Transport in Plants Flashcards

These vocabulary flashcards cover the key terms related to plant transport systems, including xylem and phloem structure, water movement pathways, and the transport of organic assimilates.

vascular system

A system of fluid-filled tubes, vessels or spaces, most commonly used for long-distance transport in living organisms; examples are the blood vascular system in animals and the vascular system of xylem and phloem in plants.

vascular

A term referring to tubes or vessels, from the Latin ‘vascul’, meaning vessel.

xylem

A tissue containing tubes called vessels and other types of cell, responsible for the transport of water and mineral salts through a plant and for support.

phloem

A tissue containing tubes called sieve tubes and other types of cell, responsible for the transport through the plant of organic solutes (assimilates) such as sucrose.

vascular tissue

A tissue in plants consisting mainly of xylem and phloem but also containing sclerenchyma and parenchyma cells.

dicotyledon

Flowering plants whose seeds contain an embryo with two cotyledons (seed leaves) and the adult plant typically has leaves with a blade (lamina) and a stalk (petiole).

eyepiece graticule

A small scale that is placed in a microscope eyepiece used for measuring specimens.

stage micrometer

A very small, accurately drawn scale of known dimensions, engraved on a microscope slide.

vascular bundle

A strand of vascular tissue running longitudinally in a plant; the arrangement of tissues like xylem, phloem, and sclerenchyma varies in different plants and organs.

parenchyma

A basic plant tissue typically used as packing tissue between more specialised structures; it is metabolically active and can function in food storage, support, and the movement of water and food products.

collenchyma

A modified form of parenchyma in which the corners of the cells have extra cellulose thickening, providing extra support, as in the midrib of leaves.

epidermis

The outer layer of cells covering the body of a plant, usually one cell thick and potentially covered with a cuticle for protection.

endodermis

The layer of cells surrounding the vascular tissue of plants, most clearly visible in roots.

sclerenchyma

A plant tissue consisting of thick-walled cells with a purely mechanical function (strength and support); mature cells are dead and walls are usually impregnated with lignin.

lignin

A hard material made by plants used to strengthen the cell walls of certain types of cell, particularly xylem vessel elements and sclerenchyma cells; it is the main material in wood.

transpiration

The loss of water vapour from a plant to its environment, mostly taking place through the stomata in the leaves.

mesophyll

The region of a leaf between the upper and lower epidermis; it includes the palisade layer (main photosynthetic layer) and the spongy layer (used for gas exchange).

stoma (plural: stomata)

A pore in the epidermis of a leaf, bounded by two guard cells and needed for efficient gas exchange.

xerophyte

A plant adapted to survive in conditions where water is in short supply.

cuticle

A layer covering and secreted by the epidermis made of a fatty substance called cutin, which helps provide protection against water loss and infection.

symplast pathway

The living system of interconnected protoplasts extending through a plant, used as a transport pathway for the movement of water and solutes via plasmodesmata.

apoplast pathway

The non-living system of interconnected cell walls extending throughout a plant, used as a transport pathway for the movement of water and mineral ions.

xylem vessel element

A dead, lignified cell found in xylem specialised for transporting water and for support; the ends of the cells break down to join with others.

xylem vessel

A dead, empty tube with lignified walls formed by xylem vessel elements lined up end to end, through which water is transported in plants.

pits

Non-lignified areas appearing as gaps in the thick walls of xylem vessels where the original unthickened cell wall containing cellulose remains; they allow water to pass between cells.

cohesion

The attraction of water molecules to each other by hydrogen bonding, helping to keep water moving as a continuous column.

adhesion

The attraction of water molecules to the hydrophilic cellulose and lignin in the walls of the xylem vessels.

mass flow

The movement of all water molecules and dissolved solutes together at the same speed, driven by a pressure gradient.

Casparian strip

A thick, waterproof, waxy band of suberin in the cell walls of the endodermis that stops water moving through the apoplast pathway.

suberin

The thick, waterproof, waxy material found in the Casparian strip and older endodermis cells.

passage cells

Cells in the endodermis that remain unthickened (retaining only the Casparian strip), allowing the symplast pathway to remain open for water movement.

assimilates

Chemical compounds made by the plant itself as a result of assimilation, such as organic solutes like sucrose and amino acids.

source

A site in a plant which provides food for another part of the plant; common examples include leaves and storage organs.

sink

A site in a plant which receives food from a source for growth, development, or storage; common examples include buds, flowers, and roots.

sieve tube element

A living cell found in phloem tissue with non-thickened cellulose walls, very little cytoplasm, no nucleus, and end walls perforated to form sieve plates.

companion cell

A cell with a nucleus and dense cytoplasm found in close association with a sieve tube element, linked via many plasmodesmata to form a functional unit.

sieve tube

A tube formed from sieve tube elements lined up end to end for the transport of phloem sap.

hydrostatic pressure

The pressure produced inside a sieve tube element by the entry of water via osmosis, creating the gradient necessary for mass flow.

co-transporter

A protein in the companion cell membrane that carries both a hydrogen ion ($H^+$) and a sucrose molecule into the cell simultaneously.