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This article in CS

  1. Vol. 20 No. 1, p. 45-47
    Received: Apr 2, 1979

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Effect of Stage of Growth, Temperature, and N and P Levels on the Hydrocyanic Acid Potential of Sorghums in the Field and Growth Room1

  1. A. M. Gorashi,
  2. P. N. Drolsom and
  3. J. M. Scholl2



Variation in hydrocyanic acid potential (HCN-p) was studied in three sudangrass [Sorghum sudanense (Piper) Stapf] strains and S. almum Parodi. Under field conditions, nitrogen application did not result in a significant change in HCN-p, but strain and stage of growth when sampled had highly significant effects. ‘Sweet’ sudan. grass and S. almum were high in HCN-p, while ‘Piper’ and Line 109 (LI09) sudangrasses were low in HCN-p. Forty-five days after planting HCN.p peaked, then dropped sharply during the following 15-day interval.

In the first experiment performed under controlled environmental conditions, HCN-p differences among the four strains were highly significant. When P concentration in Hoagland'fss solution was increased from 0.0 ppm to 31.0 ppm, HCN-p was reduced significantly. Lowering the temperature from 30 C day/20 C night to 20/10 C resulted in a highly significant increase in HCN-p. In the second growth room experiment, a low HCN-p strain, L109, was significantly lower in HCN-p than the cultivar, Piper, under three N levels. HCN-p was associated with N-level, being lowest at the low N rate. Under both 30/20 C and 20/10 C temperature regimes, HCN-p was higher when the plants were 30 days old, than when they were 45 days old. Also, HCN-p was lower at 30/20 C than at 20/10 C. When both temperature regimes were lowered to 10/10 C for 10 days, the HCN-p in 55-day old plants was greater than in the 45-day old plants. On the other hand, further reduction of temperature to −5/−5 C for one day at day 55, resulted in the lowest HCN-p 56 days after planting.

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