POLYAMINE CONCENTRATION AND ETHYLENE EVOLUTION IN TOMATO PLANTS UNDER NUTRITIONAL STRESS

Polyamine accumulation in foliage was assessed in relation to ammonium accumulation and ethylene evolution in tomato (Lycopersicon esculentum Mill.) under nutritional stress. Nutritional stresses were induced in greenhouse-grown plants in quartz sand with an NH4-based solution or with NO3-based solutions without P, K, Ca, or Mg. Plants receiving NH4-based nutrition had higher putrescine and lower spermidine concentrations than plants receiving NO3-based nutrition. Adding AOA (10(-5) M) to the nutrient solution of plants receiving NH4-based nutrition suppressed putrescine accumulation but had no effect on spermidine; silver thiosulfate (10(-5) M) had no effect on polyamine accumulation. Deficiencies had no consistent effect on polyamine accumulation relative to its accumulation under full-nutrition conditions, but adding AOA restricted putrescine and spermidine accumulation in all nutrient-deficient regimes. Foliar spermine accumulation was not affected by nutritional regime. Ammonium-based nutrition resulted in enhanced putrescine and ammonium accumulation and accelerated ethylene evolution rates relative to plants receiving NO3-based nutrition. All nutrient-deficient plants had higher ammonium accumulation, and all but P-deficient plants had higher ethylene evolution than those receiving full NO3-based nutrition. Although some variability occurred among treatments, an association among putrescine accumulation, ammonium accumulation, ethylene evolution, and stress-induced symptoms was apparent. Chemical name used: (aminooxy)acetic acid (AOA).