Govt Exams
The endodermis contains the Casparian strip, which regulates the movement of water and solutes into the vascular cylinder.
The cork cambium (phellogen) is the meristematic layer that divides to produce cork cells outwardly and phelloderm inwardly.
Aerenchyma—parenchymatous tissue with large intercellular air spaces—provides buoyancy and oxygen transport in aquatic plants.
Annual rings form due to seasonal variations in xylem formation: large earlywood cells (spring) and smaller latewood cells (summer), creating visible rings.
Collenchyma has unequally thickened primary cell walls, usually at corners, providing mechanical support while remaining flexible. It retains living protoplasm.
Bulliform cells are large, vacuolated cells on the adaxial surface of monocot leaves that control leaf rolling to reduce water loss during drought.
The phellogen typically develops from cortical or endodermal cells in dicot stems, occasionally from the epidermis, replacing the original epidermis.
Palisade parenchyma consists of elongated cells arranged perpendicular to the leaf surface, maximizing light capture for photosynthesis.
Succulent plants like cacti have specialized thin-walled parenchymatous tissues that store water. The waxy cuticle reduces water loss, not parenchyma.
Dicot roots typically show tetrarch arrangement (4 xylem groups), while monocot roots show polyarch arrangement. Triarch is less common in roots.