Which of the following is the primary pigment responsible for absorbing light energy in the visible spectrum during photosynthesis?
Answer: A
Chlorophyll a is the primary photosynthetic pigment that absorbs light in the blue and red regions of the electromagnetic spectrum.
Q.3Easy
The pH of cell sap in plant cells typically ranges between:
Answer: B
Plant cell sap is slightly acidic due to organic acids like malic acid and citric acid, maintaining pH between 4-6.
Q.4Easy
Which element is essential for the synthesis of chlorophyll molecule and forms the central atom in its structure?
Answer: B
Magnesium (Mg) is the central atom in the chlorophyll molecule, forming a coordinate bond with the porphyrin ring.
Q.5Easy
The phenomenon where plants bend towards light source is governed by which hormone?
Answer: B
Auxin causes differential elongation of cells on the shaded side, resulting in phototropic response towards light.
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Q.6Easy
The process by which plants lose water as water vapour through stomata is called:
Answer: B
Transpiration is the loss of water vapour from aerial parts of plants, primarily through stomata during daytime.
Q.7Easy
A plant cell is placed in a hypertonic solution. Which physical phenomenon occurs, and what is the correct term for it?
Answer: A
In hypertonic solutions, water moves out of the cell due to osmosis, causing protoplasm to shrink away from the cell wall - this is plasmolysis. This is a fundamental osmotic principle tested in SSC/Railway exams.
Q.8Easy
Which of the following represents the correct order of plant tissues from outside to inside in a dicot stem?
Answer: A
The correct radial arrangement in dicot stems is Epidermis (outermost) → Cortex → Vascular bundles (Phloem outer, Xylem inner) → Pith (center). This NCERT-based concept is frequently asked in SSC exams.
Q.9Easy
The phenomenon of senescence in plants is primarily controlled by which plant hormone?
Answer: C
Ethylene is the senescence hormone that promotes leaf yellowing, abscission, and fruit ripening. Cytokinins antagonize ethylene effects. This hormone physiology is important for understanding plant development.
Q.10Easy
Which of the following statements about stomata is correct?
Answer: B
Stomata generally close at night (except CAM plants) to reduce transpiration. Guard cells are rich in mitochondria and chloroplasts to provide ATP and regulate osmotic potential. This circadian regulation is fundamental to plant physiology.
Q.11Easy
Which of the following is characteristic of monocot roots?
Answer: B
Monocots typically have fibrous root systems with adventitious roots. They lack secondary growth (no cambium) and have scattered vascular bundles. Dicots have tap roots and show secondary growth.
Q.12Easy
The green color of chloroplasts is due to which property of chlorophyll?
Answer: B
Chlorophyll absorbs blue and red light but reflects and transmits green light, making plants appear green. This is why plants cannot utilize green light efficiently for photosynthesis - a fundamental physics-biology concept.
Q.13Easy
The process of nitrogen fixation in legumes is performed by which organism?
Answer: B
Rhizobium bacteria form symbiotic associations with legume roots, fixing atmospheric N2 into ammonia. The bacteria live in root nodules. This symbiotic relationship is agriculturally significant and frequently tested in competitive exams.
Q.14Easy
Which of the following organelles is responsible for synthesizing ATP through oxidative phosphorylation in plant cells?
Answer: A
Mitochondria is the powerhouse of the cell and produces ATP through oxidative phosphorylation. Chloroplasts produce ATP through photophosphorylation.
Q.15Easy
During C3 photosynthesis, the first stable product formed after CO₂ fixation is:
Answer: B
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.
Q.16Easy
Which enzyme catalyzes the carboxylation of RuBP in the Calvin cycle, and what is its full name?
Answer: A
Rubisco is the most abundant enzyme on Earth and catalyzes both carboxylation (photosynthesis) and oxygenation (photorespiration) of RuBP.
Q.17Easy
Which of the following is a C4 plant commonly cultivated in India for fodder and grain production?
Answer: B
Maize is a C4 plant with higher photosynthetic efficiency and drought tolerance compared to C3 crops like wheat and rice.
Q.18Easy
The phenomenon of etiolation in plants is characterized by:
Answer: B
Etiolation is the adaptation to grow in darkness: shoots elongate, leaves remain pale (no chlorophyll), and seedlings appear yellowish.
Q.19Easy
Which plant hormone promotes fruit ripening and is commercially used in India for tomato and mango maturation?
Answer: B
Ethylene (C₂H₄) is the ripening hormone that triggers color change, softening, and aroma development in climacteric fruits.
Q.20Easy
The double fertilization process unique to angiosperms results in the formation of:
Answer: A
One sperm nucleus fertilizes the egg (embryo), another fuses with polar nuclei (endosperm); this endosperm provides nutritive tissue for the developing embryo.
