Blackeslee first found that zygospores were formed only when mycelia of opposite sex were mated. One strain or race was called plus(+) and the other(-). Though the visible difference between these two strains occurs rarely. Whereas in contrast to this phenomena there exists another i.e. homothallism where zygospore development is completed by the same thallus and without the union of two different thalli. According to him the term ‘homothallism an ‘heterothallism ’represent monoecism and dioecism used in higher plants. Blackman has stressed not only the term ’sex’ in case where the fusing cells are not morphologically unlike. But Blackeslee has established the sexual identity of plus(+) and(-) minus strains by experimenting with many fungi species.
If the factor compatibility is take into account heterothallism can be interpreted as phenomena of sexual incompatibility. Likewise the self compatible thalli are called homothallic and self incompatible ones are heterothallic. In case of a heterothallic species the factors governing compatibility are distributed in different thalli. Hence the zygospore can only be formed when there is a mating of the thalli belonging to two compatible groups. Though thee thalli are morphologically alike but they are physiologically different . On the other hand in homothallic species the zygospores could be produced in the single thallus which bears alone the compatibility factors.
(f) Simple Septum and Dolipore Septum: -
In Ascomycetes the pore is a simple hole in the middle of the cross walls. In Basidiomycetes the pore is more complex than that found in ascomycetes and is called dolipore.
When there is pore in the septum it is called the dolipore septum. The cells communicate with one another by this minute pore only. For eg. In the hyphae of Agaricus.