A chemical abbreviation that normally denotes an alkyl group, but is occasionally used to refer to other organic groups.

2. rabies virus (Lyssavirus)
Definition:

A virus in the genus Lyssavirus (family Rhabdoviridae) that causes rabies and is transmitted through contact with the blood or saliva of an infected animal.

Rabies is an acute, normally fatal encephalitis that can infect most mammals but is found particularly in domestic dogs, cats, skunks, raccoons and bats (though bats' reputations for spreading rabies has been highly exaggerated). Rabies is characterized by burning sensations in the skin, agitation, delirium, hallucinations, excessive salivation, fear of/aversion to drinking fluids, convulsions, paralysis, and coma.

3. raceme (adj. racemose)
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

An indeterminate inflorescence in which a main main stem produces a series of flowers on lateral stalks, the oldest at the base and the youngest at the top.

4. racemic mixture (racemate)
Definition:

A mixture of equal amounts of the two stereoisomers of an optically active substance.

5. rachilla (rhachilla)
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The main stem of a grass spikelet, above the glumes.

6. rachis (rhachis)
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The main stem of an inflorescence or a pinnate leaf.

7. radially
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Arranged or having parts arranged like rays developing uniformly around a central axis.

8. radially symmetrical (radial symmetry)
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Said of an organism or organ which can be cut through the center into equal and similar parts along two or more planes; actinomorphic.

9. radiation
Definition:

1. In evolution, the process through which a group of species diverge from a single ancestral form.
2. General term referring to the emission of electromagnetic waves (e.g. heat, light. etc.) or particles (e.g. neutrons) from from a material.

10. radiation oncology
Definition:

The medical study of the use of radiation (x-rays, gamma rays or electrons) to destroy cancers.

11. radiation therapy
Definition:

The use of x-rays, gamma rays, or electrons to destroy cancerous tissue.

12. radiation therapy (radiotherapy)
Author: Guo Li
Definition:

Radiation therapy is a form of treatment for cancer or abnormal growth by irradiating the target with radioactive material which can be gamma rays, electrons, alpha particles, and positrons. Common side effects are: patients usually feel very tired during treatment. The radiated tissue looses texture, becomes red (erythematous) , hard and itchy (desquamated) ; towards the end, it can be moist and weepy. Ulceration and necrosis may be seen. Some organs in the field of radiation may be affected, e.g. pulmonary fibrosis from the treatment of breast cancer, radiation enteritis from radiation for intra-abdominal malignancies.

13. radical
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Of leaves, clustered at the base of the stem.

14. radical (free radical)
Definition:

An atom or or electrically neutral molecule that has one or more unpaired electrons in its outer orbital. Free radicals are unstable and react quickly with other atoms and molecules; because of this, they can cause damage to living tissues.

15. radical mastectomy
Definition:

The surgical removal of the breast, part of the underlying pectoral muscle and some or all of the lymph nodes under the armpit.

16. radicle
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The portion of an embryo that gives rise to the root system of a plant. Compare plumule.

17. radiculopathy
Definition:

Any disease or degeneration of the roots of nerves in the spine.

18. radio label (radiolabel)
Definition:

A mildly radioactive molecule that is used to "tag" another molecule (such as a protein) so that it can be identified as it goes through some kind of biochemical process.

19. radio ligand (radioligand)
Definition:

A small, slightly radioactive molecule that binds to a specific large molecule; the radioactivity is used so the ligand can be tracked through its reactions.

20. radio waves
Definition:

Electromagnetic radiation with wavelengths of 300 millimeters or longer (even up to several kilometers). Radiation of this type is used to broadcast radio and television signals, and has frequencies up to thousands of megahertz (or one gigahertz).

21. radioactive isotope
Definition:

An isotope of an element that has an unstable nucleus; it tries to stabilize itself by giving off ionizing radiation.

22. radiographic anatomy
Author: Guo Li
Definition:

The study of the external and internal features of the body using imaging techniques: x-rays, magnetic resonance, ultrasound, etc.

23. radioimmunoassay
Definition:

A sensitive method for detecting and measuring trace amounts of a biomolecule based on its ability to displace a radioactive version of itself from combination with its specific antibody.

24. radioisotope
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

An isotope of an element that undergoes spontaneous decay with the release of radioactive particles.

25. radiologist
Definition:

A medical doctor who specializes in radiology.

26. radiology
Definition:

A branch of medicine concerned with the diagnosis and treatment of diseases through the use of x-rays.

27. radiolucent
Author: Guo Li
Definition:

Radiolucent means a substance offers easy passage of radiation.

28. radionuclide angiography
Author: Guo Li
Definition:

Radionuclide angiography is an imaging technique by introducing radionuclides into a blood vessel so that the patency of the vessel is examined.

29. radiosensitizer
Author: Guo Li
Definition:

A radiosensitizer is a substance given to a patient to make the intended target (such as a tumor) more susceptible to the effects of radiotherapy.

30. radiosurgery
Definition:

A technique for treating inoperable brain cancers; a CT scan is used to locate the tumor, which is then bombarded with a precise, high doses of radiation.

31. radius
Author: Guo Li
Definition:

The radius is one of the two bones (radius and ulna) in the forearm. It is shorter than ulna. But of the two, only radius articulates with the carpal bones of the wrist.

32. rainwash
Author:
Definition:

The creep of soil lubricated by rain.

33. ramet
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

An individual member of a cloned strain.

34. ramping
Author:
Definition:

1. In logging, the term refers to a short road or ramp which leads down from a haul road or skid road on a steep angle to a bridge, crossing, or streambed.
2. In general engineering, the term refers to construction of a temporary access road (ramp) from a bank above, down into a streambed either by cutting into the solid bank and building the ramp from the soil taken from the cut (cut ramp) or by filling the area between the top of the bank and the streambed with gravel (fill ramp).

35. randomized, double-blind, placebo-controlled, multicenter clinical trial
Author: PharmInfoNet
Definition:

A clinical trial in which patients have been randomly assigned to receive either the study drug or alternative treatment, in which neither the patient nor the physician(s) conducting the study know which treatment is being given the patient, and in which the alternative to the study drug is a placebo; the study is conducted at several centers.

36. range
Author:
Definition:

The set of conditions throughout which an organism (e.g., plant species) naturally occurs.

37. RAPD (Random Amplified Polymorphic DNA)
Author: ForBio Ltd.
Definition:

DNA polymorphisms amplified by arbitrary primers using PCR. Useful as molecular markers.

38. rape
Author: Guo Li
Definition:

Rape is the nonconsensual penetration of vagina, anus, or mouth by penis, hand, or a foreign object.

39. raphe
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The part of the stalk of an anatropous ovule that is fused along the side of the ovule.

40. raphides
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Needle-like crystals that occur in bundles in the vacuoles of some plant cells.

41. rapids
Author:
Definition:

1. Swift turbulent flow in a rough, steep reach.
2. Fast and agitated current.
3. Stream section with considerable surface agitation, swift current and drops up to 2 m. Some waves may be present; rocks and boulders may be exposed at all but high flows. (Compare glide; riffle; run.)

42. rare species
Author:
Definition:

A species of animal or plant listed in: Section 670.2 or 670.5, Title 14, California Administrative Code; or Title 50, Code of Federal Regulations, Section 17.11 or Section 17.2, pursuant to the Federal Endangered Species Act designating species as rare, threatened, or endangered.

43. RAS oncogenes
Definition:

A family of oncogenes that encode for GTPases (enzymes located at the plasma membrane or in the cytoplasm). They were first identified as the transforming genes in the Harvey sarcoma virus (H- or Ha-ras) and the Kirsten sarcoma virus (K- or Ki-ras).

44. rate-limiting step
Definition:

The slowest step in a metabolic pathway, or the step in an enzymatic reaction that requires the greatest amount of energy to initiate.

45. ravine
Author:
Definition:

Watercourse larger than a gully, smaller than a valley, and less bold in relief than a gulch or arroyo.

46. ray
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

1. A zygomorphic flower in the family Asteraceae; a radial band of cells traversing the conducting elements in woody stems.
2. Of a compound umbel, one of the first (lower) series of branches of the inflorescence main stem.

47. Raynaud's disease
Author: Guo Li
Definition:

Raynaud's disease affects usually women starting in the late teens with Raynaud's phenomenon type of clinical picture but is bilateral and symmetric.

48. Raynaud's phenomenon
Author: Guo Li
Definition:

Raynaud's phenomenon is characterized by intermittent blanching and cyanosis of the fingers that is precipitated by cold or emotion. This condition usually involves only a few fingers. The attack can terminate suddenly with throbbing, paresthesia and rubor. Several clinical conditions are associated with Raynaud's phenomenon, among them: collagen vascular diseases, occupational exposure to toxins, thoracic outlet syndrome.

49. reach
Author:
Definition:

1. Section of stream between two specified points.
2. A length of stream, usually more or less uniform with respect to discharge, depth, area, and slope.
3. A relatively homogeneous section of a stream having a repetitious sequence of physical characteristics and habitat types.
4. A regime of hydraulic units whose overall profile is different from another reach.

50. reaches
Author:
Definition:

Term used to describe sections of a river. The upper reaches refer to the beginning of a river; the lower reaches to the final stages of a river.

51. reaction center
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A photosynthetic complex containing chlorophyll (or bacteriochlorophyll) and other components, within which occurs the initial electron transfer reactions of photophosphorylation.

52. reaction intermediate
Definition:

Any biomolecule which is created and destroyed during the course of of a particular reaction pathway.

53. reading frame
Definition:

A contiguous, non-overlapping set of triplet codoms in RNA or DNA that begin from a specific nucleotide.

54. recalcitrant
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Resistant to microbial attack.

55. recalcitrant seed
Author: ForBio Ltd.
Definition:

Seed which cannot be stored for long periods under the low temperature, dry conditions used for 'orthodox' species.

56. receptacle
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The main stem of a flower (torus); in ferns, a main stem on which sporangia arise.

57. receptor
Definition:

1. A specialized sensory nerve structure that responds to certain types of stimuli
2. a site on a cell (often on a membrane) that can combine with a specific type of molecule to alter the cell's function.

58. receptor agonist
Author: The Alzheimer's Association
Definition:

A substance that mimics a specific neurotransmitter, is able to attach to that neurotransmitter's receptor, and thereby produces the same action that the neurotransmitter usually produces. Drugs are often designed as receptor agonists to treat a variety of diseases and disorders when the original chemical substance is missing or depleted.

59. receptors
Author: Guo Li
Definition:

Receptors are structures which are specific for some molecules such that the adherence of such molecules to the receptors will effect biologic activity. Examples of receptors are: alpha and beta receptors on the blood vessels; the beta-1 receptor of the heart; the histamine receptor on mast cells.

60. recession
Author:
Definition:

Retreat of shore or bank by progressive erosion.

61. recessive gene
Definition:

A gene that is expressed only when it is present in two copies or if the other copy is missing.

62. recessive oncogene (anti-oncogene)
Author: Susan A.Hagedorn
Definition:

A single copy of this gene is sufficient to suppress cell proliferation; the loss of both copies of the gene contributes to cancer formation.

63. reclamation
Author:
Definition:

1. The engineering of derelict terrain so that it can be used for some purpose.
2. The combined process of land treatment that minimizes water degradation, air pollution, damage to aquatic or wildlife habitat, flooding, erosion, and other adverse effects from surface mining operations, including adverse surface effects incidental to underground mines, so that mined lands are reclaimed to a usable condition which is readily adaptable for alternate land uses and create no danger to public health or safety. The process may extend to affected lands surrounding mined lands, and may require backfilling, grading, resoiling, revegetation, soil compaction, stabilization, or other measures.

64. recognition sequence (recognition site)
Author: Susan A.Hagedorn
Definition:

A nucleotide sequence -- typically composed of 4, 6, or 8 nucleotides -- that is recognized by a restriction endonuclease. Type II enzymes cut (and their corresponding modification enzymes methylate) within or very near the recognition sequence.

65. recombinant clones
Definition:

Clones containing recombinant DNA molecules. See recombinant DNA technologies.

66. recombinant DNA
Definition:

A combination of DNA molecules of different origin that are joined using recombinant DNA technologies.

67. recombinant DNA
Author: Guo Li
Definition:

Recombinant DNA is a fragment of DNA incorporated artificially into the DNA molecule of a suitable vector so that it can express itself many times. This way a large quantity of the DNA in question can be obtained. The DNA is usually one that contains genes of interest, such as interferon, insulin, or growth hormone. The DNA may also be intended to fix mutated genes causing diseases, such as hemophilia or sickle cell anemia. The vector could be plasmids, bacteriophages, and cosmids (packaged plasmid DNA into a phage particle).

68. recombinant DNA technologies
Definition:

Procedures used to join together DNA segments in a cell-free system (an environment outside a cell or organism). Under appropriate conditions, a recombinant DNA molecule can enter a cell and replicate there, either autonomously or after it has become integrated into a cellular chromosome.

69. recombination (genetic recombination)
Definition:

The process by which offspring derive a combination of genes different from that of either parent. In higher organisms, this can occur by crossing over.

70. recombination frequency
Author: Susan A.Hagedorn
Definition:

The frequency at which crossing over occurs between two chromosomal loci--the probability that two loci will become unlinked during meiosis.

71. recommended limit
Author: Biological Sciences at Heriot-Watt University
Definition:

This regulatory value is the maximum concentration of a potentially toxic substance which is believed to be safe. Such limits often have no legal backing in which case a control or statutory guide level which should not be exceeded under any circumstances may be set. See control limit.

72. recruit (recruit fish)
Author:
Definition:

A juvenile fish that has survived long enough to become a part of (i.e., recruited into) a population or an exploitable segment of the population.

73. recultivation
Author:
Definition:

General expression used for the making of bare areas (raw mineral soils) fertile again through bioengineering and refertilization.

74. recurrence interval
Author:
Definition:

Expected or observed time intervals between hydrological events of a particular magnitude described by stochastic or probabilistic models (log-log plots).

75. recurved
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Curved or curled downwards or backwards.

76. redd
Author:
Definition:

Nest made in gravel, consisting of a depression dug by a fish for egg deposition (and then filled) and associated gravel mounds.

77. reducing agent (reductant)
Definition:

A molecule that donates an electron in an oxidation-reduction reaction.

78. reduction
Definition:

The gain of electrons by a molecule or ion.

79. reduction mammoplasty
Author: Guo Li
Definition:

Reduction mammoplasty is surgery to decrease the size of the breasts.

80. reduction potential
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

The inherent tendency of a compound to act as an electron donor or an electron acceptor. Measured in volts.

81. reductive dechlorination
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Removal of Cl as Cl- from an organic compound by reducing the carbon atom from C-Cl to C H.

82. reed sods
Author:
Definition:

Pieces of sod cut out from the rhizome or root areas of reed communities.

83. reef
Definition:

1. In general, any solid object that projects from a stream bed or from the floor of any other body of water.
2. Specifically, a porous, often delicate mass of calcium carbonate and some silica made up of the skeletons of marine corals and sponges. Coral reefs serve as an important focus for many shallow-water ocean ecosystems.

84. reflex sympathetic dystrophy
Author: Guo Li
Definition:

Reflex sympathetic dystrophy is characterized by burning pain and swelling with skin atrophy and increased sweat secretion.

85. reflexed
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Bent sharply downwards or backwards.

86. reflux
Author: Guo Li
Definition:

Reflux is the backward flow of fluids; for example, reflux esophagitis (inflammation of the esophagus due to stomach acid), vesicoureteral reflux.

87. regimen
Author:
Definition:

The characteristic behavior of a stream during ordinary cycles of flow.

88. regional index streams
Author:
Definition:

Streams considered typical of a region.

89. regrade
Author:
Definition:

To intentionally reconfigure the elevations and slopes on a parcel of land by means of surveying technology and construction equipment.

90. regulated flow
Author:
Definition:

The flow in a stream that has been subjected to regulation by reservoirs, diversions, or other works of humans.

91. regulation
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Proceses that control the rates of synthesis of proteins. Induction and repression are examples of regulation.

92. regulation
Author:
Definition:

Control of flow of a stream by storage or diversion.

93. regulatory enzyme
Definition:

An enzyme that regulates certain functions due to its ability to undergo a change in its catalytic activity through modification of its structure.

94. regulatory gene
Definition:

A gene that codes for a repressor protein.

95. regulatory regions or sequences
Definition:

A DNA base sequence that controls gene expression.

96. regulon
Definition:

A group of genes or operons that are regulated together even though they may be located a good distance from each other in the genome.

97. rehabilitation (rehabilitate)
Definition:

1. To improve a site ecologically without it becoming completely restored to its virgin state.
2. To help an animal recover from injury so that it is able to be re-introduced into and survive in its natural habitat.
3. To help a person recover from injury or illness so that they are able to maintain a relatively active, healthy lifestyle.

98. Reiter's syndrome
Author: Guo Li
Definition:

Reiter's syndrome is characterized by arthritis (tetrad) and inflammation of urethra, conjunctiva, and mucous membranes.

99. relative basal area
Author:
Definition:

An estimate of basal area for trees, such as produced by the Bitterlich sampling technique.

100. relative risk
Author: Biological Sciences at Heriot-Watt University
Definition:

This term may have any of the following meanings depending upon context.

1. Ratio of the risk of disease or death among the exposed to the risk among the unexposed: this usage is synonymous with "risk ratio";
2. Alternately, the ratio of the cumulative incidence rate in the exposed to the cumulative incidence rate in the unexposed, i.e. the cumulative incidence ratio;
3. Sometimes used as a synonym for "odds ratio".

101. relaxed control
Definition:

The ability of certain plasmids to continue to replicate after their bacteria stop dividing; the result is a single bacteria that contains hundreds of plasmids.

102. relaxed DNA
Definition:

DNA that isn't supercoiled.

103. relaxed mutant
Definition:

A mutant bacterium that continues to synthesize RNA in a medium that lacks certain nutrients or amino acids which that sort of bacterium normally needs present before it can make RNA.

104. relaxed plasmid
Author: Susan A.Hagedorn
Definition:

A plasmid that replicates independently of the main bacterial chromosome and is present in 10-500 copies per cell.

105. relaxing enzyme
Definition:

Any of several enzymes, such as helicase, that unwind DNA prior to its replication.

106. releasing factors
Definition:

Hormones produced by the hypothalamus which stimulate the release of other hormones in the pituitary gland.

107. relief
Author:
Definition:

The change in elevation of a land surface between two points; collectively, the configuration of the earth's surface, including such features as hills and valleys.

108. REM sleep (rapid eye movement sleep)
Author: Guo Li
Definition:

REM sleep is sleep associated with rapid, roving movements of the eyes. The EEG pattern would resemble that of alert animals and humans despite sleep is not interrupted. There is a marked reduction of skeletal muscle tone during REM sleep. REM sleep and dreaming are associated.

109. remote
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Separated from one another; separated by intervals or spaces greater than the ordinary.

110. renal
Definition:

This refers to anything associated with the kidneys.

111. renal failure (kidney failure)
Author: Guo Li
Definition:

Renal failure is the decrease in kidney function which is often reflected clinically by the elevation of serum urea nitrogen and creatinine concentrations.

Types:

• pre-renal: acute tubular necrosis
• renal: proliferative and crescentic glomerulonephritis, acute pyelonephritis, malignant nephrosclerosis
• post-renal: obstruction of the urinary tract

112. renature
Author: Susan A.Hagedorn
Definition:

The reannealing (hydrogen bonding) of single-stranded DNA and/or RNA to form a duplex molecule.

113. Rendu-Osler-Weber syndrome (hereditary hemorrhagic telangiectasia)
Author: Guo Li
Definition:

Rendu-Osler-Weber syndrome is characterized by bleeding tendency and telangiectases of the skin, mucosa of the nose, mouth, and the gastrointestinal tract. It is inherited as an autosomal dominant condition.

114. reniform
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Kidney-shaped.

115. rennet
Definition:

The inner lining of the fourth stomach of the calf of a ruminant (such as a cow). It is used to make cheese because it produces the enzyme rennin.

116. rennin (chymosin)
Definition:

A proteolytic enzyme that is used to curdle milk to make cheese. Rennin is typically used in the form of rennet, a commercial preparation taken from the abomasum of young calves, but because the demand for rennin is so great, the cheese industry is increasingly turning to rennin-producing microbes such Mucor miehei and Mucor pusillus.

117. Rep protein
Definition:

1. A protein that triggers a plasmid's replication.
2. An acronym for repetitive extragenic palindromic protein; this protein is an enzyme produced by a mutant strain of E. coli that unwinds the DNA helix.

118. repent
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Said of a stem that is prostrate and rooting at the nodes.

119. repetatur (rept.)
Definition:

This Latin term, which is frequently used in medicine and pharmacy, means "let it be repeated".

120. replacement vector
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A cloning vector, such as a bacteriophage, in which some of the DNA of the vector can be replaced with foreign DNA.

121. replica plating (replica plate)
Definition:

A lab technique used mainly for identifying and selecting mutant colonies of a microorganism when the mutant can only be selected against. The microorganisms are cultured on a plate of agar, then a replica is made by blotting the colonies with a membrane and blotting the membrane on another plate. This results in all colonies from the first plate being in identical locations on the second plate. The second plate either contains some substance which kills off the mutation of interest, or lacks a substance necessary for the mutant to grow. Later, it is determined which colonies on the first plate failed to grow on the second plate.

122. replicase (RNA replicase)
Definition:

A type of RNA polymerase which uses RNA molecules as a template for making new RNA molecules (a process which works exactly the same as the replication of DNA molecules).

123. replication (DNA replication)
Definition:

The process of making an identical copy of a section of duplex (double-stranded) DNA, using existing DNA as a template for the synthesis of new DNA strands. In humans and other eukaryotes, replication occurs in the cell nucleus.

124. replication fork
Definition:

A Y-shaped region in a chromosome that serves as the growing site for DNA replication.

125. replicon
Definition:

A plasmid that has the ability to replicate.

126. replisome
Definition:

A multi-protein complex that promotes the synthesis of DNA at the replication fork.

127. replum
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A longitudinal partition in an ovary, formed between parietal placentas.

128. reporter gene
Definition:

A gene that is used to locate or identify another gene.

129. repose
Author:
Definition:

The stable slope of a bank or embankment, expressed as an angle or the ratio of horizontal to vertical projection.

130. repressible enzyme
Definition:

In bacteria, an enzyme whose creation is inhibited when its reaction product is plentiful.

131. repression
Definition:

The inhibition of a gene's expression; this is typically caused by the change in the activity of a regulatory protein.

132. repressor
Definition:

A type of protein molecule that binds to DNA that shuts up transcription of a gene. See: operon or operator.

133. reproductive adaptation
Author:
Definition:

A peculiarity of the reproductive mechanism of a species that results in it being better fitted to its environment (e.g., prolonged seed dormancy).

134. reproductive endocrinologist
Author: Fertilitext
Definition:

An ob-gyn who specializes in the treatment of hormonal disorders that affect reproductive function.

135. reproductive surgeon
Author: Fertilitext
Definition:

An ob-gyn or urologist who specializes in the surgical correction of anatomical disorders that impair reproductive function.

136. reproductive toxicology
Author: Biological Sciences at Heriot-Watt University
Definition:

Reproductive toxicology is the study of the effects of chemicals on the adult reproductive and neuroendocrine systems, the embryo, fetus, neonate and prepubertal mammal.

137. res ipsa loquitur
Author: Guo Li
Definition:

This is a Latin term which means "the thing speaks for itself".

It is a legal term for a method of alleging malpractice against a health care provider. Essentially, the allegation goes like this: "the patient was well before and sustained this condition only after having been cared for by you, therefore something must be wrong with your care". There are three conditions which must be met for res ipsa loquitur to be used:

1. in the ordinary course of affairs, the accident would not have occurred if reasonable care had been used
2. the thing that caused the accident was under the exclusive control of the defendant
3. the plaintiff did not contribute to the occurrence of the accident

138. resect
Definition:

To remove part or all of an organ or tissue.

139. resectable
Author: PharmInfoNet
Definition:

Capable of being removed by surgery

140. reservoir
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

In epidemiology, the organism or environment that normally harbors a pathogen.

141. reservoir
Author:
Definition:

Man-made body of water created by the damming, or the backing-up, of a river.

142. resident
Definition:

A physician who has completed medical school and an internship and is in the process of receiving specialized training.

143. residual volume (RV)
Author: Guo Li
Definition:

The gas remaining in the lung after a maximum expiratory effort.

144. residue
Definition:

A single unit within a polymer, such as an amino acid within a polypeptide; this term reflects the fact that sugars, nucleotides, and amino acids usually lose a few atoms (usually hydrogens and oxygens) when they're added to a larger molecule.

145. resistance factor (R Factor)
Definition:

A self-replicating fragment of nucleic acid that confers drug resistance and is transmitted from one bacterium to another via conjugation.

146. resoiling
Author:
Definition:

The process of artificially building or reconstructing a soil profile.

147. resolution
Definition:

Degree of molecular detail on a physical map of DNA, ranging from low to high.

148. respiration
Definition:

A catabolic process that involves the exchange of oxygen and carbon dioxide between the body and the environment, the exchange of those gases within the body, and the oxidation of nutrient molecules for energy production.

149. respiratory acidosis
Author: Guo Li
Definition:

Respiratory acidosis is the clinical condition in which the patient has acidic pH in his/her blood because of inadequate elimination of carbon dioxide. In a pure respiratory acidosis, the pH decreases by 0.08 for an increase in PCO₂ of 10 mm mercury.

150. respiratory distress of newborn
Author: Guo Li
Definition:

Respiratory distress of a newborn is observed within 1 to 6 hours of birth and characterized by rapid grunting respiration, cyanosis, and retraction of the intercostal muscles on inspiration. It can be either of pulmonary or extrapulmonary causes. The most common cause is hyaline membrane disease which occurs in preterm infants. Other causes are: aspiration of fluid or meconium, pneumothorax, and pneumonia.

151. respiratory distress syndrome
Author: Guo Li
Definition:

Respiratory distress syndrome is observed within 1 to 6 hours of birth and characterized by rapid grunting respiration, cyanosis, and retraction of the intercostal muscles upon the infant taking a breath. It can be either of pulmonary or extrapulmonary causes. The most common cause is hyaline membrane disease which occurs in preterm infants. Other causes are: inhalation of clear fluid or meconium, pneumothorax, and pneumonia.

152. respiratory failure
Author: Guo Li
Definition:

Respiratory failure is either the abnormality of oxygenation or of carbon dioxide elimination. Arterial blood gas analysis of blood taken from an artery confirms the degree of failure. Although the values of PO₂ less than 60 mmHg and PCO₂ higher than 50 are often used as criteria for respiratory failure, the clinical picture of the patient is important to recognize impending failures.

153. restoration
Author:
Definition:

Measures undertaken to return a degraded ecosystem's functions and values, including its hydrology, plant and animal communities, and/or portions thereof, to a less degraded ecological condition.

154. restoration measure
Author:
Definition:

A restoration measure consists of one or more features or activities, at a geographic site, that is intended to cause a desirable change in an ecological resource and results in a positive environmental output. Many restoration measures are combinations of several features and activities.

155. restore
Author:
Definition:

To renew, rebuild, or reconstruct to a former state.

156. restriction
Author:
Definition:

Artificial or natural control against widening of a channel, with or without construction.

157. restriction enzyme (restriction endonuclease)
Definition:

A protein that recognizes specific, short nucleotide sequences and cuts DNA at those sites. Bacteria contain over 400 such enzymes that recognize and cut over 100 different DNA sequences.

158. restriction enzyme cutting site
Definition:

A specific nucleotide sequence of DNA at which a particular restriction enzyme cuts the DNA. Some sites occur frequently in DNA (e.g., every several hundred base pairs), others much less frequently (rare-cutter; e.g., every 10,000 base pairs).

159. restriction fragment
Definition:

A section of double-stranded DNA which is produced by the action of a restriction endonuclease on the parent DNA.

160. restriction fragment length polymorphism (RFLP)
Definition:

Variation between individuals in DNA fragment sizes cut by specific restriction enzymes; polymorphic sequences that result in RFLPs are used as markers on both physical maps and genetic linkage maps. RFLPs are usually caused by mutation at a cutting site. See marker.

161. resupinate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Twisted through 180°, e.g. as with the ovary of most orchids.

162. retard
Author:
Definition:

Noun A bank-protection structure designed to check/slow the riparian velocity and induce silting or accretion.

163. retention basin (retention dam)
Author:
Definition:

A flood control structure that holds back flood water for a short period to take the peak off a downstream flood. The dam on a retention basin is usually provided with an opening too small to allow the full flood flow to pass. This restriction forces water to collect in the basin behind the dam, but as soon as the storm peak passes the basin quickly drains. Most of the time the basin is dry.

164. retention pond
Author:
Definition:

A retention pond allows water to be held as long as possible and may or may not allow for the controlled release of water. In some cases, the water is allowed to seep into the permeable banks or gravel strata in the foundation.

165. reticulate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Forming a network.

166. reticuloendothelial system
Definition:

A system of phagocytes (cells</>A which engulf and devour other cells) which can be found all over the body but are mostly concentrated in the liver, spleen, lymph nodes, and bone marrow, and are a part of the body's immune system.

167. reticuloendothelial system (RES, mononuclear phagocyte system)
Author: Biological Sciences at Heriot-Watt University
Definition:

This is the system of cells which have the ability to take up and retain certain dyes and particles ingested by a living animal.

168. retina
Definition:

The retina is the innermost layer of the eyeball (the outermost layer being the sclera and the cornea, the middle layer is choroid and the ciliary structures). The retina is the place where the image created by the lens of the eye is focused; the information from this image is turned into nerve impulses, which are then sent to the brain via the optic nerve.

169. retinaculum
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A hook-like structure to which another structure is tethered; in orchids and members of the family Asclepiadaceae, the structure to which pollen masses are attached; in Acanthaceae, the persistent stalk of an ovule.

170. retinal detachment
Author: Guo Li
Definition:

This is the separation of the retina from the pigment epithelium. It can be spontaneous or due to trauma to the eye. Immediate medical attention is needed.

171. retinitis pigmentosa
Definition:

A hereditary eye disease caused by a recessive gene where the retina progressively degenerates. Symptoms include progressive blindness, beginning with night blindness and followed by gradual loss of peripheral vision and pigment migration.

172. retinoblastoma
Author: Guo Li
Definition:

Retinoblastoma is the most common malignant intraocular neoplasm of infants, about half of all children with retinoblastoma may be inherited as an autosomal dominant trait, in which case, the cancer afflicts both eyes.

173. retinopathy
Author: PharmInfoNet
Definition:

A disease of the small blood vessels in the retina of the eye.

174. retinopathy
Definition:

This is a medical term for any disease or disorder of the retina of the eye.

175. retrofit
Definition:

To modify a device or machine after it's been purchased, either to improve on a design element or to replace a malfunctioning component.

176. retrograde ejaculation
Author: Fertilitext
Definition:

Ejaculation backwards into the bladder instead of forward through the urethra.

177. retrogression
Author:
Definition:

Reversal of stream grading (i.e., aggradation after degradation or vice versa).

178. retrorse
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Directed backwards or downwards. Compare antrorse.

179. retrotransposon
Author: Edward Bollenbach
Definition:

DNA fragments copied from viral RNA with reverse transcriptase that insert in the host chromosomes.

180. retrovirus
Definition:

Any virus in the family Retroviridae that has RNA as its nucleic acid and uses the enzyme reverse transcriptase to copy its genome into the DNA of the host cell's chromosomes. Many cancers in vertebrates are caused by retroviruses.

181. Rett's syndrome
Author: Guo Li
Definition:

Rett's syndrome is characterized by autism, dementia, and ataxia; it affects mainly girls. It is an X-linked dominant condition.

182. return flow
Author:
Definition:

That portion of the water previously diverted from a stream, and subsequently, returned to that stream or to another body of ground or surface water.

183. retuse
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

With a very blunt and slightly notched apex.

184. reverse electron transport
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

The energy-dependent movement of electrons against the thermodynamic gradient to form a strong reductant from a weaker electron donor.

185. reverse transcriptase
Definition:

An enzyme found in retroviruses that enable the virus to make DNA from viral RNA.

186. reverse transcription
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

The process of copying information found in RNA into DNA.

187. revetment
Author:
Definition:

Bank protection by armor, that is, by facing the bank or embankment with erosion resistant material.

188. revetment wall
Author:
Definition:

A wall made of concrete, stone, wood, or other materials which is built against a stream bank or a steep slope to prevent erosion.

189. revolute
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Rolled downwards or backwards.

190. Reye's syndrome
Author: Guo Li
Definition:

Reye's syndrome is characterized by encephalopthy (degenerative changes to the brain) and fatty degeneration of the liver, kidney, and brain. It is associated with a viral infection of the upper respiratory tract and the use of salicylates (such as aspirin).

191. Rezulin (troglitazone)
Definition:

This is a prescription medication used to treat Type II diabetes. It is especially used to treat people who do not respond to other treatments.

192. Rh factor
Definition:

An antigen that may or may not be present on the surface of human blood cells. If a person's blood has the antigen, their blood type is "positive"; if they do not, it is "negative." The Rh factor is important mainly because if a woman who is Rh- conceives a child who is Rh+, the mixing of their bloods in the placenta may provoke an immune reaction in the mother that can cause a life-threatening agglutination of the fetus' blood cells.

The Rh factor is so named because it was first identified in Rhesus monkeys. See also ABO blood group.

193. rhabdosarcoma
Definition:

A very dangerous cancer which develops from striated muscle tissue. There are three major forms:

1. alveolar rhabdosarcoma: this cancer, which most often afflicts adolescents, typically develops in the extremities, body or eye cavities.
2. embryonal rhabdosarcoma: this cancer, which strikes infants and young children, develops in the head, neck, extremities or lower genitourinary tract.
3. pleiomorphic rhabdosarcoma: this cancer strikes adults and typically develops in the extremities.

194. rheumatic fever
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

An inflammatory autoimmune disease triggered by an immune response to infection by Streptococcus pyogenes.

195. rheumatic heart disease
Author: Guo Li
Definition:

Rheumatic heart disease results from single or repeated attacks of rheumatic fever that produce rigidity and deformity of heart valves such that stenosis or regurgitation results.

196. rheumatoid arthritis
Author: Guo Li
Definition:

Rheumatoid arthritis is symmetrical (occuring in the same joint on both sides of the body) erosive (joint-destroying) polyarthritis (arthritis in several joints) with positive rheumatoid factor.

197. rheumatoid factor
Author: Guo Li
Definition:

This is a heterogenous group of autoantibodies directed against human IgG which is elevated with many clinical conditions, among them: rheumatoid arthritis, systemic lupus erythematosus, Sjogren's syndrome, polymyositis, scleroderma, tuberculosis, leprosy, syphilis, and subacute bacterial endocarditis.

198. rheumatologist
Definition:

A medical doctor who specializes in rheumatology.

199. rheumatology
Definition:

A branch of medicine concerned with the diagnosis and treatment of arthritis.

200. rhinitis
Author: PharmInfoNet
Definition:

Inflammation of the nasal mucosa (mucous membranes in the nasal cavities).

201. rhinorrhea
Definition:

Rhinorrhea is the medical term for a runny nose.

202. rhipidium
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

An inflorescence of cymose units, the lateral branches developed alternately in opposite directions.

203. rhizobia
Author: Susan A.Hagedorn
Definition:

Bacteria in a symbiotic relationship with leguminous plants that results in nitrogen fixation.

204. rhizoid
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A thread-like, unicellular absorbing structure, occurring in fern gametophytes and in some non-vascular plants.

205. rhizome
Definition:

A horizontal underground stem which can send out both shoots and roots; rhizomes sometimes have thickened areas that store starch.

206. rhizome chaff
Author:
Definition:

Mechanically chopped-up pieces of thin rhizomes spread on the ground and covered with soil so they can take root and form new plants.

207. rhizome cutting
Author:
Definition:

Part of a thick rhizome, which may take root and form a new plant.

208. rhizophore
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A leafless stem that produces roots.

209. rhizosphere
Author: Susan A.Hagedorn
Definition:

The region of the soil on and around plant roots.

210. rhizosphere
Author:
Definition:

The zone of soil in which interactions between living plant roots and micro-organisms are found.

211. rhomboid
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Quadangular, with the lateral angles obtuse.

212. rib wall
Author:
Definition:

Usually a rock, rock gabion, or broken concrete structure constructed across a stream below a dam or weir to raise the water level in a pool below the dam or weir. (This can be used in lieu of a fishway in some cases. Also used to slow down high water velocities.)

213. ribonuclease
Definition:

A nuclease that catalyzes the breaking of some linkages between nucleotides in RNA.

214. ribonucleoprotein
Definition:

A conjugated protein (such as telomerase) that contains a ribonucleic acid molecule as a prosthetic group.

215. ribonucleoside
Definition:

A nucleoside in which purine or pyrimidine base is linked to a ribose molecule.

216. ribonucleotide
Definition:

A nucleotide in which a purine or pyrimidine base is linked to a ribose molecule.

217. ribophage
Definition:

A bacteriophage that has an RNA-based genetic structure.

218. ribophorin
Definition:

Any of several glycoproteins in the endoplasmic reticulum that aid ribosomes during the cotranslational insertion of certain proteins.

219. riboprine
Definition:

An anti-cancer drug.

220. ribose
Image: View the chemical structure
Definition:

A five-carbon sugar that is a structural component of ribonucleic acid, riboflavin and other nucleotides and nucleosides.

221. riboside
Definition:

A glycoside that has ribose as its sugar component.

222. ribosomal RNA (rRNA)
Definition:

A class of RNA found in the ribosomes of cells.

223. ribosome binding site
Author: Susan A.Hagedorn
Definition:

The region of a messenger RNA molecule that binds the ribosome to initiate translation.

224. ribosomes
Definition:

Small cellular components composed of specialized ribosomal RNA and protein; site of protein synthesis. Found in three places in eukaryotic cells:
 

1. free in the cytoplasm,
2. attached to the endoplasmic reticulum,
3. and in mitochondria


See ribonucleic acid (RNA).

225. ribovirus
Definition:

A virus that has RNA as its genetic material.

226. ribozyme (RNA enzyme)
Definition:

A molecule of ribonucleic acid that has catalytic activity.

227. rickettsias
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

Obligate intracellular parasites which cause a variety of disease, including typhus and Rocky Mountain spotted fever.

228. ridgeline
Author:
Definition:

A line connecting the highest points along a ridge and separating drainage basins or small-scale drainage systems from one another.

229. Riedel's thyroiditis
Author: Guo Li
Definition:

This is swelling/inflammation of thyroid gland in which the gland is of a woody consistency and adheres to the neck structures; the normal microscopic cellular pattern of the organ is totally lost.

230. riffle
Author:
Definition:

1. Shallow section of a stream or river with rapid current and a surface broken by gravel, rubble or boulders. (Compare glide; rapids; run.)
2. A reach of stream in which the water flow is rapid and usually more shallow than the reaches above and below. Natural streams often consist of a succession of pools and riffles. (Sometimes incorrectly referred to as a "ripple.")

231. rill
Author:
Definition:

1. One of the first and smallest channels formed by surface runoff.
2. A small erosional channel, usually in parallel where surface waters run on steep unprotected soils.
3. A very small brook or trickling stream of water.

232. rilling (rill erosion)
Author:
Definition:

Development of numerous small, closely spaced channels resulting from the uneven erosion of soil by running water.

233. riparian
Author:
Definition:

1. On, or pertaining to, the banks of a stream. (As in riparian vegetation or riparian woodland.)
2. Pertaining to the banks and other adjacent, terrestrial (as opposed to aquatic) environs of freshwater bodies, watercourses, and surface-emergent aquifers (e.g., springs, seeps, oases), whose imported waters provide soil moisture significantly in excess of that otherwise available through local precipitation - soil moisture to potentially support a mesic vegetation distinguishable from that of the adjacent more xeric upland.

Source: Warner and Hendrix. Riparian Resources of the Central Valley and California Desert. 1985. California Department of Fish and Game.

234. riparian area
Author:
Definition:

The area between a stream or other body of water and the adjacent upland identified by soil characteristics and distinctive vegetation. It includes wetlands and those portions of floodplains and valley bottoms that support riparian vegetation.

235. riparian land
Author:
Definition:

Land situated along the bank of a stream or other body of water.

Source: "Resource Conservation Glossary." Third Edition.

236. riparian vegetation
Author:
Definition:

1. Vegetation which occurs in and/or adjacent to a watercourse. For the purpose of administering Fish and Game Code Section 1600, et seq., this should be expanded to include vegetation adjacent to lakes as well.
2. Vegetation growing on or near the banks of a stream or other body of water on soils that exhibit some wetness characteristics during some portion of the growing season.
3. Vegetation which occurs along watercourses, and is structurally or floristically distinct from nearby, non-streamside vegetation.
4. Riparian vegetation is terrestrial vegetation that grows beside rivers, streams, and other freshwater bodies and that depends on these water sources for soil moisture greater than would otherwise be available from local precipitation.

Source: Warner, R.E. and Hendrix, K.M., eds. 1984. California Riparian Systems, Ecology, Conservation, and Productive Management. California Riparian Systems Conference, U.C. Davis. September 1981. University of California Press. Berkeley, California.

237. riparian wetland
Author:
Definition:

Riparian vegetation composed primarily of woody hydrophytes (e.g., such as willows, alders, cottonwoods, sycamores, box elders, aspens, etc.).

238. riparian woodland (riparian forest)
Author:
Definition:

1. The broad-leaved and winter deciduous, phreatophytic tree formation that lines watercourses.
   Source: Ornduff, R. "An Introduction to California Plant Life." 1974.
2. Streamside forest composed of either wetland species (e.g., willow, cottonwood, etc.) or non-wetland species (e.g., oak, walnut, California bay).

239. riprap
Author:
Definition:

1. Layer of large, durable materials (usually rocks; sometimes car bodies, broken concrete, etc.) used to protect a stream bank or lake shore from erosion; may also refer to the materials used.
2. A layer of irregularly placed stones or debris positioned on the bank of a stream or beside a levee to resist the eroding action of flowing water.

240. risk
Author: Biological Sciences at Heriot-Watt University
Definition:

This term must not be confused with the term "hazard". It is most correctly applied to the predicted or actual frequency of occurrence of an adverse effect of a chemical or other hazard.

241. risk assessment
Author: Biological Sciences at Heriot-Watt University
Definition:

Risk assessment is the identification and quantification of the risk resulting from a specific use or occurrence of a chemical, taking into account the possible harmful effects on individual people or society of using the chemical in the amount and manner proposed and all the possible routes of exposure. Quantification ideally requires the establishment of dose-effect and dose-response relationships in likely target individuals and populations. Compare risk evaluation.

242. risk evaluation
Author: Biological Sciences at Heriot-Watt University
Definition:

Risk evaluation involves the establishment of a qualitative or quantitative relationship between risks and benefits, involving the complex process of determining the significance of the identified hazards and estimated risks to those organisms or people concerned with or affected by them.

243. risk factor
Author: PharmInfoNet
Definition:

Anything that raises the chance that a person will get a disease.

244. risk management
Author: Biological Sciences at Heriot-Watt University
Definition:

Risk management is the decision-making process involving considerations of political, social, economic and engineering factors with relevant risk assessments relating to a potential hazard so as to develop, analyse and compare regulatory options and to select the optimal regulatory response for safety from that hazard. Essentially risk management is the combination of three steps: risk evaluation, emission and exposure control, and risk monitoring.

245. risperidone (Risperdal)
Definition:

This antipsychotic drug is used to treat schizophrenia.

246. river
Author:
Definition:

A large stream, usually active when any streams are flowing in the region.

247. river continuum
Author:
Definition:

Gradual changes in the biological community of a river as energy sources and physical conditions change from headwaters to lowlands.

248. river-type fish
Author:
Definition:

Anadromous fish that rear for a year or more in rivers.

249. RNA (ribonucleic acid)
Definition:

A chemical found in the nucleus and cytoplasm of cells; it plays an important role in protein synthesis and other chemical activities of the cell. The structure of RNA is similar to that of DNA. There are several classes of RNA molecules, including messenger RNA, transfer RNA, ribosomal RNA, and other small RNAs, each serving a different purpose.

250. RNA life
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A hypothetical life form lacking DNA and protein which may have existed on early earth and in which RNA served both a genetic coding and a catalytic function.

251. RNA processing
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

The conversion of a precursor RNA into its mature form.

252. rock
Author:
Definition:

1. Cobble, boulder, or quarry stone used as a construction material.
2. Hard natural mineral, in formation or in piles of talus or detritus.

253. rock fill dam
Author:
Definition:

A dam composed of large, broken, and loosely placed or pervious rocks with either an impervious core or upstream facing or surface layer.

254. rodenticide
Definition:

Any chemical used to kill rodents (rats, mice, etc.)

255. roiled
Author:
Definition:

Water that has been made turbid by the addition of sediment.

256. root
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

The water- and mineral-absorbing part of a plant which is usually underground, does not bear leaves, tends to grow downwards and is typically derived from the radicle of the embryo. See adventitious.

257. root cutting
Author:
Definition:

Part of a root of a woody plant which, under suitable conditions, takes root and forms a new plant.

258. root nodule
Author: Mirrored from Tsute Chen's Glossary of Microbiology
Definition:

A tumor-like growth on plant roots that contains symbiotic nitrogen-fixing bacteria.

259. root pressure
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Pressure in the roots which, when the shoot is cut off, will cause liquid to ooze from the root stump; the mechanisms and tissues involved in this process are not clearly understood.

260. root sprout
Author:
Definition:

A living shoot which grows from the root of a plant whose above-ground portion has been cut down.

261. rootball (root ball)
Author:
Definition:

Nursery transplant with root stock and soil held together by burlap or other wrapping.

262. rootlet
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

A radicle; a little root or small branch of a root.

263. rootstock
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A short, erect, swollen structure at the junction of the root and shoot systems of a plant.

264. roseate
Author: Mirrored from Dave Sutton's Aquatic Plant Glossary
Definition:

Rose-colored or rose-shaped.

265. rosette
Definition:

A group of organs or other body features, such as leaves or hair, which are clustered and crowned around a common point of attachment.

266. rostellum
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A beak-like upward extension of the stigma in orchids.

267. rosulate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Clustered into a rosette.

268. rotate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

1. Verb: To turn.
2. Adjective: Circular and flattened, e.g. of a corolla with a very short tube and spreading lobes.

269. rotation
Author:
Definition:

The planned number of years between successive cuttings of a forest; livestock grazing strategy in which cattle are moved from one pasture to another during the grazing season.

270. rough endoplasmic reticulum
Definition:

A type of endoplasmic reticulum, an organelle found in eukaryotic cells, which has a large number of ribosomes attached all over it. It is important to the making of proteins and in preparing secretions of the cell.

271. roughness coefficient
Author:
Definition:

Designated by "N" in Manning’s flow equation, the roughness coefficient is an expression of the resistance to flow of a surface such as the bed or bank of a stream.

272. rubble
Author:
Definition:

1. Rough, irregular, water-worn rock fragments of random size.
2. Stream substrate particles between 64 and 256 mm (2.5 and 10 inches) in diameter.

273. rubella
Author: Guo Li
Definition:

Rubella is a viral infection by the rubella virus. Rubella infection during pregnancy is associated with fetal malformations, bleeding, and other deleterious effects, so vaccination against this virus for women of childbearing age is suggested and the best time is the immediate postpartum period. The serum rubella antibody is measured and its result is interpreted as follows:

ranges (in IU/mL):

 

no immunity             < 10.0
equivocal               10.0 - 14.9
immunity                15.0 - 200.0
high immunity           > 200.0

274. ruderal
Author:
Definition:

Weedy vegetation growing on compacted, plowed, or otherwise distrubed ground and showing a preference for this type of habitat.

275. rudimentary
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Poorly developed and not functional. Compare vestigial, obsolete.

276. rugose
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Deeply wrinkled.

277. rugulose
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Covered with tiny wrinkles.

278. rule
Definition:

A statement of conditions, effects, or phenomena typically observed in a given situation or process.

279. rumen
Definition:

The first four stomach compartments in ruminant animals (such as cattle and deer).

280. ruminate
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

Mottled in appearance, e.g. of bark, or of the food reserves in a seed.

281. run (fish run)
Author:
Definition:

A group of fish migrating in a river (most often on a spawning migration) that may comprise one or many stocks.

282. run (stream)
Author:
Definition:

Swiftly flowing stream reach with little surface agitation and no major flow obstructions. Often appears as a flooded riffle. (Compare glide; riffle; rapids.)

283. run-off (runoff)
Author:
Definition:

1. Water flowing in a river as a result of snow melt or heavy rains.
2. The part of precipitation and snowmelt that reaches streams (and thence the sea) by flowing over the ground.
3. The portion of rain or snow that does not percolate into the ground and is discharged into streams instead.
4. That part of water yield that appears in streams. Expressed in acre feet per year.

284. runcinate
Definition:

Deeply lobed and with the lobes slanted away from the apex.

285. runner
Author: Mirrored from Jim Croft's Flora of Australia
Definition:

A slender, prostrate or trailing stem which produces roots and sometimes erect shoots at its nodes.

286. rust
Definition:

A type of club fungus that is a parasite on plants. The most common rust is Puccinia graminis (black stem rust in wheat).