Physiological and Morphological Responses of Nitrogen-Fixing Red Alder (Alnus Rubra) and Sitka Alder (Alnus Viridis Ssp. Sinuata) to Flooding: Inter- and Intraspecific Comparisons

Red alder (Alnus rubra) and sitka alder (A. viridis ssp. sinuata) are nitrogen-fixing woody species that grow sympatrically along the Pacific coast of North America. Red alder is found in poorly drained lowlands, as well as in soils of moist upland slopes, whereas sitka alder generally colonizes well-drained soils. To identify factors that contribute to flood tolerance in these two species and to determine whether red alder progeny from naturally wet and dry sites vary genetically in their capacity to tolerate flooding, I conducted greenhouse experiments subjecting both species to a short term flood of 20 days, red alder to a long term flood of 50 days, and seedling progeny of red alder to a flood of 20 days. Relative growth rate (RGR), the primary criterion of flood tolerance, was consistently negative for sitka alder while the RGR of red alder remained positive with a decline of only 36% relative to the controls. Nitrogenase activity ceased after 24 h of flooding in both species but returned in red alder after 50 days of continuous flooding, which corresponded with the development of hypertrophied lenticel tissue on nodule surfaces proximate to the Frankia vesicles in adjacent cells within the nodule. Red alder developed extensive adventitious and new secondary roots during the flood, while sitka alder formed few adventitious roots, lost much of its root and leaf biomass, and showed no restoration of growth during flooding or recovery. Differences in flooding response of red and sitka alder serve as a partial explanation for the different patterns of distribution of these species and suggest some adaptations in red alder that permit flood tolerance. Intraspecific comparisons of red alder families showed a significant correlation between flood tolerance and change in root to shoot (RS) ratio during the experimental flood indicating that plants which were able to maintain RS ratios similar to those under preflood conditions had greater flood tolerance. Seedling progeny showed consistently high variation in flood tolerance but little variation between wet and dry sites. Traits that confer tolerance to flooding within the red alder species appear to be traits controlled more strongly at the individual plant level than at the population level.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Batzli, Janet McCray

Contributors dc:contributor

• Dawson, Jeffrey O.

• Biology, Plant Physiology

Language dc:language

eng

Identifier

(MiAaPQ)AAI9834652

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/85397