Govt. Exams
Entrance Exams
Phloem fibers (bast fibers) provide mechanical support to vascular bundles and stems while permitting the translocation function of sieve tubes and companion cells.
Stomatal pits create a humid chamber that reduces the vapor pressure gradient between intercellular spaces and external environment, thereby minimizing transpirational water loss.
Gymnosperms lack vessel elements and rely on tracheids with bordered pits for water conduction, which is less efficient than angiosperm vessel elements.
Dicots develop secondary tissues (secondary xylem and phloem) through vascular cambium activity, creating dense wood that provides greater mechanical strength than herbaceous monocots.
Aerenchyma consists of large air-filled intercellular spaces that facilitate gas exchange and provide buoyancy in aquatic plants.
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.
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.
