Auxin and Auxinic Herbicide Mechanism(s) of Action - Part 2 - Advanced Glossary

ACC oxidase

The enzyme in the ethylene biosynthesis pathway converting ACC (1-aminocyclopropane-1-carboxylic acid) to ethylene.

ACC synthase

The enzyme in the ethylene biosynthesis pathway converting SAM (S-adenosyl-methionine) to ACC (1-aminocyclopropane-1-carboxylic acid).


A chemical compound that can donate a proton


Having a pH lower than 7, having a higher concentration of H+ ions.


A negatively charged ion.


Adenosine 5'-triphosphate

auxinic herbicide

The first selective organic herbicides developed. This family of herbicides is described as synthetic auxins, growth regulators with herbicidal action, or herbicides with growth regulatory activity.


Unidirectional transport from the apex to the base.


A regulatory protein that has four high-affinity calcium binding sites. The calmodulin-calcium complex can bind to and activate several enzymes.

cell wall

A thin, mechanically strong structure surrounding all plant cells consisting of a complex mixture of polysaccharides and other polymers that are secreted by the cell and are assembled into an organized network linked together by a mixture of covalent and noncovalent bonds. Cell walls regulate cell volume and determine cell shape.


A compartment in a plant or animal cell surrounding the nucleus in which many cell organelles and molecules are suspended.


The liquid substance of protoplasm, excluding all the organelles such as nuclei, plastids, ribosomes.


Process whereby molecules move from areas of higher concentration to areas of lower concentration.


The release of a proton from a molecule due to a change in pH.


(deoxyribonucleic acid) The molecule that encodes genetic information. DNA is a double-stranded molecule held together by weak bonds between base pairs of nucleotides. It is the fundamental substance of which genes are composed.


Movement from the cytoplasm to the cell wall region; out of the cell.


Found naturally in an organism.


Special protein molecules which function in catalyzing chemical reactions.


The downward curvature of leaves that occurs when the upper side of the petiole grows faster than the lower side.


A plant hormone produced by most plant tissues involved in fruit ripening, seed germination, senescence, abscission, and other aspects of plant development.


Applied externally; not from within the organism.


A special class of wall-loosening proteins which cause cell wall expansion by loosening the hydrogen bonding between wall polysaccharides.

fatty acids

A class of compounds containing a long hydrocarbon chain and a terminal carboxyl group. Fatty acids can be saturated (containing no carbon-carbon double bond), monounsaturated (containing one carbon-carbon double bond), or polyunsaturated (containing multiple carbon-carbon double bonds).

growth regulators

Mode of action of herbicides that mimic plant hormones causing unregulated growth.


A chemical reaction in which some reactant combines with water and splits the water into hydrogen and hydroxyl ions.


Excessive development of an organ or part; exaggerated growth or complexity.


Movement from the cell wall region into the cytoplasm; into of the cell.


Molecules with a positive or negative charge.


Having chemical properties relating to lipids (lipid-like), nonpolar compounds that are highly soluble in organic solvents, but not water; hydrophobic.

mechanism of action

The specific process inhibited by a herbicide.


A general term referring to the change of a herbicide from an active to an inactive state.


An essential amino acid found in cereal, whole grains, sesame and sunflower seeds, and yeast.


A sequence of interconnecting enzyme reactions.


Negative log of the hydrogen ion concentration (pH = -log [H+]), the higher the pH of an environment the less H+ ion concentration, the more basic the environment becomes.


Phospholipids containing inositol involved in linking extracellular signals to intracellular responses, or signal transduction.


A a membrane lipid called a phosphoinositide. Phosphoinositides are phospholipids containing inositol involved in linking extracellular signals to intracellular responses, or signal transduction.


The process in which plants use light energy to make sugars and other organic food molecules from carbon dioxide and water.

plasma membrane

The semi-permeable membrane that surrounds the protoplasm of a cell.


More hydrophilic or water loving.

protein kinases

Enzymes that phosphorylate proteins using ATP.


Large molecules composed of one or more chains of amino acids in a specific order. Proteins are necessary for the structure, function, and regulation of the organism's cells, tissues, and organs. Each protein has a unique function determined by its shape.


A positively-charged atomic particle; a hydrogen ion H+.


Special proteins in the cell membrane that bind to a signal or chemical messenger from the environment and transmit signals to the cell to initiate a response.

secondary messengers

Transient secondary signals inside the cell that greatly amplify the original signal.


The inherent ability of a plant to survive and reproduce after herbicide treatment. This implies that there was no selection or genetic manipulation to make the plant tolerant; it is naturally tolerant.


The vacuolar membrane in plant cells.


The process whereby a receptor initiates one or more sequences of biochemical reactions that connect the stimulus to a cellular response.


The loss of water as vapor from plants at their surfaces, primarily through stomata.

turgor pressure

The positive pressure built up when water is compressed.


A membrane-bound (tonoplast) space larger than a vesicle which stores material, either dissolved in water or as a crystalline or flocculent mass. Vacuoles are key organelles for storage of compounds and osmoregulation in plants.