The anatomical feature that distinguishes protoxylem from metaxylem is:
Answer: B
Protoxylem forms first during primary development with narrow vessels and is often crushed, while metaxylem forms later with wider vessels and persists.
Q.42Medium
In xerophytic plants, the cuticle is typically:
Answer: B
Xerophytes have a thick, waxy cuticle that reduces water loss through transpiration, an important adaptation to arid environments.
Q.43Medium
The pith in a dicot stem is composed of:
Answer: A
Pith consists of parenchyma cells that serve for storage and may become lignified with age; it is surrounded by the vascular cylinder.
Q.44Medium
Which of the following cells in xylem are living at maturity?
Answer: C
Xylem parenchyma cells remain alive at maturity and are involved in storage and lateral transport, unlike tracheids and vessels which are dead at maturity.
Q.45Medium
In hydrophytes, the absence of extensive xylem development is primarily because:
Answer: A
Hydrophytes living in aquatic environments have reduced xylem development as water provides mechanical support (buoyancy) to the plant body.
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Q.46Medium
In a transverse section of a typical dicot root, which tissue layer is responsible for initiating lateral roots?
Answer: C
The pericycle is the outermost layer of the stele (inside endodermis) and gives rise to lateral roots and the vascular cambium during secondary growth.
Q.47Medium
The stomatal density in mesophytic plants compared to xerophytic plants is typically:
Answer: A
Mesophytes have higher stomatal density as water is readily available, while xerophytes have lower stomatal density as an adaptation to reduce water loss.
Q.48Medium
The lenticels in woody stems are primarily involved in:
Answer: C
Lenticels are porous structures in the periderm (cork) that allow gaseous exchange (respiration) to occur in woody stems where stomata are absent.
Q.49Medium
In a transverse section of a typical monocot stem, the vascular bundles are arranged in a scattered pattern throughout the ground tissue. Which of the following anatomical features best explains why monocots can tolerate continuous growth and damage to their vascular tissues better than dicots?
Answer: A
The scattered distribution of vascular bundles in monocots (polystelic arrangement) means that damage to one bundle doesn't severely compromise the entire plant's transport system, unlike the concentric arrangement in dicots where the vascular cylinder is a continuous ring. This provides functional redundancy and allows monocots like grasses to survive grazing and mechanical damage.
