PARENT SESSION
Oral Session # 8: Plant Ecology I: Physiology and Function I.
Presiding: E Hamerlynck
Monday, August 4. 8:00 AM to 11:30 AM, SITCC Meeting Room 200.

Maternal CO₂ affects seed nitrogen and seedling growth but not uptake and assimilation in wheat.

Kline, Kerry^*,1, BassiriRad, Hormoz¹, ¹ University of Illinois at Chicago, Chicago, Illinois, USA

ABSTRACT- Seedling growth and vigor, two factors that impact seedling establishment and plant community dynamics, are highly influenced by maternal as well as current environmental conditions. We obtained seeds that were produced under ambient and elevated CO₂ from the Maricopa Free Air Carbon Dioxide Enrichment (FACE) site in Arizona and evaluated the CO₂ effects on the growth and physiology of the subsequent generation. We assessed seed quality by determining carbon to nitrogen (C:N) ratio and the concentrations of calcium (Ca²⁺), potassium (K⁺), magnesium (Mg²⁺), ammonium (NH₄⁺), nitrate (NO₃^-), phosphorus (P), and total nitrogen (N) in the seeds. We also examined NO₃^- uptake capacity and whole-plant NO₃^- assimilation. Seed NO₃^- concentration was undetectable, but analysis of other elements showed no significant changes in the concentrations of Ca²⁺, K⁺, Mg²⁺, and P in response to elevated maternal CO₂. Seed N and NH₄⁺ concentrations were, however, lower in elevated compared to ambient produced seeds. This lower seed N concentration may explain why eight-day old seedlings produced from elevated maternal CO₂ weighed significantly less by at least 20% than ambient-produced seedlings regardless of the their current CO₂ conditions. Elevated maternal CO₂ seedlings had a significantly higher NO₃^- uptake rate than the ambient ones, but this effect was present only if the growth CO₂ was also elevated. We also examined whole-plant NO₃^- reduction and found that elevated CO₂ in either the maternal or current environment had no affect on whole plant NO₃^- assimilation. The data suggest that maternal CO₂ does not alter NO₃^- uptake capacity or assimilation, yet the early seedling growth is clearly stunted in offspring of high CO₂ plants. We believe that this maternal effect on the subsequent generation is mediated through an effect on total seed N concentration.

Key words: seedling growth, elevated CO₂, seedling physiology