Radial spines
Cactus grower terms
Spines located on the periphery of the areole.
Glossary of terms
A reference section with categories and short explanations.
Radicle emergence
Cactus grower terms
The emergence of the embryonic root through the rupture of the testa during seed germination.
Radish-like roots
Cactus grower terms
(Not napiform) thickening of the taproot.
Rarity
Cactus grower terms
Rarity, a rare specimen; an exceptionally rare plant both in terms of being held in collections and of occurring in natural conditions.
Receptacle
Cactus grower terms
The upper expanded part of the pedicel.
Receptaculum
Cactus grower terms
(Lat. term receptaculum - receptacle - the axis of the flower on which the sepals, petals, stamens, carpels are arranged) - a term used by many cactologists to denote the receptacle specific to all higher cacti.
Recessive
Cactus grower terms
(From Latin recessus - retreat, removal) - an allele whose phenotypic expression in the heterozygote is masked by the dominant allele.
Reciprocal crosses
Cactus grower terms
(From Latin reciprocus - mutual) - two crosses characterized by a mutually opposite combination of the trait under study and the sex of the forms participating in these crosses.
Reduction
Cactus grower terms
Decrease in size of plant organs or tissues.
Regeneration
Cactus grower terms
Restoration by a living organism of lost body parts.
Relative humidity
Cactus grower terms
Expressed as the ratio of the concentration of water vapor contained in the air to its maximum saturated state at a given air temperature. As temperature increases, relative humidity decreases.
Relict plants
Cactus grower terms
Dying out; surviving in small numbers.
Replantation
Cactus grower terms
Engraftment (survival) of a detached organ.
Rhizoctoniosis
Cactus grower terms
Fungal disease of cacti.
Root collar
Cactus grower terms
The point where the roots transition into the stem.
Root hairs
Cactus grower terms
Absorbing, dying off as the root grows.
Root parasites
Cactus grower terms
Plant pests that damage roots.
Root primordia
Cactus grower terms
Groups of cells from which new roots develop.
Root suckers
Cactus grower terms
Shoots arising from adventitious buds.
Root system
Cactus grower terms
The collection of a plant's underground roots. The taproot system has a primary root and lateral roots; the fibrous or fasciculate system — the primary root is weakly developed or dies early, and adventitious roots form a cluster, a fascic…
Rooting
Cactus grower terms
The process of root formation.
Rootlets
Cactus grower terms
Thin lateral root branches that break off when the root is removed from the soil.
Rootstock segments
Cactus grower terms
Parts of a long cactus shoot, each of which is used as a rootstock without being rooted.
Rootstocks
Cactus grower terms
Plants onto which scions are grafted. They primarily perform the function of roots, and their task is to actively supply the scion (see below) with nutrients.