Govt Exams
Sieve plate perforations with reduced cell wall material allow efficient translocation of assimilates between sieve tube elements with minimal resistance.
Xylem fibers, which constitute a significant portion of secondary xylem, have thick lignified walls that provide tensile strength to the wood.
Mesophytes have higher stomatal density as water is readily available, while xerophytes have lower stomatal density as an adaptation to reduce water loss.
The pericycle is the outermost layer of the stele (inside endodermis) and gives rise to lateral roots and the vascular cambium during secondary growth.
Vessel elements in angiosperms have perforations (lacking end walls) allowing efficient water transport, while tracheids with bordered pits provide both transport and mechanical support.
Xerophytes like Nerium have reduced intercellular spaces (not large) to minimize water loss. They have sunken stomata, thick cuticle, and multiple palisade layers.
Hydrophytes living in aquatic environments have reduced xylem development as water provides mechanical support (buoyancy) to the plant body.
Xylem parenchyma cells remain alive at maturity and are involved in storage and lateral transport, unlike tracheids and vessels which are dead at maturity.
Pith consists of parenchyma cells that serve for storage and may become lignified with age; it is surrounded by the vascular cylinder.
Xerophytes have a thick, waxy cuticle that reduces water loss through transpiration, an important adaptation to arid environments.