Arboriculture Glossary of Terms
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- obliquepertaining to leaf shape. lopsided. with one side larger than the other.
- obtusepertaining to leaf shape. rounded to approaching semicircular.
- ODPMOffice of the Deputy Prime Minister
- oedemasee edema.
- OHSAOccupational Health and Safety Act (Canada)
- open-face notchwedge-shaped cut (approximately 70 degrees or greater) used in felling trees or removing tree sections (contrast with conventional notch and Humboldt notch).
- Ophiopogon jaburans Ophiopogon jaburans
- Ophiopogon japonica ‘nana’ Ophiopogon japonica ‘nana’
- opposite leafpertaining to leaf or branch arrangement. leaves or branches situated two at each node. across from each other on the stem (contrast with alternate and whorled).
- ordertaxonomic group below the class level but above the family level.
- organellesSpecialized membrane-bound part of a cell
- organic1) a substance containing carbon. 2) a substance. especially a fertilizer or pesticide. of animal or vegetable origin (contrast with inorganic).
- organic fertilizerfertilizer derived from plants or animals (contrast with inorganic fertilizer).
- organic layerlayer of organic matter at the soil surface
- organic mattermaterial derived from the growth (and death) of living organisms. The organic components of soil (see compost. green mulch. . and mulch).
- OSHAOccupational Safety and Health Administration; Occupational Safety and Health Act (U.S.)
- Osmanthus fragransKwai-Fah
- osmosisdiffusion of water through a semi-permeable membrane from a region of higher water potential (lower salt concentration) to a region of lower water potential (higher salt concentration).
- osmotic pressurepressure generated by the movement of water across the cell membrane caused by the difference between solute concentrations on each side.
- outriggersprojecting or extendible structures used for stabilization on aerial devices. cranes. and other vehicles that support elevated or outstretched loads.
- ovaryin trees and other plants. the part of the flower that produces the ovules and becomes the fruit at maturity.
- ovipositing (oviposition)laying of eggs by insects.
- OWdeadwood
- oxygen diffusion rate (ODR)Rate at which oxygen can be replenished if it is used by respiring plant roots or replaced by water