Growth and dry matter partitioning in sugar beet plants (Beta vulgaris L.) under moderate drought

Growth response of sugar beet plants to drought stress applied at different growth stages has been investigated. Cessation of watering imposed moderate water stress and resulted in the reduction of the relative water content of young and old leaves maximally by 6%. However, water content in taproot was more drastically decreased than in the shoot. Water withholding reduced dry matter accumulation and leaf assimilatory expansion when imposed at successive growth stages, especially in the case of earlier stress application. Substantial change in distribution pattern was observed when stress affected foliar development, more than 80% of dry matter was accumulated in the taproots. Water shortage negatively influenced both taproot and sugar yield by 16-52%, depending on the stress timing in the season. Drought stress did not change the sucrose concentration but when occurred in foliar and early stage of root development, decreased the contents of important non-sugar compounds like potassium and -amino-N solutes in the final yield. Overall, data concerning the different water status in particular organs implies that a hydrodynamic equilibrium does not exist within the sugar beet plant as a response to water stress. Drought imposed on the earlier stage, most drastically influenced plant growth and final yield. When water stress occurs at the end of crop cycle, sugar beet plants had a higher ability to recovery their growth.