Which of the following is one of the key adaptive features of fungal spores that aid them in long-distance transmission?
निम्नलिखित में से कौन सा कवक बीजाणुओं (fungal spores) का एक प्रमुख अनुकूलन लक्षण है जो उन्हें लंबी दूरी के संचरण (long-distance transmission) में सहायता करता है?
Fungal spores carried through the upper atmosphere over hundreds of kilometers (e.g., urediniospores of Puccinia graminis, conidia of Alternaria and Cladosporium) are exposed to severe environmental hazards: intense solar ultraviolet (UV) radiation and severe desiccation.
Melanin deposited in the cell walls acts as a powerful photoprotective pigment and free-radical scavenger, absorbing lethal UV-B/UV-A radiation and conferring structural rigidity against desiccation.
Airborne spores rely entirely on passive wind currents (anemochory) and do not possess flagella (flagella are present only in aquatic motile zoospores, not aerial spores).
Therefore, high melanin content is the key adaptive feature ensuring spore survival during long-distance transmission.
Correct Answer: Option 3 (High melanin contents).
विस्तृत व्याख्या:
Spore Adaptations for Aerobiological Dispersal (कवक बीजाणुओं के अनुकूलन):
Fungal spores carried through the upper atmosphere over hundreds of kilometers (e.g., urediniospores of Puccinia graminis, conidia of Alternaria and Cladosporium) are exposed to severe environmental hazards: intense solar ultraviolet (UV) radiation and severe desiccation.
Melanin deposited in the cell walls acts as a powerful photoprotective pigment and free-radical scavenger, absorbing lethal UV-B/UV-A radiation and conferring structural rigidity against desiccation.
Airborne spores rely entirely on passive wind currents (anemochory) and do not possess flagella (flagella are present only in aquatic motile zoospores, not aerial spores).
Therefore, high melanin content is the key adaptive feature ensuring spore survival during long-distance transmission.
Correct Answer: Option 3 (High melanin contents).
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Which of the following was responsible for the extinction of the Banana Variety "Gros Michel" from the market due to its high susceptibility?
अपनी अत्यधिक संवेदनशीलता के कारण केले की किस्म "ग्रोस मिशेल" (Gros Michel) के बाजार से विलुप्त/हटने के लिए निम्नलिखित में से कौन सा रोगकारक उत्तरदायी था?
Panama Disease of Banana and Gros Michel Extinction:
During the first half of the 20th century, 'Gros Michel' was the dominant commercial export banana cultivar worldwide.
In the 1950s, an epidemic of Panama wilt caused by Fusarium oxysporum f. sp. cubense race 1 (Foc race 1) wiped out commercial plantations of 'Gros Michel' across Central America and the Caribbean.
This forced the global banana industry to completely abandon 'Gros Michel' and switch to resistant cultivars belonging to the Cavendish subgroup (which are resistant to race 1, though now threatened by Tropical Race 4 / TR4).
Bacterial wilt / Moko disease is caused by Ralstonia solanacearum race 2, but the historical cultivar extinction was caused by Foc race 1.
Panama Disease of Banana and Gros Michel Extinction (पनामा विल्ट - ग्रोस मिशेल का संकट):
During the first half of the 20th century, 'Gros Michel' was the dominant commercial export banana cultivar worldwide.
In the 1950s, an epidemic of Panama wilt caused by Fusarium oxysporum f. sp. cubense race 1 (Foc race 1) wiped out commercial plantations of 'Gros Michel' across Central America and the Caribbean.
This forced the global banana industry to completely abandon 'Gros Michel' and switch to resistant cultivars belonging to the Cavendish subgroup (which are resistant to race 1, though now threatened by Tropical Race 4 / TR4).
Bacterial wilt / Moko disease is caused by Ralstonia solanacearum race 2, but the historical cultivar extinction was caused by Foc race 1.
Magnaporthe oryzae (anamorph Pyricularia oryzae) causes the devastating blast disease.
Host Range (A & B): It infects exclusively monocotyledonous crops of the grass family (Poaceae), including rice (Oryza sativa), wheat (Triticum aestivum - wheat blast), barley, finger millet, and foxtail millet. It does not infect dicots.
Transmission (C): It is internally and externally seed-borne as well as aerially dispersed by wind-blown conidia.
Motility (D): It belongs to the Ascomycota and produces pyriform, 2-septate, 3-celled non-motile conidia.
Thus, statements (A), (C), and (D) are correct.
Correct Answer: Option 4 ((A), (C) and (D) only).
विस्तृत व्याख्या:
Characteristics of Magnaporthe (Pyricularia) (मैग्नापोर्थे / ब्लास्ट रोगजनक):
Magnaporthe oryzae (anamorph Pyricularia oryzae) causes the devastating blast disease.
Host Range (A & B): It infects exclusively monocotyledonous crops of the grass family (Poaceae), including rice (Oryza sativa), wheat (Triticum aestivum - wheat blast), barley, finger millet, and foxtail millet. It does not infect dicots.
Transmission (C): It is internally and externally seed-borne as well as aerially dispersed by wind-blown conidia.
Motility (D): It belongs to the Ascomycota and produces pyriform, 2-septate, 3-celled non-motile conidia.
Thus, statements (A), (C), and (D) are correct.
Correct Answer: Option 4 ((A), (C) and (D) only).
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Choose the correct answer from the options given below:
सूची-I को सूची-II के साथ सुमेलित कीजिए:
नीचे दिए गए विकल्पों में से सही उत्तर चुनिए:
List - I
List - II
A
Turret in a microscopeटरेट
I
Lever beneath the opening in the stage consists of a shutter-like group of metal leaves which regulate the amount of light coming through the slide on the stageस्टेज के छिद्र के नीचे का लीवर जिसमें धातु की पत्तियों का एक समूह होता है जो स्टेज पर स्लाइड से होकर आने वाले प्रकाश की मात्रा को नियंत्रित करता है
B
Condenser in a microscopeकंडेनसर
II
Revolving plate which bears the objective lens, attached at the lower end of the tube; can be turned to change the objective lensघूमने वाली प्लेट जो अभिदृश्यक लेंस धारण करती है, ट्यूब के निचले सिरे से जुड़ी होती है जिसे लेंस बदलने के लिए घुमाया जा सकता है
C
Arm of a microscopeसूक्ष्मदर्शी की भुजा
III
Short metal tube that contains a lens that fits into the top of the tubeछोटी धातु की नली जिसमें एक लेंस होता है जो ट्यूब के शीर्ष पर फिट होता है
D
Ocular lensऑक्युलर लेंस (नेत्रिका लेंस)
IV
Nearly C-shaped pillar arising from the base that supports the stage and ocular componentsआधार से उठने वाला लगभग C-आकार का स्तंभ जो स्टेज और ऑक्युलर घटकों को सहारा देता है
Turret (Revolving nosepiece): The rotating disc at the base of the body tube that holds the objective lenses ($10\times, 40\times, 100\times$) and allows them to be revolved into position $\rightarrow$ (II).
Condenser / Iris Diaphragm assembly: Located beneath the stage opening, fitted with an iris diaphragm consisting of overlapping metal leaves to adjust light intensity and cone angle reaching the specimen $\rightarrow$ (I).
Arm: The curved, C-shaped vertical metal backbone connecting the base to the body tube, providing mechanical support for the stage, focus knobs, and optical head $\rightarrow$ (IV).
Ocular lens (Eyepiece): The upper optical cylinder inserted into the top of the body tube, which magnifies the primary image formed by the objective $\rightarrow$ (III).
Components of Compound Microscope (संयुक्त सूक्ष्मदर्शी के भाग एवं उनके कार्य):
Turret (Revolving nosepiece): The rotating disc at the base of the body tube that holds the objective lenses ($10\times, 40\times, 100\times$) and allows them to be revolved into position $\rightarrow$ (II).
Condenser / Iris Diaphragm assembly: Located beneath the stage opening, fitted with an iris diaphragm consisting of overlapping metal leaves to adjust light intensity and cone angle reaching the specimen $\rightarrow$ (I).
Arm: The curved, C-shaped vertical metal backbone connecting the base to the body tube, providing mechanical support for the stage, focus knobs, and optical head $\rightarrow$ (IV).
Ocular lens (Eyepiece): The upper optical cylinder inserted into the top of the body tube, which magnifies the primary image formed by the objective $\rightarrow$ (III).
Saprotrophs: Feed entirely on non-living dead organic matter; cannot infect living tissue.
Necrotrophs: Actively kill living plant host cells by secreting toxins and cell wall degrading enzymes, and subsequently colonize and feed on the dead plant tissue (e.g., Sclerotinia, Botrytis).
Hemibiotrophs: Initially establish an asymptomatic biotrophic relationship with living host cells, but later switch to a destructive necrotrophic phase killing the host tissues (e.g., Colletotrichum, Magnaporthe).
Biotrophs: Obligately require living host cells throughout their life cycle, deriving nutrition via haustoria without immediately killing host cells (e.g., rusts, powdery mildews).
Transitioning from dead to strictly living host requirements gives the sequence: (A) $\rightarrow$ (D) $\rightarrow$ (C) $\rightarrow$ (B). Correct Answer: Option 2.
विस्तृत व्याख्या:
Trophic continuum from Dead to Living (पोषण विधियों का सातत्य - मृत से जीवित):
Saprotrophs (मृतोपजीवी): Feed entirely on non-living dead organic matter; cannot infect living tissue.
Necrotrophs (ऊतकक्षयी परजीवी): Actively kill living plant host cells by secreting toxins and cell wall degrading enzymes, and subsequently colonize and feed on the dead plant tissue (e.g., Sclerotinia, Botrytis).
Hemibiotrophs (अर्ध-बायोट्रोफ): Initially establish an asymptomatic biotrophic relationship with living host cells, but later switch to a destructive necrotrophic phase killing the host tissues (e.g., Colletotrichum, Magnaporthe).
Biotrophs (अविकल्पी परजीवी): Obligately require living host cells throughout their life cycle, deriving nutrition via haustoria without immediately killing host cells (e.g., rusts, powdery mildews).
Transitioning from dead to strictly living host requirements gives the sequence: (A) $\rightarrow$ (D) $\rightarrow$ (C) $\rightarrow$ (B). Correct Answer: Option 2.
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