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  • Author or Editor: Kathleen M. Ready x
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Many people want to use hydroponics in production of plants but often are hobbyists with limited access to the reagents necessary to formulate a nutrient solution. Several readily available commercial fertilizers and chemicals with tomato-(Lycopersicon esculentum Mill.) as the test plant were used to develop a nutrient solution. A 20-8.8-16.6 IN-P-K) general purpose fertilizer was added (1 g/liter) to deionized water to make a basic solution. This solution was fortified with slow-release fertilizer (approx. 17N-2.6P-8.5K with Ca, Hg, and minor elements) at 1 g/liter added directly to hydroponics vessels. Tomato developed severe foliar symptoms of Ca deficiency in this medium. Addition of CaSO4 or CaCO3 at 0.5 or 1 g/liter to give a solid phase of these chemicals in the vessels prevented development of symptoms of Ca deficiency; however, plants now showed symptoms of Mg deficiency. Addition of MgS0 at 0.25 g/liter to the basic solution prevented symptoms o Mg deficiency. Analyses confirmed that leaf N, P, K, Ca, and Mg were sufficient.

This solution was as good as Hoagland's No. 1 solution for growth of tomato, marigold, and cucumber and was better than Hoagland's solution for growth of corn and wheat.

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Studies of ethylene evolution by tomato (Lycopersicon esculentum Mill.) fruit were conducted with plants receiving NH4-N or NO3-N nutrition. Fruit of plants grown with NH4-N had a higher occurrence of blossom-end rot (BER), higher NH4-N concentrations, and higher ethylene evolution rates than fruit from plants grown with NO3-N. Fruit of plants grown with NO3-N showed no enhancement in ethylene evolution with BER development. Fertilizing these plants with Ca(NO3)2 doubled the average Ca concentration of fruit and restricted BER development. Ammonium suppressed Ca accumulation in fruit relative to those grown with NO3-N. Ethylene evolution increased as fruit from plants receiving NO3-N ripened, but without a concomitant increase in NH4-N concentrations in the fruit. Ammonium accumulation in fruit induced BER and enhanced ethylene evolution. These relationships were unique, for NH4-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.

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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.

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