Plant Biology and Applied Biology MCQs

Rain does spread spores and bacteria, but this option excludes dust blowing and wind blowing, both of which are well-established vectors for plant pathogens.

While rain and wind spread pathogens, this option wrongly excludes birds and dust, which also carry fungal spores and bacterial agents over long distances.

This includes birds, dust, and wind but wrongly excludes rain; rain splash is a major mechanism for dispersing plant pathogens like fungal spores.

Bacteriophages infect bacteria and mycoviruses infect fungi, but this option wrongly excludes plants, which are hosts to numerous viruses like Tobacco Mosaic Virus.

Plants are indeed infected by viruses, but bacteria (by bacteriophages) and fungi (by mycoviruses) are also susceptible, making this option incomplete.

This excludes fungi, but mycoviruses are well-documented viral pathogens of fungal species.

This describes an exergonic process; photosynthesis is endergonic, absorbing light energy and storing it as chemical potential energy in glucose molecules.

Oxidation of food releasing CO₂ and water describes cellular respiration, which is the reverse of photosynthesis.

Intake of oxygen and release of CO₂ describes aerobic respiration, not photosynthesis; in photosynthesis, CO₂ is absorbed and O₂ is released.

Vegetative propagation does produce clones, but it can also be practiced through most of the year using cuttings, layering, and grafting, making statement 3 also correct.

Statement 2 is incorrect because vegetative propagation actually perpetuates viruses since the daughter plant carries the same viral load as the parent; only meristem culture can eliminate viruses.

Statement 2 is wrong; vegetative propagation spreads viruses rather than eliminating them because the entire parental genome, including any viral infection, is passed to progeny.

Soil mineral composition matters for long-term growth, but the immediate cause of transplant failure is physical damage to delicate root hairs during uprooting.

Root hairs do not grip soil too hard; they are fragile unicellular extensions that break easily during transplantation, leading to reduced water and nutrient absorption.

While leaf damage can stress a plant, the primary cause of transplant mortality is the loss of root hairs, which are essential for water and mineral uptake.

Violet light is partially absorbed by chlorophyll, but orange is not a primary absorption peak; the strongest absorption occurs in blue and red wavelengths.

Indigo is partially absorbed but yellow and green wavelengths are largely reflected or transmitted by chlorophyll, not strongly absorbed.

Yellow light falls in the region of minimal chlorophyll absorption; plants reflect yellow-green light, which is why they appear green.

Epiphytes are not parasites; they manufacture their own food through photosynthesis and do not derive nutrition from the host plant.

Epiphytes typically grow on tree branches to reach sunlight, not to obtain shade; they are light-seeking organisms.

Epiphytes obtain water from rain, dew, and atmospheric moisture, not from the host plant's vascular system.

Rhizobium forms symbiotic nodules on roots of leguminous plants (pulses), not rice; it is specific to the legume family.

Mycorrhizal fungi assist in phosphorus uptake for many crops but are not the primary biofertiliser specifically associated with rice cultivation in flooded paddies.

Azotobacter is a free-living nitrogen fixer used for crops like wheat and maize, but for rice specifically, blue-green algae are the well-known biofertiliser.

This incorrectly matches wood with leaf; wood is secondary xylem tissue derived from the stem, not the leaf.

This incorrectly matches fruit with leaf; fruit is the mature ovary, not derived from leaves.

This incorrectly matches seed with stem; the seed develops from the ovule, not the stem.

Trace elements support plant nutrition but do not induce parthenocarpy (seedless fruit development).

Mineral solutions provide nutrients but cannot trigger fruit development without fertilisation; hormone application is required for parthenocarpy.

Radioactive fertilizers have no role in inducing seedless fruit; this is a distractor with no scientific basis for parthenocarpy.

While temperature does influence some flowering responses, it is not the primary reason desert flowers bloom at night; herbivory pressure during the day is the key factor.

Lunar phases have no established role in controlling the blooming time of desert plants.

Nocturnal insect activity aids pollination, but the reason flowers bloom at night is to avoid daytime herbivory, not because insects are active at night.

Grafting between unrelated families almost always fails because the vascular tissues cannot form a functional union due to genetic incompatibility.

Different chromosome numbers can cause graft incompatibility; success requires similar genetic makeup for proper cambial connection.

Monocots generally lack a vascular cambium, making grafting between a monocot and dicot practically impossible.