Date of Award:

1999

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Natural Resources

Department name when degree awarded

Rangeland Resources

Advisor/Chair:

Martyn M. Caldwell

Abstract

Although considerable research has addressed effects of elevated ultraviolet-B (UV-8) radiation on vegetative plant structures and processes, the reproductive biology and patterns of inheritance of UV-B tolerance have received much less attention. I examined the effects of UV-B radiation on pollen of 34 taxa. I also addressed questions concerning the patterns of inheritance of UV-B tolerance in Arabidopsis thaliana and examined potential cumulative carryover effects of UV-B exposure through multiple generations of this species.

In the first study, a significant reduction in pollen germination occurred in only five species, but pollen tube growth in more than half of the species exhibited significant reductions . Proportionate to their numbers in this survey of 34 taxa: Monocotyledonous species were more sensitive to UV-8 than the dicotyledonous species, wild species were more sensitive than cultivated species, and pollen from plants growing in the field was somewhat more sensitive than pollen from plants grown in the greenhouse. The results also suggested a possible adaptation to UV-8 radiation during the course of the season.

The second study probed patterns of inheritance of UV-8 tolerance. General combining ability and specific combining ability were both significant for several traits in Arabidopsis. This suggests that plant breeders may develop UV-8 tolerant strains of plant species both in the form of pure lines and hybrids.

In the third experiment, I found that a significant carryover effect of UV-B exposure through multiple generations Arabidopsis thaliana was evident in a subsequent generation, in either the presence or absence of UV-B, once differences in the reactions of different ecotypes were taken into account. However, instead of an expected accumulation of UV-B effect as a greater number of generations were exposed to the radiation, there was an apparent reversion of the cumulative, carryover effect. This was evident in that plants exposed to seven generations of UV-B exhibited much less carryover effect than did plants exposed for only three generations.

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