PARENT SESSION
Poster Session 1: Photosynthesis and Water Relations
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Combined drought and freezing temperature tolerance for seedlings of two subspecies of sagebrush (Artemesia tridentata).

Lambrecht, Susan^*,1, ¹ San Jose State University, San Jose, CA, 95060

ABSTRACT- Most studies of climate change effects on plants have been concerned with the performance of mature plants, but the response of seedlings to climate change has often been overlooked. However, the seedling stage is essential to plant survival in current or new ranges as climate changes. Big sagebrush (Artemesia tridentata) is a dominant plant throughout much of the arid West. Future climate scenarios for the Western United States include increased variability in climate patterns, such as rainfall and night freezing events. I examined the growth and photosynthetic response of seedlings exposed to two different levels of moisture availability in combination with a hard freezing event. In a greenhouse, I grew seeds of two different subspecies of A. tridentata, one native to mountainous areas (Mountain big sagebrush) and the other native to the Great Basin area (Basin big sagebrush). Under high moisture availability, photosynthetic capacity of Mountain sagebrush averaged about twice that of Basin sagebrush. The drought treatment had a relatively greater impact on photosynthetic capacity of Basin sagebrush than Mountain sagebrush, reducing photosynthetic capacity by about 75% as opposed to 60%, respectively. In contrast, the freezing treatment reduced photosynthetic capacity of the Mountain sagebrush by about 78%, while Basin sagebrush was unaffected when grown under high moisture availability. However, photosynthetic capacity of Basin sagebrush grown under the drought treatment was more sensitive to freezing, which reduced photosynthetic capacity by about 50%. In contrast, drought did not increase the susceptibility of Mountain sagebrush seedlings to freezing. These results demonstrate that different subspecies native to contrasting environments may have quite dissimilar responses to various aspects of climate change. Furthermore, the susceptibility of plants to an aspect of climate change may be modified by other simultaneously occurring factors, such as the combination of drought and freezing.

Key words: Artemesia tridentata, seedling, climate change, photosynthesis