Biology ETDs


Mary G. Mayes

Publication Date



Tribulus terrestris L. (T. terrestris) is a late summer annual inhabiting relatively dry areas of southwestern United States. In the more northern latitudes of the Southwest, seeds do not germinate until about the middle of July when both day and night temperatures are high and the seasonal rains have started. The vinelike plant grows prostrate with a prominent deep penetrating taproot and even-numbered, pinnately compound leaves. The leaflets vary from three to seven pairs, are oblong, entire, folding together along the leaf axis at night or in windy or unusually cool weather. The flowers are usually lemon yellow, solitary, and axillary. Bristles on the ovary sometimes resemble additional stamens. The fruit is flat, consisting of five nutlets which separate at maturity. Each nutlet is armed with two strong spines on its dorsal surface and often a third oriented ventrally. Two to five seeds are produced in each nutlet. These seeds have no endosperm at maturity and the embryos are able to survive long periods of dormancy under very dry conditions. T. terrestris grows in various soils and is often found near Salsola pestifer (Russian Thistle). It may be found almost anywhere in the desert areas of the Southwestern States where minimal quantities of water and warm day and night temperatures prevail. T. terrestris originated in the Mediterranean Region of Europe. It is transported by animals and other objects to which the spiny horns become attached.



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Degree Name


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Department Name

UNM Biology Department

First Committee Member (Chair)

Howard J. Dittmer

Second Committee Member

William Clarence Martin

Third Committee Member

Martin William Fleck

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Biology Commons