Showing 71–80 of 207 questions
The calcium pump in plant cell vacuole membrane is primarily involved in:
A
Maintaining osmotic potential
B
Regulating turgor pressure
C
Sequestering calcium ions for cellular signaling
D
Photosynthesis regulation
Correct Answer:
C. Sequestering calcium ions for cellular signaling
Explanation:
Calcium pumps actively transport Ca²⁺ into vacuoles, serving as a calcium reservoir for second messenger signaling in plant cells.
During C3 photosynthesis, the first stable product formed after CO₂ fixation is:
A
Glucose
B
3-Phosphoglycerate (3-PGA)
C
Ribulose-1,5-bisphosphate (RuBP)
D
Pyruvate
Correct Answer:
B. 3-Phosphoglycerate (3-PGA)
Explanation:
In the Calvin cycle, RuBP combines with CO₂ to form 3-PGA (3-carbon compound), which is the first stable product detected in C3 plants.
Which enzyme catalyzes the carboxylation of RuBP in the Calvin cycle, and what is its full name?
A
Rubisco (Ribulose-1,5-bisphosphate carboxylase/oxygenase)
B
Phosphofructokinase
C
Aldolase
D
Pyruvate dehydrogenase
Correct Answer:
A. Rubisco (Ribulose-1,5-bisphosphate carboxylase/oxygenase)
Explanation:
Rubisco is the most abundant enzyme on Earth and catalyzes both carboxylation (photosynthesis) and oxygenation (photorespiration) of RuBP.
The phenomenon where plants show reduced photosynthesis when exposed to high oxygen concentrations is called:
A
Warburg effect
B
Crabtree effect
C
Pasteur effect
D
Joule effect
Correct Answer:
A. Warburg effect
Explanation:
The Warburg effect in plants refers to photorespiration, where high O₂ competes with CO₂ for Rubisco binding, reducing net photosynthesis.
Mycorrhizal associations in plants primarily enhance the uptake of which nutrients?
A
Nitrogen and potassium
B
Phosphorus and micronutrients
C
Calcium and magnesium
D
Sulfur and iron
Correct Answer:
B. Phosphorus and micronutrients
Explanation:
Arbuscular mycorrhizal fungi increase plant access to phosphorus and micronutrients (Zn, Cu) through their extensive hyphal networks in soil.
The casparian strip in plant roots is composed primarily of:
A
Cellulose and pectin
B
Suberin and lignin
C
Chitin and protein
D
Keratin and elastin
Correct Answer:
B. Suberin and lignin
Explanation:
The casparian strip is a hydrophobic barrier of suberin and lignin in the endodermis that prevents apoplastic transport and regulates ion uptake.
Which of the following is a C4 plant commonly cultivated in India for fodder and grain production?
A
Wheat
B
Maize (Corn)
C
Rice
D
Barley
Correct Answer:
B. Maize (Corn)
Explanation:
Maize is a C4 plant with higher photosynthetic efficiency and drought tolerance compared to C3 crops like wheat and rice.
The quantum yield of photosynthesis (φ) represents:
A
The number of CO₂ molecules fixed per photon absorbed
B
The wavelength of light absorbed
C
The rate of electron transport
D
The concentration of chlorophyll
Correct Answer:
A. The number of CO₂ molecules fixed per photon absorbed
Explanation:
Quantum yield is the ratio of CO₂ fixed to photons absorbed, typically 0.05-0.1 (5-10 CO₂ per 100 photons).
Guttation in plants occurs due to:
A
Transpiration
B
Root pressure and high humidity conditions
C
Photorespiration
D
Osmotic stress
Correct Answer:
B. Root pressure and high humidity conditions
Explanation:
Guttation is the exudation of xylem sap through hydathodes, caused by positive root pressure, especially in early morning when transpiration is low.
The turgor pressure in plant cells is maintained by which osmotically active substances?
A
Cellulose and starch
B
Soluble sugars, organic acids, and mineral ions
C
Proteins and lipids
D
Chlorophyll and carotenoids
Correct Answer:
B. Soluble sugars, organic acids, and mineral ions
Explanation:
Osmotically active solutes like glucose, sucrose, malate, and K⁺ ions accumulate in vacuoles to maintain turgor pressure and cell rigidity.
