Plant Root Morphology and Anatomy Flashcards

Vocabulary flashcards covering the morphology, anatomical structures, primary and secondary growth, and classification of plant roots based on lecture notes.

Root Cap

A protective, multi-layered cell sheath covering the root apex that guards the growing tip, which is absent in parasitic haustorial roots and mycorrhizal roots.

Zone of Elongation

A smooth region a few millimeters long located behind the root cap that responsible for driving length growth, produced by cells of the apical meristem.

Zone of Maturation

The root region covered with numerous fine root hairs that absorb water and mineral salts, where total length remains constant for a species as older lower hairs shed and new upper ones form.

Exodermis / Suberized Zone

The bare, non-smooth root zone exposed after root hairs shed, where cell walls become suberized (suberin layer in Magnoliopsida, suberoid layer in Liliopsida) for protection and lateral roots emerge.

Root Collar

The transitional axis region of the plant that connects the root directly to the stem.

Taproot System

A root system featuring a dominant, strongly developed primary taproot with branching lateral roots, typical of class Magnoliopsida and gymnosperms.

Fibrous Root System

A root system in which the primary root aborts and numerous adventitious roots of similar size arise in a cluster at the stem base, typical of class Liliopsida.

Adventitious Root

Roots originating from non-root vegetative structures such as stem nodes, leaf axils, or along the stem, often forming supportive prop roots.

Tuberous Root

A modified swollen root adapted for storing nutrient reserves, seen in plants such as carrot, ginseng, and Stephania (Bình vôi).

Haustorial Root

A parasitic root that penetrates host plant tissues to extract nutrients, lacking a root cap.

Aerial Root

An above-ground root exposed to the air containing chlorophyll for photosynthetic assimilation or serving to anchor climbing plants to support structures.

Primary Root Anatomy of Class Magnoliopsida

Axially symmetrical root layout featuring a thick cortex ($\frac{2}{3}$ of cross section), a thin vascular cylinder ($\frac{1}{3}$), a Casparian strip endodermis, and $\text{10}$ or fewer alternating primary xylem and phloem bundles.

Primary Root Anatomy of Class Liliopsida

Root anatomy featuring a single-layer suberoid zone, a U-shaped endodermis with passage cells, a developed vascular cylinder with more than $\text{10}$ vascular bundles, large metaxylem vessels, and a sclerified pith, lacking secondary growth.

Casparian Strip

A band of suberin impregnating the radial and transverse walls of endodermal cells in primary Magnoliopsida roots, regulating the entry of water and solutes into the stele.

Passage Cells

Unthickened, thin-walled endodermal cells located opposite xylem poles in a U-shaped endodermis that facilitate water and mineral transfer into the vascular cylinder.

Pericycle

A single or multi-celled layer positioned directly inside the endodermis that retains meristematic capability to form lateral roots in the suberized zone.

Cork Cambium (Phellogen)

A lateral secondary meristem in Magnoliopsida roots formed in the cortex that generates protective cork (bần) externally and phelloderm (lục bì) internally.

Vascular Cambium

A lateral secondary meristem situated between primary xylem and phloem in Magnoliopsida roots that produces secondary phloem outward and secondary xylem inward, causing xylem to occupy the center.

Velamen

A multi-layered, sponge-like modified epidermis found on the aerial roots of epiphytic orchids that functions to absorb ambient atmospheric moisture.

Root Structure Zones

The functional longitudinal regions of a young root, comprising the root cap, meristematic apical zone, zone of elongation, zone of maturation (root hair zone), and suberized zone.