Companion cells are exclusively associated with which of the following?
Answer: B
Companion cells are specialized parenchymatous cells that remain alive and are attached to sieve tube elements in the phloem.
Q.42Easy
In a typical angiosperm leaf, the tissue responsible for gas exchange is primarily:
Answer: B
The spongy mesophyll contains intercellular spaces and is located below the palisade layer, facilitating gas exchange through stomata.
Q.43Easy
Which of the following is NOT a function of collenchyma?
Answer: C
Collenchyma provides mechanical support with flexibility but does not transport water and minerals; that function belongs to xylem.
Q.44Easy
Which of the following tissues is responsible for secondary growth in dicot stems?
Answer: A
Vascular cambium produces secondary xylem and phloem, while cork cambium produces cork and secondary cortex, together contributing to secondary growth.
Q.45Easy
In monocot roots, the absence of secondary growth is primarily due to:
Answer: A
Monocots lack a functional vascular cambium, which is essential for secondary growth, hence they remain herbaceous throughout life.
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Q.46Easy
In xerophytic plants, which adaptation reduces the surface area for transpiration?
Answer: A
Xerophytes have a thick, waxy cuticle and stomata sunken in pits (crypts), which reduces direct exposure to air and decreases transpiration rate.
Q.47Easy
The prismatic crystals often found in vacuoles of plant cells serve primarily to:
Answer: A
Calcium oxalate crystals store excess calcium ions and help maintain osmotic balance in plant cells.
Q.48Easy
Which type of vascular bundle arrangement is characteristic of monocot stems?
Answer: A
Monocot stems have numerous scattered collateral vascular bundles distributed throughout the ground tissue, unlike the organized ring in dicots.
Q.49Easy
In a transverse section of a dicot leaf, which tissue is primarily responsible for light absorption and sugar production?
Answer: A
Palisade mesophyll consists of tightly packed columnar cells with numerous chloroplasts oriented toward light, maximizing photosynthetic efficiency.
Q.50Easy
Which of the following is a characteristic feature of secondary xylem in dicots?
Answer: A
Secondary xylem in dicots shows growth rings (annual rings) due to variations in cell size and wall thickness between spring wood and autumn wood formed in different seasons.
Q.51Easy
The endodermis in roots is primarily characterized by the presence of:
Answer: A
Casparian strips are band-like thickening of suberin and lignin on radial and transverse walls of endodermis that regulate water and mineral movement into the stele.
Q.52Easy
In a monocot stem, the vascular bundles are typically:
Answer: A
Monocot stems have scattered vascular bundles distributed throughout the ground tissue (atactostele), unlike dicots where they form a ring.
Q.53Easy
Which tissue is responsible for the continuous growth in diameter of dicot stems?
Answer: B
Vascular cambium produces secondary xylem inward and secondary phloem outward, causing increase in diameter (secondary growth) of dicot stems.
Q.54Easy
The tissue that replaces epidermis in older roots and stems of woody plants is:
Answer: A
Periderm (cork) is produced by cork cambium and replaces the epidermis in older roots and stems, providing protection.
Q.55Easy
The primary function of root hair cells is to:
Answer: B
Root hairs are unicellular extensions of root epidermis that greatly increase absorptive surface area for water and mineral uptake.
Q.56Easy
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.57Easy
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.58Easy
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.59Easy
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.60Easy
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.
