PW03 Plant Toxicology and Soil Interactions
Exhibit Hall
8:00 AM - Wednesday, 12 November 2003
(PW064) New approaches in predicting cadmium partitioning in plants.
Van der Vliet, L1, Hale, B1, 1 University of Guelph, Guelph, Ontario, Canada
ABSTRACT- Laboratory experiments on metal accumulation by plants are often conducted in plant systems that are metal stress naïve, and are thus unable to detect changes in uptake that occur as a result of long-term metal exposure. Our experiment examines differences in Cd uptake and translocation between two durum wheat cultivars, Triticum turgidum L. cvs. Kyle and Arcola. Transpiration and Cd uptake were measured at several different life stages, utilizing a unique double exposure method that allowed resolution of short-term uptake and long-term accumulation in metal naïve and metal exposed plants. Plants were grown hydroponically and exposed to 0 
g/L or 10 ppb g/L (8.90 x 10-8 M) elemental Cd throughout their lifecycle. At the seedling, tillering, heading and grainfill stages, root solution was replaced with 10 g/L 106Cd for 9 or 21 hours; transpiration was concurrently measured using the weight difference method. Following short-term exposure with 106Cd, tissues were acid digested and Cd concentrations (106Cd and elemental Cd) were determined by ICP-MS. Transpiration correlated with shoot Cd accumulation only at the seedling and tillering stage. Long-term Cd exposure increased transpiration rates in Kyle at tillering and heading. Seedlings did not exhibit the same Cd accumulation trends as plants at older life stages. Long-term Cd exposure increased Cd root uptake in Arcola, but not Kyle, at tillering, heading and grainfill. Differences in development affected short-term Cd accumulation in the shoots. We conclude that risk assessment and prediction of Cd partitioning in plants can improve by utilizing: (i) transpiration rates, which can provide qualitative information on differential shoot Cd accumulation at the seedling and tillering stage; (ii) life stage identification, which is critical for accurate characterization of short-term shoot Cd accumulation at heading and grainfill; (iii) double exposure technique, which can collect short-term and long-term accumulation data, and elucidate the effect of long-term Cd exposure on Cd uptake (iv) life stage testing, which can identify characteristics of young seedlings that cannot be "scaled up" to predict how plants will respond over their lifetime.
Key words: transpiration, pre-exposure, metal stress, durum wheat