Short day plants (SDPs): Physiologically "long-night plants" (e.g., rice, soybean, chrysanthemum) that require an uninterrupted dark period exceeding a critical duration to induce flowering. If this critical night period is interrupted by even a brief flash of light, flowering is completely inhibited. (Correct answer)
Long day plants (LDPs): Require photoperiods longer than a critical daylength (or short nights) to trigger floral induction (e.g., wheat, oat).
Day neutral plants (DNPs): Initiate flowering after reaching vegetative maturity without dependence on night or day length (e.g., tomato, sunflower).
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17
ICAR JRF 29 Jun 2024Shift 1
MCQ (Single Correct)+4−1
Which of the following is NOT a significant contributor to greenhouse gas emissions from livestock farming?
Carbon dioxide ($CO_2$): Directly respired by animals but constitutes part of the short-term biogenic carbon cycle (rapidly re-absorbed by feed crops through photosynthesis), making direct livestock $CO_2$ a non-significant net anthropogenic greenhouse driver compared to enteric methane and nitrous oxide. (Correct answer)
Methane ($CH_4$): A potent greenhouse gas heavily produced by enteric fermentation in ruminants and anaerobic manure lagoons.
Nitrous oxide ($N_2O$): An exceptionally potent greenhouse gas emitted during the storage, handling, and application of livestock manure and urine.
Ammonia ($NH_3$): A significant livestock-related atmospheric pollutant and indirect greenhouse contributor causing soil acidification.
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Calcareous or alkaline soils: Under high pH ($pH \gt 7.5$) and abundant free calcium carbonate ($CaCO_3$), iron precipitates into insoluble ferric hydroxides and carbonates ($Fe(OH)_3$), severely reducing bioavailable $Fe^{2+}$ and triggering characteristic lime-induced iron chlorosis in young leaves. (Correct answer)
Salt affected soils: Primarily induce osmotic drought and specific ion toxicities (excess $Na^+$ and $Cl^-$).
Acidic soils: Low pH increases iron solubility, frequently causing iron toxicity rather than deficiency.
Neutral soils: Offer optimal micronutrient availability without precipitation.
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19
ICAR JRF 29 Jun 2024Shift 1
MCQ (Single Correct)+4−1
EDV (Essentially Derived Varieties) are those which are derived from
Essentially Derived Variety (EDV): Under international plant breeders' rights (UPOV and PPV&FR Act), an EDV is defined as a variety predominantly derived from an initial variety, retaining its essential genotype characteristics, generated through genetic engineering (transformation), induced mutation, somaclonal variation, or repeated backcrossing. (Correct answer)
Crossing two commercial varieties: Represents standard conventional hybridization that generates new recombinant genetic combinations, not an EDV.
Introduced hybrid: Represents an exotic germplasm introduction.
Wide hybridization with wild relatives: Pre-breeding introgression, not an EDV.
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20
ICAR JRF 29 Jun 2024Shift 1
MCQ (Single Correct)+4−1
What is the role of "companion planting" in agriculture?
Companion planting: The agricultural practice of planting mutually beneficial plant species in close physical association to deter pests (e.g., marigold with tomato to repel nematodes, or aromatic herbs to mask crop scents), attract beneficial pollinators, or supply shade/support. (Correct answer)
Crop rotation: The sequential cultivation of different crop families over successive seasons to restore soil fertility.
Hydroponics: The technique of growing crops in water containing dissolved mineral nutrients without soil.
Cover cropping: Growing dense vegetation to protect against erosion and reduce soil compaction, not increase it.
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