Which of the following is the primary source of energy for plant cells?
Answer: A
Photosynthesis is the primary source of energy for plant cells as it converts light energy into chemical energy in the form of glucose.
Q.2Easy
The dark reaction of photosynthesis does not require which of the following?
Answer: C
Dark reactions (Calvin cycle) do not directly require light; they use ATP and NADPH produced from light reactions to fix CO2.
Q.3Easy
Which hormone promotes cell elongation and is responsible for apical dominance?
Answer: B
Auxin promotes cell elongation and causes apical dominance by inhibiting lateral bud growth through differential distribution.
Q.4Easy
The phenomenon where plants grow towards light is called:
Answer: B
Phototropism is the directional growth response of plants towards light, mediated by differential distribution of auxin.
Q.5Easy
Which of the following processes does NOT require energy (ATP)?
Answer: B
Diffusion is a passive process that does not require ATP; substances move along the concentration gradient.
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Q.6Easy
During photosynthesis, the light-independent reactions occur in which compartment of the chloroplast?
Answer: A
The Calvin cycle (light-independent reactions) takes place in the stroma of chloroplasts, where CO2 is fixed and glucose is synthesized.
Q.7Easy
Which element is essential for the synthesis of chlorophyll and is present at the center of the chlorophyll molecule?
Answer: B
Magnesium is the central atom in the porphyrin ring of chlorophyll molecules, making it essential for photosynthetic light absorption.
Q.8Easy
Which of the following hormones primarily promotes stomatal closure in response to water stress?
Answer: B
Abscisic acid is the stress hormone that promotes stomatal closure during drought by reducing guard cell turgor pressure, thereby reducing water loss.
Q.9Easy
In phloem transport, the source is typically the:
Answer: B
The source in phloem transport is any photosynthetically active tissue, primarily mature leaves, which produce and load photosynthates into sieve tubes.
Q.10Easy
Which of the following is the primary pigment involved in capturing light energy during photosynthesis?
Answer: A
Chlorophyll a is the primary pigment that directly participates in the photochemical reactions of both PSI and PSII, while other pigments act as accessory pigments.
Q.11Easy
The rate of transpiration is LEAST affected by which of the following factors?
Answer: B
Soil pH has minimal direct effect on transpiration rate. Primary factors affecting transpiration are light, humidity, temperature, and wind velocity.
Q.12Easy
In C4 photosynthesis, the primary CO2 acceptor molecule is:
Answer: B
In C4 plants, CO2 first combines with PEP (3-carbon molecule) to form oxaloacetate (4-carbon), which is why it's called C4 photosynthesis.
Q.13Easy
Which hormone is primarily responsible for closing stomata under water stress conditions?
Answer: B
ABA accumulates in guard cells during water stress and causes stomatal closure by reducing turgor pressure in guard cells.
Q.14Easy
A student observes that a plant kept in a completely dark room still shows some gas exchange. This can be attributed to:
Answer: B
In darkness, photosynthesis stops, but aerobic respiration continues, consuming O2 and releasing CO2, resulting in measurable gas exchange.
Q.15Easy
During photosynthesis, the splitting of water molecules occurs in which compartment of the chloroplast?
Answer: B
Water photolysis (photosystem II) occurs in the thylakoid lumen where oxygen is released as a byproduct.
Q.16Easy
In the Calvin cycle, which enzyme catalyzes the fixation of CO2?
Answer: A
RuBisCO is the most abundant enzyme on Earth and catalyzes the carboxylation of RuBP with CO2 in the dark reactions.
Q.17Easy
The Q10 value for enzyme-catalyzed reactions is typically:
Answer: B
Q10 of 2.0-3.0 indicates that enzyme activity doubles or triples with every 10°C increase in temperature, typical for biological systems.
Q.18Easy
The grana in chloroplasts are composed of:
Answer: A
Grana are stacks of thylakoids arranged vertically, while stroma lamellae are unstacked thylakoids connecting different grana.
Q.19Easy
The phenomenon where plants lose water in liquid form through hydathodes is called:
Answer: B
Guttation occurs when root pressure forces water out through hydathodes (water pores) as liquid water droplets, typically at night.
Q.20Easy
Which of the following enzyme complexes in the thylakoid membrane is responsible for water splitting and oxygen evolution?
Answer: B
Photosystem II contains the oxygen-evolving complex (OEC) with a manganese cluster that catalyzes water splitting, releasing O2, H+, and electrons.
