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Citrus ID

 

Australian Desert Lime

 

Synonyms

 

Triphasia glauca Lindl., Atalantia glauca (Lindl.) Benth. (sec. Swingle and Reece 1967)

Cultivar or taxon

 

Citrus glauca (Lindl.) Burkill (sec. Mabberley 2004, Bayer et al. 2009); Eremocitrus glauca (Lindl.) Swingle (sec. Swingle and Reece 1967; sensu Tanaka sec. Cottin 2002)

Description

 

Crown compact or open, weeping. First-year twig surface glabrous; second- or third-year twig surface striate; thorns absent or not persistent; prickles absent or not persistent. Petiole glabrous; length short or medium; wings absent. Leaflets one, margins bluntly toothed, shade leaflet blades flat, sun leaflet blades flat or weakly conduplicate. Scent of crushed leaflets sweetly dough-scented. Fruit as broad as long or longer than broad; rind light green with some break to yellow (5), green-yellow (6), or yellow (7-10); rind texture smooth (1-3); firmness membranous; navel absent; flesh green/greenish; taste sour.

Swingle and Reece (1967) provided the following additional information on the species:

"The typical form of this species as it occurs in southeastern Queensland, Australia, is a small tree or a large shrub, sometimes growing as a thorny bush only a few feet in height. F. M. Bailey described it as "a rigid glaucous shrub of 2 or 3 ft., often armed with straight or incurved axillary spurs of 1/2 in. or under…" However, Flanders (1932, p. 278) figured a giant tree at Chinchilla, Layton County, in Queensland, some 130 miles west-northwest of Brisbane, that had a single trunk, about 25 feet in height and measuring 20 inches in diameter at 2 feet above the ground. The round crown was about 28 feet across. Such a tree undoubtedly grew where its roots had access to ground water.

The leaves are gray-green, very thick and leathery, usually oblong, linear- or elongate-obcuneate, obtuse at the apex, often emarginate, 25-40 x 4-10 mm. Both surfaces show appressed, grayish hairs and have a thick cuticle with sunken stomata. The leaves are more or less paraheliotropic (on the edge to the light) and have no clearly defined upper and lower surfaces (Swingle 1914, figs. 5, 6, 7). Flowers very small, 3-5 mm long and 5-8 or 10 mm across, borne singly or in groups of 2 or 3 in the axils of the leaves on slender pedicels, 4-6 mm long, flowers 3-5-merous, with 4 (sometimes 3) times as many stamens as petals, stamens short, filaments slender, 4-5 mm long (sometimes slightly united at the base according to Bailey); pistil short, 3-4 mm long, ovary ovate with 3-5 locules; fruits subglobose or obovoid, 7-12 x 8-10 mm, pulp-vesicles small, subglobose, on short, slender stalks and nearly free from one another; seeds small, oval, 5-6 x 3-4 x 2.5-3 mm, testa rough, monoembryonic. Young plants growing in the greenhouse at Washington, D.C., had very slender, straight or slightly upcurved thorns, 25-35 mm long but only 1-1.5 mm diam.; young trees growing out of doors at Riverside and Indio, California, show much stouter spines, 2-3 mm diam., but seldom as long as 35 mm. The twigs on young plants are usually very slender, 1-2 mm diam., and for several years bear very narrow, slender leaves or cataphylls, 18-30 x 1-2 mm, and make very slow growth; as soon as an extensive root system has developed, the young tree grows upward rapidly, producing larger leaves on slightly stouter twigs, 2-3 mm diam., that often show only very short spines or none."

Notes

 

Swingle and Reece (1967) additionally noted that:

“The Australian desert lime, Eremocitrus glauca, is a pronounced xerophyte, the only one found thus far in the orange subfamily (fig. 3-38). It is able to withstand severe drouth and hot dry winds. Under such conditions the leaves fall off and the leafless gray-green twigs (resembling those of the smoke tree, Dalea spinosa, and the paloverdes, common in the arid regions of the southwestern United States and northern Mexico) carry on photosynthesis on a reduced scale. The seedling develops an enormous root system before making vigorous aerial growth and developing full-sized leaves (young seedlings bear only very slender cataphylls). The roots are able to endure rather high concentrations of salts in the soil moisture and are much less susceptible to boron poisoning than are those of Citrus. When in a dormant condition this species is able to withstand, without injury, temperatures of ten or more degrees below freezing Fahrenheit (-5.5° C or lower)[ed.: corrected from error in original publication]. It probably possesses a higher zero point of growth and, in consequence, a greater dormancy in late winter and early spring than Citrus. It apparently ranks next to, but does not equal, the kumquats in possessing both winter dormancy and resistance to cold.”

In the analysis by Bayer et al. (2009), Eremocitrus glauca emerged sister to Microcitrus australis, in a strongly supported clade including other species recognized in Microcitrus by Swingle.

References

 

Andrews, J. and W.H. Maze. 1933. Some climatological aspects of aridity in their application to Australia. Abstract of Proceedings of the Linnean Society of New South Wales. 58: 105–120.

Bayer, R.J., D.J. Mabberley, C. Morton, C.H. Miller, I.K. Sharma, B.E. Pfeil, S. Rich, R. Hitchcock, and S. Sykes. 2009. A molecular phylogeny of the orange subfamily (Rutaceae: Aurantioideae) using nine cpDNA sequences. American Journal of Botany 96: 668–685.

Cottin, R. 2002. Citrus of the World: A citrus directory. Version 2.0. France: SRA INRA-CIRAD.

Flanders, S.E. 1932. Observations concerning a citrus relative native to Australia. California Citrograph 17: 278, 307–308.

Mabberley, D.J. 2004. Citrus (Rutaceae): A review of recent advances in etymology, systematics and medical applications. Blumea 49: 481–498.

Swingle, W.T. 1914. Eremocitrus, a new genus of hardy drouth-resistant citrus fruits from Australia. Journal of Agricultural Research. 2: 85–100.

Swingle, W.T. and P.C. Reece. 1967. The botany of Citrus and its wild relatives. In: Reuther, W., H.J. Webber, and L.D. Batchelor (eds.). The Citrus industry. Ed. 2. Vol. I. University of California, Riverside. http://lib.ucr.edu/agnic/webber/Vol1/Chapter3.html.

Resources

 

Search for this cultivar in NCBI Entrez or NCBI Nucleotide

Additional information on this species at University of California: Riverside Citrus Variety Collection

 

Citrus ID Edition 2
October, 2011
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