Fig. 4. Incremental nitrogen uptake efficiency (NUE) (quadratic component of the regression equations listed in Table 2) as related to leaf area expansion between 2 Dec. and 31 May for Swingle (SWL) and Volkamer (VLK) seedlings with the 7 mg N L^-1 (N7) and 70 mg N L^-1 (N70) treatments.