Plant Anatomy and Physiology: Root Zoning, Leaf Structure, and Transpiration

A collection of vocabulary flashcards covering macroscopic and microscopic root zoning, leaf tissue anatomy, and the mechanics of water transport and transpiration.

Root Cap

A protective, thimble-shaped mass of cells at the apex of the root that shields the apical meristem from mechanical abrasion.

Epidermis

The outermost single layer of cells in the root from which root hairs emerge.

Root Hairs

Microscopic lateral extensions of epidermal cells that drastically maximize surface contact area for water and mineral absorption.

Cortex

A broad region of parenchymal cells beneath the epidermis serving as a storage zone for metabolic starch and a pathway for absorbed water.

Endodermis

The innermost cellular layer of the cortex that regulates the entry of minerals into the vascular cylinder.

Casparian Strip

A hydrophobic strip within the endodermis used to regulate the entry of minerals into the vascular cylinder.

Osmotic Pathway Mechanism

A passive physical process governed by concentration gradients where water moves from higher water potential (soil) to lower water potential (cell sap).

Spongy Mesophyll

Loosely arranged, irregularly shaped cells featuring prominent internal air spaces to facilitate internal circulation and gas exchange.

Palisade Mesophyll

Columnar, tightly packed cells located under the upper epidermis that serve as the primary site for light absorption and carbohydrate synthesis.

Vascular Bundles (Veins)

Direct structural extensions of the stem vascular bundles housing xylem to supply water and phloem to export sugars.

Xylem

Tissues within the veins that supply water and minerals required for photosynthesis.

Phloem

Tissues within the veins used to export synthesized sugars to the rest of the plant.

Stomatal Complexes

Microscopic specialized pores predominantly in the lower epidermis that regulate the entry of $CO_2$ and the exit of water vapor and $O_2$.

Guard Cells

A pair of specialized, crescent-shaped epidermal cells that control the opening and closing of a stoma in response to internal cellular turgor pressure.

Transpiration

The physiological process where plants lose water vapor through their open stomatal pores into the external atmospheric matrix.

Transpiration Pull

A phenomenon operating as a hydraulic vacuum that draws the water column upward through the stem conduits from the root core.

Cohesion

The property of water molecules binding tightly to one another via hydrogen bonds, facilitating an unbroken mechanical pull.

Adhesion

The property of water molecules clinging to the hydrophilic walls of the narrow xylem vessels.