Entrance Exams
Govt. Exams
Aerenchyma consists of large air-filled intercellular spaces that facilitate gas exchange and provide buoyancy in aquatic plants.
Calcium oxalate crystals store excess calcium ions and help maintain osmotic balance in plant cells.
Companion cells are living cells derived from the same mother cell as sieve tubes; they provide metabolic support and regulate loading/unloading of photosynthates.
Radial arrangement of xylem and phloem in alternate pattern is typical of dicot roots, where xylem arms point toward the periphery and phloem patches lie between them.
Xerophytes have a thick, waxy cuticle and stomata sunken in pits (crypts), which reduces direct exposure to air and decreases transpiration rate.
The mestome sheath, composed of sclerenchyma fibers, surrounds the vascular bundle and provides mechanical strength to the leaf structure.
Tracheids lack perforation plates, have oblique overlapping end walls with bordered pits, and are found in both gymnosperms and angiosperms, conducting water more slowly than vessel elements.
Dicot petioles typically have multiple vascular bundles arranged in a ring or scattered pattern, while monocots have scattered bundles throughout.
The Casparian strip is an impermeable band of suberin and lignin that prevents lateral movement of water and minerals, forcing them through the endoderm symplastically.
Monocots lack a functional vascular cambium, which is essential for secondary growth, hence they remain herbaceous throughout life.