Fig. 6. Proportional contribution of preheading andpostheading of shoots absorption Cd to the grain Cdcontent of mature rice plants (n = 3). The Cd con-centration in grains that received Cd before or afterheading is expressed as a proportion of the Cd accumu-lated with continuous Cd treatment. The different low-ercase letters represent the significant difference betweenthe means of two cultivars as tested by the Student's t-test(P < 0.05).