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Ammonium as a factor in ethylene production in plants under environmental stress
Abstract
Plants subjected to various environmental stresses often manifest high ethylene evolution and symptoms of epinasty, chlorosis, necrosis, and cupping of leaves. These symptoms are similar to those of ammonium toxicity. The objective of this study was to investigate the relationship of ammonium accumulation and ethylene production in the expression of toxic symptoms of plants with different stresses. Under greenhouse conditions, tomato plants (Lycopersicon esculentum Mill., 'Heinz 1350' and neglecta-1) were grown in quartz sand medium with nutrient-deficient, liquid medium at various pH values and in soil-based medium with flooding, drought, or saline stress. Both tomato lines had high ethylene evolution accompanied with appearance of toxic symptoms in response to ammonium nutrition, but 'Heinz 1350' was more sensitive to ammonium toxicity than neglecta-1. Plants grown on NH$\sb4$-based nutrition with pH buffering by CaCO$\sb3$ had low ammonium accumulation and low ethylene evolution and had no toxic symptoms. NO$\sb3$-based nutrition with high acidity (pH 3.5) slightly increased ammonium accumulation but had no effect on ethylene evolution. Urea nutrition with pH 3.5 increased ammonium accumulation and ethylene evolution by plants expressing toxic symptoms. NO$\sb3$-based nutrition with K, Ca, or Mg deficiency, flooding, or salinity enhanced ammonium accumulation and ethylene evolution by plants which also expressed stress-induced symptoms. The application of 10$\sp{-5}$ M (aminooxy)acetic acid (AOA) suppressed ethylene evolution and ammonium accumulation and prevented the appearance of stress-induced symptoms. Application of 10$\sp{-5}$ M silver thiosulfate (STS) delayed ethylene evolution and appearance of toxic symptoms but had no suppressive effect on ammonium accumulation. Plants grown on NH$\sb4$-based nutrition had high putrescine concentration and low spermidine concentration. High spermidine concentration and low putrescine concentration occurred in plants grown on NO$\sb3$-based nutrition. Application of AOA suppressed accumulation of putrescine by plants grown on NH$\sb4$-based nutrition or by plants grown on NO$\sb3$-based nutrition without P, K, Ca, or Mg. Application of STS had no effect on polyamine accumulation. In general, high ethylene evolution occurred on plants with relative high ammonium and putrescine accumulation regardless of source of environmental stresses. The hypothesis proposed here is that under environmental stress, the accumulation of ammonium stimulates biosynthesis of ethylene which in turn promotes the development of toxic symptoms.
Subject Area
Agronomy|Plant sciences
Recommended Citation
Feng, Jinan, "Ammonium as a factor in ethylene production in plants under environmental stress" (1992). Doctoral Dissertations Available from Proquest. AAI9233060.
https://scholarworks.umass.edu/dissertations/AAI9233060