Entrance Exams
Govt. Exams
Petioles contain multiple vascular bundles arranged in characteristic patterns - often arc-shaped or scattered, providing strength and flexibility.
Angiosperm xylem consists of vessels (main conducting element), tracheids, xylem parenchyma (storage), and xylem fibers (support).
Collenchyma provides mechanical support with flexibility but does not transport water and minerals; that function belongs to xylem.
The cork cambium originates from the endodermis or outer cortical cells and produces cork and phelloderm as part of the periderm.
Aerenchyma is specialized parenchyma with large air spaces that provides buoyancy and allows diffusion of gases in hydrophytes.
Desert plants (xerophytes) have smaller leaves, thicker cuticles, and often sunken stomata to minimize water loss through transpiration.
Radial arrangement is characteristic of monocot roots where xylem and phloem alternate on different radii. When they're on the same radii, it's called conjoint arrangement.
In monocot roots, the pericycle is usually uniseriate and gives rise to lateral roots, unlike in dicots where it's multiseriate.
In a young dicot stem, the sequence from outside is: cuticle, epidermis, cortex (containing hypodermis and endodermis), vascular bundles, and central pith.
The Casparian strip in endodermis is impregnated with suberin, making it impermeable to water and solutes, thus forcing them through the endodermal cells.