R
- raceme
- (adjective racemose) an indeterminate inflorescence in which the main axis produces a series of flowers on lateral stalks, the oldest at the base and the youngest at the top; cf. spike.
- rachilla (rhachilla)
- the axis of a grass spikelet, above the glumes.
- rachis
- (plural rachises; rachides) the axis of an inflorescence or a pinnate leaf; for example ferns; secondary rachis is the axis of a pinna in a bipinnate leaf distal to and including the lowermost pedicel attachment.
- radial
- with structures radiating from a central point as spokes on a wheel, for example, the lateral spines of a cactus.
- radiate
- of daisies, of a capitulum, with ray florets surrounding disc florets.
- radical
- springing from the root; clustered at base of stem.
- radicle
- the part of an embryo giving rise to the root system of a plant; cf. plumule.
- rainforest
- a forest dominated by broad-leaved trees with dense crowns that form a continuous layer (canopy) and with one or more of the following growth forms: epiphytes, lianas, treeferns, palms; eucalypts absent or are present only as isolated emergen, e.g. in Victoria, mesic vegetation is dominated by trees other than eucalypts, often with lianas and epiphytes.
- ramet
- an individual member of a clone.
- ray
- 1. zygomorphic (ligulate) flowers in a radiate flowerhead, that is, ray-florets/flowers, for example Asteraceae.
- 2. each of the branches of an umbel.
- receptacle
- the axis of a flower, in other words, floral axis; torus; for example in Asteraceae, the floral base or common receptacle is the expanded summit of the peduncle on which the flowers are inserted.
- recurved
- bent or curved backwards or downwards.
- reflexed
- bent sharply back or down.
- registered name
- a cultivar name accepted by the relevant International Cultivar Registration Authority.
- registered trade mark
- a trade mark formally accepted by a statutory trade-mark authority and distinguished by the international ® sign.
- registration
- 1. the act of recording a new cultivar name with an International Cultivar Registration Authority.
- 2. recording a new cultivar name with a statutory authority like the Plant Breeder’s Rights Office.
- 3. recording a trade mark with a trade marks office. Compare registered trade mark.
- regular
- see actinomorphic.
- reniform
- kidney-shaped.
- reticulate
- forming a network (or reticulum), e.g. veins that join one another at more than one point.
- retrorse
- directed backwards or downwards; cf. antrorse.
- retuse
- with a blunt (obtuse) and slightly notched apex.
- revision
- an account of a particular plant group, like an abbreviated or simplified monograph. Sometimes confined to the plants of a particular region. Similar to a monograph in clearly distinguishing the taxa and providing a means for their identification; compare monograph.
- revolute
- rolled under (downwards or backwards), for example when the edges of leaves are rolled under towards the midrib; compare involute.
- rhachis
- see rachis.
- rhizome
- a perennial underground stem usually growing horizontally. See also stolon.
- rhombic
- like a rhombus: an oblique figure with four equal sides; compare trapeziform, trullate.
- rhomboid
- a four-sided figure with opposite sides parallel but with adjacent sides an unequal length (like an oblique rectangle); see also rhombic.
- rhomboidal
- a shape, for instance of a leaf, that is roughly diamond-shaped with length equal to width.
- root
- a unit of a plant's axial system which is usually underground, does not bear leaves, tends to grow downwards, and is typically derived from the radicle of the embryo.
- root hairs
- outgrowths of the outermost layer of cells just behind the root tips, functioning as water-absorbing organs.
- rootstock
-
short, erect, swollen structure at junction of a plant's root and shoot systems, for example a corm. Also used to describe:
1. a part of a budded or grafted plant which supplies the roots, also called a rootstock, or plants grown specifically to produce these.
- 2. plants or seeds with some specific attribute, for instance virus-free plants.
- rosette
- when parts are not whorled or opposite but appear so, due to the contractions of internodes, e.g. the petals in a double rose or a basal cluster of leaves (usually close to the ground) in some plants.
- rostrate
- with a beak.
- rotate
- circular and flattened; for example a corolla with a very short tube and spreading lobes (for instance some Solanaceae).
- rudimentary
- poorly developed and not functional; compare vestigial.
- rugose
- wrinkled.
- rugulose
- finely wrinkled.
- ruminate
- (usually applied to endosperm). irregularly grooved or ridged; appearing chewed. (a common type of endosperm in Myristicaceae).
- runcinate
- sharply pinnatifid or cleft, the segments directed downward.
- runners
- see stolon.
- rupicolous
- rupestral, saxicolous, growing on or among rocks. (compare epilithic, lithophytic)
- rush
- a plant belonging to the family Juncaceae or, more loosely, applied to various monocotyledons.
Read more about this topic: Glossary Of Botanical Terms