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- DEDDutch elm disease
- deficiencypertaining to plant nutrition. lack or insufficient quantity of a required element.
- defoliationloss of leaves from a tree or other plant by biological. chemical or mechanical means (as opposed to natural shedding).
- degree daya measure of heat accumulation over time that allows comparison of the daily average temperature and a given temperature base. Used to plan. monitor. or schedule plant or pest management. Also growing degree day.
- dehiscentsplitting apart. Describes the release of seed capsules at maturity.
- dehydrationLoss of water from plant tissue
- deicing saltsA combination of salts that are spread to keep areas such sidewalks and roadbeds free of ice
- denitrificationprocess of reducing nitrates to nitrogen gases.
- dentatehaving serrations (teeth) perpendicular to the leaf margin (compare to serrate).
- desalinated waterseawater that has undergone treatment to remove much of the salts.
- descenderdevice used to control friction when descending a climbing line (contrast with ascender).
- desiccationsevere drying out. Dehydration.
- design criteria1) aspects of the landscape or site and the required functions to be served by the plant that must be considered in plant selection. 2) factors considered in the design of equipment.
- design factorfactor by which the rated or minimum breaking strength of a rope or piece of equipment is divided to determine its working-load limit. For example a rated strength of 10.000 lbs. and a design factor of 2.0 would result in a safe working load of 5.000 lbs. (compare with safety factor).
- determinate growthdevelopment to a point characterized by a fixed number of leaves or other lateral organs (contrast with indeterminate growth).
- diagnosisl) process of identifying a causal agent by analyzing signs. symptoms. site conditions. patterns. climate. cultural history. and other factors. 2) the conclusion from the process.
- dibdiameter inside bark
- dicotsee dicotyledon.
- dicotyledonplant with two cotyledons in its embryo. Dicotyledons constitute the larger of the two great divisions of flowering plants. and typically have broad. stalked leaves with netlike veins (contrast with monocotyledon).
- diebackcondition in which the branches in the tree or other plant crown die from the tips toward the main stem.
- dielectricinsulating (nonconducting) material.
- differentiationprocess in the development of cells in which they become specialized for various functions.
- diffuse porouspattern of wood development in which the vessels and vessel sizes are distributed evenly throughout the growth ring (contrast with ring porous).
- DINacronym for Deutsches Institute fiir Normung. a national consensus standards-setting body in Germany.
- DIN 18916in Germany. standard that addresses plants and planting in the landscape industry.
- DIN 18919in Germany. standard that addresses development and maintenance of green areas.
- DIN 18920in Germany. standard that addresses the protection of trees on construction sites.
- dioecioushaving male and female flowers borne on separate individuals of the same species (contrast with monoecious).
- direct cable systemin tree support systems. simple tree cabling system joining two branches or leaders with a single cable (contrast with box cable system and triangular cable system).
- direct contactany part of the body touching an energized conductor.
- directional pruningproviding clearance by pruning branches that could significantly affect the integrity of utility facilities or other structures. and leaving in place branches that could have little or no effect.
- diseasecondition that impairs the performance of one or more vital functions. Usually associated with biotic or parasitic agents (contrast with abiotic disorder).
- disease complexcombination of factors contributing to the stress or decline of a tree.
- disorderabnormal condition that impairs the performance of one or more vital functions. Often associated with noninfectious agents or abiotic factors (contrast with disease).
- Disteltype of friction hitch used in climbing and rigging.
- divisionphylum. Taxonomic group below the kingdom level but above the class level.
- division phylumtaxonomic group below the kingdom level but above the class level.
- dominant leaderthe one stem that grows much larger than all other stems and branches; at least one third larger than lateral branches nearby.
- dormancyperiod of naturally reduced physiological activity in the organs of a plant with the potential for reactivation of growth.
- dormantin a period of dormancy.
- dormant budbud originally developed in a leaf axil and connected to the pith by a bud trace that has not been stimulated to mature and grow. Some buds remain dormant throughout the life of a woody plant.
- dormant oilssee horticultural oils.
- double braidrope construction consisting of a braided core within a braided rope. both of which carry part of the load (contrast with kernmantle rope).
- double crotchtechnique consisting of tying one climbing line or two climbing lines into two places in a tree.
- double figure-S knotfigure-8 knot tied with two strands of rope.
- double fisherman's bendin arboriculture. the name used for a knot that is commonly used to join two ropes or two ends of the same rope. as when forming a Prusik loop. Grapevine knot.
- double half hitchtwo half hitches tied in a series.
- double hitchtechnique consisting of securing a tree section with two load lines in rigging.
- double-lockingpertaining to a carabiner. requiring two distinct motions to prepare the gate to open.
- double serratetoothed margin of a leaf. with smaller teeth within the teeth.