Resource Acquisition and Transport in Vascular Plants

Vocabulary flashcards covering resource acquisition, transport pathways, water potential, and nutrient distribution in vascular plants.

Xylem

Vascular tissue that pulls water and minerals up from the roots to the leaves using negative pressure generated by evaporation.

Phloem

Vascular tissue that pushes sugars via positive pressure from where they are produced or stored to where they are needed.

Phyllotaxy

the arrangement of leaves on a stem, which is a species-specific trait important for light capture.

Alternate phyllotaxy

A leaf arrangement characterized by having one leaf per node; also known as spiral phyllotaxy.

Opposite phyllotaxy

A leaf arrangement characterized by having two leaves per node.

Whorled phyllotaxy

A leaf arrangement characterized by having more than two leaves per node.

Self-pruning

A process where nonproductive, shaded leaves undergo programmed cell death and drop when their photosynthesis rate falls below their respiration rate.

Leaf area index

The ratio of total upper leaf surface of a plant divided by the surface area of land on which it grows.

Mycorrhizae

Mutualistic associations between roots and soil fungi (hyphae) that increase the surface area for absorbing water and minerals, especially phosphate.

Apoplast

The transport pathway consisting of everything external to the plasma membranes of living cells, including cell walls, extracellular spaces, and dead cell interiors.

Symplast

The transport pathway consisting of the cytosol of all living cells in a plant and the connecting plasmodesmata.

Transmembrane route

A transport route where water and solutes repeatedly cross plasma membranes as they pass from cell to cell.

Proton pumps

Membrane proteins in plants that establish membrane potential by pumping $H^+$.

Water potential ($\Psi$)

A physical property measured in megapascals ($MPa$) that predicts the direction of water flow across a membrane, influenced by solute concentration and physical pressure.

Megapascal ($MPa$)

The unit of pressure used to measure water potential ($\Psi$).

Plasmolysis

The shrinking of the protoplast away from the cell wall when a flaccid cell is placed in an environment with a higher solute concentration.

Solute potential ($\Psi_S$)

Also called osmotic potential, it is directly proportional to molarity; the $\Psi_S$ of pure water is $0$.

Pressure potential ($\Psi_P$)

The physical pressure on a solution.

Protoplast

The entire cell content of a plant cell, excluding the cell wall.

Turgor pressure

The positive pressure exerted by the protoplast against the cell wall.

Aquaporins

Transport proteins in the cell membrane that facilitate the passage of water.

Bulk flow

The movement of a fluid driven by a pressure gradient, required for long-distance transport.

Casparian strip

A waxy layer in the endodermal wall that blocks apoplastic transfer of minerals from the cortex to the vascular cylinder.

Transpiration

The evaporation of water from a plant's surface, mainly through stomatal pores.

Guttation

The exudation of water droplets on the tips or edges of leaves, caused by root pressure at night.

Cohesion-Tension Hypothesis

States that transpiration provides the pull for the ascent of xylem sap and water cohesion transmits this pull along the entire length of the xylem.

Cavitation

The formation of a water vapor pocket that breaks the chain of water molecules in the xylem.

Abscisic acid (ABA)

A hormone produced in response to water deficiency that signals guard cells to close the stomata.

Xerophytes

Plants specifically adapted to arid (dry) climates.

Translocation

The process by which the products of photosynthesis are transported through the phloem.

Sugar source

A plant organ that is a net producer of sugar, such as a mature leaf.

Sugar sink

A plant organ that is a net consumer or depository of sugar, such as roots, buds, and fruits.

Self-thinning

The dropping of sugar sinks like flowers or seeds when there are more sinks than the sources can support.