Herbicide and Nonherbicide Injury Symptoms on Spring Wheat and Barley

Appendix 3

Alkaline soil -- Any soil that has a pH value >7.3.

Biotype -- A group of plants within a species that has biological traits that are not common to the population as a whole.

Chloroplast -- A membrane-enclosed structure that contains the green pigment molecules (chlorophyll) essential for photosynthesis (i.e., food production).

Chlorosis -- A yellowing in plant color due to a decline in chlorophyll levels.

Contact herbicide -- A general classification for herbicides that are unable to move within a plant. A contact herbicide's effectiveness is highly dependent upon uniform coverage of treated soil or plant tissue.

Culm -- The stem of a grass plant.

Denitrification -- The biochemical reduction of nitrate or nitrite to gaseous nitrogen either as molecular nitrogen or as an oxide of nitrogen.

Herbicide mode of action -- The sequence of events from absorption of the herbicide into the plant through plant death. Refers to all plant-herbicide interactions.

Herbicide site of action -- The primary biochemical site that is affected by the herbicide, ultimately resulting in the death of the plant. Also referred to as herbicide mechanism of action.

Necrosis -- The death of a specific plant tissue while the rest of the plant is still alive. Necrotic areas are generally dark brown in color.

Peduncle -- Culm area just below the head and above the uppermost leaf of a barley or wheat plant.

Phloem -- Plant tissue that functions as a conduit for the movement (translocation) of sugars and other plant nutrients.

Postemergence application -- A time of herbicide application occurring after the crop and weeds emerge from the soil. Also referred to as a foliar application.

Preemergence application -- A time of herbicide application occurring after a crop is planted but before the crop or weeds emerge from the soil.

Preplanting application -- A time of herbicide application occurring before the crop is planted. Often followed by an incorporation (mechanical mixing) into the top 1 to 2 inches of soil. Often referred to as preplant incorporation treatment.

Pycnidium -- A microscopic fruiting body that houses fungal spores.

Soil pH -- The degree of acidity (or alkalinity) of a soil measured by an electrode or indicator at a specified soil-water ratio and expressed on a pH scale of 1 to 14.

Rosette -- Short, bunchy habit of plant growth.

Systemic herbicide -- A general classification for herbicides that are able to move away from the site of absorption to other parts of the plant.

Translocation -- The movement of water, plant sugars and nutrients, herbicides, and other soluble materials from one plant part to another.

Xylem -- Plant tissue that functions as a conduit for the upward movement (translocation) of water from the roots to above-ground plant parts.

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