''Tuctoria'' is a genus of three species of grass in the family

Poaceae Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns an ...

. Spiralgrass is a common name for plants in this genus. These are bunchgrass species that are found in vernal pools of central California and Baja California, Mexico. The plants are annuals that germinate under water in the spring and grow submerged for weeks. After the pools dry down, the grasses initiate a new set of foliage that lasts for one to two months until flowering and fruiting are complete.

Taxonomy

The genus was circumscribed by John R. Reeder in 1982. Along with '' Orcuttia'' and ''

Neostapfia ''Neostapfia'' is a genus of endemic Californian bunchgrasses, in the subfamily Chloridoideae of the grass family, Poaceae. The only known species is ''Neostapfia colusana'', with the common name Colusa grass. Distribution ''Neostapfia colusana ...

'', ''Tuctoria'' is one of three genera in the tribe Orcuttieae, previously outlined by Reeder in 1965. All three ''Tuctoria'' species were formerly assigned to ''Orcuttia'', the

type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * Ty ...

genus of Orcuttieae. Reeder erected ''Tuctoria'' after determining that the three species were more closely related among themselves than to any of the other ''Orcuttia'' species. Shared features include chromosome numbers, the spiral arrangement of spikelets on the rachis, the absence of juvenile leaves, the presence of lodicules, and the presence of an epiblast in the seed embryos. The name ''Tuctoria'' is an

anagram An anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once. For example, the word ''anagram'' itself can be rearranged into ''nag a ram'', also the word ...

of ''Orcuttia''. Recent (2010)

molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

analysis suggests that ''Tuctoria'' is not

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

as currently circumscribed, and is in need of

taxonomic Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

revision.

Description

''Tuctoria'' species have their spikelets spirally arranged on the axis; lemmas are entire (with a smooth, even margin) or denticulate (finely toothed), and often have a centrally placed short, sharp tip (mucro). The inflorescence is not cylindrical (as in ''Neostapfia''), and the spikelets are laterally flattened. The lemmas are narrower, the tip is mucronate or otherwise entire or denticulate. The caryopsis is not sticky, and the brown

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...

is visible throughout the light-colored pericarp.

Species

There are three species in ''Tuctoria''. *''

Tuctoria fragilis ''Tuctoria'' is a genus of three species of grass in the family Poaceae. Spiralgrass is a common name for plants in this genus. These are bunchgrass species that are found in vernal pools of central California and Baja California, Mexico. The pla ...

'' (originally described as ''Orcuttia fragilis'' by Jason Richard Swallen in 1944). Found in Baja California (Mexico), it has culms up to long, inflorescences often numbering several from the upper nodes, and a caryopsis that is somewhat pear-shaped and wrinkled. *''

Tuctoria greenei ''Tuctoria greenei'' is a species of grass endemic to California. Its common names include awnless spiralgrass and Greene's tuctoria. It is included by the California Native Plant Society on list 1B.1 (rare, threatened, or endangered). It is also ...

'' (originally ''Orcuttia grenei'' − Vasey). Found in California, it has culms less than long, with the inflorescence terminal on the flowering culm. The caryopsis is long and oblong, and wrinkled. *'' Tuctoria mucronata'' (originally ''Orcuttia mucronata'' − Crampton). Endemic to Solano County south of

Dixon Dixon may refer to: Places International * Dixon Entrance, part of the Inside Passage between Alaska and British Columbia Canada * Dixon, Ontario United States * Dixon, California * Dixon, Illinois * Dixon, Greene County, Indiana * Dixon, Indi ...

, Northern California. Its inflorescence is partially included in the upper lead, and its lemmas taper gradually to a mucronate tip. The caryopsis is smooth, measuring long.

Ecology and distribution

''Tuctoria'' species are endemic to seasonal pools in the southwestern US. Like all species in tribe Orcuttieae, the growth of ''Tuctoria'' species is initiated underwater. When pools dry, the plants undergo a metamorphosis whereby aquatic foliage is replaced with terrestrial foliage. The terrestrial foliage has Kranz anatomy, indicating the use of C-4 photosynthesis. This adaptation help the plants survive the longs periods of drought-like conditions experienced when the pools dry. In years with little rainfall, their seed banks remain dormant until a season of rainfall that is adequate to fill the pool basins. In ''T. greenei'',

germination Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, fer ...

is almost entirely dependent upon a combination of anaerobic conditions and light. This strategy helps the plant begin germination when pool basins are filled with water. In years of low precipitation, the soil subsurface is likely to be anaerobic or hypoxic, and inhibit germination. ''Tuctoria greenei'' is of high conservation concern in California, as vernal pool systems are in decline due to agricultural development and urban expansion.

References

External links