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Perpendicular

Denoting the latest stage of English Gothic church architecture, prevalent from the late 14th to mid 16th centuries and characterized by broad arches, elaborate fan vaulting, and large ...

ground cover

ground cover   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015

...cover The area of ground that is covered by a plant when its canopy edge is projected downwards perpendicularly...

sea-floor spreading

sea-floor spreading   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015

...that the ocean floor is created at the spreading (accretionary) plate margins within the ocean basins. Igneous rocks rise along conduits from the mantle , giving rise to volcanic activity in a narrow band along the mid-ocean ridges. The newly formed oceanic crust spreads perpendicularly away from the...

cover

cover   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015

...In descriptions of plant communities, the proportion of ground, usually expressed as a percentage, that is occupied by the perpendicular projection down on to it of the aerial parts of individuals of the species under consideration. The most widely used visual scales are the Domin scale and the Braun-Blanquet five-point scale. A more objective estimate may be obtained using a pin-frame or point-quadrat...

Cartesian projection

Cartesian projection   Quick reference

A Dictionary of Ecology (5 ed.)

Reference type:
Subject Reference
Current Version:
2015

...projection A mapping technique in which every plane in the area being mapped is projected on to a plane in the map and every line on to a line. Each point in the area under study is identified by three values, representing its location in relation to three mutually perpendicular axes (the Cartesian coordinates of the point). These coordinates are transformed mathematically into a homogeneous set of four coordinates which can then be plotted to produce a graphic representation (a map). The word ‘Cartesian’ is derived from the name of the French...

DNA and RNA

DNA and RNA   Reference library

Encyclopedia of Evolution

Reference type:
Subject Reference
Current Version:
2005

...why the amounts of G and C, and of A and T, are approximately the same in DNA. The sugar phosphate backbones of the two chains are on the outside. They are twisted into a helical structure and carry the negative charges on the phosphate groups. The bases lie on the inside, perpendicular to the axis of the helix. The double helix structure resembles a spiral staircase, with the base pairs forming the steps. The model requires the two strands to run in opposite directions. Looking along the helix, therefore, one strand lies in the 5′ to 3′ direction, while its...

skeletagenous septum

skeletagenous septum  

One of a series of segments which develop along the notochord and are separated by myosepta. Septa occur in two planes. Dorsal and ventral septa are plate-like processes which grow dorsally and ...
oriented meiotic division

oriented meiotic division  

An oocyte meiotic division, as in Drosophila where the spindles are oriented in single file with their long axes perpendicular to the egg surface. The nucleus farthest from the surface functions as ...
pulsed-field gradient gel electrophoresis

pulsed-field gradient gel electrophoresis  

A technique for separating DNA molecules by subjecting them to alternately pulsed, perpendicularly oriented electrical fields. The technique has allowed separation of the yeast genome into a series ...
phycoplast

phycoplast  

An array of microtubules that organizes cell division following mitosis in certain algae. Unlike the phragmoplast found in dividing cells of plants and many algae, the phycoplast consists of ...
ground cover

ground cover  

The area of ground that is covered by a plant when its canopy edge is projected downwards perpendicularly.
Cartesian projection

Cartesian projection  

A mapping technique in which every plane in the area being mapped is projected on to a plane in the map and every line on to a line. Each point in the area under study is identified by three values, ...
anisotropy

anisotropy  

A directional property of crystals and fibers having a high degree of molecular orientation. Anisotropic substances have different physical properties when tested in different directions. When a ray ...
transect

transect  

A straight line across an expanse of ground along which ecological measurements are taken, continuously or at regular intervals. Thus an ecologist wishing to study the numbers and types of organisms ...
surface tension

surface tension  

Symbol γ. The property of a liquid that makes it behave as if its surface is enclosed in an elastic skin. The property results from intermolecular forces: a molecule in the interior of a liquid ...
ground cover

ground cover   Quick reference

A Dictionary of Plant Sciences (4 ed.)

Reference type:
Subject Reference
Current Version:
2019
Subject:
Science and technology, Life Sciences
Length:
21 words

...cover The area of ground that is covered by a plant when its canopy edge is projected downwards perpendicularly...

transect

transect   Quick reference

A Dictionary of Biology (8 ed.)

Reference type:
Subject Reference
Current Version:
2019
Subject:
Science and technology, Life Sciences
Length:
53 words

...of ground along which ecological measurements are taken, continuously or at regular intervals. Thus an ecologist wishing to study the numbers and types of organisms at different distances above the low-tide line might sample at five-metre intervals along a number of transects perpendicular to the...

skeletagenous septum

skeletagenous septum   Quick reference

A Dictionary of Zoology (4 ed.)

Reference type:
Subject Reference
Current Version:
2014
Subject:
Science and technology, Life Sciences
Length:
83 words

...septum One of a series of segments which develop along the notochord and are separated by myosepta . Septa occur in two planes. Dorsal and ventral septa are plate-like processes which grow dorsally and ventrally to the notochord; horizontal septa bisect this plane perpendicularly. Mesenchymal cells migrate to the skeletagenous septa during the gastrula stage of embryogenesis to form sclerotomic tissue ( see somite ). At the junction between the myoseptum and skeletagenous septum vertebrae develop; they are consequently intersegmental...

phycoplast

phycoplast   Quick reference

A Dictionary of Biology (8 ed.)

Reference type:
Subject Reference
Current Version:
2019
Subject:
Science and technology, Life Sciences
Length:
74 words

...phycoplast An array of microtubules that organizes cell division following mitosis in certain algae, e.g. Chlamydomonas . Unlike the phragmoplast found in dividing cells of plants and many algae, the phycoplast consists of microtubules arranged perpendicular to the axis of the mitotic spindle and parallel to the plane of formation of the new cell wall. The new wall may form by infurrowing from the existing walls or by deposition of a cell plate...

cover

cover   Quick reference

A Dictionary of Plant Sciences (4 ed.)

Reference type:
Subject Reference
Current Version:
2019
Subject:
Science and technology, Life Sciences
Length:
72 words

...In descriptions of plant communities, the proportion of ground, usually expressed as a percentage, that is occupied by the perpendicular projection down on to it of the aerial parts of individuals of the species under consideration. The most widely used visual scales are the Domin scale and the Braun-Blanquet 5-point scale. A more objective estimate may be obtained using a pin -frame sample of a point quadrat...

medullary ray

medullary ray   Quick reference

A Dictionary of Biology (8 ed.)

Reference type:
Subject Reference
Current Version:
2019
Subject:
Science and technology, Life Sciences
Length:
108 words

...medullary ray ( ray ) Any of the vertical plates of parenchyma cells running radially through the cylinder of vascular tissue in the stems and roots of plants. In cut timber they appear as lines radiating from the centre of the cut surface of a log, perpendicular to the growth rings. Each may be one to many cells in width. Primary medullary rays occur in young plants and in those not showing secondary thickening; they pass from the cortex through to the pith. Secondary medullary rays are produced by the vascular cambium and terminate in xylem and...

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