LEAF PHOTOSYNTHESIS, BIOMASS PRODUCTION AND WATER AND NITROGEN USE EFFICIENCIES OF TWO CONTRASTING NAKED VS. HULLED OAT GENOTYPES SUBJECTED TO WATER AND NITROGEN STRESSES

Water and nitrogen (N) are the two most important factors influencing the growth and yield of oat (Avena sativa). A pot culture study was conducted to determine the physiological and biomass production of contrasting oat genotypes to water and N supply conditions. With sufficient water, biomass yield of the naked ‘Shadow’ was 12.4% and 10.0% greater than ‘Bia’ in the treatments 750 and 1250 mg N pot−1, respectively, but ‘Bia’ produced greater grain yield than ‘Shadow’. Under severe water stress conditions, increasing N supply decreased PN mainly due to the reduction of gs and E. ‘Shadow’ had higher chlorophyll and leaf N than ‘Bia’, while there were no differences in plant total N, NuptE and NUE. With increasing N application and water stress, WUEL and WUEP both increased. NUE was inversely related with increasing N rates and water stress levels, resulting in a trade-off relationship between WUEP and NUE.