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Glossary: R is for ... radicle, rain, and rootlet.
by Ariadne Unst

Glossary of R...

r-selection (n.)
Natural selection in situations that favor a high reproductive rate (r). This results in a species that survives by producing many young with minimal (or zero) individual resource investment by the parents; eggs or newborns are often abandoned. (r-selected, adj.)

raceme (n.)
An inflorescence where the flowers are arranged singly on distinct but similar unbranched pedicels.

radicle (n.)
Embryonic root.

ramose (adj.)
Branched; branchy.

randomization (n.)
Randomization (in scientific experiments) provides data observations that are independently distributed, as required for the valid application of statistical methods. By random allocation of experimental units and the sequence in which trials are conducted: (1) effects of extraneous factors are averaged out; (2) experimenter bias is removed. The use of controls can help varify randomization.

rain forest (n.)
The tropical rain forest is a girdle of evergreen forest that encircles the Earth between the tropics.
Temperature needs to exceed 21ºC and not exceed 36ºC.
Moisture of at least 150 cm is required, distributed evenly through the year.
Species variety is unusually high: more than 25 species of tree over 30 cm in diameter grow in a single hectare. Temperate forests have far fewer. Even in the rich temperate forests of USA's Appalachia, it is rare to find 12 in a similar area.
The largest continuous rainforest is in tropical America, centered on the Amazon Basin.
Not the same as jungle.

rare (adj.)
A species that is uncommon.
Locally Rare: A species that is found in only a few places within a particular region. It is often more common elsewhere.

rhizome (n.)
An underground rootlike stem that is able to producing new roots from its base and new leaves or stems from its upper surface.

R horizon (n.)
The soil horizon below the C horizon.

root (n.)
Large subterranean structure of a plant that provides anchorage. Roots uptake most of the water and nutrients for the plant.

root hair (n.)
Elongated cells, erect on the surface of a small rootlet, shortly behind the growing tip.

rootlet (n.)
Small side branch from a root.

rosette (n.)
A cluster of leaves arranged in a circule at the base of a plant; also called the basal rosette.