مرکز منطقه ای اطلاع رساني علوم و فناوري -

چكيده لاتين :

The seasonal changes of leaf physiological traits and its relationship with abiotic factors (photosynthetic active radiation-PAR, leaf temperature-Tleaf, air temperature-Tair, Tleaf - Tair- (delta)T) were studied on sugar beets grown under the semi-arid conditions of central Greece. Sugar beet (Beta vulgaris L.) cv Rizor was established in a Randomised Complete Block design experiment for two years (2004-2005). From early June till the end of October, 11 determinations of leaf physiological traits (intracellular to ambient CO2 concentration-ci, transpiration rate-E, stomatal conductance-gs, net photosynthesis-A, instantaneous water use efficiency-A/E, photosynthetic water use efficiency-A/gs, chlorophyll content-SPAD, carbon isotope discrimination- (delta), N concentration and specific leaf area-SLA) took place. Temperatutes (Tleaf and Tair) and (delta)T were higher in 2004 when water budget (WB, precipitation + irrigation - evapotranspiration) was more negative. Also, seasonal mean of carbon isotope discrimination ((delta)) and net photosynthesis (A) were lower in 2004 to compare to 2005. A gradual decline with the progress of the growing season was found for A, (delta), gs, E, SLA and leaf N concentration while the adverse trend was evident for water use efficiencies (WUE, A/E and A/gs). PAR was positively related with gs and E and negatively with A/E. Temperatures (Tair and Tleaf) had a positive effect on E and a negative one on A/E. High temperatures (35-37 °C) degraded leaf chlorophyll but temperatures higher than 37 °C tended to increase chlorophyll content. (delta)T (transpirational cooling) was negatively related with gs, E, and A and positively with A/E and A/gs. Both E and A were regulated by gs which was kept higher or slightly lower than 0.10 mol m^-2 s^-1, a limit indicative of severe drought in C3 species. Positive relationships were found between A, leaf N concentration and SLA. SLA is an indicator of resource-use strategy and can provide useful information about abiotic factor effects on sugar beet physiology and yield. (delta) was negatively related with A/gs showing that it can be an indirect assessment of WUE at leaf level.