CH29 BIO111

Xylem

Vascular plant tissue consisting mainly of tubular dead cells that conduct most of the water and minerals upward from the roots to the rest of the plant

Abscisic Acid (ABA)

A plant hormone that slows growth, often antagonizing the actions of growth hormones. Two of its many effects are to promote seed dormancy and facilitate drought tolerance

Xylem

Vascular plant tissue consisting mainly of tubular dead cells that conduct most of the water and minerals upward from the roots to the rest of the plant

Abscisic Acid (ABA)

A plant hormone that slows growth, often antagonizing the actions of growth hormones. Two of its many effects are to promote seed dormancy and facilitate drought tolerance

Cohesion Tension Hypothesis

The leading explanation for the ascent of xylem sap. It states that transpiration exerts pull on xylem sap, putting the sap under negative pressure or tension, and that the cohesion of water molecules transmits this pull along the entire length of. The xylem from shoots to roots

Flaccid

Limp, Lacking turgor

Casparian Strip

A water impermeable ring of wax in the endodermal cells of plants that blocks the passive flow of water and solutes into the stele by way of cell walls

Rhizobacteria

A soil bacterium whose population size is much enhanced in the rizosphere, the soil region close to a plants roots

Transpiration

The evaporative loss of water from a plant

Phloem sap

The sugar rich solution carried through a plant’ sieve tubes

Ectomycorrhizae

Associations of a fungus with a plant root system in which the fungus surrounds the roots but does not cause invagination of the host cell’s plasma membrane

Endophyte

A fungus that lives inside a leaf or other plant part without causing harm to the plant.

Solute Potential

A component of water potential that is proportional to the molarity of a solution and that measures the effect of solutes on the directions of water movement; also called osmotic potential it can be either zero or negative

Xerophyte

A plant adapted to an arid climate

Nitrogen Fixation

The conversion of atmospheric nitrogen to ammonia.

Circadian Rhythm

A physiological cycle of about 24 hours that persists even in the absence of external cues

Micronutrient

An essential element that an organism needs in very small amounts

Turgor pressure

The force directed against a plant cell wall after the influx of water and swelling of the cell due to osmosis.

Apoplast

Everything external to the plasma membrane of a plant cell, including cell walls, intercellular spaces, and the space within dead structures such as xylem vessels and tracheids

Loam

the most fertile soil type, made up of roughly equal amounts of sand, silt, and clay

Phloem

Vascular plant tissue consisting of living cells arranged into elongated tubes that transport sugar and other organic nutrients throughout the platn

Sugar sink

A plant organ that is a net consumer or storer of sugar. Growing roots, buds, stems, and fruits are examples of sugar sinks supplies by phloem.

Sugar source

A plant organ in which sugar is being produced by either photosynthesis or the breakdown of starch. Mature leaves are the primary sugar sources of plants

Essential element

A chemical element required for an organism to survive, grow, and reproduce

Macronutrient

An essential element that an organism must obtain in relatively large amounts

Translocation

the transport of organic nutrients in the phloem of vascular plants

Osmosis

The diffusion of free water molecules across a selectively permeable membrane

Rhizosphère

The soil region close to plant roots and characterized by a high level of microbiological activity

Nitrogen Cycle

The natural process by which nitrogen, either from the atmosphere or from decomposed organic material, is converted by soil bacteria to compounds assimilated by plants. This incorporated nitrogen is then taken in by other organisms and subsequently released, acted on my bacteria, and made available again to the nonliving environment.

Arbuscular Mycorrhizae

Associations of a fungus with a plant root system in which the fungus causes the invagination of the host cells’ plasma membranes.

Wilting

The drooping of leaves and stems that occurs when a plant cells become flaccid.

Water potential

the physical property predicting the direction in which water will flow, governed by solute concentration and applied pressure.

Pressure Potential

A component of water potential that consists of the physical pressure on a solution, which can be positive, zero, or negative

Turgid

Swollen or distended, as in plant cells.

Symplast

In plants, the continuum of cytoplasm connected by plasmodesmata between cells

Plasmolysis

A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment

Aquaporin

A channel protein in the plasma membrane of a plant, animal, or microorganism cell that specifically facilitates osmosis, the diffusion of free water across the membrane

Humus

Decomposing organic material that is a component of topsoil

Hydroponic culture

A method in which plants are grown in mineral solutions rather then in soil.

Nodule

A swelling on the root of a legume. They are composed of plant cells that contain nitrogen fixing bacteria of the genus Rhizobium

Bulk Flow

The movement of a fluid due to a difference in pressure between two locations

Protoplast

The living part of a plant cell, which also includes the plasma membrane

Crassulacean acid Metabolism (CAM)

An adaptation for photosynthesis in arid conditions, first discovered in the family crassulaceae. in this process, a plant takes up co2 at night when stomata are open and incorporates it into a variety of organic acids; during the day, when stomata are closed, co2 is released from the organic acids for use in the Calvin cycle

Xylem Sap

The dilute solution of water and dissolved minerals c arrived through vessels and tracheids

Bacteroid

A form of the bacterium Rhizobium contained within the vesicles formed by the root cells of a root nodule

Endodermis

In plant roots, the innermost layer of the cortex that surrounds the vascular cylinder.

Megapascal (MPa)

A unit of pressure equivalent to about 10atm of pressure

Cation Exchange

A process in which positively charged minerals are made available to a plant when hydrogen ions in the soil displace mineral ions from the clay particles.