PARENT SESSION
Contributed Oral Session 28: Plant Physiology: Effects of Ozone CO₂, and Cavitation
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 519 B, Level 5, Palais des congrès de Montréal

Elevated CO₂ alters xylem sap profile of amino acids and their supply rate to the shoot.

BassiriRad, Hormoz¹, Sehtiya, Harbans¹, ¹ Department of Biological Sciences, Chicag, IL, USA

ABSTRACT- Seeds of elm were germinated and the seedlings were subsequently grown under ambient (370 ppm) and elevated (520 ppm) levels of CO₂ in naturally lit greenhouses. The main objective of this study was to determine if CO₂ enrichment alters xylem sap profile of various nitrogen (N) pools and their fluxes to the shoot. After 75 days of CO₂ treatment, sap exudates were collected by pressurizing the intact/decapitated root systems to a hydrostatic pressure gradient of 0.5 MPa. Xylem N content was dominated by nitrate and amino acids. Fluxes of nitrate and amino acids to the shoot increased by roughly 50 and 40% respectively when plants were grown under high CO₂. We measured the individual amino acids and found that the most abundant amino acids in the sap were asparagine and glutamine. Elevated CO₂ significantly increased the sap concentration of these and twelve other amino acids. Furthermore, fluxes of all amino acids (except lycine) to the shoot increased in response to CO₂ enrichment. This positive CO₂ response ranged from 95% for glycine to only 7% for glutamate. The results have significant implications for N supply and metabolism in a CO₂ enriched atmosphere.

Key words: Amino acids, Xylem sap, Elevated CO2