Masters Theses

Date of Award

3-1975

Degree Type

Thesis

Degree Name

Master of Science

Major

Forestry

Major Professor

Eyvind Thor

Committee Members

Charles Pless, Vernon Reich

Abstract

The large percentage of seed of low viability produced by yellow-poplar (Liriodendron tulipifera L.) is perhaps the most important problem in seed orchards of this species. Low viability is related to the effects of honeybees (Apis mellifera L.) on cross pollination. Since honeybees can also be managed by man, it seems reasonable to use them to increase seed set in yellow-poplar. The objective of this study is to determine the movement of pollen by honeybees in a yellow-poplar orchard. This information may be useful in determining management procedures, such as number and distribution of hives in the orchard. In a yellow-poplar seed orchard at the University of Tennessee Plant Science Farm, seven grafted yellow-poplars were selected. A yellow-poplar in the middle of the orchard was used as the source tree. Three holes were drilled in its trunk, and these holes were filled with a radioactive solution (P32), which was used as labeling material, about a week before the yellow-poplar flowers bloomed. At each distance of 40, 160, and 355 feet east and southwest of the source tree, a sample tree was selected. When the trees started flowering a full strength beehive was placed near the source tree. Twelve days after the last day of injection of P32 (May 7), five flowers were picked from each selected tree; flowers were also picked on May 8, 9, 11, and 16. Each flower sample was broken into three parts (petals, top gynoecium, and bottom gynoecium), and each part was placed in a vial and measured in a liquid scintillation system. Eighty-four out of 450 flower samples had a CPM (count per minute) significantly higher than background (P < 0.05). There were significant (P = .05) differences among the high CPM flower sample numbers for petals, top gynoecia, and bottom gynoecia; petal samples more often had a high CPM. No significant (P = .05) difference was observed between the total numbers of significant (P < 0.05) flower samples east and southwest of the source tree. There was no significant difference between number of high CPM samples of two sample trees located the same distance from the source tree. The equation of the regression line for the association between the significant (P < 0.10) numbers of samples and the distance from the source tree is: Y = 24.65 - .0366X where X is distance in feet from the source tree. The correlation coefficient r was .765, slightly smaller than that required for significance at the 5 percent level.

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