Govt Exams
Periderm (cork) is produced by cork cambium and replaces the epidermis in older roots and stems, providing protection.
Vascular cambium produces secondary xylem inward and secondary phloem outward, causing increase in diameter (secondary growth) of dicot stems.
Monocot stems have scattered vascular bundles distributed throughout the ground tissue (atactostele), unlike dicots where they form a ring.
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.
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.
Palisade mesophyll consists of tightly packed columnar cells with numerous chloroplasts oriented toward light, maximizing photosynthetic efficiency.
Monocot stems have numerous scattered collateral vascular bundles distributed throughout the ground tissue, unlike the organized ring in dicots.
Calcium oxalate crystals store excess calcium ions and help maintain osmotic balance in plant cells.
Xerophytes have a thick, waxy cuticle and stomata sunken in pits (crypts), which reduces direct exposure to air and decreases transpiration rate.
Monocots lack a functional vascular cambium, which is essential for secondary growth, hence they remain herbaceous throughout life.