NEET Botany: Plant Anatomy

Cards · 57

Meristematic Tissue

Tissues composed of actively dividing, undifferentiated cells with dense cytoplasm and thin cellulose walls.

Apical Meristem

Meristem at root and shoot tips responsible for primary growth and increase in plant length.

Intercalary Meristem

Meristem derived from apical meristem occurring between mature tissues, regenerating parts in grasses.

Lateral Meristem

Cylindrical meristems like fascicular vascular cambium and cork cambium that cause secondary growth in girth.

Parenchyma

Living, thin-walled simple tissue with intercellular spaces performing photosynthesis, storage, and secretion.

Collenchyma

Living mechanical tissue with corner thickenings of cellulose, hemicellulose, and pectin, lacking intercellular spaces.

Sclerenchyma

Dead, lignified mechanical tissue with thick walls and narrow lumina, providing structural rigidity.

Sclereids

Spherical or oval sclerenchyma cells with very thick walls and narrow pits, common in fruit pulp and seed coats.

Xylem

Complex vascular tissue conducting water and dissolved minerals upwards while providing mechanical support.

Tracheids

Elongated, dead, tube-like xylem cells with tapering ends and lignified walls with pits.

Xylem Vessels

Long cylindrical tubes made of dead, lignified vessel elements with perforated end walls; characteristic of angiosperms.

Xylem Fibres

Highly thickened, dead sclerenchymatous cells with obliterated central lumina, offering mechanical support.

Xylem Parenchyma

Only living component of xylem; thin-walled cells that store food materials and conduct water radially.

Phloem

Complex vascular tissue responsible for translocating organic nutrients from source to sink.

Sieve Tube Elements

Long, enucleated living cells joined end-to-end with perforated sieve plates, conducting food in angiosperms.

Companion Cells

Specialized parenchymatous cells closely associated with sieve tubes, regulating sieve tube pressure via their nucleus.

Phloem Parenchyma

Elongated, living cells that store resins, latex, and mucilage; absent in most monocotyledons.

Phloem Fibres (Bast Fibres)

Sclerenchymatous dead cells providing strength to secondary phloem; commercially used from jute, flax, and hemp.

Protoxylem

The first formed primary xylem elements, typically possessing narrower vessels and annular or spiral thickenings.

Metaxylem

The later-formed primary xylem characterized by wider tracheary elements and pitted or reticulate thickenings.

Endarch Xylem

Primary xylem arrangement where protoxylem lies toward the centre (pith) and metaxylem toward the periphery; typical of stems.

Exarch Xylem

Primary xylem arrangement where protoxylem lies toward the periphery and metaxylem toward the centre; typical of roots.

Cuticle

Waxy layer of cutin covering the outer surface of epidermis to prevent water loss; absent in roots.

Stomata

Microscopic epidermal apertures surrounded by two guard cells, regulating gas exchange and transpiration.

Guard Cells

Specialized cells bordering stomata; bean-shaped in dicots and dumb-bell shaped in monocots/grasses.

Subsidiary Cells

Specialized epidermal cells adjoining guard cells that assist in stomatal movements.

Stomatal Apparatus

Morphological unit consisting of the stomatal aperture, the pair of guard cells, and surrounding subsidiary cells.

Trichomes

Multicellular epidermal hairs on stems that prevent water loss and may secrete defensive chemicals.

Root Hairs

Unicellular, tubular extensions of root epidermal cells (epiblema) specialized for water and mineral absorption.

Cortex

Ground tissue region located between the epidermis and the central stele or vascular bundle ring.

Hypodermis

Sub-epidermal layer providing mechanical support; collenchymatous in dicot stems, sclerenchymatous in monocot stems.

Endodermis

Innermost layer of the cortex consisting of tightly packed barrel-shaped cells regulating solute entry into the stele.

Casparian Strips

Suberin-impregnated water-impermeable bands on the radial and tangential walls of endodermal cells.

Pericycle

Layer of cells just inside the endodermis giving rise to lateral roots and secondary meristems.

Stele

Central core of stem and root containing all tissues interior to the endodermis (pericycle, vascular bundles, pith).

Open Vascular Bundle

Vascular bundle containing intrafascicular cambium between xylem and phloem, capable of secondary growth (typical of dicot stems).

Closed Vascular Bundle

Vascular bundle lacking cambium, incapable of secondary growth (typical of monocots).

Radial Vascular Bundle

Arrangement where xylem and phloem lie on alternate radii separated by non-vascular tissue; found in roots.

Conjoint Vascular Bundle

Bundle where xylem and phloem are jointly situated on the same radius; common in stems and leaves.

Dorsiventral Leaf (Dicot Leaf)

Leaf with distinct upper (adaxial) and lower (abaxial) surfaces, typically having more stomata on the lower surface.

Isobilateral Leaf (Monocot Leaf)

Leaf with identical upper and lower surfaces, bearing equal numbers of stomata on both sides.

Palisade Mesophyll

Vertically elongated, closely packed photosynthetic parenchyma cells situated beneath the adaxial epidermis in dicot leaves.

Spongy Mesophyll

Loosely arranged, irregularly shaped photosynthetic cells with large intercellular air spaces located below palisade tissue.

Bulliform Cells

Large, empty, colourless adaxial epidermal cells in grasses that roll leaves inwards during water stress to minimize loss.

Vascular Cambium

Meristematic cylinder giving rise to secondary xylem internally and secondary phloem externally during secondary growth.

Interfascicular Cambium

Cambium formed from medullary ray parenchyma cells joining the intrafascicular cambium into a continuous ring.

Spring Wood (Early Wood)

Secondary xylem formed in spring characterized by wider vessels with larger lumina and lighter appearance.

Autumn Wood (Late Wood)

Secondary xylem formed in winter/autumn characterized by narrower vessels, thicker walls, and higher density.

Annual Ring

Concentric layer of wood composed of one spring wood ring and one autumn wood ring, used to estimate tree age.

Heartwood (Duramen)

Dark, non-functional central secondary xylem filled with tannins, resins, and gums, providing microbial resistance and support.

Sapwood (Alburnum)

Peripheral, light-coloured living region of secondary xylem involved in conducting water and mineral salts.

Cork Cambium (Phellogen)

Secondary lateral meristem developing in cortical regions that produces phellem to the outside and phelloderm inside.

Cork (Phellem)

Outer protective dead tissue produced by phellogen with suberized, impervious walls preventing water loss and infection.

Secondary Cortex (Phelloderm)

Inner parenchymatous tissue layer produced by the phellogen during secondary dermal growth.

Periderm

Collective protective secondary tissue consisting of phellogen, phellem (cork), and phelloderm.

Bark

Non-technical term referring to all tissues exterior to the vascular cambium, including periderm and secondary phloem.

Lenticels

Lens-shaped aerating pores in the periderm of woody stems that facilitate gaseous exchange.