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Polyamine accumulation is a response of plants to various environmental stresses. Polyamine accumulation was assessed in relation to ammonium accumulation and ethylene evolution in tomato (Lycopersicon esculentum Mill.) under nutritional stress. Nutritional stresses were imparted on plants grown in quartz sand culture under greenhouse conditions with NH4-based modified Hoagland's solution or with NO3-based solutions without P, K, Ca, or Mg. The plants receiving NH4 nutrition were grown with or without 10-5 M (aminooxy)acetic acid (AOA) or 10-5 M silver thiosulfate (STS). Plants on nutrient deficient solution were grown with or without the AOA. When plants appeared with toxic or deficient symptoms, the new fully expanded leaves were collected and extracted by 5% perchloric acid for polyamine analyzes by HPLC. Plants receiving NH4-based nutrition had high putrescine and low spermidine concentrations. High spermidine and low putrescine concentrations occurred in plants receiving complete NO3-based nutrition. For plants receiving NH4-based nutrition, application of AOA suppressed accumulation of putrescine but had no effect on spermidine, and STS had no effect on polyamine accumulation. For plants receiving NO3-based nutrition without P, K, Ca, or Mg, the application of AOA restricted accumulation of putrescine and spermidine. High putrescine concentration was accompanied by high ammonium accumulation, high ethylene evolution, and stressinduced symptoms, indicating an association between polyamine accumulation and other stress-related phenomena.
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).
Several factors inducing physiological stress in plants were investigated for their effects on foliar ammonium accumulation and ethylene evolution in tomato (Lycopersicon esculentum Mill.). Plants grown on ammonium nutrition (0.015M NH4 +) in solution culture had elevated rates of ammonium accumulation and ethylene evolution relative to plants grown on nitrate nutrition at the same molar concentration. Inhibitors of ethylene action (0.001 mM Ag+) or synthesis (0.01 mM amino-oxyacetic acid) restricted ammonium accumulation and ethylene evolution relative to rates by untreated controls receiving ammonium nutrition. The inhibitors lessened the expression of ammonium toxicity. Stress from salinity, drought, or flooding in soil increased ammonium accumulation and ethylene evolution. Plants infected with root-knot nematode had variable rates of ethylene evolution in response to variations in ammonium accumulation. Ammonium accumulation and ethylene evolution appear to be factors in the expression of physiological stress.