For three successive growing seasons (1999–2001), a completely randomized block design experiment was established at the surrounding area of each of four sugar beet processing plants of Hellenic Sugar Industry SA, Greece (a total of 12 experiments). Nitrogen was applied at five rates (0, 60, 120, 180 and 240 kg N ha−1) and six replications per rate. Nitrogen fertilization had site‐specific effects on quantitative (fresh root and sugar yields) and qualitative (sucrose content, K, Na, α‐amino N) traits. When data were combined over years and sites, fresh root and sugar yields were maximized at high N rates (330.75 and 295 kg N ha−1 respectively), as derived from quadratic functions fitted to data. In three trials, increased N rates had negative effects on root and sugar yield. These sites were characterized by high yield in control plots, light soil texture (sand > 50 %) and low CEC values. When data were converted into relative values (the ratio of the trait values to the control mean of each experiment), root and sugar yield was found to be maximized at higher N rates (350 and 316 kg N ha−1, respectively). Sucrose content was strongly and linearly reduced by the increased N rates when data were combined but a significant reduction with increasing N rates was found in only two sites. Non‐sugar impurities (K, Na, α‐amino N) were positively related to the increased N rates when data were combined. Sodium and α‐amino N showed to be most affected by N fertilization as positive relationships were found in six and eight of 12 locations, respectively. Increased N supply resulted in higher soil NO3‐N concentrations (0–90 cm depth) at harvest which were related with amino N contents in sugar beet roots (in 1999 and 2001).

An indirect method of leaf area measurement for Rizor sugar beet cultivar was tested. Leaves were sampled during two growing seasons in a Randomised Complete Block Design experiment. For 2002 samplings, leaf area [cm 2 ] was linearly correlated with maximum leaf width [cm] using all leaf samples (r 2 = 0.83, p<0.001) or using the means of the 8 sampling occasions (r 2 = 0.97, p<0.001). Correlations between leaf area and leaf midvein length [cm] were weaker (r 2 = 0.75, p<0.001 and r 2 = 0.93, p<0.001, respectively). For 2003 samplings, the area estimated by the equations was highly correlated to the measured leaf area.

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In two successive years (2003 and 2004), a set of 16 commercial sugar beet cultivars was established in Randomized Complete Block experiments at two sites in central Greece. Cultivar combination was different between years, but not between sites. Leaf sampling took place once during the growing season and leaf area, LA [cm 2 ], leaf midvein length, L [cm] and maximum leaf width, W [cm] were determined using an image analysis system. Leaf parameters were mainly affected by cultivars. Leaf dimensions and their squares (L 2 , W 2 ) did not provide an accurate model for LA predictions. Using L×W as an independent variable, a quadratic model (y = 0.003 x 2 -1.3027 x + 296.84, r 2 = 0.970, p<0.001, n = 32) provided the most accurate estimation of LA. With compromises in accuracy, the linear relationship between L×W and LA (y = 0.5083 x + 31.928, r 2 = 0.948, p<0.001, n = 32) could be used as a prediction model thanks to its simplicity.Additional key words: leaf length; leaf width; morphology; non-destructive methods.

In a two-year (2002)(2003) field study, six sugar beet cultivars were arranged in a Randomised Complete Block design with six replications. The aim of the work was to study the root shape variability using an image analysis system and to relate root shape parameters [area (A, cm 2 ), maximum length (L, cm), maximum width (W, cm), average radial (AR, cm), radial variation (RV), circularity (Circ), elongation or the ratio W/L (El) and shape factor (SF)] with yield [fresh root weight (FRW), sugar yield (SY)] and quality [sucrose content % fresh root weight (SC), K, Na, D-amino N]. The main factors (year, site, cultivar) and their interaction had smaller effects on root shape parameters than on yield and its components. Cultivar affected only W but it had a significant impact on all quantitative and qualitative traits. No significant relationship between root W and yield or quality was found for cultivars. Significant, positive relationships between A and FRW or K in roots were found for the year × site × cultivar interaction. SC in roots was related with more rounded roots as revealed by the relationships between SC and Circ or El. Also, rounded roots were related with increased accumulation of K and decreased Na concentrations in sugar beets.

Six leaf samplings were conducted in two sunflower (Helianthus annuus L.) hybrids during the 2006 growing season in order to evaluate a simple model proposed for leaf area (LA) estimation. A total of 144 leaves were processed using an image analysis system and LA, maximum leaf width (W) [cm], and midvein length (L) [cm] were measured. Also, LA was estimated using the model proposed by Rouphael et al. (2007). Measured LA was exponentially related with L and W, and the W-LA relationships showed higher r 2 . Estimated LA was strongly and exponentially related with L. Strong, linear relationships with high r 2 between estimated and measured LA confirmed the high predictability of the proposed model.Additional key words: Helianthus annuus; leaf length; leaf width; non-destructive methods.

Selective absorption (SA) of K over Na (i.e. the preferential absorption of K over Na) has been proposed as a Na tolerance mechanism but genotypic variation for this trait has not been assessed with sugar beet in the field. Thus, the aim of this study was to explore the variation of SA in 14 sugar beet cultivars and to relate SA with yield and root quality in two sites of central Greece (Amfithea and Pyrgetos). Genotypic variation for SA was significant and the SA values were higher in Pyrgetos, the site with the lower soil K and Na concentrations. In Pyrgetos, a favourable environment for sugar beet growth, cultivars yielded more and root quality was better. In that site, a negative relationship between SA and yield (fresh root weight, sugar yield) was found indicating that strong Na exclusion from root is a disadvantage for high yielding. Negative SA–yield relationships were evident in Amfithea when five cultivars with very low SA values (<1.00) were excluded from the analysis. Combined all the cultivars, curvilinear functions were the best‐fitted curves for the SA–yield relationships. In Amfithea, where sugar beets had lower water content in root (WCR), a significant, positive correlation between SA and % sucrose content in fresh root weight was found. This finding was ascribed to the dilution of sucrose in roots due to the increased WCR as a result of the increased root Na concentration. In both sites, SA was positively related with root K concentration and negatively with Na concentration. The positive correlations between SA and root α‐amino N concentration indicated that sugar beet N nutrition could be affected by the genotypic ability to exclude Na from the root.