University of Utah

About: University of Utah is a education organization based out in Salt Lake City, Utah, United States. It is known for research contribution in the topics: Population & Medicine. The organization has 52894 authors who have published 124076 publications receiving 5265834 citations. The organization is also known as: The U & The University of Utah.

Streamside trees that do not use stream water

Abstract: A LONG-STANDING axiom is that plant distribution is strongly influenced by soil moisture content1,2. While it has been shown that plant taxa inhabiting streamside communities receive or use more water3, it is assumed that this water is obtained from the stream adjacent to where they are found growing. Here we show, using hydrogen isotope ratio analyses at natural abundance levels, that mature streamside trees growing in or directly next to a perennial stream used little or none of the surface stream water. The deuterium to hydrogen content of both source and xylem waters indicated that mature trees were using waters from deeper strata. Although adult trees may have roots distributed continuously throughout a soil profile, it seemed that the most active sites of water absorbtion were limited to deeper soil layers. In contrast, small streamside individuals appeared to use stream water, whereas small non-streamside individuals used recent precipitation as their primary water source. Our analyses provide both a relatively non-destructive method for assessing water sources of plants and a means of assessing potential competitive interactions among cooccurring taxa. In addition, the method may aid in resolving the role of water in determining plant distributions in areas characterized by sharp soil moisture gradients.

Evolutionary and Ecological Aspects of Photosynthetic Pathway Variation

Abstract: C4 and CAM photosynthesis are evolutionarily derived from C3 photosynthesis. The morphological and biochemical modifications necessary to achieve either C4 or CAM photosynthesis are thought to have independently arisen numerous times within different higher plant taxa. It is thought that C4 photosynthesis evolved in response to the low atmospheric CO2 concentrations that arose sometime after the end of the Cretaceous. Low CO2 concentrations result in significant increases in photorespiration of C3 plants, reducing productivity; both C3-C4 intermediate and C4 plants exhibit reduced photorespiration rates. In contrast, it may be argued that CAM arose either in response to selection of increased water-use efficiency or for increased carbon gain. Globally, all three pathways are widely distributed today, with a tendency toward ecological adaptation of C4 plants into warm, monsoonal climates and CAM plants into water-limited habitats. In an anthropogenically altered CQ2 environment, C4 plants may lose their competitive advantage over C3 plants. 411

Tetramesityldisilene, a stable compound containing a silicon-silicon double bond

Abstract: Irradiation of 2,2-bis(2,4,6-trimethylphenyl)hexamethyltrisilane in hydrocarbon solution produces tetramesityldisilene, which can be isolated as a yellow-orange solid stable to room temperature and above in the absence of air Like the olefins of carbon chemistry, tetramesityldisilene undergoes addition reactions across the silicon-silicon double bond