Ethylene Evolution and Polyamine Accumulation by Tomato Subjected to Interactive Stresses of Ammonium Toxicity and Potassium Deficiency

Tomato plants ( Lycopersicon esculentum Mill. ‘Heinz 1350’, yellow-green-5 , and neglecta- 1) were grown in sand culture with 15 m m or and with K + varying from 0 to 8 m m . Other nutrients were provided at the concentrations of Hoagland's solution. The medium supplying was buffered with CaCO 3 (pH 6.9) or was unbuffered (pH 3.4). Silver ions (0.01 μ m ) were incorporated in the nutrient solution in one experiment. Ammonium nutrition relative to nutrition elevated rates of ethylene evolution from all genotypes, but yg- 5 and neg- 1 showed resistance to toxicity and exhibited relatively low ethylene evolution. Ethylene evolution declined as K + supply increased. Accelerated rates of ethylene evolution did not occur at tissue K + concentrations >10 g·kg −1 of the dry weights of shoots with nutrition, but higher K + levels were required with nutrition. Putrescine concentrations in leaves of ‘Heinz 1350’ supplied with were 2 to 5 times greater than in leaves of plants supplied with . Potassium deficiency increased putrescine accumulation regardless of N form. Spermidine concentrations in leaves of plants supplied with were lower than in those supplied with , whereas spermine concentrations were unaffected by treatments. ‘Heinz 1350’ grown in -based nutrient solutions with 0.01 μΜ Ag + had low rates of ethylene evolution and developed few symptoms of toxicity. Quantities of ethylene and putrescine produced by tomato genotypes susceptible to the nutritional stresses were linked directly to the degree of stress imposed, and symptoms of toxicity were related to increased ethylene synthesis.