Plant Nutrition and Transport

Vocabulary

active transport

movement of material across the cell membrane against its concentration gradient, requiring the cell to expend energy

apoplast

the continuous network of cell walls and extracellular spaces in plants through which materials can pass without having to go into the cell itself

aquaporin

a transport protein in a cell membrane that allows for osmosis, the diffusion of water across a semipermeable membrane.

Casparian strip

a water-impermeable ring within the roots that regulates water uptake

cortex

endodermis (inner layer) of the root

humus

the layer of decaying plants and animals found in the upper levels of soil that provides nutrients to plants

macronutrient

a nutritional element plants need in quantities greater than 1 milligram per gram of mass of the plant

micronutrient

a nutritional element needed by plants in quantities less than 100 micrograms per gram of mass of the plant

mutualistic relationship

a relationship between organisms of different species in which both organisms benefit

mycorrhiza (plural, mycorrhizae)

the symbiotic relationship between plant roots and fungus found within the soil

nitrogen fixation

the conversion of atmospheric nitrogen into ammonia, a form that is more usable by plants

nodule

a structure found on the roots of nitrogen-fixing plants that contain symbiotic bacteria that fix nitrogen

osmosis

the movement of water molecules across a semipermeable membrane from an area of lower concentration of solute to higher concentration of solute

phloem

the series of tissues that transport sugars and other materials from the leaves of plants to their roots

plasmodesma (plural, plasmodesmata)

a small channel between mesophyll cells and bundle-sheath cells through which molecules pass between carbon fixation in the mesophyll cells and the Calvin cycle in the bundle-sheath cells; this channel extends through the cell wall of a plant cell and directly connects the cytoplasm of adjacent plant cells

pressure flow model

a model of plant transport based on the osmotically generated pressure that moves materials between sources and sinks

root

organ of a vascular plant that provides water and mineral support and anchors a plant to the soil

sink

the location in plants where the synthesized materials are transported, such as the roots

source

the location in plants where the synthesized materials originate, such as the leaves

stoma (plural, stomata)

small opening mostly found on the undersides of leaves that allows for gas exchange between the plant and the external environment

strigolactone

molecule produced by plant roots that signals to attract mycorrhizae hyphae

symbiosis

the ecological relationship between two or more organisms that live in direct contact

symplast

the network in cell interiors of plant cells through which materials can pass uninterrupted via plasmodesmata

translocation

the transport of materials through the phloem of vascular plants

transpiration

the loss of water from the plant leaves through the stomata as a result of temperature and humidity (faster at higher temperatures and slower in humid conditions)

transpiration-cohesion-tension model

the model used to describe how water is pulled from the roots, up the stems, and out of the leaves.

water potential

the tendency of water to move from areas of high concentration to those of low concentration

xylem

a vein-like tissue that carries water from roots and stems to leaves