Date of Final Oral Examination (Defense)

12-2011

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Biology

Department

Biology

Major Advisor

Marcelo Serpe, Ph.D.

Abstract

Lomatium dissectum (Nutt.) Mathias & Constance is a perennial plant found across much of western North America. For disturbed lands within this range, there is interest in using L. dissectum in restoration. A problem in the propagation of L. dissectum is that at the time of dispersal the seeds are dormant. Thus, prior to usage in restoration projects the type of dormancy and the procedures necessary to release dormancy in these seeds must be determined. Determining the type of dormancy and the treatments necessary to break dormancy in L. dissectum seeds was the primary focus of this study. To approach this problem I examined the effect of different constant and alternating temperature regimes on embryo growth and germination. I also evaluated the effect of plant hormones on seeds. Embryo growth and germination of seeds under field conditions was monitored and the soil temperature and moisture conditions correlated to changes in embryo elongation and seed germination. Finally, I explored seed dormancy in L. dissectum seeds collected over an elevation gradient. Exposure to 5°C stimulated embryo growth and germination. Exposure for more than 12 weeks was necessary for maximum embryo growth and germination. Exposure to 10°C and alternating between 4°C and 14°C did not result in better embryo growth or germination than exposure to only cold, moist conditions. Hormones did not enhance embryo growth or germination, nor did they serve as a substitute for seed exposure to cold, moist conditions. Based on these laboratory results, I determined that Lomatium dissectum seeds have deep complex morphophysiological dormancy. Seeds placed in the field supported the laboratory findings as the best embryo growth and germination occurred after exposure to the cold, moist temperatures experienced in winter. Seeds collected at different elevations varied in the period of moist, cold temperature required to break dormancy. However, the differences were not consistent between the two years tested. Consequently, these differences may not reflect environmental adaptations to elevations but may be the result of the environmental conditions at each site during seed development.

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