QUANTITATIVE EFFECT OF ROOT LEAF GROWTH-RATE ON ROOT YIELD AND QUALITY PARAMETERS IN SUGAR-BEET/

Although the known literature does not suggest that leaf canopy and ac tive photosynthesis are limiting factors in sugar beet growth, the par titioning of photosynthetic products into the two main plant parts (ro ot and top) is the most critical factor affecting sugar beet yield and quality under Mediterranean climatic conditions (Greece). A three-yea r survey, over four growing areas, on representative commercial sugar beet fields was conducted to quantify sugar yield and root quality res ponses to different root and leaf growth rates. The data collected est ablished that any differentiation regarding PTOP (Top leaf mass as a p ercentage of the total plant mass) was associated with corresponding d ifferentiations in sugar yield and quality parameters for a long perio d of the harvesting time. Statistically significant correlations of PT OP were found in June with sugar content (- negative) and Na content o f roots (+ positive) of sugar beet being harvested in successive perio ds of time. A higher correlation was established with the quality rati o QR (sugar content to Na content of roots). The top leaf differentiat ion was found to be influenced by the nutritional status of the sugar beet plants and, moreover, by any factor regulating the quantitative p lant response to certain nutrient levels (location, year, interactions ). Average values of the QR and the regression rate (slope) of sugar c ontent as a function of Na content of roots, were used as indices to c lassify sugar beet growing areas on the basis of beet technological va lues. Evaluation and interpretation of these indices as well as agrono mic implications are discussed. Further investigations to determine lo cal factors associated with beet quality parameters are needed.