''Tuctoria'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of three species of grass in the family Poaceae. Spiralgrass is a common name for plants in this genus. These are

bunchgrass Tussock grasses or bunch grasses are a group of grass species in the family Poaceae. They usually grow as singular plants in clumps, tufts, hummocks, or bunches, rather than forming a sod or lawn, in meadows, grasslands, and prairies. As perenni ...

species that are found in

vernal pool Vernal pools, also called vernal ponds or ephemeral pools, are seasonal pools of water that provide habitat for distinctive plants and animals. They are considered to be a distinctive type of wetland usually devoid of fish, and thus allow the safe ...

s of central

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

and

Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...

, Mexico. The plants are annuals that

germinate 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 ...

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 A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanism ...

and

fruiting In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering. Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in particula ...

are complete.

Taxonomy

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

Orcuttia ''Orcuttia'' is a genus of grass in the family Poaceae. Plants grow up to tall, usually with many stems emerging from the base of the plant, and forming a tuft. The spikelets (groups of flowers) are several-flowered, with reduced upper florets. ...

'' and '' Neostapfia'', ''Tuctoria'' is one of three genera in the

tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide usage of the term in English is in the discipline of anthropology. This definition is contested, in part due to confli ...

Orcuttieae, previously outlined by Reeder in 1965. All three ''Tuctoria'' species were formerly assigned to ''Orcuttia'', the type 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 number Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectivel ...

s, the spiral arrangement of spikelets on the

rachis In biology, a rachis (from the grc, ῥάχις [], "backbone, spine") is a main axis or "shaft". In zoology and microbiology In vertebrates, ''rachis'' can refer to the series of articulated vertebrae, which encase the spinal cord. In this c ...

, the absence of juvenile leaves, the presence of

lodicule A spikelet, in botany, describes the typical arrangement of the flowers of grasses, sedges and some other Monocots. Each spikelet has one or more florets. The spikelets are further grouped into panicles or spikes. The part of the spikelet that ...

s, and the presence of an

epiblast In amniote embryonic development, the epiblast (also known as the primitive ectoderm) is one of two distinct cell layers arising from the inner cell mass in the mammalian blastocyst, or from the blastula in reptiles and birds, the other laye ...

in the seed embryos. The name ''Tuctoria'' is an anagram of ''Orcuttia''. Recent (2010) molecular phylogenetic analysis suggests that ''Tuctoria'' is not monophyletic as currently circumscribed, and is in need of taxonomic revision.

Description

''Tuctoria'' species have their spikelets spirally arranged on the axis;

lemmas Lemma may refer to: Language and linguistics * Lemma (morphology), the canonical, dictionary or citation form of a word * Lemma (psycholinguistics), a mental abstraction of a word about to be uttered Science and mathematics * Lemma (botany), ...

are entire (with a smooth, even margin) or denticulate (finely toothed), and often have a centrally placed short, sharp tip (mucro). The

inflorescence An inflorescence is a group or cluster of flowers arranged on a Plant stem, stem that is composed of a main branch or a complicated arrangement of branches. Morphology (biology), Morphologically, it is the modified part of the shoot of sperma ...

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 In botany, a caryopsis (plural caryopses) is a type of simple fruit—one that is monocarpellate (formed from a single carpel) and indehiscent (not opening at maturity) and resembles an achene, except that in a caryopsis the pericarp is fuse ...

is not sticky, and the brown embryo is visible throughout the light-colored

pericarp Fruit anatomy is the plant anatomy of the internal structure of fruit. Fruits are the mature ovary or ovaries of one or more flowers. They are found in three main anatomical categories: aggregate fruits, multiple fruits, and simple fruits. Aggr ...

Species

There are three species in ''Tuctoria''. *'' Tuctoria fragilis'' (originally described as ''Orcuttia fragilis'' by

Jason Richard Swallen Jason Richard Swallen (May 1, 1903 -April 22, 1991) was an American botanist specializing in grasses. Born in Alliance, Ohio, Swallen graduated from Ohio Wesleyan University (AB 1924) and Kansas State Agricultural College (MS 1925). He spent t ...

in 1944). Found in

(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'' (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 The grass ''Tuctoria mucronata'', which is known by several common names including prickly spiralgrass, Solano grass, and Crampton's tuctoria, is a federally listed endangered species, endangered plant species Endemism, endemic to two counties in ...

'' (originally ''Orcuttia mucronata'' − Crampton).

Endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

Solano County Solano County () is a county located in the U.S. state of California. As of the 2020 census, the population was 453,491. The county seat is Fairfield. Solano County comprises the Vallejo–Fairfield, CA Metropolitan Statistical Area, which i ...

south of Dixon, 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 Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

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 bank A seed bank (also seed banks or seeds bank) stores seeds to preserve genetic diversity; hence it is a type of gene bank. There are many reasons to store seeds. One is to preserve the genes that plant breeders need to increase yield, disease res ...

s remain dormant until a season of rainfall that is adequate to fill the pool basins. In ''T. greenei'', germination 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 Hypoxia means a lower than normal level of oxygen, and may refer to: Reduced or insufficient oxygen * Hypoxia (environmental), abnormally low oxygen content of the specific environment * Hypoxia (medical), abnormally low level of oxygen in the t ...

, and inhibit germination. ''Tuctoria greenei'' is of high conservation concern in California, as

systems are in decline due to agricultural development and urban expansion.

References

External links