2Aristotle University of Thessaloniki, School of Agriculture, Laboratory of Soil Science, 541 24 Thessaloniki, Hellas, Greece.
3Hellenic Sugar Industry SA, Agronomic Research Service, 574 00 Sindos, Hellas, Greece.
In a three-year (2004-2006), field experiment, we aimed to study changes in leaf physiological traits (leaf water potential-Ψleaf, leaf water content-LWC, carbon isotope discrimination-Δ, specific leaf area-SLA, chlorophyll content as assessed by SPAD and modified SPAD-MSPAD) and elemental composition (K, Na, Ca, Mg, K/Na, Ca/Mg, total leaf salinity-TLS) of sugar beets (cv. Rizor) grown under Mediterranean, irrigated conditions. Each year, soil moisture content (SMC) and leaf parameters were determined 11 times from early June to the end of October. Growing seasons differed as regards water inputs with 2004 being the driest and 2006 being the wettest. Leaf physiology and chemistry showed plasticity to water availability and significant differences were found between years (except for Ca), sampling time and their interaction. Ψleaf, LWC, Δ, SLA, K/Na and Ca/Mg were positively affected by SMC while the adverse was evident for chlorophyll content (SPAD and MSPAD), Na, Ca, Mg and TLS. As a Chenopodiaceae, sugar beet used leaf succulence, lowering SLA, to cope with water shortage and maintain LWC ca 90%. Low SLA was related with low Ψleaf and Δ values. Succulent leaves were characterized by increased leaf salinity and chlorophyll accumulation, which was ascribed to increased Mg concentrations. Leaf salinity and mainly Na had a negative impact on Δ. Antagonistic effects of K on Na or Mg and synergistic effects of Na on Ca and Mg were recorded.