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This article in AJ

  1. Vol. 66 No. 5, p. 673-675
     
    Received: Jan 22, 1974


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doi:10.2134/agronj1974.00021962006600050020x

Nonionic Surfactant Effects on Growth and Porosity of Barley Roots1

  1. R. J. Luxmoore,
  2. N. Valoras and
  3. J. Letey2

Abstract

Abstract

Nonionic surfactant materials were applied in both solution and soil culture to assess the direct surfactant and the soil-surfactant interaction effects on root dry weight and root porosity (gas space volume per unit root volume) of barley (Hordeum vuigare L.).

Plants were grown for 28 days in solution culture with nonionic surfactant Soil Penetrant 3685 up to 100 ppm. Root dry weight was significantly reduced at 40 ppm and was further reduced to 32% of control plant root weight at 100 ppm. Root porosity, determined by the pycnometer method decreased from 13% (control) to 9% with 20 to 80 ppm surfactant. At 100 ppm, porosity was 4.5%. These results suggest that surfactant penetrated the root at concentrations above 20 ppm and caused flooding of intercellular gas spaces. At a high concentration (> 40 ppm) root growth decreased and the surfactant inhibited root tip meristematic processes. Soil Penetrant was more toxic to roots than Water In surfactant and this more oxic than Aqua Gro surfactant in a soil having little water repellency. Adsorption of surfactants by soil reduced the toxicity to roots. In a water repellent soil, root growth at 28 days was greatly enhanced with a 5,000 ppm addition of either Aqua Gro or Water In indicating more favorable soil-plant water relations. In both soils root dry weight was reduced at high surfactant concentration, however, there were no significant effects on root porosity (mean value 5.7%) suggesting that root tip physiology was more affected by surfactants than internal root morphology.

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