Past Questions — 2025

To determine the safest insecticide for vegetables among the given options, we must evaluate the toxicity, persistence, and regulatory status of each chemical: 1. **Malathion (Option b):** This is an organophosphate insecticide. It is widely recognized as one of the safer insecticides for use on food crops because it is rapidly degraded by hydrolysis and metabolism in mammals, meaning it has low mammalian toxicity and a relatively short residual life on produce compared to organochlorines. It is frequently recommended for vegetable crops for controlling aphids, flies, and beetles. 2. **Carbaryl (Option a):** A carbamate insecticide. While used on vegetables, it is generally more toxic to bees and has a higher toxicity profile in certain environments compared to the targeted application of Malathion in many integrated pest management (IPM) guidelines. 3. **Aldicarb (Option c):** A carbamate systemic insecticide. It is extremely toxic (highly acute toxicity) and has been banned or severely restricted in many countries due to its danger to humans and the environment. It is not considered 'safely recommended' for general vegetable use. 4. **Endrin (Option d):** An organochlorine insecticide. Endrin is highly persistent in the environment and bioaccumulates in the food chain. Due to its extreme toxicity and environmental persistence, it has been banned globally under the Stockholm Convention on Persistent Organic Pollutants (POPs). Therefore, Malathion is the most appropriate and safest choice among the provided options for vegetable application.

The question describes a specific type of pollination. Let's analyze the options: 1. Autogamy: This is the transfer of pollen grains from the anther to the stigma of the same flower. It is the most extreme form of self-pollination. This matches the definition provided in the question. 2. Geitonogamy: This is the transfer of pollen from the anther of one flower to the stigma of another flower on the same plant. While genetically similar to autogamy, it involves different flowers. 3. Xenogamy: This is the transfer of pollen from the anther of one flower to the stigma of a flower on a different plant of the same species (cross-pollination). 4. In vitro fertilization: This is a laboratory procedure where an egg is fertilized by sperm outside the body (typically in animals/humans), and is not a natural pollination process in plants. Therefore, the correct term for pollination within the same flower is Autogamy.

The concept of male sterility, specifically the genetic basis of cytoplasmic-genetic male sterility (CGMS), was pioneered by Nilsson and Ehle. In 1925, they conducted landmark research on the plant species *Crepis* (hawksbeard), where they discovered that male sterility could be inherited and controlled by both nuclear genes and cytoplasmic factors. This discovery laid the foundation for the commercial production of hybrid seeds in agriculture, as it eliminated the need for laborious manual emasculation. Regarding the other options: - Shull (George Shull) is primarily known for his work on heterosis (hybrid vigor) and the development of hybrid corn. - Jones and Davis are not the primary figures associated with the foundational discovery of the male sterility concept in plant breeding literature. - Jenson is not associated with the primary discovery of male sterility.

The term 'self-incompatibility' was coined by G.H. East in 1898. Self-incompatibility (SI) is a genetic mechanism in flowering plants that prevents self-fertilization and promotes cross-pollination by inhibiting the growth of pollen tubes from the same plant or plants with the same genotype. G.H. East's pioneering work on the genetics of maize and other plants contributed significantly to the understanding of these breeding barriers. Options a, b, and c (Harrington, Stout, and Lewis) are associated with other areas of botany and genetics but did not coin this specific term.

The history of plant breeding distinguishes between early anecdotal hybridization and systematic, scientific hybridization. Joseph Koelreuter (1735–1802), a German botanist, is widely credited with initiating systematic hybridization on a scientific basis. He conducted rigorous experiments with Nicotiana (tobacco) and other plants, introducing controlled pollination techniques and documenting the inheritance of traits, which laid the groundwork for later geneticists. Analysis of other options: - Shull (George Shull) is famous for his work on heterosis (hybrid vigor) in Maize in the early 20th century, which came long after the initial scientific basis of hybridization was established. - Knight (Charles Knight) worked on fruit hybridization, but his contributions were not the foundational starting point for systematic scientific hybridization. - Patel is not recognized as the pioneer of systematic hybridization in the context of general plant breeding history.

Emasculation is the process of removing the anthers or stamens from a bisexual flower before they release pollen. This is a critical step in controlled hybridization to prevent self-pollination and ensure that the female parent is fertilized only by the desired pollen from a different male parent. 1. Why 'Self pollinated plants' is correct: In naturally self-pollinating species (like peas or wheat), the pollen is released and reaches the stigma of the same flower very quickly. To achieve a cross (hybridization), the breeder must manually remove the male organs (emasculation) to prevent the plant from pollinating itself. 2. Why other options are incorrect: - Male sterile plants (a): These plants lack functional pollen; therefore, there are no viable anthers to remove. Emasculation is unnecessary. - Self incompatible plants (c): These plants have a genetic mechanism that prevents their own pollen from fertilizing their own ovules. Since self-pollination is naturally blocked, emasculation is not required. - Dioecious plants (d): In dioecious species, male and female flowers are on separate plants. The female flower naturally lacks stamens, making emasculation unnecessary.

Maize (Zea mays) is a monoecious plant, meaning it has separate male and female flowers on the same plant. The male flowers (tassels) are located at the top, and the female flowers (ears/silks) are located lower down on the stalk. Cross-pollination is primarily ensured by a mechanism called Protandry. Protandry is a form of dichogamy where the pollen is shed from the anthers (male phase) before the stigmas (silks) of the same plant become receptive (female phase). This temporal separation prevents self-pollination and promotes cross-pollination via wind. Analysis of other options: - b. Self-incompatibility: This is a genetic mechanism that prevents self-fertilization even if pollen reaches the stigma; it is not the primary driver in maize. - c. Protogyny: This is the opposite of protandry, where the female organs mature before the male organs. This does not occur in maize. - d. Genetic diversity: This is a result of cross-pollination, not the mechanism that causes it.

In plant breeding and genetics, a backcross is defined as the crossing of an F1 hybrid (the offspring of two different parents) with one of its parents or an individual genetically identical to one of its parents. This technique is primarily used to recover a specific trait or a high percentage of the recurrent parent's genome into the hybrid line. Here is why the other options are incorrect: - a. Test cross: A test cross is a specific type of backcross where the F1 hybrid is crossed specifically with the homozygous recessive parent to determine the genotype of the F1 individual. - b. F1 cross: This is not a standard technical term for this specific process; F1 usually refers to the first filial generation resulting from a cross between two pure-breeding parents. - d. Interspecific crossing: This refers to crossing between two different species, which is unrelated to the generational crossing of an F1 hybrid with its own parent.

Protected cultivation (such as greenhouses or polyhouses) allows for the precise control of environmental factors to optimize plant growth. The primary reason for high production is the increase in photosynthetic efficiency. This is achieved through several mechanisms: 1) CO2 Enrichment: In enclosed structures, CO2 levels can be increased (CO2 fertilization), which directly boosts the rate of photosynthesis. 2) Light Management: Use of specialized covers can optimize light transmission and diffusion. 3) Temperature and Humidity Control: Maintaining an ideal climate prevents stress and keeps the stomata open for longer periods, facilitating better gas exchange. Why other options are incorrect: - b. High Oxygen: High oxygen levels can actually lead to photorespiration (especially in C3 plants), which reduces photosynthetic efficiency and yield. - c. High temperature: While warmth is beneficial, 'high' temperature (excessive heat) can cause heat stress, denature enzymes, and increase transpiration rates, leading to wilting. - d. Less CO concentration: Lower CO2 concentrations would limit the rate of photosynthesis, leading to lower production, not higher.

Plant breeding began the moment humans started cultivating plants. The oldest and most fundamental method of plant breeding is 'Selection'. Early farmers observed natural variations in crops and consciously chose (selected) the seeds from the healthiest, largest, or most productive plants to sow in the next season. This is known as Mass Selection. Why other options are incorrect: - Introduction (a): This involves bringing a plant variety from one geographical location to another. While ancient, it is a method of acquiring germplasm rather than the primary breeding process of improving a crop. - Hybridization (b): This is a more advanced scientific method involving the crossing of two genetically different parents to combine desirable traits. This requires a deeper understanding of genetics and controlled pollination. - Back crossing (d): This is a specialized form of hybridization used to transfer a specific trait (like disease resistance) from a donor parent into a high-yielding recurrent parent. It is a sophisticated technique developed long after basic selection.

To determine which method is not used for asexually propagated crops, we must analyze the biological basis of each breeding method: 1. **Plant Introduction (a):** This involves bringing a plant variety from one location to another. It can be applied to any crop, whether it is propagated by seeds (sexually) or by vegetative parts (asexually). 2. **Mutation Breeding (b):** This involves inducing genetic changes using chemicals or radiation. Since mutations occur at the DNA level, they can be induced in any plant. In asexually propagated crops, a desirable mutant can be easily multiplied and maintained as a clone. 3. **Clonal Selection (c):** This is specifically designed for asexually propagated crops. It involves selecting a superior individual (clone) from a mixed population of vegetatively propagated plants and multiplying it to maintain its exact genotype. 4. **Pure Line Selection (d):** A 'pure line' is the progeny of a single, self-fertilized, homozygous plant. This method relies entirely on **sexual reproduction** (specifically self-pollination) to achieve homozygosity. Because asexually propagated crops are multiplied vegetatively (clones) and do not rely on the creation of homozygous seed lines for their primary propagation, the concept of a 'pure line' (which requires seed production from a single selfed plant) is not applicable to them. Therefore, Pure line selection is used exclusively for sexually propagated self-pollinated crops.

Air layering (also known as gootee) is a method of asexual propagation where a branch is induced to form roots while still attached to the parent plant. For this process to be successful, high humidity and moderate temperatures are essential to prevent the rooting medium (usually sphagnum moss) from drying out and to stimulate root initiation. In the context of the Indian climate (relevant to the MPSC exam), the monsoon season, which typically falls between July and August, provides the ideal atmospheric moisture and temperature conditions. - Options a, b, and c (February-March, May-June, November-December) generally coincide with drier or colder periods where the rooting medium would dry out quickly, leading to the failure of the graft unless intensive artificial irrigation is provided.

Bulk population breeding (also known as the Bulk Method) is a breeding technique used primarily in self-pollinated crops to develop improved varieties. In this method, the F2 generation and subsequent generations are grown in a large 'bulk' without individual plant selection until a later stage (usually F5 or F6). 1. Why Small Grain Crops: This method is highly suitable for small grain crops (like wheat, rice, barley, and oats) because they produce a large number of seeds per plant. This allows the breeder to maintain a large population size in a relatively small area, ensuring that genetic diversity is preserved through natural selection until the lines become homozygous. 2. Why other options are incorrect: - Fruit crops (a), Vegetable crops (b), and Flower crops (d) often have larger seed sizes, lower seed production per plant, or longer juvenile periods. Managing these in a 'bulk' population for several generations would be logistically impossible due to the massive amount of space required to maintain the necessary population size to prevent genetic drift.

Heterosis, commonly known as hybrid vigor, refers to the phenomenon where the progeny of two genetically diverse parents exhibits superior qualities (such as growth rate, yield, or fertility) compared to either of the parents. The term 'heterosis' was formally introduced and coined by George Harrison Shull in 1914. While other scientists like Davenport and East contributed significantly to the early study of inbreeding and hybridity around the same era, it was Shull who provided the terminology and the conceptual framework for the systematic breeding of hybrids in maize. Option (a) Davenport worked on early hybrid studies but did not coin the term; Option (c) and (d) are chronologically or conceptually incorrect regarding the origin of the term.

Step-by-step reasoning: 1. Smut fungi (caused by Ustilaginales) are typically systemic infections that often enter the plant through the seed or seedling. Therefore, systemic fungicides are required for effective control. 2. Plantvax is a trade name for Carboxin, which is a systemic fungicide specifically developed and widely used for the control of smut diseases (such as Loose Smut of wheat). 3. Vitavax (option a) is also a Carboxin-based product, but in many classical plant pathology textbooks and exam contexts, 'Plantvax' or 'Carboxin' is specifically highlighted for smut. However, Vitavax is more commonly associated with seed treatment for a broader range of fungi including scabs. 4. Dithane M-45 (option b) and Dithane Z-78 (option d) are based on Mancozeb, which is a contact fungicide. Contact fungicides are generally ineffective against systemic smut infections because they cannot penetrate the plant tissue to reach the internal mycelium. Therefore, Plantvax (Carboxin) is the most specific and widely used systemic agent for smut fungi.

Apical dominance is a phenomenon where the main central stem of the plant grows more strongly than the side stems. This occurs because the apical meristem (the growing tip of the shoot) produces a hormone called Auxin (specifically Indole-3-acetic acid or IAA). Auxin is transported downwards from the tip; as it accumulates in the axillary buds, it inhibits their growth, preventing the development of lateral branches. If the apical tip is removed (decapitation), the source of auxin is eliminated, allowing cytokinins to promote the growth of lateral buds, resulting in a bushier plant. Why other options are incorrect: - b. Ethylene: Primarily involved in fruit ripening and abscission of leaves/flowers. - c. Cytokinins: These hormones generally act antagonistically to auxins in this context; they promote lateral bud growth and counteract apical dominance. - d. GA (Gibberellins): Primarily responsible for stem elongation, seed germination, and flowering, but not the primary driver of apical dominance.

Early blight of potato is caused by the fungus Alternaria solani. This pathogen is an Ascomycete that reproduces asexually by producing spores called conidia. These conidia are typically multicellular, beaked, and borne on short conidiophores, which are then dispersed by wind and water to infect other plants. Regarding the other options: - Uredia (b), Telia (c), and Aecia (d) are specific spore-producing structures associated with rust fungi (order Pucciniales), which are Basidiomycetes. Rust fungi have complex life cycles involving these different spore stages, whereas Alternaria solani does not produce these structures.

Chlorophyll is a pigment essential for photosynthesis in plants. Structurally, it consists of a porphyrin-like ring (a tetrapyrrole) with a long hydrophobic phytol chain. At the center of this porphyrin ring is a single atom of Magnesium (Mg), which acts as the core metal. This magnesium ion is crucial for the molecule's ability to absorb light energy and transfer it to the reaction center. Analysis of other options: - Ni (Nickel): Not a core component of chlorophyll; it is generally not required for photosynthesis. - Fe (Iron): While iron is essential for chlorophyll synthesis (as a cofactor for enzymes) and is the core metal of heme and cytochromes, it is not the central metal of the chlorophyll molecule itself. - Cu (Copper): Copper is used in plastocyanin (an electron carrier), but it is not the core metal of chlorophyll.

The opening and closing of stomata is primarily governed by the turgidity of the guard cells. When guard cells take up water (due to an influx of potassium ions K+ and subsequent osmotic movement of water), they become turgid. Because the inner walls of guard cells are thicker and less elastic than the outer walls, the cells bow outward, pulling the stomatal pore open. Conversely, when guard cells lose water, they become flaccid, and the pore closes. Why other options are incorrect: - a. Circadian rhythm: While the biological clock can influence the timing of stomatal movement, it is a regulatory signal, not the physical mechanism that causes the opening/closing. - b. Pressure of gases: Gas exchange occurs through the stomata, but the pressure of gases inside the leaf does not mechanically drive the opening or closing of the pore. - c. Genetic clock: Similar to circadian rhythms, genetics provide the blueprint for how the plant responds to stimuli, but the immediate physical cause is hydraulic (turgor pressure).

Step-by-step reasoning: 1. Storage fungi are microorganisms that infect grains after harvest, typically during storage in warehouses or silos. They are characterized by their ability to grow at lower moisture contents than field fungi. 2. Aspergillus is a genus of fungi well-known for causing storage rots in food grains (such as maize, wheat, and rice). Some species, like Aspergillus flavus, are particularly dangerous because they produce aflatoxins, which are carcinogenic and toxic to humans and livestock. 3. Evaluating other options: - Rhizobium (a): This is a genus of nitrogen-fixing bacteria that forms symbiotic relationships with legumes; it is not a fungus and does not cause grain rot. - Cercospora (b): This is a genus of fungi that primarily causes leaf spot diseases in the field (foliar pathogens), not storage rot. - Mucor (c): While Mucor can be found on decaying organic matter and some fruits/vegetables (as a zygomycete), it is not considered a 'major' storage fungus for food grains compared to the prevalence and economic impact of Aspergillus and Penicillium. 4. Therefore, Aspergillus is the most accurate answer among the given choices.

In plant nutrition, essential elements are those without which a plant cannot complete its life cycle. These are divided into macronutrients and micronutrients. 1. **Zn (Zinc)**: An essential micronutrient required for enzyme activation and the synthesis of auxin (growth hormone). 2. **Ca (Calcium)**: An essential macronutrient critical for cell wall stability (as calcium pectate) and cell signaling. 3. **Mo (Molybdenum)**: An essential micronutrient required for the functioning of nitrate reductase and nitrogenase enzymes. 4. **Na (Sodium)**: While sodium is beneficial for some specific plants (like halophytes) and can sometimes substitute for potassium (K) in certain physiological processes, it is not required by the vast majority of plant species to complete their life cycle. Therefore, it is classified as a 'beneficial' or 'non-essential' element for most plants. Comparing the options, Zn, Ca, and Mo are universally recognized as essential elements, whereas Na is not.

Step-by-step reasoning: 1. The question asks for the term describing a scenario where a single gene influences multiple, seemingly unrelated phenotypic traits. 2. Pleiotropy (from Greek 'pleion' meaning more and 'tropos' meaning way) is the genetic phenomenon where one gene affects multiple traits. A classic example is Sickle Cell Anemia, where a single mutation in the hemoglobin gene leads to various effects including anemia, organ damage, and resistance to malaria. 3. Analysis of other options: (b) Heteroploidy refers to having a chromosome number that is not an exact multiple of the haploid set. (c) Polyploidy is the condition of possessing more than two complete sets of chromosomes (e.g., triploid, tetraploid). (d) Monoploidy refers to having a single set of chromosomes. Since options b, c, and d relate to chromosomal number (ploidy) rather than gene expression effects, they are incorrect.

Step-by-step reasoning: 1. **Function of Root Hairs**: Root hairs are unicellular elongations of the epidermal cells (specifically trichoblasts). Their primary biological function is to increase the surface area of the root system, allowing for the maximum absorption of water and dissolved minerals from the soil via osmosis and active transport. 2. **Analysis of other options**: - **Root cap (a)**: This is a protective layer of cells at the tip of the root that protects the apical meristem as the root pushes through the soil; it does not absorb water. - **Epidermis (b)**: While root hairs are part of the epidermis, the general epidermal layer acts as a boundary. The specialized 'hairs' are the specific structures evolved for absorption. In a multiple-choice context, 'Root hairs' is the more precise and correct answer than the general 'Epidermis'. - **Endodermis (d)**: This is the innermost layer of the root cortex. Its primary role is to regulate the flow of water and minerals into the vascular cylinder (stele) via the Casparian strip, rather than absorbing them from the soil.