RBSE SS Agricultural Biology flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Photosystem II function

Pigment-protein complex in thylakoid membranes that absorbs light, splits water to release oxygen, and donates electrons to the photosynthetic electron transport chain.

RuBisCO enzyme role

Enzyme catalysing CO2 fixation onto RuBP in the Calvin cycle; it also binds oxygen, causing photorespiration, and is the most abundant protein on Earth.

Water potential equation

Total water potential equals solute potential plus pressure potential plus gravitational potential; pure water at atmospheric pressure has zero potential.

ABA and stomatal closure

Abscisic acid accumulates under drought, triggers potassium efflux from guard cells, lowers turgor, and closes stomata to reduce transpirational water loss.

Mendel law of segregation

Two alleles of a gene separate during meiosis so each gamete receives only one allele; random fertilization of gametes produces the 3:1 monohybrid F2 ratio.

Test cross purpose

Crossing an individual of unknown genotype to a homozygous recessive parent; offspring ratios reveal whether the tested parent was homozygous dominant or heterozygous.

Recombination frequency formula

Percentage of recombinant progeny among total progeny in a cross; one percent recombination equals one map unit or centimorgan on a linkage map.

Cytoplasmic male sterility

Maternally inherited inability to produce viable pollen caused by mitochondrial genes; used with restorer lines to produce hybrid seed without hand emasculation.

Broad-sense heritability

Ratio of total genetic variance to phenotypic variance, expressed as a percentage; high values indicate that phenotype reliably reflects genotype for selection.

Cropping intensity formula

Total cropped area divided by net sown area, multiplied by 100; values above 100 percent indicate more than one crop grown per year on the same land.

Intercropping definition

Growing two or more crops simultaneously in the same field in definite row proportions, chosen to use resources such as light, water, and nutrients more efficiently.

Critical growth stage irrigation

Growth stage at which water shortage most reduces yield, such as crown root initiation in wheat or flowering in pulses, so irrigation is prioritized then.

Integrated nutrient management

Combining organic manures, biofertilizers, and mineral fertilizers to sustain soil fertility and crop yield while minimizing nutrient losses and environmental harm.

Soil bulk density

Oven-dry mass of soil divided by its total volume including pore space, expressed in grams per cubic centimetre; compacted soils have higher values.

Cation exchange capacity

Total quantity of exchangeable cations a soil can hold, reported in centimoles of charge per kilogram; clay and organic matter increase this capacity.

Nitrification process

Microbial oxidation of ammonium to nitrite by Nitrosomonas and then to nitrate by Nitrobacter, making nitrogen available to plants but also leachable.

Fertilizer grade meaning

Three numbers giving percent nitrogen, available phosphorus expressed as P2O5, and soluble potassium expressed as K2O in a fertilizer product.

Soil erosion control factors

Universal soil loss equation combines rainfall erosivity, soil erodibility, slope length and steepness, cover management, and support practice to estimate soil loss.

Chewing versus sucking insects

Chewing insects bite plant tissue and are controlled by stomach poisons; sucking insects pierce and extract sap, needing systemic or contact insecticides.

Disease triangle concept

A plant disease develops only when a susceptible host, a virulent pathogen, and a favourable environment occur together; management can target any of these.

Koch's postulates

Criteria proving a pathogen causes a disease: consistent association, pure culture isolation, reproduction of symptoms on inoculation, and re-isolation of the same organism.

Economic threshold level

Pest population density at which control measures should begin to prevent the pest from reaching the economic injury level and causing unacceptable loss.

Gross margin calculation

Gross return from a crop minus variable costs of producing it; fixed costs are excluded, allowing comparison of competing enterprises within a farm.

Benefit-cost ratio

Total gross return divided by total cost of an enterprise; a value greater than one means returns exceed costs and the enterprise is profitable.

Diffusion of innovations

Process by which an innovation spreads among farmers, categorized as innovators, early adopters, early majority, late majority, and laggards over time.

Extension demonstration method

Group teaching method showing a new practice in the field; result demonstrations compare treatments while method demonstrations teach a specific skill step by step.

Walkley-Black method

Wet oxidation of soil organic carbon by potassium dichromate and sulfuric acid, followed by titration; organic matter is estimated as carbon multiplied by 1.724.

Seed germination percentage

Number of normal seedlings produced divided by total seeds sown, multiplied by 100; a standard laboratory test of seed quality and planting value.

Leaf area index

Total leaf area of a crop divided by the ground area it occupies; values indicate canopy density and light interception and relate to yield.

Randomized complete block design

Field experiment design in which each treatment appears once per block and blocks are randomized; blocks absorb field variation and improve precision of treatment comparison.

Urea nitrogen calculation

Fertilizer quantity equals required nutrient divided by nutrient fraction; for 60 kilograms of nitrogen per hectare, urea at 46 percent needs about 130 kilograms.

Water use efficiency

Crop yield produced per unit of water used, expressed in kilograms per millimetre or per cubic metre; higher values indicate more efficient water use.