Ethylene evolution and polyamine accumulation by tomato subjected to interactive stresses of ammonium toxicity and potassium deficiency

Ethylene evolution and polyamine accumulation by tomato subjected to interactive stresses of ammonium toxicity and potassium deficiency

1989

A:PS

Tomato plants (Lycopersicon esculentum Mill. `Heinz 1350`, yellow-green-5, and neglecta-1) were grown in sand culture with 15 mM NH4+ or NO3- and with K+ varying from 0 to 8 mM. Other nutrients were provided at the concentrations of Hoagland`s solution. The medium supplying NH4+ was buffered with CaCO3 (pH 6.9) or was unbuffered (pH 3.4). Silver ions (0.01 uM) were incorporated in the nutrient solution in one experiment. Ammonium nutrition relative to NO3- nutrition elevated rates of ethylene evolution from all genotypes, but yg-5 and neg-1 showed resistance to NH4+ 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 of the dry weights of shoots with NO3- nutrition, but higher K+ levels were required with NH4+ nutrition. Putrescine concentrations in leaves of `Heinz 1350` supplied with NH4+ were 2 to 5 times greater than in leaves of plants supplied with NO3-. Potassium deficiency increased putrescine accumulation regardless of N form. Spermidine concentrations in leaves of plants supplied with NH4+ were lower than in those supplied with NO3-, whereas spermine concentrations were unaffected by treatments. `Heinz 1350` grown in NH4+-based nutrient solutions with 0.01 uM Ag+ had low rates of ethylene evolution and developed few symptoms of NH4+ 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 NH4+ toxicity were related to increased ethylene synthesis. [AS]

v.114(4):651-655, AMERICAN SOCIETY FOR HORTICULTURAL SCIENCE, JOURNAL

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