Field Measurements of Photosynthesis and Leaf Growth Rates of Three Alpine Plant Species

Author

Douglas A. Johnson, Utah State University

Date of Award:

5-1973

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Wildland Resources

Department name when degree awarded

Range Science

Committee Chair(s)

Martyn M. Caldwell

Committee

Martyn M. Caldwell

Committee

Kathryn Johnson

Committee

Russell Moore

Committee

James Ehleringer

Committee

Dennis Ballinger

Committee

Rita Belserene

Abstract

Leaf photosynthetic measurements using a portable ¹⁴Co₂ field system were carried out and correlative leaf relative growth rates, RGR, were determined at different leaf positions of three alpine plant species throughout the growing season. Initially there was a period of high leaf RGR associated with a period of increasing photosynthetic activity. Following this stage was a long period of no net change in length of the living leaf. During this period, photosynthetic activity generally increased to a maximum level and then decreased steadily. The final ontogenetic stage was a period of negative leaf RGR denoting leaf senescence which was associated with a marked decline in leaf Co₂ uptake. Ontogenetic timing of these alpine species is geared with the surge and decline of individual leaf photosynthetic activity so that one to several leaves operating at near maximal photosynthetic capacity are always maintained during the growing season for each plant. These findings are discussed in relation to their adaptive significance for these species.

Checksum

52902247a31719f39380c3b3f9e8219f

Recommended Citation

Johnson, Douglas A., "Field Measurements of Photosynthesis and Leaf Growth Rates of Three Alpine Plant Species" (1973). All Graduate Theses and Dissertations, Spring 1920 to Summer 2023. 6269.
https://digitalcommons.usu.edu/etd/6269