Prepare for NEET Biology Plant Growth and Development with MCQs & PYQs on NEET.GUIDE. Get free practice, previous year questions, and expert insights on plant hormones and growth regulators.
The 'Richmond-Lang effect', which refers to the delay of senescence in leaves by cytokinins, is primarily attributed to their influence on:
Ethylene production
Cell wall synthesis
Nutrient mobilization
Stomatal closure
Which plant hormone is primarily responsible for inducing dormancy in seeds and buds, enabling them to withstand unfavorable environmental conditions?
Gibberellin (GA)
Auxin (IAA)
Cytokinin (CK)
Abscisic Acid (ABA)
A short-day plant is exposed to a flash of red light during the critical dark period. This is immediately followed by a flash of far-red light. What is the most likely outcome?
Flowering will be inhibited.
Flowering will be promoted.
The plant will become a long-day plant.
The far-red light will have no effect.
A plant species exhibits a critical dark period of 14 hours. Which of the following light/dark regimes would MOST LIKELY prevent flowering?
10 hours light / 10 hours dark
14 hours light / 10 hours dark
10 hours light / 14 hours dark
15 hours light / 9 hours dark
A long-day plant with a critical dark period of 9 hours is grown under short-day conditions. Which treatment is MOST LIKELY to induce flowering?
Increasing the ambient temperature during the dark period.
Spraying the plant with gibberellins during the light period.
Interrupting the dark period with a brief exposure to red light.
Exposing the plant to far-red light at the end of the dark period.
Phytochrome is involved in many plant responses besides flowering. Which of the following is NOT a known role of phytochrome?
Seed germination
Shade avoidance response
Regulation of stomatal closure
Photomorphogenesis
Researchers discover a new plant pigment, 'florigen X,' that they hypothesize is the elusive 'flowering hormone.' Which experiment would provide the STRONGEST evidence for this hypothesis?
Measuring florigen X levels in leaves of plants grown under different light regimes.
Applying purified florigen X to the apical meristem of a non-induced plant and observing flowering.
Demonstrating that florigen X synthesis is regulated by phytochrome.
Grafting a leaf from a photoperiodically induced plant onto a non-induced plant of the same species and observing flowering in the recipient plant.
A dormant seed of a desert plant imbibes water but fails to germinate even under optimal temperature and oxygen availability. Which of the following is the MOST LIKELY explanation for this continued dormancy?
Insufficient light exposure to trigger phytochrome conversion.
Presence of inhibitors like abscisic acid in the seed coat.
Immature embryo requiring a period of after-ripening.
Hard seed coat impermeable to oxygen, preventing respiration.
Which of the following combinations of factors is MOST LIKELY to break seed dormancy in a species exhibiting combinational dormancy?
Exposure to high temperatures followed by gibberellic acid application.
Scarification followed by exposure to high oxygen levels.
Cold stratification followed by exposure to light.
Soaking in water followed by exposure to ethylene.
The ratio of ABA to GA in a dormant seed is typically high. Which of the following changes during seed germination is MOST directly responsible for shifting this balance and promoting growth?
Increased ABA degradation and decreased GA degradation.
Increased GA biosynthesis and decreased ABA biosynthesis.
Transport of ABA out of the embryo and GA into the embryo.
Inactivation of ABA receptors and activation of GA receptors.
