Ethylene Evolution by Tomatoes Stressed by Ammonium Nutrition

Studies of ethylene evolution by tomato ( Lycopersicon esculentum Mill.) fruit were conducted with plants receiving NH 4 -N or NO 3 -N nutrition. Fruit of plants grown with NH 4 -N had a higher occurrence of blossom-end rot (BER), higher NH 4 -N concentrations, and higher ethylene evolution rates than fruit from plants grown with NO 3 -N. Fruit of plants grown with NO 3 -N showed no enhancement in ethylene evolution with BER development. Fertilizing these plants with Ca(NO 3 ) 2 doubled the average Ca concentration of fruit and restricted BER development. Ammonium suppressed Ca accumulation in fruit relative to those grown with NO 3 -N. Ethylene evolution increased as fruit from plants receiving NO 3 -N ripened, but without a concomitant increase in NH 4 -N concentrations in the fruit. Ammonium accumulation in fruit induced BER and enhanced ethylene evolution. These relationships were unique, for NH 4 -N accumulation did not seem to be a naturally occurring phenomenon in ripening fruit or in fruit that have BER arising from other causal factors.