Biology ETDs

Publication Date

4-27-1972

Abstract

Quaking aspen (Populus tremuloides Michx.) primarily reproduce by suckering (i.e., root sprouting). Numerous environmental variables have been suggested as causes of this phenomenon, the most notable of which is soil temperature. Studies demonstrating thermal regulation of sprouting indicate the involvement of growth hormones. The only class of hormones to elicit a response similar to sprouting is the cytokinins. Other hormones, no doubt, function in this process as well (e.g., auxins). To substantiate the idea that thermal regulation of sprouting is primarily a function of thermal regulation of cytokinin activity, and to determine the importance of other environmental factors in this scheme, various measurements of field conditions and several laboratory experiments were employed. They included the following: (1) soil temperature and moisture measurements (8 cm depth) at each of eight meadow positions from May 15, 1971 through October 31, 1971; (2) azimuth reading of the aspect of each position; (3) soil texture and organic matter analysis at each position; (4) a count of the numbers of sprouts that had invaded the meadow through each position; (5) laboratory experiments involving the number of sprouts produced at 4 C, 6 C, 11 C, 13 C, 18 C, 20 C, 27 C, and 30 C; and (6) extraction and bioassays for cytokinins produced by root sections under the aforementioned temperature regimes. Via stepwise regression and regression analyses it was shown that in this subalpine meadow 91.9% of the variation in soil moisture was accounted for by the per cent silt, and 66% of the variation in soil temperatures was accounted for by soil moisture. A very significant regression exists of numbers of sprouts invading the meadow on soil temperature at each position. Laboratory experiments showed that there exist "cause­effect" type relationships between soil temperature, cytokinin levels, and sprout production of root sections. From this evidence and that provided by earlier investigations, it was hypothesized that when no factor is severely limiting, sprouting and generally aspen invasion is primarily a thermally controlled process. Thermal control is accomplished through alteration of cytokinin activity levels.

Language

English

Document Type

Thesis

Degree Name

Biology

Level of Degree

Masters

Department Name

UNM Biology Department

First Committee Member (Chair)

James Roman Gosz

Second Committee Member

Loren David Potter

Third Committee Member

Gordon Verle Johnson

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