Effects of Temperature and CO(2) Enrichment on Carbon Translocation of Plants of the C(4) Grass Species Echinochloa crus-galli (L.) Beauv. from Cool and Warm Environments

Plants of Echinochloa crus-galli from Québec and Mississippi were grown under two thermoperiods (28°C/22°C, 21°C/15°C) and two atmospheric CO₂ concentrations (350 and 675 microliters per liter) to examine possible differential responses of northern and southern populations of this C₄ grass species. Translocation was monitored using radioactive tracing with short-lived ¹¹C. CO₂ enrichment induced a decrease in the size of the export pool in plants of both populations. Other parameters did not strongly respond to elevated CO₂. Low temperature reduced translocation drastically for plants from Mississippi in normal CO₂ concentration, but this reduction was ameliorated at high CO₂. Overall, plants from Québec had a higher ¹¹C activity in leaf phloem and a higher percentage of ¹¹C exported, whereas these northern plants had lower turnover time and smaller pool size than plants from the southern population.